Heating Help

Just Don't Get Modcon Boiler Pump Charts!

Can someone explain to me what the delta T rise on a modcon boiler circulator sizing chart relates to? For example, a Lochinfar 55 reads 3 gpm at a 35 degree rise, 4 gpm at a 25 degree rise, and 5 gpm at a 20 degree rise. Rise of what? The water is circulating in the primary loop at a rate that hardly allows for any temperature drop from one end to the other, and this is temperature drop, not rise. Also, the circulator they send with the boiler will move water thru the primary at 9 gpm, not 5, never mind 3! How doI "design" for a 35 degree delta T rise? and what is with the oversized circulators? Do i need to worry about any of this, as long as i am always moving a minimum of 3 gpm thru the heat exchanger?

rise or drop, it's still ∆T

And with a mod/con, ∆T drives boiler efficiency.  I just look at the HX head loss curves and choose my own circ.  It's always smaller than whatever they show in the manuals -- a 3-speed circ set on low and still overpumping is not a good way to run a system.

You might want to look at a B&G/Laing ecocirc e3 for the boiler loop.  A Taco 003 will do the job but uses ~5x the electricity.  A 003-VS-VV would allow the boiler to modulate flow to maintain ∆T but will costs about the same as a VDT version.

So, Nobody can Explain

how delta T is used in these charts?

ced48

The slower the water is pumped through the HX, the higher the Delta T (rise). That being said, I have never heard a logical reason for choosing one over the other. All the manufacturers list these figures, and I'd love to hear, straight from the horses mouth. There are those that proclaim loudly that their answer is fact, but can't answer "why". I'll watch this thread, and hope I can learn as well.

I called tt and

asked which circ to use on the first tt prestige I installed {a 175 in my own home}, and the tech told me a 0011 would be best he said I could even go 0013, and I asked why? The unit has a relatively low pressure loss and flows pretty free why do I want 31gpm and 31ft pump? He said just flow as much as you can, you wont be sorry, I asked why and he didnt really give me an answer, just said move it as fast and as much as you can.... I installed a 0011 for the primary loop and didnt ask anymore questions it works very well.... on a 1 1/4 x1" pre sec system...

sure, that will work...

but it won't come close to maximizing boiler efficiency.

SMALL PUMPS

The lower the flow rate the lower the head pressure in the HX. The lower the gpm the smaller the pipe size needed. The higher the rise the lower the return temp.

gpm = btu/hr/ (delta-t x 500) still applies. As does the down stream formula. What's goes into a tee still must leave a tee in the form of gpm. If I run my boiler on a 40 rise and your taking it out on a 20 delta I have a better shot at seeing a nice cold return temp then running the boiler and system side on the same rise or delta-t.

100,000 btu/hr on a 40 = 5gpm
100,000 btu/hr on a 20 - 10gpm

Still moving 100,000 btu's. Also remember most boilers are not using supply side sensors and rely on monitoring needed system temp at the boiler. I personally use Viessmann and we use supply sensor in the LLH. Who cares what the boiler water temp is, it's the system temp that matters.

Chris

So why would the TT tech spec such a large circ for a fire tube hx design in heat pros case?

Totally agree with your post is TT tech out of his mind?

You Have to Remember

There are more guys installing these types of boilers who do not understand a lot of what we do. So it's a CYA from the mfg because he knows the provided pump with provide the adequate flow. They charts are meant for guys like us that understand gpm and btu/hr are two totally different things. Gallons per minute is just a conveyor belt moving btu/hr.

I have had....

I have had this very discussion with Rick Mayo, the Denver TT trainer.He doesn't know why they put in the big circs either. It may be a CYA for people that pipe the boiler incorrectly. He stated correctly that, you should be shooting for a wide delta t. 20 degree or more. He also acknowledged that the tt 110 boilers cannot achieve that as packaged.
Carl

the efficiency is more about

the return temperature to the boiler with condensing equipment, don't get to hung up on exact delta T, it's a manufacturers guideline, and a moving target.

Size the pump for adequate flow to scrub away the heat energy and prevent the HX from over-heating.

With small tube type HX the additional velocity can help keep the tubes free of deposits, but excessive velocity creates noise and potential erosion corrosion.

The lower the return temperature the more it condenses and the higher the efficiency.

Same holds true for cast or copper tube boilers BUT you need to stay above the dewpoint of the fuel to keep the HX and vent pipe dry and healthy, with non condensing equipment..

This is exactly why

I don't like boilers with factory-provided circulators.  Say hi to Rick for me.

Thank You

for the insight you guys, at least I don't feel quite as stupid. Do you feel that I will be shortening the life of the HX by running just 3.5 gpm thru it? In this case, I am not going to go primary/secondary, because it is just a simple loop. Triangle Tube gives a design like this as a preferred piping method for their Solo boilers. Lochinvar told me they were okay with it, and that primary/secondary would be a bit overkill in this type of system.

Also-

I will be piping an indirect DHW with a flow rate of about 8 gpm, so this should help keep the HX clean.

I called TT this morning

So, after explaining to him what I was told, he said he tells people that call in to go with a larger pump because that will give them the most likely chance the system will "work" no matter how they piped it... When in fact all he wants is 15gpm at 2ft of head {pllus your piping loss which is minimal depending on check valves and configuration} so lets say 4 ft to be safe, a 007 could do that, lol. I have already done 2 175's with 0011's one being in my own home, they are both working great, but I am going to swap out the 0011 on my unit tonight for an Alpha 15-55, which I will be able to dial rite into 15gpm and then I will see the difference in performance. If it works fine, than that will be the pump to go with because its $100 less than a 0011 and uses under 50 watts vs over 200 watts with the 0011 {not to mention the errosion difference, I used L tubing because I was using the bigger pump}... I just wish I didn't pipe it for the 0011 because I changed my t spacing to accomidate the 0011, now the alpha is going to be turned the other way, damn-it...

I'm kind of aggrivated because I know this was the only area I was fuzzy on, I didnt understand why they list such big pumps in the manual, So I asked the supply house, and a few other guys {even talked about it on here}, then called tech support and determined the 0011 was the way to go, Which in all honesty does work and the unit is functioning well, but I went against my better judgment and did what I was told.... I should have trusted the math.... If you need 15gpm at 2ft of head dont install a pump that pumps 28ft at 2ft of head...
I will let everyone know what I find with the alpha... I believe I have one on the shelf at the office, if not my order goes in tonight so I'll have one on Thursday...

I am not a fan of the install instructions with the tt, look at fig 9 on page 21 http://www.triangletube.com/documents/1/Prestige%2060%20175%20250%20399%20TriMax%20Manual%20052912.pdf I would never do the purge system how they drew it...

You'd never...

Get the air out!

Exactly, Z

I feel bad for the tech that doesn't know better and follows the instructions to the letter, you can purge that until the city runs out of water and it will never work lol...

What would

Prevent the air from coming out either of the two air vents?

And as far as

Purging, If you shut every valve in the system except for the feed and the return valve of the loop your purging you get the air out.

Uncle john did you look at the drawing?

You shut every valve and open the purge valves and it will be locked lol...

There is NO way to purge that system... The water will go rite out the purge valve without even entering the zone...

Trace it with your finger the water comes in the zone valve will take a right and go rite down to the purge valve, never even entering the zone itself... The purge valve and isolation valve above it need to be swapped... Obviously someone drew that on a monday..

The water will never push past the circ, through the emmiters, through the check valve, the closed ball valve {lol} and out the purge tee, when it can simply come out the purge valve 18" away...

I think

That you think the feed water line is teed into the return, it's not. There is no dot on the drawing. The water will enter the bottom of the big air bleed go through the pump through the zone out the purge vale. Look also where the supply goes to the indirect, that is not a four way tee, no dot there.

