Heating Help

Buffer tank ,Mod Con, how to?

I have a natural gas Weil McClain 155 ultra (128,000 btuh)Mod Con with ODR installed in my home to manufacture spec (primary /secondary) with an indirect as priority 1 but the boiler is 2 times the size needed. My heat loss is 62,500. I have the high fire rate set to 55% (70,400btu) and the low to 20% (25,600) which is lowest setting and might set the high a bit lower to 52%,.Boost is off and it modulates at default 5 on 5 off. Should i raise to 6 on 6 off ? I also have a 008 delt pump for my four zone pumping, is this useful in this application or a problem?
I'm thinking about a buffer tank but not sure how they are installed to cure short cycle issues i am having.Its bumping off the bottom so to speak.I tried slaving two of my four zones together which works at temps greater than 144 targets but would like lower temps.I don't think more base board will do the trick as i have whats needed now to heat at 140/design 0.
I would love some suggestions on buffer size. Is bigger better?How is it piped?
How much lower will it get my temps down?Is a water heater tank a good option/insulated very well?
 I have an 1 1/2 manifold/header with 3/4 branches off the mains, can i just send it from supply via 3/4 branch to the tank and back to the return 3/4 branch with no zone valve so its always pumped through when a zone calls/pump turns on) for heat unless ball valves are closed(this allows me to shut off in summer).
do i need to up size my expansion tank also to match the new volume?
Ty in advance for any help,Ron
Do you live near Newton NJ and want some work/lol?

mass confusion

Buffers can be good, but keep this in mind. Your boiler works best in low fire, target temp is only part of what determines firing rate, the load is the other part. Since not too many reset curves are load matching, thermostats will cycle. When a system with mass cycles the beginning of each cycle will present a load (ability to suck up btus) to the boiler that is not representative of the load on the house. Consequently the boiler ramps up to a higher firing rate than is actually required. What could be near constant low fire burn becomes cycling and less time in low fire.

Anyway optimizing cycling and firing rate is more complicated than just adding mass.

I'd start by testing your assumptions about your heat loss, it may be lower than you think. (If you are not doing night setback) why don't you see how low you can actually go with the firing rate cap? If winter finally hits you might even get some design conditions, to test.

Zoning is also part of the problem, I favor single "zones" with TRV's doing flow modulation, slow the flow where it's not needed instead of shutting it off totally. For those who want more control but don't want to loose all the benefits of optimized operation, tekmar makes great integrated zone/reset controls that sync. zone operation and give autonomy over reset curve to the thermostats. In this system turning down the thermostats equates to shifting down the reset curve. The new house control series 400,401,402 are awesome, and more affordable than the original 4 wire TN4 stuff.

I'd look at the control side before you start cutting pipe.

mass confusion

double post

mass confusion

Dan, while it's not a huge problem, why don't you give your web people some work fixing this double post bug, it happens when you take a long time to finish a post... you get asked to enter your password and security test over again and it results in a double post.

ty

well if this is what i hope it can  then I'm in.
can this thing look ahead and see the bottoms pushing up then open up a zone to help keep me stay in low fire? then turn around and turn off the zone that met its need and open another? I'm willing to keep all zones at 1 temp throughout the season if it means constant comfort/savings/condensing/modulation.
I can do all this myself when i see it happening i just turn off  1 zone and turn on h another and so forth.
also is the piping of a buffer as easy as I said in my post? new larger expansion required also? in addition to the control from Tekmar are they both good upgrades? i would like to condensate often as i can......Ty again for help, Ron

Boiler cycling

What is the boiler actually shutting off on?

Loss of demand from zones? If this is the problem, try running a lower reset temperature.

Internal temp controls? If this is the trouble, then I would start looking at volume of water flow, and limiting the firing rate further.

As part of flow issues, what is the zone pump set to do?

other? Shifting priority demand?

ty,ty,ty,ty

"What is the boiler actually shutting off on?