PS
I see it now. No return ball valve. Missed it last night and this morning , sometimes I have to look three times.

LOL

Yah, unclejohn I figured you would see it after a while, lol.. I was looking at the drawing to see why they wanted a check valve in the primary {I don't put checks in the primary with out DHW} but they show it in all the drawings, and I noticed the backwards purge station, I have been doing this long enough where I wouldn't pipe it that way no matter what they draw, but Im sure it has tripped up someone...

It's a typo

For sure fig. 10 has it right.

It's a typo

For sure fig. 10 has it right.

The Math Never Lies

Have faith in it. Took me a long time to accept it and have never been burnt by it.

I am also a firm believer

in the math, thats why it was tough for me to go against it, but I figured the tt tech would know better lol, oh well, "done rite the second time is the result of a lesson learned"

Math

Using your example on the primary side..
100,000 btu/hr on a 40 = 5gpm
100,000 btu/hr on a 20 - 10gpm

Now, let's use 2 gpm on the secondary side. At 5 gpm, 40* delta t, 60% of that 40* DT , or 24* is returned to the boiler immediately, unused. At 10 gpm, 20* delta t, 80% of that 20* DT, or 16* is returned to the boiler immediately, unused. When the game is all about return temps., which is better?

The Math

Let's use 160 degree water. 2gpm system side flow and the 5gpm out of the boiler. Piped pri sec.

Flowing 5 to the tee you take 2 and your are returning 2 on a 20 degree delta.

(160 x 3) + ( 140 x 2) = 5x

480 + 280 = 760/5 = 152 degree water back

Flowing 10 to the tee you take 2 and returning on the same 20
(160 x 8) + (140 x 2) = 10X
1280 + 280 = 1560/10 = 156 degree water back

The problem with this is the boiler wouldn't be making either 5 or 10 gpm under this load. But if this was a fixed load then the lower gpm brings back the lower return water temp.

If

your calculation was physically possible, that is what would happen.We're not comparing 2 different flow rates at the same delta-t. Just tell me why mine is not correct.

I don't Understand

Your formula. The one I posted was based on what leaves a tee must go into a tee using the system side delta of 20. If I use a system side delta of 40 I would drop return temp even more on my side.

(3 x 160) + (2 x 120) = 5X
480 + 240 = 720/5 = 144

The logic of the boiler installed is going to play a role in this, ie modulation rate. I can still be 90 plus efficient without condensing. This is what is going to happen piped pri/sec. Use a LLH and it's a different formula and ball game. A Mod/Con is going to ramp down so my boiler side flow rate is going to decrease. I'm accustomed because I use Viessmann to having a sensor in the LLH.

Sorry

I can't write it any simpler than I did.

Hey Paul

I made this for the system flow greater then boiler flow to calculate supply temp using a low loss header. I tried twice but I guess you cannot upload Excel Spreadsheets.

So We are On the Same Page

Let's use the attached. The math comes out the same way as I calculated above. The boiler modulation rate is going to change on the fly thus reducing F1

Here is the Opposite Side

The attached is boiler flow less then system flow. I think the variable here is that the boilers logic is going to consistently change it's T1. This is why I would like to see more mfg's using supply/llh sensors.

chris

I understand hydraulic seperation. The fundamental question is.....Do you want the boiler to modulate because you are not drawing the btus off the primary,or do you want it to modulate based on what is happening on the secondary side? Figure 11  shows exactly what I am describing with my math.

The Secondary Side

What's important is that the system gets the water temp and btu/hr it wants not the boiler side. That's why I feel boilers using supply temp sensors perform better then those that do not. Not many use them.

Kis

Keep it simple

Bumble Bee

would be the perfect boiler pump -- if Taco would just make it in other sizes.

I size ~5F below boiler ∆T alarm level, then find the nearest match -- ignoring brand or style.  This approach has led me to selections as diverse as an ecocirc e3 and an Armstrong S25.  No disappointments so far.

I was thinking the

same exact thing, if they would make a bumble bee with a nice straight/curve 22 head 22gpm it would be perfect... I like the 15ft 15gpm of the regular bee for 90% of zone duty, but for a primary even in the low loss tt boilers you will want about 5gpm more...

just give us

a few different 00 ends and I'll be happy.  The 0010 is almost a perfect match for 399k fire-tube designs.

With the System Flow

being slower than the boiler, the return water will be warmer, thus causing the boiler to modulate lower. However, the system return water will be even warmer the next go round, modulating down until it can' modulate any lower. Won't the net result be a boiler that short cycles like crazy?

A BTU is a BTU

Your boiler has a Minimum fire it will only modulate down so far. It doesn't matter what you do with the gpm and delta t It is a fixed number. Your system can only absorb so many BTU's at a given average temp this is also fixed.
Your boiler will run more efficiently with a wider delta t.
Carl

I Think That

is what I am saying. A delta T of only 5, or so, is not going to make for a very efficient system.

How do you determine D/T

Hi,
Been trying to educate myself on these systems for the past month and a half.
What I can't seem to get is the 20-30* and more D/T's I am seeing, and reading about in my Alpine manual. I read, after the zone has stabilized, a D/T of 5-8* max.
I have done the measurements on the LCD screen, and also on the pipes themselves raped in black friction tape with an inferred gun. The readings were very similar. I just don't see where D/T's of 20* and more come from. Can someone explain what I am missing.

Thanks,

Tom

Pump

I don't know if your talking about your boiler side or system side. Can you clarify please. The two reasons why a small delta-t. Either your pump is oversized or your boiler is oversized. Lasers suck by the way. Suggest you invest in a digital strap on multi temp meter. Cooper makes one in the three Benji area. It will take 4 temps at once and calculate delta for you. I have one and it works like a champ.

The universal hydronic formula of GPM = BTU/HR / (DELTA-T x 500) is all the math you need.

Zone pumps

Chris,
 
Thank you for the reply.
Not to bore you but this is my situation:
Last Spring I had my heating system replaced with a new one.
Its a 2300sq/ft 1860ish Sea Captains house on Cape Cod.
Had a highly recomended plumber install the system.
Its an Alpine 150 and 4 Taco 007 zone valves.
He never did a heatloss and I wound up with a boiler that is over twice the size I need. I soon realized that he had no idea on how to size a boiler or how to set it up properly.
I have been reading all I can for the last couple of months to get up to spped and see what can be done.
The primary pump is the Grundfos UP 26-99. Probably way oversized also.

I will look for that Cooper strap on temp gauge. Wha does "in the three Benji area"  mean?
It sure looks like the Taco 007 is pumping way to much for the kitchen zone anyway.

Tom

Suggest You Start

With a new heat loss room by room and then broken out zone by zone. I don't like zoning with pumps as you tend to over pump the zones. At first glance the best way to fix is going to be by adding a buffer tank for the boiler side, then change the zone pumps to zones valves and use a Taco Bumblee Bee as a system pump. Your ok with the 26-99 as your boiler pump. I'd get my system side under control first then play with the boiler pump. Is the boiler also doing DHW? Attached is the Alpine flow chart and I also put the Grundy 26-99 Curve on it.

Temp guage

Check out this one http://www.firedragonent.com/DM6802B.htm
I have had one for 2 years and it works well.
3 benji's = $300
Carl

Testo

I like testo http://www.testo.com/online/abaxx-?$part=PORTAL.INT.SimpleContentDesk&$event=show-from-menu&categoryid=23775814

D/T's

Thank you all for the replies.

Chris I did look at the Alpine chart but because of the D/T's I read I am way off the chart as to primary flow rates. I am way too low with D/T's ofonly 5-8*.
The P/S plumbing looks OK except for the zone pumps being on the return side not the supply side as shown in the manual.  