Loss of demand from zones?"
 I have four baseboard zones all 3/4 copper uninsulated or 3/4 pex supplies/returns depending. my heat loss is based on 0 degree design
zone1 has 43' of baseboard and 100' coppper supply/return zig zagging about the ceiling in basement to feed it. about 18 elbows heat loss is 15,285 in this area i could add/use 2000 more btuh for this area
zone 2 = also in basement can be joined to zone 1 if needed and is 12' of base with 26' of s/r pipe copper pipe 7 elbows. heat loss calculation is 7000 in this area.
zone 3=has 68' of baseboard, 93' of s/r copper and a toe kick 5150 btu.and could use another 2000 btuh to help out. heat loss is 25,038 in this area.
zone 4 = 46' baseboard 130' s/r pex 3/4 could use 3000 to help out in a cold bath with big windows. heat loss is 14459 in this area
Now I can run 2 and 3 together or 1 and 4 together at an ODR of 10 with max high of 170 and low of 120 (target 154 and modualate 20%  till zone temps are good(about 1 and a half hour haul for 2 degree set back).But when I set the high at 160 and low at 110 , the target is 140 and ill short cycle in less then 10 min.
"Internal temp controls? If this is the trouble, then I would start looking at volume of water flow, and limiting the firing rate further."
Could be flow( I have a 008 delta pump set in the mid range for 20 degree delta) I have run tests all the way up and down but the temps just creep higher til short cycle begins. I have the low  fireing rate down to 20% ( lowest setting on priority 2) Have high fire set to 55%

As part of flow issues, what is the zone pump set to do? 55% which should equal about a 20 delta at higher temps.

"other? Shifting priority demand? " Not sure what u mean here
Ty again for help....any ideas?

running a lower reset temperature.

The trouble with an oversized boiler is that running a lower reset temperature is no help at all for two reasons. First of all, the boiler will not modulate down low enough to achieve that lower temperature except by cycling, and even if you get it, the lower temperature you get, the less heat will be removed from the boiler and into the building, so it will cycle more than ever.

We talked about some things that might help a little in another thread here. I have the same boiler he has, but smaller, and mine is oversized also (though it is the smallest in the product line). Unfortunately, the most effective thing that can be done is to run higher temperatures so that the thermostat shuts off sooner. Trouble with this is the higher temperatures reduce the efficiency of the boiler when it is running, and reduces or prevents condensing. It can also reduce comfort.. It is really important to not oversize the boiler. If it is oversized, everything else is a band-aid.

temp/load/head

The ultra Always starts out at 50% and waits ( at least a min ) before deciding what it needs to modulate up or down to. Now I have a high fire rate of 55% set so it can only increase 5%. If this buffer tank is installed and is insulated anything like my indirect(1/2 degree loss per hr) the temp in it should be close to my target is because of previous cycles.  I would think the mass should be there but not so much load, yes? How this helps I'm not sure of yet,lol.
Does the head it creates become a problem? I would like the buffer installed behind my system and on the floor less than 36" tall (was thinking of a horizontal tank)but I have other options. Would I have to up size the 008 pump or keep the tank higher than the pumps?
Then again is a controller playing/shifting zones a bit the better option as all my homes zones end up a bit warmer/ready for target temps as a result. Like I said I can force it to modulate all day if i had the time to hang around,lol.
But the result is warmer temp in the house across the zones, the indoor feed back can help with some of that I guess, not sure how much the thing can do though or even if that means lower temps to condensate. I assumed from some other reading that the mass of buffer was solution but the controller sounds beneficial also.

oversizing

It's not all bad, if you look at efficiency charts for mod-cons you will see that the efficiency goes up at lower firing rates, condensing at higher operating temperatures is also an effect of running in low fire. An oversized boiler although bad for many reasons, can potentially be more efficient than a smaller boiler if it's forced to run in low fire.

Try setting your max to 25% (if you can do a DHW demand override), and see if you can still heat your house, it's a great way to see what your actual heat loss is (minus passive gains).

The zone sync. feature alone on the tekmar controls are very helpful with cycling. It's not the end of the world for your boiler to turn on and off, you just don't want a bunch of small zones calling randomly and causing your boiler to have lots of short (less than 2-3 min.) burns.

I think buffers are more useful for fixed firing rate boilers, the problem of mod cons "seeing" mass as load complicates the use of buffers.

delta-t

The way I see it.....Running a delta-t circulator will actually make the short cycling problem worse.Keep in mind the system(delta-t) circulator is basically scavenging what it needs from the boiler primary loop(circulating at 12.1 gpm). When the delta-t sees cold return temps, it will slow the pump, allowing more water that has not been affected by radiation to immediately return to the boiler.

I disagree with scott on this

the purpose of a buffer is to reduce cycling.

if the mod/con doesn't cycle when it sees the return water, then you don't need a buffer. this will occur with any system with a heat load over the min-modulation of the mod/con boiler.