The kitchen zone is slightly less than 100' ttal so using a head of 6' and the Taco chartI read 13GPM. That seems gawd awful high unless I am doing something wrong.

My thought was to replace the zone pumps with the correct sized ones after determining the correct size.
There is also a Superstor SSU-45 plumbed into the system.
Do you think by getting the zones flowing a the 2-4GPM rate it will help with the D/T's?

Tom

Heatloss

Chris,

I have done a Slant/Fin heatlosson the home so so have the room to room numbers.

Tom

Heatloss

Chris,
One other question if I may.
As I look at the Alpine manual why does the boiler head loss vary with D/T?
I thought the head loss was a fixed number due to flow restriction and did ot vary.

Tom

Head Loss

In the HX is dependent on the flow rate through it. The less flow the lower the head loss. You still need to maintain a minimum flow so you don't flash to steam. Giannoni HX's (Your Alpine) are tight and thus why the American mfgs thst use it size boiler pumps for a 20-25 degree delta. I'm a Viessman. guy and all our pumps are sized for a 40 as a boiler pump.

Are you still confused?

Hey Ced48, are you still struggling with the charts?

You Bet!

But I think I know what I am going to do as far as pumps and piping. I still do not understand where the delta t numbers in the charts come from, or their useful meaning. I had assumed that the boiler makers were being way over cautious when recommending boiler pumps. This is however, hurting the efficiency of how these primary/secondary piped systems function.

∆T numbers on charts

Are simply the result of dividing BTUs by 500 and again by GPM.  Based on what I see, the manufacturers assume far more external (loop) head loss than what we build.  If you know what you're doing, just use the head loss curves for the HX and pick the smallest pump that gets the the job done (I use 5F below ∆T alarm level) at full fire.

So, I Divide 44,000 BTU's

by 500, then by GPM, in this case 3. I come up with 29.33, right? Is this the delta t number, and what does it mean?

Also, What Do You

think of running 3.5 GPM thru a small baseboard loop and thru the boiler, no primary/secondary? The boiler being a Lochinvar 55, 44,000 BTU net. Boiler chart says 3 gpm with 35 degree delta t. The 3.5 GPM would be controlled by a Quicksetter balancing valve, so there would always be that flow rate. Water temp could be controlled by the outdoor sensor, but that's it.

That's Fine

You'll move 3.5gpm but your boiler rise will continually change. As the emitter or room begins to satisfy and not absorb the btu/hr out of the conveyor belt your boiler rise will decrease and the burner will back off until obviously setpoint. Your designing for your rise for the coldest day of the year just like a heat loss. Outdoor reset helps..

Lochinvar WHN055

Has an output driven by boiler ∆T.  If you use a circulator with a 0-10V input it will modulate flow to maintain ∆T.

Really

The rep has been up my butt maybe I should take a look at it. Does it have an onboard pump it communicates with or do you have to add it? Thanks..

just a 0-10V output

as far as I know.

The problem IMO is cost and availability of appropriate pumps.  Residential-sized smart circs available here thus far have not offered external control inputs even as an option.  Compared with a standard (F3) 00 circulator, Taco wants ~105% more for a VSF3 and ~138% more for a VDT3.

I've setup some ganged mod/cons where we just paralleled the boiler 0-10V input with the pump 0-10V input and tweaked the pump controller settings to make it approximate the boiler curve.  Not ideal, no separate PID loop, but it still works better than 99% of what we see out there.

By the Way,

I know what delta t means, I just don't understand how it is used in sizing a primary loop in this boilers.

ced48

How did you come up with the 3.5 gpm for the baseboards? Generally, that would be a 35000 btu loop.

I agree

Hi,
I am also having have a dificult time understanding where the 20-30* D/T is coming from. I certainly don't see it on the LCD of my Alpine. I see maybe 5-8* after a zone stabilizes.  As I read at the manual, the flow rate through the boiler is inverse to the D/T. The greater the D/T the lower the flow rate required. Is not the D/T they are talking about the diference between the input and the output temps to the boiler?  At the 3-5* I see I am way of the chart as the lowest published D/T is 35 at 7.9gpm*. I have measured the temps with a IR gun and get similar readings. This is driving up "WALL" so to speak. Can someone clear this up for us?

Thanks,

Tom 

BTU/HR

Your leaving out one factor in the equation btu/hr.

gpm = btu/hr / (delta-t) x 500

Smaller the delta-t the less btu/hr the boiler is putting out. Temp rise is not constant that's why it is a modulating boiler. Only constant is flow. What goes in a tee must leave a tee and the boiler is a tee. Small delta means your emitters are not pulling out the btu/hr, your boiler flow is much higher then your system flow and or a combination of both.

Forget the boiler for a minute and let's talk about the system side. What is the over all heat loss, how many zones and what is the heat loss of each zone? What is each zones delta-t?

Paul-

I have about 75 feet of baseboard in the loop, which is split into two equal circuits, with a common supply and return.

OK

Roughly 1.7 per split. Just wanted to make sure it wasn't an arbitrary number.

And to Add-

Right now, the loop, with the two circuits, as well as an old steel boiler vessel, is be pumped with a good old Taco 007. The system works fantastic, as is, but the boiler has to go from the basement to the first floor. This is thanks to "Sandy", otherwise I would not be doing this conversion, that I hope turns into an upgrade, rather than the alternative.

About 33,000 BtU Heat Loss

1 zone, single split loop, 2 equal circuits, I assume something like a 20 degree delta t. I know the boiler is oversized, but it's as small as they get. I figure if I set the ramp up at 70 percent, i should be just fine. With the boiler able to modulate down to about 8.8 net Btu's, short cycling should not be a problem.

Chris

The D/T seems to be roughly about the same for each zone.
The downstairs zone minus the kitchen has 46' of standart slant/fin. There is another 50 or so feet of semi insulated piping running to and from. The two rooms that add up to the 46' are actually 2 zones fed by one thermostat. I did that so as to help unload the oversized boiler. 
I turned the thermostat for the test up and the others down. Ran the boiler at 150*. After the boiler stabilized at 150 the return temps were running about 4-5* cooler. It did have a hard time keeping 150 at min mod and was creaping up a degree every 30 sec or so but so was the return temp.
The primary circuit is feb by a Grundfos 26-99 FC set to the lowest speed.
Please clarify that the 20-30* D/T I should be able to see  on the LCD scree on the boiler when set to read In and out temps is that correct?

I m not sure if the plumber plumbed the primary circuit wrong, It looks correct per the manual. The only difference is the zone pumps are in the return line not the feed line.
Do you think a Hydrolic seperator would be a better choice for a P/S plumbed mod com? 

Tom

Zones Are Over Pumped

The zone delta is a system issue not a boiler issue. Boiler can't do nothing for you for that. The conveyor belt is moving btu/hr (flow) too fast around the zone and the emitter cannot take it away. I'm not a believer in zoning with pumps unless those were Taco Bumble Bee's or Alphas.

If your zone supply is leaving 150 it should be returning from the zone 130. That's the standard 20 degree delta. So, if you were moving 1gpm through that zone you'd be moving 10,000 btu/hr. Think about each zone, what was the heat loss of each zone and at what water temp at design did you need. Then find the ODR chart in the manual, find the outdoor temp that matches what's happening now and see what your supply water temp should be. You should also measure the emitters and calculate the needed water temp at design. One hundred fifty degrees on a 40 degree day is pretty hot water. After that deduct 20 degrees and that should be the return providing the zone pump is correct. Get your zones under control first. Since you have an installed system we have to work backwards from the system side to the boiler not the boiler to the system side.

Chris

Thanks for the reply.