But it only happens when you are over that load. the buffer tank is there for the 50%+ of the time that many systems are under the min-mods of the boilers on the system. If your min mod is more than 50% of your peak load, then you're in cycle-town for more than 80% of your heating hours.. close to 90%!

I agree that zone sync is a great alternative as well. but an oversize boiler will NEVER be more efficient than a right sized boiler. A right sized boiler is under 50% max fire for nearly all of the heating hours already, and you don't pick up that much going lower... whatever you gain would be lost with the problems of an oversized boiler.

the only difference is that with mod/con boilers you should be sizing by MINIMUM modulation as well as maximum. if your boiler has 4x the max output over another, but the same minimum (not that those exist, but still...)... then it's not "oversized".

boiler cycling

What is the boiler shutting off on? Is it the zones getting warm and causing the demand for heat to go away, or something else?

I don't know what ty means.

If it is like mine,

it shuts off on the high limit of the differential around the reset curve. The default differential is +|- 5F. In my small zone, I changed it to +7F | -8F to lengthen the cycles. I also moved the reset curve up a little to make the load consume more heat. This lowers the efficiency and condensing somewhat, but it is probably better than rapid cycling.

When the boiler is too large, the U-control reduces the firing rate as much as it can (to 20% of maximum), and that is so much more than the load that the temperature increases until it hits the high limit. Then the circulators continue to run and gradually lower the boiler water temperature. Eventually it gets down to the low limit whereupon the boiler fires again, etc. That is all it can do.

Now the U-control cannot really manage if the boiler is significantly oversized. One problem is that it starts at about 50% firing rate and since the water temperature is below the set point, it gradually increases the firing rate until it gets close to the upper limit. But the temperature goes up much faster than the control can follow it, so it hits the top. Similarly on the way down. Lowering the maximum firing rate allows the temperature to go up more slowly and gives the control more time to lower the firing rate. I have diddled mine so that works pretty well except in warm weather, when it is hopeless. But no matter what I do, it cycles on and off because it cannot modulate down to the rate actually needed by the building.

Even if I had a boiler half the size, it would not work in warm weather, though it would be a lot better.

test

OK, so the pump was part of the problem yes, but not all. I took the return sensor from the pump off to force it into full speed all the time. it let my burns get longer and the bottom temp did not push up so quickly. The top temp stays pretty steady until the bottom one goes up a degree there bye making the boilers 20% low fire "too much",(its easier to heat warmer water). So if I had more baseboard/better baseboard/larger mass or more to heat it may not happen. Hey Jean , good news, you can lower the high fire rate, it still starts at 50 to 55 then right away jumps down to set temp, i tried 45% today and it worked. I'm glad i have a 008 instead of a 007, it would happen even quicker as the 007 pumps a bit faster. So i would love to know more about a buffer and how its piped. TY means thank you......but really I thank you all.
PS, the controller looks like a great option if it can mange all the parameters

Boiler cycling

Okay, looks like you've made some progress.

Zone 2 with only 12 feet of baseboard is too small of a zone, and it would be best to physically re pipe that zone in series with one of the other zones, preferably one on the same floor of the house, and on the same side also, so the need for heat would be at the same points of the day.


For example: the boiler cycles every 5 minutes on for 5 and off for 5, so that's a 10 minute cycle. or 5 cycles per hour

So you need to add a 5 minute buffer to eliminate cycling on limit.

http://www.cemline.com/products/brochures/seb.pdf

firing rate

According to the manual, you can adjust the max firing rate down to 21%, and minimum to 20%

Installation manual version...

"According to the manual, you can adjust the max firing rate down to 21%, and minimum to 20%"

I have the Ultra 3 manual, and it says the minimum setting for the maximum firing rate is "ignition rate".
The Ultra 3 UE manual (for the current boilers), says 21%, as you say. So it will depend on just what boiler and controller the o.p. has.

I can't find that

I looked at the ultra 3 manual, and see the same thing. Can you post a link to your manual.

post a link to your manual.

See page 89 of this manual. This is for Ultra 3 UE boilers. Since mine is the earliest Ultra 3, it is not listed in the manual. Actually, I may have the U-control for a UE model in there because the original U-control got flooded (long story) and the W-M rep gave me a new controller. There were quite a few different versions of the Ultra 3. Mine was installed May 2009.

http://www.weil-mclain.com/en/multimedia-library/pdf/weil-mclain-pdf/products/boilers/gas-boilers/ultra-series-3-ue/ug3_boiler_manual.pdf

If you go here

http://www.weil-mclain.com/en/our-products/boilers/gas-boilers/gas-boiler-ultra-series-3-ue.aspx

and select Discontinued Boilers, you can see some of the earlier ones and their installation manuals. Called Boiler Manuals.

How to plumb & control

If you have a mod/con & wish to add a Buffer Tank, how would you plumb it and how would you setup the controls on the boiler to maximize the benefits of being able to run the mod/con for longer periods on low fire & low return water temps?

Thank You:

Tim

Options

In this case, we are investigating possible alternatives to adding a buffer tank.

How to plumb

There are a few different ways to plumb in a buffer tank.

1- Install into the return side of the boiler loop. Causes 100% of the flow to the boiler to go through the tank first.

2- Use the buffer to create a p/s piping interface.
Supply and return of the boiler on one side (supply from boiler on top, return to boiler on bottom) And on the opposite side (supply to system on top, and return from system on the bottom.)

I generally prefer method 2 for heating application and method 1 for chiller application, but if the tank is big enough, either way will work.

In either method, no additional controls are required, but you can add a tank sensor to prevent the boiler from running if the temp in the tank is warm enough, or as the sole boiler demand control.

The Buffer tank will not cause a lower return temp


Also important, in applications where indirect dhwh is connected, pipe in a way that the dhwh loop is not effected by the buffer, otherwise the buffer may get to hot for its intended purpose.

method 3

is on the outlet of the boiler, which is the method I prefer.

then you can't satisfy your load until after the tank is heated.

heat in the bottom, out of the top as well... but that requires a sensor watching the outgoing water temps... then you don't initiate a demand until the tank is depleted. That typically requires external controls but some mod/cons have external sensing capabilities.

control

Rob,

Low firing rates produce more condensation (higher efficiency) than do high firing rates,
IE. a big boiler modulated down and making 60k will burn less fuel than a small boiler in high fire making the same 60k. Do we agree here?

I have demonstrated (years ago) in my own house that an oversized boiler can be "forced" to operate highly efficiently and without excessive cycling. I don't use a buffer, just the mass of a slab, a fixed min firing rate, and an interval based reset control. I could see how an oversized boiler in a low mass situation could be paired with a buffer to accomplish the same thing. I'm certainly not recommending intentional over-sizing, but with some out of the box thinking an oversized unit can be wrangled to run efficiently, even potentially exceeding the efficiency of a smaller boiler that spends much more of it's time in a higher firing rate.

Most boiler firing rate logic is determined by the "perceived" load, not necessarily the actual load. If ample amounts of cool return water are provided the boiler will generally ramp up to maintain target.. thus adding mass to an oversized boiler can have the unintended consequence of unnecessarily ramping up the firing rate. Agreed?

I have noticed some real improvement in the logic used to govern the firing rate and burn periods on the newer generation Viessmans. They are much less eager to reach target in a hurry, and more willing to allow an over-shoot in the interest of prolonging the burn.

To the other poster that complained about the expense of Tekmar. I say look again, the new wiring centers and house controls are fairly reasonable. If all you want is zone sync. you can skip the house control and do this with a wiring center and Tn2 stats alone.

Agree

but with the same boiler firing logic determining when to fire, the apparent load on a boiler should not be any different with a buffer on the supply, or the return.

I don't believe you will ever get better efficiency out of an oversized boiler than a right sized boiler. By what I see with bin data (and I'm going to contradict the other post I made last night with the 50%-80% stuff, as I stopped looking at heating HOURS and starting looking at heating BTUs with my bin data):

1. Right sized boiler will be at under 20% modulation (min mod) for about 10-15% of heating BTUs per year.
2. Same boiler will be in the 20% to 50% range for about another 45% of heating BTUs.
3. and will be over 50% mod (where oversizing could help) for about 40% of heating BTUs.

If you double the boiler output, you are now:
1. in Cycletown (under 20%) for 45% of heating BTUS
2. at 50% or under for 55% of heating BTUS.

So you've only increased the percent of BTUs in the "sweet spot" by about 10% of total. But you've increased the percentage of your load that is cycling by about 30-35% of total.

That can't be great for the lifespan of the boiler, or for its efficiency, though post purge controls could help. and I dont' think going with a 50% oversize or anything like that yeilds much different results... your cycle period is going to increase faster than your "sweet spot" increase because cycle period BTUs occur at lower, more frequent loads and your sweet spot is extending into colder, less frequent hours.