All three zones are plumbed with Taco 007 pumps including the Superstor.
 The formula seems to shows that lowering the GPM in a zone will increase the raidiated heat thus lowering the return temp. I see the Slant/fin chart shows greated BTU's at 4GPM than 1GPM which is confusing.
So basically what you are saying is that if one lowers the flow rate in a zone it will  raise the D/T. At this point I guess I need to carefully measure each loop for actual length from and back to th boiler apply the corrections for each elbow and valve etc, and get the head for that zone. One question here, as it is pumped P/S do I not need to add in the head of the boiler itself? Then apply that to the charts and pick a pump that gived the correct flow rate of 2-4 GPM in the zone. It seem it would be nice to make pumpsthat you could dial in the exact rate you want.

 

No No No

Let's start by doing the heat loss, room by room and the. find the heat loss of the zone. Once yu know the zone heat loss we can then calculate the required flow rate.

Yep

Taco Delta T circ, or Taco Bumblebee

Yes

That would be the non math approach.

Here Is How You Get A 40 Boiler Rise

This is basically a Viessmann Vitodens 100 WB1B10-26 and even a Navien CH-210. My system side is running on the standard 20 degree delta. It's your design day and everything is calling. This is when my system flow rate is greater then my boiler flow rate. The trick is even though the boiler is making 180 look at the supply temp out. Can you heat the space? At this snapshot in time the boiler is making 4x40x500 = 80,0000 btu/hr.

If anyone wants the spread sheet just email me and I'll send it your way. I have it the opposite way as well. When boiler flow is larger then system flow. Spreadsheet makes it easier then using the calculator. You can't upload spreadsheet here sorry..

Chris

Sorry if I missed it but yes I  have a done a Slant/Fin heatloss for the house and do have room by rooom and thus zone heatloss numbers.
Tom

Don't Leave Us in Suspense

Share them?

Tom

Here is your Alpine. I used the 13.8gpm boiler flow rate based on the pump curve of the GRUPS26-99. I made an assumption that your system flow needed in this snapshot is 8gpm using 150 degree boiler water temp. Tried to mimic what your seeing. Am I close?

13.8 x (6x500) = 41,400 btu/hr

Your better off changing the boiler pump to a Taco 00R (0015) Speed 1 - It will get your boiler flow rate down to the 8gpm 35 degree rise so you can scrub out the btu/hr in the boiler. Still need to get your zone pumps under control though.

In Reading Over

this thread, one simply solution has been proposed to pump sizing, that being letting the boilers onboard computer regulate the flow speed based on delta t, using a variable speed circulator. Is there any concern that such a system could allow the flow rate to drop below the minimum recommended?

Not at all

This wouldn't be new just new to us. They have been doing
this across the pond for years. The boilers logic wouldn't allow
for a low flow situation.

Thanks, Chris-

Would I half to be concerned about to much flow? If not, isn't this the perfect solution, while maybe a little pricey?

Too Much Flow On Which Side

The boiler side or the system side? Maybe we should start fresh on RISE..

The boiler pump chosen is going to move it's flow CONSTANT. Meaning, whenever there is a call for heat and the boiler runs so will the pump. You cannot change that. It's a fixed speed pump. Look at the Alpine curves I posted above. Tom has a Grundfos 26-99 which is pushing 13.gpm across the boiler. That never changes. What changes is how many btu/hr is being carried by that 13gpm and that my friends is going to be dictated by the boiler rise or the difference between the boiler supply and return temp. Rise is not a constant and is continually moving up and down. Modulation!

I'm not a big fan of the pumps that are sized based on the recommendation of 20 or 25 degree rise. This means you have to move a lot of water off to the system side to scrub out the boilers made btu/hr. You end up with a small rise and this is what causes SHORT CYCLING.

If one zone is calling and you only have a flow rate of 3gpm where do you think that other 10gpm is headed? It is b-lining right back to the boiler. It has no choice. I'll say it again, What goes into a tee must leave a tee!

You system flow rate can be designed for what ever you want it to but you really want high gpm on the system side low gpm on the boiler side. Size the boiler pump based on the flow and head of largest rise avail for that boiler and your system side for the standard 20 degree delta. This way you can take as much as the boiler gpm you can leaving little, ideally none, to b-line back to the boiler. You want your emitters to scrub off the btu/hr and send the coldest water back. You better make sure you have enough emitter and you better make sure that mixed supply water temp is going to do the job.

The best way to read the chart is this. The pump you choose will move the stated gpm based on the HX head loss (plus fudge factor) to get the full rated output of the boiler at the given delta-t (temp rise). There it is again that Universal Hydronics Formula that our friend Mr Barba has imprinted and stamped into my head!

gpm = btu/hr / (Delta-T x 500)

So when we say the boiler will just mod down to low fire, we are saying the burner will, not the gpm across the HX. You still need to get rid of the btu/hr being carried. So if your moving 13 and can only take 1,2,3,4 your going to short cycle and/or stay out of condensing mode quite a bit of the time.

You could say that it's not the boiler that is over sized it's the pump. There are plenty of condensing boilers out there way over pumped. We like big pumps, they move more water.

A few points Ced48...

"Can someone explain to me what the delta T rise on a modcon boiler circulator sizing chart relates to? ...  ...The water is circulating in the primary loop at a rate that hardly
allows for any temperature drop from one end to the other, and this is
temperature drop, not rise"

At equilibrium, the deltaT rise in the boiler is equal to the deltaT drop across your heat emitters.  The deltaT versus flow chart is correct, but the pump recommendations to achieve those flows are not.  I think the manuals are intentionally highly conservative.  Lochinvar is probably assuming that you are assuming a very wide allowable margin of error, with the possible use of glycol in high concentration.  This seems to be consistent with the other feedback you're getting here.  Keep in mind the tables are only valid at full fire output, and the deltaTs are always proportionally less if the burner is modulating, which is like 99% of the time.

"How do I "design" for a 35 degree delta T rise?" 

This is a retrofit.  It has already been designed.  The fintube is already in place and you must work with what is there.  "The system works fantastic, as is..."  So it's fair to say your home heats pretty evenly and the most difficult to heat rooms are still warm enough during the coldest parts of the year?  Hypothetically, If the current delta's are around 5 to 10 degrees, I do not think it's wise to spec a pump for 35 degrees.  (Yeah I know, 20 @ 33,000btus)  It might work fine, but I think that might be a high number for a lot fintube systems.  Especially if your emitters are in series and span different rooms on the same loop.  What I'm saying is, don't go out and buy another single-speed pump specifically for that system delta.  Get something that is adjustable and capable of additional flow to match what you are delivering now.  And yes, you will have no problem moving the additional gpm required to achieve the lower system deltas in the boiler pump charts.  Even if you wanted a delta of 10 (which I recommended starting off with) you do not need a primary/secondary.


"A delta T of only 5, or so, is not going to make for a very efficient system."

In your simple straight through one pump system, the delta T is not the main indicator of efficiency.  That is only one parameter of many.  Remember, your new boiler will/should be heating the water to a temperature dictated by the ODR curve.  Almost all of your efficiency will be coming from the combination of ODR, modulation, and condensing technology.  Increasing the deltaT by 10 or 15 degrees is nothing compared to having the boiler reset the setpoint from 180 to 110 over the course of the season.

Thank You, Eastman-

Your thoughts are more or less inline with mine. I am just trying to make as much sense out of everything as I can. My understanding of how a system gives up it's BTU's puts flow rate at an almost insignificant factor in efficiency and delta T. This is why I felt, and still do, that running at 3.5 GPM constant makes sense. I will have a flow above the boiler"s minimum, yet slow enough to keep the 3/4" baseboard quiet.