Have fun with this one

OK today i wanted to run a test to help me determine a few things and would love to know what you all see. By the way my manual says 21% was my min low high fire rate(but does say model specific).
Test is  to determine if I'm getting all the heat/flow /BTU to and out of my baseboard.
settings, its 50 degrees outside today,120 min 180 max and set fire rate to 65% high, 20% my settings are to promote a  140 target. which slant fin gives me ratings for. 10 ODR. All stats would ask for 2 degree set back.all four zones.My oo8 taco is set for full output. Test takes 46 min to complete when all 4 zones met the 2 degree climb. I ran a 10 degree delta he whole way and was modulating at 34% within 5 min and through out. it would mod down to 20% or up to 40 now and then to keep pace. flu temp was 129, blower was 2000,
now slant fin says 300 btuh per ft but they add 15% so lets call it 255 per ft
i have 170' of baseboard x255 = 43350
plus a 5150 btu at 140 degrees  toe kick which works well on high its a 6/8 total = 48500
219' of copper connecting these together some on cold walls some in ceilings none of it is insulated i think this losses 50 btu per ft = 10950
196 of pex i guessed 10 per ft  x 10 = 1960 
so 61,410 btuh of radiation at 140 degrees.
my tests resulted in the boiler modulating at 32% which i think means either 155,000x.32% btu ultra (49600) or 128000 actual output ( 40960) which do I use? its called a 155,000 but the output says 128,000?
So 61410 less the 40,960 is big to me but the 49,000 could mean lots o dust bunnies and 50 % of the basebaord is painted.
Could this be a flow problem or sounds normal?
Now what did you mean that a buffer will not lower temps? would I not be able to run cooler temps? is there another way when set up that i could? mixing of some kind?

Buffer

In order remove heat from the water, you need load. The buffer tank will not add load. All the buffer tank does is add a time delay to the flow of water / btu's , and therefore extend run time.

Now depending how it's piped, it will act as a mixing point, blending different water temps together, but p/s piping does that on its own. The main thing the buffer will do is add a time delay to the flow of the boiler loop. The pump for the boiler will move 14 gallons in one minute. If you add a 70 gallon buffer tank to the boiler loop, it will take 5 minutes for water leaving the boiler to return back to it, hence time delay. The purpose of the time delay would be to allow for the boiler to run longer, and in that longer run time, hopefully the return from the system will drop on its own giving the boiler something to heat.

The rated EDR is based on clean baseboard, and a specific room temp and boiler water temp.

primary

I'll put this out there, for what it's worth, I do not like manufacturers drawings for boiler primary. Under all conditions, too much boiler temperature water is recicrculated immediately back to the boiler. I would prefer the boiler loop expanded and the system within, using closely spaced tee's as primary to insure the return temps reflecting the system. After all, the system is desiged based on return water temperatures being a certain temperature.I wouldn't consider something inefficient to try and create efficient boiler operation. I would rather run a second indirect off the boiler  loop and preheat my DHW rather than waste it.

Would that really do much good?

My indirect runs two or three times a day (40 gallon nominal) for about 10 minutes each time. That is about all the hot water I use.

So if I stuck another indirect in series with the primary loop to preheat the water going into the indirect, just how much heat could I put in there in 24 hours? It would be less than what now goes into the indirect because the indirect I now have gets 175F water, and the primary loop, when heating the house never exceeds 134F, and on design day it is closer to 112F.

When my main (radiant) zone is running, it takes about the same flow as the boiler loop. When both zones are running, it takes more flow in the secondary than in the boiler loop, so none returns directly. Only when the small zone is running alone does most of the water flow backwards through the closely-spaced Ts. Why is this a problem? The boiler already modulated down as far as it can in this condition, so the return water temperature is about as low as it is going to get whether it goes it goes through through that zone or not.

how much?

So what is the boilers max fire rate 100% ..... is it 128,000? or 155,000?
if it is 128,000 as I think , then I have a water flow problem or my baseboards are clearly not radiating as intended by a drop of 33% on top of the 15% i already removed from fin rating chart yes?
I think I'm going to take some temps from the individual zone 3/4 returns and see how close they are to readings on the boilers. if they are close to the boilers/manifolds readings then its my baseboard thats not up to snuff(matching up to test ).....if they(temps) are off by 33% or so then the flow would be a problem(faster needed). Am I right in this thinking?  Now Im sure some heat mixes from the manifold and creeps away from the tees to readings along the manifold (location of boiler sensors)and could be skewed a bit. But my problem of bump up from bottom temps is real, So I need to remove doubts about flow from all this thinking before moving forward.
My thinking is if my return temps are actually lower then stated by sensors by 20% or more it tells me that I need to get more of those temps(water) into boiler loop. I could do that by volumne(buffer) or by speed yes?

primary secondary

DELETED. double post.

primary secondary

is primary secondary. how much heat is extracted is about flow rates and temperatures, not how many different sets of closely spaced tees you are using. The best way to avoid hot water return is not to use primary/secondary... but then you better manage those flow rates well.