To refresh, the system is a split loop, with 2, 3/4" circuits, and a 1" common supply and return. Primary/secondary will not be used, as it is just plain unnecessary and redundant. I will be running an indirect at about 8 GPM, which should do a great job of keeping the HX scrubbed.

Well, if I'm off track on any of my ideas, let me have it! This has all be very informaitve to me, and thanks again to all.

the problem is with a high deltaT

is that your particular house may not heat evenly.  Take a look at the output curve for a fintube emitter.  The relationship between water temperature and heat output is complicated by air convection.  If you have multiple fintube units in series, and enforce a high delta on the system, the first heat emitter could easily put out double the heat that the last one on that loop is delivering.  If the loop spans multiple rooms, the room at the end of the run may never get warm enough even though the first room is overheating.

I think 6gpm would be more typical for this type of system as that corresponds to about 10 degrees at 33k btus if I recall correctly.  And that's not a fast water velocity.  6gpm is about the *minimum* flow taco recommends in 1-inch copper to keep bubbles from accumulating.  (about 3 for 3/4 inch)

Maximum Flow

for 3/4" baseboard is 4 GPM. The house heats very evenly right now.

where did you see that?

can you point me to that information?

By the way, I'm not recommending running 6gpm through 3/4 inch baseboard.  You would have 3gpm in each loop, with a total of 6gpm through the 1-inch common, boiler, and system pump.

Not-

both circuits will have almost the same flow, not each, 50 percent less. That is why the common pipe is oversized.

??

Not sure I understand what your saying.  You wanted 3.5 gallons through the boiler right?  That would be 1.75 gallons through each loop.

No-

I think 3.5 gallons GPM in the 1" will give you about 3.2 in the 2, 3/4" pipes. Isn't a question of volume?

No

You are making a critical mistake.  (Probably won't matter in the end but this is quite an important detail to get wrong here.)


                                             1.75gpm
  3.5gpm                      ------------------------                 3.5gpm
>-------------------------- Tee                        Tee------------------------------------>
                                   -------------------------
                                             1.75gpm

Think of a car analogy

Suppose you have 10 cars per minute going down a two lane one way street.  The street forks into two one lane streets.  Some cars go left, some go right, but together, there must still be 10 cars per minute.  So something like 3cpm to left and 7cpm to the right.  Or 5 and 5cpm.  But certainly you can't have 8cpm and 8cpm.  That would imply cars were magically dropped from the sky onto the road.

Here's another example:

Suppose you're canoeing down a river.  You pass a sign that says this river has a flow rate of 350,000 gpm.   You continue down river until you approach a fork.  You go to the right.  There's another sign that says this branch has a flow of 120,000gpm.  What is the flow in the other branch?  It's 350,000 - 120,000 = 230,000 gpm.  The two branches together must add up to 350,000gpm.

You're probably thinking of velocity.  (feet per second) 

Here's The Possible Problem Eastman

First the boiler pump is going to operate at is given curve based on the head it is coming against. Second, the rise in the boiler is going to be very small and he is going to get very limited time in actual condensing mode unless he puts a ton of emitter in the spaces to scrub the btu/hr being delivered boiler. His best bet to gain the most in efficiency is to size the boiler pump based off the minimum flow and head requirement from the boiler mfg which is generally a 35 rise and pipe with a LLH and then size his system flow based on a 20. Let's leave dollars on the sideline and talk about best practice.

I disagree

Best practice in this case is to *not* use a primary/secondary configuration.  The deltaT is not the main driver of efficiency for this system.  He can set the flow rate to whatever he desires using any number of common products.

Sorry But Wrong

You want him to move 6gpm. He would never get in condensing mode until he sees a minimum of 140 degree supply water temp providing his CO2 is a constant 7. Dew point changes. If he sizes his boiler pump for a 40 Rise and his system side for a 20 he has the best chance of removing boiler btu/hr created thus giving him the lowest return water temp at a much higher system supply water temp as long as he is using a LLH. He just needs to make sure he has enough emitter for the reduced supply water temp at design temp.

how about we flesh that out...

Hypothetically, let's say the system needs 160 degree water with a 20 degree delta on the coldest days we're anticipating.  A 20 degree delta across the secondary loops implies they're returning 160 - 20 = 140 degree water.  Now if the primary loop is operating with a 40 degree delta, the boiler must be outputting 180 degree water.  So the boiler is running at 180/140, and the secondary loops are running at 160/140.  Why not just dump the primary/secondary and lower the ODR curve by 20 degrees?  How is a boiler running at 180/140 more efficient than one that is running at 160/140?

dump the primary/secondary

only works if (a) the boiler HX can handle the required water flow and (b) the emitter system can lose heat fast enough.  In the case of a water-tube mod/con HX paired with low-temp radiant floors a conflict usually arises.

Yeah, but

Ced48 is a real person with existing fintube emitters.  There is very little hydraulic resistance.  He's posted his system specs earlier a few times.  He wants to use a firetube boiler and install it in a closet.

don't get me wrong

I'm a huge fan of direct-pumped firetube mod/cons.  Just need to me absolutely certain that both source and sink are sized using one set of assumptions.

?

What assumptions are you referring to?

can't reply to threads having titles that begin with punctuation marks

Assumptions = ∆T in this case, on which both boiler and baseboard should be able to agree.  I'd probably install a Bumble Bee and see what I could get.

The forum doesn't allow a response to a ? mark?

Really

Can't click

on the reply link to the right of the post if the title is ? or . or similar.  No problem replying to other posts or the thread in general.

Any thoughts on...

my earlier response?  How is 180/140 more efficient than 160/140.  There's no zoning here so it's not like the total system flow is throttling up and down at all. 

not much difference

I can see -- other than a tad more pumping energy with the lower ∆T.  I aim for 30F with radiators when designing - we usually end up closer to 25F once the system is fully balanced.

Eastman

Haven't responded because Easter with the family. I will though. Be patient and enjoy your holiday with your family.

this what i

enjoy though

No No

You can't change the parameters in the middle of the game. Plus who said I needed to run 180 degree water? Of course running less then 180 is more efficient not arguing that. You advise to run a 6 degree delta-t above not a 20.

6 degrees? I feel like you are going in circles...

Here is the text I was replying to...

"You want him to move 6gpm. He would never get in condensing mode until
he sees a minimum of 140 degree supply water temp providing his CO2 is a
constant 7. Dew point changes. If he sizes his boiler pump for a 40
Rise and his system side for a 20 he has the best chance of removing
boiler btu/hr created thus giving him the lowest return water temp at a
much higher system supply water temp as long as he is using a LLH. He
just needs to make sure he has enough emitter for the reduced supply
water temp at design temp."

My point is there's no reason for Ced48's system to have a primary/secondary.  You seem to be advocating for one based on the grounds that it would be significantly more efficient.  Hence the following reply regarding that efficiency:

"Hypothetically, let's say the system needs 160 degree water with a 20
degree delta on the coldest days we're anticipating.  A 20 degree delta
across the secondary loops implies they're returning 160 - 20 = 140
degree water.  Now if the primary loop is operating with a 40 degree
delta, the boiler must be outputting 180 degree water.  So the boiler is
running at 180/140, and the secondary loops are running at 160/140. 
Why not just dump the primary/secondary and lower the ODR curve by 20
degrees?  How is a boiler running at 180/140 more efficient than one
that is running at 160/140?"

Let me clarify the above example:  The 160 system supply is the temp entering the fintube.  The 180 boiler output is the temp of the water leaving the boiler before being mixed down in the hydraulic separator.  Note that parameters are not being changed, this is simply an example of a condition where "boiler flow is larger then system flow."

Take a look at the 40 Rise.pdf you posted earlier.  That document, once again, describes the condition when system flow in the secondary exceeds the flow through the boiler.  Notice that T3 is equal to T4, in other words, even though there is a pri/sec, the return water from the fintube is the same temperature as the water entering the boiler.