Wider

The first thing I would look at doing is to get rid of the pri/sec. It is most likely only allowing a 20-25 delta across the boiler. You need to widen that delta enabaling you longer run times. I'd pop on a low loss header and size my boiler pump for a 40.

What delta are you running the VDT 's on? If you are running a 25 or 30 you also not pulling many gpm off the secondary side on the small zones which is just sending hot water back to the boiler.

My feable mind,lol

I currently have the 008 set to max flow / not at variable speed because it was fighting the whole process, it would slow or (speed up rarely) So because it spent most of its time running slow and the boiler loop was all that was being accounted for. Things got better right away in tests once I got more flow.
Does this design  do the trick and still keep the warranties from Weil Mclain?
http://www.cemline.com/products/brochures/seb.pdf
I keep thinking , why cant I just pipe from my supply header with 3/4 like all the other zones into a buffer tank then out to the return like all the other zones with 3/4.This as my feeble mind sees it just creates a large zone (mass) that's open all the time(no zone valve) waiting for the pump to kick on.
Then when a zone calls ,the buffer and the zone calling both flow when the 008 comes on. The buffer adds mass (or does it piped with only 3/4?)that cannot be heated so fast and keeps me in p/s to Weil Mclains liking.
I would love a delta of 20  though. thats why i got the pump in the first place. But the lower water temp for modulating takes priority I think, yes?
PS. I have another issue to think about/ lol I did switch the direction of flow through a zone to better accommodate hierarchy of need on zone 3 when I re did things and zone 3 has  a toe kick heater. The heater is run with mono flow tees x 2 off the main with 1/2" copper ......I think that still works correctly yes?

Because

If it is piped like a zone, it will only every see one temp, hot supply, and will have a hard time ever cooling down.

In your case I think programming, and maybe minor piping tweaks to balance the zones is all you need.

You may never get the Ideal b/c the boiler is too big, but I can tell you that you can make it workable w/o major reworking.

Adding a buffer is a last resort. Buffer tanks are not cheap, most are built for commercial use, and therefore require ASME rating, which adds big money to the cost.

When you first posted about your system, I was under the impression that it was all new, baseboard and all, and sized to run low temps. I now know that is not the case.

With dirty baseboard, you will not get the heat emission you planned on, especially at low temps.

The first thing you should do is break out the vacuum and clean the baseboard, and be sure to keep curtains away.

Next, I would try bumping up the low end of the reset warmer, to force more btus to emit into the space.

40 degree delta

Running a 40 degree delta would be fine, but that has to be accomplished by load, not the boilers pump. The best way to accomplish that is by what is called load stacking.

Load stacking would be more like what Paul48 is eluding to. Form a "extended primary" and have all the secondaries tie back to it with close tees (requiring a pump for each zone/secondary). What this would do is cause the first secondary to be the hottest, then the next would be a little cooler, and the next a little cooler still, and so on.

But this strategy would require a different control set up, and a lot of re piping.

In order for this to work, the U control would have to have only one in put demand to run, and no reset for the b/c of the dhwh

The way it would work would be as follows: boiler would have to run hotter on a call for heat like 180 supply. That 180 supply would first be sent to the dhwh and and it would remove some heat leaving say 170 supply after mixing into the header, then the next zone would draw on it and remove more heat leaving say 165 after mixing into the header, and so on. It also would require the use of pump controllers to provide pump start/stop and boiler demand.

I don't believe the boiler in this case would benefit, b/c all zones require the same temps. A better application would be radiator or baseboard loop, then in floor heat, cause the in floor can utilize the lower temp water during all outside conditions.

A low loss header is no more than a miniature buffer tank.

Sizing the boiler pump for a 40 degree delta would cause the flow through the boiler to drop by 50% at least. This will cause an increase in delta, but by causing the supply to get hotter, because there would be more dwell time in the boiler.