From my perspective, the parameters are not being changed.  180 boiler output is the direct result of the other parameters. 

My advice, in a nutshell, is to buy a pump that is at least capable of producing the target flow necessary to achieve 10 degrees.  Because that is a good starting point for a small fintube system.  If a target flow can be achieved to hit that delta, then there's no point in the pri/sec.  Just use the ODR to lower the water temps to maintain thermal efficiency throughout the seasons.

30,000 btu/hr = 6gpm x 500 x 10 degrees delta.

Confusion

I was referring to Tom's posting with his oversized Alpine 150.. The 40 rise was also based on design conditions. In either case we would be running 180 supply but my return to my boiler would be 140 and yours 160, The only time your boiler temp rise is going to match the charts is when you need the full out put of the boiler.

Just talking about Ceds system

Yeah, I haven't looked at any of Tom's posts, my analysis is strictly for Ced's system and is most likely not applicable to any other person's.

Anyways, back on track:

"In either case we would be running 180 supply but my return to my
boiler would be 140 and yours 160, The only time your boiler temp rise
is going to match the charts is when you need the full out put of the
boiler."

Speaking specifically about Ced's system here.  Is my example not correct?  For a system that needs a secondary supply of 160 and returns 140 at design, the boiler would be operating at 180/140.  Assuming you are enforcing a 40 degree delta across the boiler.

here are some numbers

Hi,
I want to thank you all for the help,I am learning a lot and really enjoying learning how to hopefully be able to set up my system to operate efficiency.

I am currently in Paris, France, not Maine, but have been to the one in Maine also, so do not have all the numbers with me. I will be home on this comming Tuesday.

The downstairs rooms (3) that I have been using as a sample all run off the same thermostat. The total slant/fin length is 46'. There is another, I am just guessing here,  50 or so feet of insulated piping associated with the zone. The total heatloss at design temp is 17,500. As I read the S/F baseboard chart I will need a temp of about 150 to get the needed heat. So is my reasoning right that if I need 17,500 btu's of heat for a 20* D/T that is about 1.8 GPM?
At an oat temp of 40* the heatloss is 9700 btu. So does that mean I will need less than 1 Gpm ? That doesn't seem right although it is 2am here.
As always any thoughts or suggstions I look forward to.

Another question for Chris

Chris,

I am having a hard time understanding some of what you are saying.

"Your system flow rate can be designed for what ever you want it to but you really want high gpm on the system side low gpm on the boiler side. Size the boiler pump based on the flow and head of largest rise avail for that boiler and your system side for the standard 20 degree delta"

If I take the largest zone I have which is 107' of baseboard using 150* water and a D/T of 20*, I come up with 4.2GPM.
The Alpine manual calls for a range of 7.9GPM at 35* D/T to 13.8GPM at 20* D/T in the primary loop.
What I don't get how you can get D/T's on the primary loop of 30-40* if you are returning 150* primary water and mixing it with 130* secondary water. That would mean boiler input water would have to be 120*-130*.I just don't see how you can have a higher D/T on the primary circuit then the secondary.

I know I must be missing something here.

Tom  

∆T

You Have to Grasp This

Those are the flow rates that will get you the full output of the boiler at that given rise. Your boiler delta-t or rise is not a constant. It is a moving target. What isn't a moving target is the flow or gpm that moves across the heat exchanger.

In the case below the boiler pump is always moving the stated flow rate based on the boiler rise you chose.

7.9 x 35 x 500 = 138,250 Btu/hr
13.8 x 20 x 500 = 138,000 Btu/hr

If I run the 20 Rise flow rate (13.8) in your zone call example my boiler return would be 144 degrees. 13.8 x 6 x 500 = 41,400 Btu/hr Boiler output

If I run the 40 Rise flow rate (7.9) in your zone example my boiler return would be 139 degrees. 7.9 x 11 x 500 = 43,450 Btu/hr Boiler output


Both are predicated that you are running 150 Supply and 130 Return on your system side. Your piped pri/sec but you cannot by your zone need pull out the entire boiler flow. What you can't goes back to the boiler. That's why the 20 Rise in this example has a higher return water temp. You have more flow of 150 degree water going back vs the amount of flow in the 40 rise flow rate example.

I will get to the condensing mode faster choosing the 40 Rise flow rate pump then you will with the 20 Rise flow rate pump. At a 140 supply 120 return system temp you would think you would be condensing right.

Same zone flowing 4.2

20 Rise = 134 Degree boiler return - Might condense
40 Rise = 129 Degree boiler return - Will be condensing

Well, Just to Get Back

to my situation, Chris, if I install a variable speed pump, controlled by the boiler's computer, would it prevent the flow from every falling below the required minimum? And what will keep the pump from getting the flow moving to fast? Also, is the boiler's delta T pre -programed by the manufacturer, and, or , is it adjustable? (Lochinvar Knight)

everything is adjustable

I wouldn't be surprised if you could even set two different deltas, one for the fintube, and one for the indirect tank.  (have to dig through the settings to confirm)

I have to ask Ced48, what did you think of my earlier examples and analogies?  Are you still not convinced regarding the flow rates?

It's Pretty Much

Defined in the manual on page 37. Pri/Sec piping..

http://www.lochinvar.com/_linefiles/WH-I-O-Rev%20K.pdf

Manual always rules unless your up for an adventure.

I Still Think Flow Rates

are based on the available volume in each of the two differently sized pipes. If the flow rate of the 3/4" pipes were half of the 1", what did we gain by upsizing the common pipe?

Well...

Let me rephrase what you wrote:

If you have 1.75 gpm in one 3/4 inch loop.  And another 1.75gpm in the other 3/4 inch loop.  And then the two lines come together and go into a 1 inch pipe.  Then you are asking what is to be gained by having the 1 inch pipe?  What is gained is a lower water velocity in the 1 inch common.  If the common pipe was only 3/4 inch, the velocity (feet per second) would have to double in the common pipe.  By up sizing the common piping you are preventing higher velocities.

Everyone here is implicitly assuming that when you say you want 3.5 gpm through the boiler, you are actually saying 3.5 through the boiler, hence 1.75 through each of the two even loops.  For example: here's Paul48's response to you earlier:

"Ok.  Roughly 1.7 per split. Just wanted to make sure it wasn't an arbitrary number."

Maybe I don't understand the layout correctly, but I assure you, the system as I understand it would function as I have described. 

What I am Saying

is that water traveling thru 2, 3/4" pipes will move at roughly the same rate as the water moving thru 1, 1" pipe, pushed by the same circulator, 12 percent less to be exact. maybe we are taking about two different things. I am not taking about pressure drop, or head. They will be divided in half.

Does this look like your system?

Drawing

Yes, That's It-

Has anyone every talked wit a tech rep at Lochinfar? Boy, the guy I got was not very knowledgable-

I have not...

But anyways, looking at your system:

When you say you want 3.5gpm through the boiler, that's flow 'z' right?  --same flow through the pump and 1 inch common pipe, right?

To Be Perfectly Honest

I have no idea what I want, other then a pump that will keep the boiler running smoothly. I am going to pipe it directly, no primary/secondary. The boiler chart says I need 3 gallons per minute with a 35 degree delta t, and 5 gallons per minute with a 20 delta t. I started this post to try to understand how one can possibly obtain those temperature differentials with the manufactures provided pump spinning water thru a tiny primary loop at 10 gpm, or so. This still makes no sense. It is impossible to get a delta t of more than a couple of degrees, maybe not even.

How much water, GPM, do I have to move thru what is going to be a boiler and the system to keep it running, and not shorten the HX lifespan?

Would a variable speed circulator solve all of these problems? The manual does not address this issue to the extent that I can fully comprehend the whole thing. Will the pump flow be less than 3GPM at times because of delta t? And is this okay?

I notice that all charts refer to these flow rate a maximum fire, so at minimum fire do we need a lot less flow? Well there, maybe that will clear up my dilemma a bit.

FLOW DOES NOT CHANGE

When using a FIXED SPEED PUMP! The universal hydronics formula

gpm = btu/hr / (DELTA-T x500)

DELTA T CHANGES. Flow or gpm is a conveyor belt moving btu/hr. Change delta, change but/hr, but FLOW is the same!

SO YOU WILL ALWAYS MOVE the gpm or flow where the pump operates based on the entire system head when piped direct!

required speed

Varies with firing rate.  What's your system head at 3 GPM?  I'd probably be looking at an ecocirc e-Series for this.

In a perfect world, you'd use a properly sized ∆T-controlled circulator.  A Taco HEC-2 (Bumble Bee) is oversized and would be operating at the edge of stability.  I don't believe they make a VDT version of the 005.

We really do need some smaller smart circs...

Yes, I Understand Flow

will always be the same with a fixed speed pump. What I don't understand is whether or not a boiler computer controlled variable speed pump will guarantee enough flow to prevent problems that the boiler maker is trying to guard against wit these minimum flows.

Again, in this case, how do I know wether I need 3 GPM or More? They give these delta t numbers in the charts, but they can"t tell me how I can obtain them.

Can anyone tell me how, with a primary loop, flowing water at these fast rates, a delta t of 35 degrees be possible? And no, I'm not doing primary/secondary, but the combined boiler system design presents the same problem, but much more doable because at least the building will be taking some of the BTU's.

System Head Is

6, more or less.

6' at 3 GPM

Is a bit below the curve of a 006.  Taco makes a 006-VVF4 which the Lochinvar could control via its 0-10V output.

Taco, how about some more pump end options for the HEC?

edit:  While you're at it, give us a 0-10V input along with the internal controls.

@SWEI

SWEI, is there an unsafe minimum variable speed flow on these mod/cons?  I mean, can you really have max delta T at minimum modulation using a 0-10volt variable speed pump.

Is it wise to allow, say a Lochinvar WHN 55 to modulate the pump all the way down to say: 0.6 gpm at its minimum firing rate of 10,500 btu with a 35 degree delta?  I didn't see anything in the manual suggesting this is not acceptable.

Lochinvar controls

Will deal with it, including pre- and post-purge cycles.

Here's Another

question- Which is more important, delta T or GPM? If the delta t is right, does boiler flow matter?

∆T and GPM

are inexorably intertwined.  If either is right, the other will also be.  The boiler does not sense or monitor flow, so as long as you stay away from the ∆T alarm threshold it will be happy.

@Ced48

The deltas and corresponding flows are correct in the boiler chart, one can compute this directly with the formula: gpm = btu/hr / (DELTA-T x500).  They are two sides of the same coin.  It is the pump recommendation that is incorrect.  If you install the suggested pump you will *not* get the flow necessary to achieve the delta.  Look at it this way: hypothetically, if you had an adjustable pump that you could configure to whatever flow you desired, and you set it for 3.5 gpm, then yes, you will get a deltaT of 35 degrees.  But, that is only at full 55,000 btu burner output.  If the boiler is modulating to something, oh say about half that (27,500), then you will get half the deltaT.  (17.5 degrees)

"question- Which is more important, delta T or GPM? If the delta t is right, does boiler flow matter"
They are one in the same.  If you get 35 degrees at full fire, then you can be assured the boiler has the recommended flow at full fire.  And that flow rate would be 3.5gpm. 

If you install the recommended pump though, you will not get 3.5gpm and you will not get a 35 delta T.   Remember, the pump recommendations are wrong.  They are grossly conservative in case you screw up.

Great Questions

These are great questions. I have been wondering  myself abut the same ones.
If larger primary D/T's like 30-40* are best for efficiency what is the reason for choosing something lower.?
Tom

something lower

is just "they way we've always done it" over here.  When you combine that with a generous allowance for idiotic piping, you end up with the manufacturers recommending (or even supplying) pumps which are oversized in about 95% of the installs we see.

Okay Eastman,

Thank you, I see where these gpm numbers on the charts come from, PHEW!

But-How can you possibly get a delta T of 20, never mind 35, on a tiny primary boiler loop?
They don't make pumps that small.

simple

Lochinvar is assuming...  let me say that again, they are *assuming,* that the btus the boiler is putting into the primary, are being removed by your system.  Simultaneously.  1 btu in, 1 btu out.  35 degree rise at the boiler, 35 degree drop across the fintube.

If you just had a primary and no fintube, or no secondary loops, the temperature would immediately fly up to the setpoint and the boiler would shut off.

***************************************************************************
Does this make sense?  Lochinvar doesn't know anything about your system side.  But they expect you to hook up your new boiler and freshly piped primary to something that is capable of removing the thermal energy (the btus).  And you are.

Let's say after all this you did decide to install a pri/sec.  Now your question makes more sense:

 "But-How can you possibly get a delta T of 20, never mind 35, on a tiny primary boiler loop?  They don't make pumps that small"

Yeah, if you had a pri/sec arrangement, the boiler pump would have to be quite small.  That's why SWEI and others ignore the manufacturer and spec their own much smaller pumps.  You would have a small pump on the boiler primary loop and a more regular sized one for the system fintube loops.

But, you are not doing that.  The boiler loop is also the system fintube loop.  The pump size required is neither small nor large.  You need a regular sized pump.

And, regarding the pumps...

Just get an adjustable pump, not a variable one, but one that can be set to a variety of fixed speeds.

All of the following would work fine:
Taco bumblebee
Grundfos Alpha
The B&G one SWEI recommended.
Wilo makes an adjustable one too.

All the above are normal sized residential circs.  Your system is not unique.  It is very small with very little hydraulic resistance.  Keep in mind your system runs fine with just one 007.  The firetube boiler you want has about the same hydraulic resistance as your current one.  Nothing in your system is really going to change much.

And Now I Know

why they provide the pump they do-they are assuming a delta T as small as 10 degrees.

What I am going to do is put a temperature gauge into the system return of the in place system, and confirm the actual delta T, running a Taco 007. This will let me know if I am going to have to make any alterations to the existing piping in order to achieve a low enough delta T. Again, thanks for your help.

@Ced48

"And now I know why they provide the pump they do-they are assuming a delta T as small as 10 degrees."

Ced, it's not that they are assuming a 10 degree delta.  (I hope you don't feel like I'm trying to antagonize you here.)  They're assuming that you are going to do all kinds of crazy things with the primary piping.  Like 100 foot runs of 1/2 inch pipe.  Or 50% glycol concentrations.

They are worried that you are going to add a lot of hydraulic resistance and end up with delta Ts of 50 or 60 degrees.

@Ced48 Furthermore...

You have been convinced by others that 35 degrees is a good starting point.  I would not advise that you start there.  The advantages of a high delta are most likely not applicable to your specific system.  You can adjust the ODR curve to achieve the same effect.  System deltas for residential fintube tend to be much lower.  For example, taco recommends 10 degrees.

But a Higher Delta T

would require even less flow, right?

Why do you care

about less flow?

Not joking.  Real question.
********************************************
I mean, yeah, less flow rate, definitely.  But what's wrong with more flow?  Are you worried about the head loss and pump requirements?

*********************************************
Think about it, let's say your current delta is 10 degrees.  And now your new system is 35.  Is your house going to heat evenly?  The fintube at the end of the loop is 25 degrees cooler than before, or the fintube at the beginning is 25 degrees hotter than before.  Something is going change here.  Some rooms are going to get hotter or cooler.  Are these changes going to be good or bad?