Certainly before I would recommend adding a buffer tank, I would try tweaking the system to get better performance with what is there.

reply

"Certainly before I would recommend adding a buffer tank, I would try tweaking the system to get better performance with what is there"
Yupper, thats what I hope to do 1st get stable. Get my lowest temps with good cycles then see where to go from there. Ill post back with results on testing today sometime.
Hey Furnace, what say you on my piping idea for buffer? Its the easiest fix /piping right now as im set up for adding a zone now. Am I off my rocker?

ODR

Raising the min OD reset will force the max temp to be the target. Won't that just make his short cycling problem worse?Wouldn't lowering the max ODR to try to force the controller to make the min temp the target be a better solution? A little foggy this morning.

The buffer won't work

piped that way, like I said before, it would only see hot water. And once hot, it would stay hot.

Boiler Delta

there is a reason they give different flow rates and boiler head. Boiler is oversized, by increasing the delta on the boiler side and lowering the flow rate you can then exhaust the primary loops btus into the secondary side running at a 20 or 25. The use of a LLH will allow for a blend with the warmer return water back into the supply keeping the cooler water heading back to the boiler. It is also the least intrusive piping change as well as more cost effective. Boiler pump change to a UPS15-58 or Taco 00R.

If you could

change the way the boilers algorithm worked, I would agree with you, but unless you use a 3rd party control, and reset the boiler to use a remote firing rate, you cant.

As far as I'm aware of there is no setting in the boilers control to tell it what delta you want to maintain.

So, my point remains, reduce the size of the pump, and reduce the flow through the boiler.

Reduce the flow, and you will increase the delta, but by way of increasing supply temp. The boilers control does not attempt to maintain a specific delta t, but only uses the supply and return sensors to see whether its making progress or not, and how fast.

By the way, a third party (tekmar for example) firing rate control, may be a good option. This is something that would be minimally invasive.

why would you replace the pump

wider firing differential would help... twice the difference is twice the firing length. but trying to achieve this with a slower pump just makes a short cycle worse. you have to get all the water in the circuit through the boiler fast enough to move the BTUs out.

slowing down the boiler circuit will not help achieve that. increasing flow in the secondary circuit would, if we do have a situation where we are heating the boiler, but not the rest of the circuit, too fast.

You don't get to cheat unless that boiler circuit has a... wait for it... buffer tank on it and the problem is already too little flow. but just changing the speed of water around a ring of pipe, without actually extracting those BTUs at a different rate, isn't going to change anything.

Rob

Don't know much about the Ultra itself but since the boiler is oversized wouldn't it make sense to get the boiler side delta out to 40 reducing the flow rate out to a LLH. From there he can run his 20 with the VDT. If His heatloss is only 60K wouldn't getting 7gpm out of the boiler be better for him then the 13gpm? The boiler return would be seeing substaintially colder return water temps.

have to be clear

heat output = GPM x 500 x DT

If you cut flow in half and double the DT you haven't increased apparent heat output. To increase the DT without cutting the flow, you have to increase the load (pull the heat out faster). That means higher flow on the load circuit, not the boiler circuit, unless you are already under-pumped on the boiler circuit which is nearly impossible in most cases.

Increasing the FIRING DIFFERENTIAL, or Hysteresis setting on a boiler, will increase the firing time linearly. If it's set to fire to a 20 degree rise, changing that to a 40, with a 10 degree increase in supply water temp to make the average temp work out, would double your run times over what you are seeing now. That is helpful. In fact the advanced boiler controls with 'variable' boiler differentials will do that automatically in low load conditions to reduce boiler cycling.

but you can't increase output or reduce cycling by slowing down flow. Ever. In any circumstance. The only thing reducing flow can do is increase temperature rise which might be of value in some circumstances, but not this one.


If you have an oversized boiler, simply your options are only:

1. Zone Syncronization controls
2. Buffer Tank
3. Wider firing differentials (NOT loop Delta-T's)
4. Less, larger zones with higher flow rates and hopefully some mass like radiators or slab floors.


Wider Loop Delta-Ts might be better from a condensation standpoint and thus for efficiency: that's true, though I don't think most boiler manufacturers will allow you to run a 40 degree rise across their heat exchangers, most want you to stop at 30. But that will not help an oversize boiler with cycling control, it will only help with condensing efficiency. And Frankly, I am not even convinced it will help with that as I believe outgoing exhaust temps are related to the supply, not the return temps, but I am not a boiler engineer and I'm not sure which is most important for efficiency, return or supply temp.