Because With a 10 Degree

delta T, I would have to run 9 GPM or so, thru the boiler, right?

Nope

Earlier you said your home needs a max of 33,000 btu's per hour right?

gpm = btu/hr / (DELTA-T x500)

33,000 / (10 x 500) = 33,000 / 5000 = 6.6 gpm

At full fire you would get a higher delta.  But at 33,000, the most your system can utilize, you only need 6.6 gpm to hit a 10 degree delta.  The fintube can't dissipate full fire output, and you should just use the electronic settings available on the WH 55 to cap the boiler output at 33,000.

*************************************
To drive this home.  If you were to buy a taco bumble and utilize its delta T function, if the pump was set for 10 degrees, then one could expect a flow rate of 6.6gpm when the burner is running at 33,000 btu.  When the boiler is modulating at something less, say half (16,500 btus), then the bumblebee would reduce the flow rate to half (3.3gpm) in order to maintain the 10 degree delta.

Yes, That's Right, But

even 6.6 GPM is to much flow for 3/4" baseboard.

Now we are getting somewhere....

Ok, Ced48,

I am very glad you bring this up.  I have been trying for months to point out a mistake you are making in your target flow and head loss analysis.

Look at the schematic I drew.  The 6gpm flow is in the 1inch common supply and return.  In each 3/4 loop, you will only have 3gpm.  You have to believe me.  It is physically impossible any other way.

*****************************
Can someone else jump in here and confirm????

I Thought We Would

get back to this area of conversation. I think the flow thru my 3/4"piping will be just a little slower than the 1". You believe it will be 50 percent less. One of us is wrong, the other right. It is simple physics, if there is such a thing. I wish somebody else would help decide this problem we have here.

HELPPPPP

People look at the drawing and tell him!

Each side loop is the same.

If flow z = 6gpm
Then: flow x = 3gpm to the left.
And: flow y = 3gpm to the right.

Likewise, if flow z = 3.5 gpm
Then: flow x = 1.75gpm to the left.
And: flow y = 1.75gpm to the right.

^^^^^This is what we are talking about forum members.^^^^

Yes, and If You Are Right

my life will be a whole lot simpler. For once, I hope I'm wrong!

Eastman Is Correct

The 1" will carry the 6 to the point you want to split it in half. Caleffi Quicksetters would work nice to make sure each loop is seeing the 3.

Thanks

Take another look at my examples an analogies I posted earlier, ced48.  What goes into a tee must come out.  If you are putting 6gpm into a tee, a total of 6gpm must be coming out. (3+3 going out balances the 6 going in)  All Tees are like this, the diameter of the pipe is irrelevant.

Okay Eastman,

I guess you are right-Not that I not convinced, I just would like to see this in writing somewhere, so I can see where my logic went wrong. Physics was probably the toughest
Class I had in high school. Any books you can suggest or perhaps was Eastman's post edited by Dan, adding the information that wasn't there earlier. Like I said earlier, I'm tickled pink to be wrong.

I will try to find a published example...

for you.

Watch This

http://www.taco-hvac.com/media_library.html?f=a2&sl=165&hs=

Multi-Temp Multi load Part 2 . It gets Eastman's point across.

Watch This

http://www.taco-hvac.com/media_library.html?f=a2&sl=165&hs=

Multi-Temp Multi load Part 2 . It gets Eastman's point across.

Here's something...

This is kind of a silly website and a bit out of context but, here you go:

http://www.comfort-calc.net/primary-secondary_piping_tutorial.html

-Flow in Relationship to Tees-
"Now with all the above explained let's look at what is happening in the system. We will look first at the primary loop drawings 1 - 3. There are two rules we must remember when piping p/s.  The first is "What enters a tee exits a tee". It has nowhere else to go and cannot stay in the tee. If 10 gpm enters a tee it must exit at 10 gpm. It does not have to exit in equal flow rates out of the tee as you will see later. But, for ease of explanation let's assume as the 10 gpm enters the tee, 5 gpm goes out the branch and the other 5 gpm moves between the tees."

book recommendation

I would recommend the latest edition of John Siegenthaler's Modern Hydronic Heating.

But honestly, you don't need to read a book for this.  Grab a 1 gallon jug.  Fill it up with water.  Go outside.  Go to the top of a small hill.  Dig a small trench down one side and another going down the other side. (Make sure they come together at the top.) Dump the water into the trenches where they join at the top of the hill.  You dumped one gallon, some went left and some went right.  But together there must still be one gallon of water on the ground.  Go back home and fill the jug again and dump it again.  Do this once a minute.  You are dumping one gallon per minute onto the ground.  Some goes left some goes right.  But together there must be 1 gpm flowing down the hill.  Not 2 gpm.  That would imply that 1 gpm is magically appearing from somewhere else.  Notice that the size of the trenches, the opening on the jug, all of that is irrelevant.

If you can cram 6gpm into a tee, then 6 gpm total is going to come out.  Perhaps the tee explodes, or perhaps some supernatural being is playing tricks, but barring all that, what goes must come out.

*****************************************
By the way, did you see the other thread I started on this topic?  Several more people have weighed in now.  Everyone unanimously concurs that if 6 goes in then 3 and 3 are coming out.  So hopefully you are truly convinced now.

So....

At this point, perhaps you're wondering --"what again was this significance of all these flow rates?"

Here's the deal, along time ago when you were doing estimates for head loss @ target flows, you were doing them wrong.  Most of the examples on the internet are for pri/sec systems, and most of the advice you have been given has been too general and doesn't address your specific system.  Not only were you using a rule of thumb that has a huge margin of error, you were plugging in the wrong numbers.

You wanted to do something that is not covered in the manual. (ditch the pri/sec)  Can you do it?  If you use really rough worst case estimates and then plug in the wrong worst case numbers, it gives the impression that it could only work at the highest possible boiler deltas.

But....  If you are going to do something that is not covered by the installation manual, should you be using rough rule of thumb estimates in the first place?  (Never mind plugging in the wrong info.)  H*ll no.  Estimates are based on more complicated and fundamental equations.  There are lower level, more fundamental, more complicated, and infinitely more precise equations that describe these relationships.  You should be using those equations.

Now, people might complain, "That's too difficult.  How can you recommend that the laymen attempt such calculations."  Don't worry.  That's why this site exists.  If you can't do it I will.

Moving on....  I calculated the head loss accurately (not an estimate) along time ago for 6gpm.  (3 in each branch)  The common ecm residential circs all can easily exceed that flow rate through your system.  Directly pumped.

Conclusion:  Weather you decide 10, 20, or a 35 degree delta is necessary --all of the common adjustable ecm circs will be able to hit the necessary target flows.  Nothing is being damaged.  My only two concerns are that at a 35 degree delta, a)there is a small risk bubbles could accumulate and airlock the system, and b) much more likely, your home won't heat evenly like it is now.

Personally, I'd go with a bumble bee, just because it would be fun to play with the delta T function.  And also, I ?believe? it can be swapped out with your 007 in case it gets hit by lightning or something crazy like that.

Bumblebee

I just called Taco and confirmed that the Bumblebee is a direct bolt in replcement for the 00 series. The data sheets do show a 1/16" difference in flange distances but the tech rep confirmed it is a direct replacement.
Tom

Hey, I Finally Get IT!

The problem my peanut sized brain was having was thinking that GPM and velocity were one in the same. My thinking that the water in the smaller pipes had to be traveling at about the same rate of speed was correct, but not relevant. GPM is how much water, volume, is being delivered per minute, not how fast. I really want to thank Eastman for sticking with me on this, and for of all the time he put into my problem. Also, thank you Chris and all the rest.