On the Right Track

So in the end, getting the delta wider on the boiler side (pri), ie 40, while still maintaining the 20 on the system side (sec) is a logical approach. In Viessmanns world 40 is the way to go for boiler delta and flue temp is generally 20 degrees higher then return water temp.

kind of

not for cycling control.

You'll pick up a little condensing efficiency that way, but you are doing nothing to control cycling. If you don't care about that, so be it... the thread is about buffer tanks, so I am assuming that was still the main focus.

good to know about the viessman DT spec though. If anyone was going to 'break the rules' I'd expect it was them :D

I could not agree more.

Well said.

I wouldn't

I wouldn't replace the pump. I was trying to make the case to not lower the flow through the boiler.

Paul 48

Maybe you misinterpret my meaning.

By increasing minimum reset temp, I'm referring to the water temp, not outside temp.

Increasing the minimum reset temp will cause the boilers target temp to go up, but it will also cause more btu's to emit from the baseboard to the air.

The higher the water temp is compared to the space temp, the more btu's will transfer to the space, causing a higher spread from supply to return. But, too high a temp will prevent condensing. Originally I believe the minimum target was 80, and the boiler short cycled on internal temp limit, because the water temp was too close to the space temp and the btu's were not transfering to the space.

Foggy

I thought his problem was that he could not transfer enough btu's to the space without the boiler hitting its limit. I didn't realize he was not getting enough heat to the living areas.

Its not

that he does not get heat to the space, but that the boilers heat output to the water does not match what the space is absorbing, so the boiler shuts off on limit.

Meaning there is more boiler capacity then available load.

flow

Flow through the boiler is fixed by the boiler circulator.The boiler maintains the Delta-t in a round-a-bout way, based on the information you give it vs its own sensors.It adjusts its own firing rate accordingly. Raising supply temps will always raise return temps regardless of radiation.Thereby shortening the time it takes for the boiler to reach its high limit.Especially if the problem already exists.

Raising supply temps will always raise return temps regardless of radiation.

That is true. But the situation is really quite complex. If I raise the supply temperature, the emitters will emit more heat. If the boiler can modulate down nearly far enough, raising the supply temperature may just sink enough heat into the house zone so that the boiler need not drop out of modulation and hit the high limit -- not the one at about 210F, but the one just above the reset curve. In the case of my boiler this is not enough. My minimum temperature is now 110F (I wanted it to be about 80F) and it still cycles, but not as fast as it used to.

It's not shutting

off on the high limit, but the reset limit.

Yes, raising the supply water will ultimately raise the return temp.

Energy flows from High to low, and the higher the spread the faster. I don't care what kind of energy it is. In this case it is heat energy.

If the room temperature is 70 and the supply water is 80, that's a 10 degree difference.

If the room temp is 70 and the supply water is 90, that's a 20 degree difference.

The greater the difference between water temp and room temp, the more heat emission there will be from the boiler water to the room ultimately causing a greater difference from the water leaving the boiler to the water returning to the boiler.

The boiler has a minimum output of 25600 btu, and in order to get the boiler to run continuously on a call for heat, the heat emission from the baseboard has to match that #. In order for that to happen, the difference between the supply water, and the room temperature has to have a certain spread.

The spread can be achieved by either arising the supply temperature, or lowering the room temperature, or a combination of the two.

confused?

sorry for any cunfusion but my space does get heat. in my test above i gave all the outcomes. it took only 45 min to raise all the zones 2 degress.
with that said i did the test to see how many btus my furnace was using per hr with all zones calling and trying to determine if those btus where being used by the baseboard.
my thought was if not being used then there could be a flow problem or a radiant release problem with the baseboards.
The test for me at least shows there is some type of problem along those lines because im not using 33% of the btus.
The boiler puts out 120,000 btu.
it ran at 32% the whole time.
i have 61,410 worth of baseboard output.
32% of 128,000 is 40960......where is the other 20 450 btu going? Well back in the boiler raising the bottom temp and pushing the top....thats where i think its going.....question is why? im thinking flow because even with dust bunnies i aint losing no 33% but who knows? now the boiler pump is stronger than the system pump so i guess its sucking it all in by design then?

yupper

yes thats what im talking about....slant fins test rating are based though on my test senerio 70 degree indoor temp ......supply water at 140! So i still want to know about that 32% and i want my jets to win and 3 other teams to lose! lol

lost and found

Hello,
32% of 128,000 is 40960......where is the other 20 450 btu going?32% of 128,000 is 40960......where is the other 20 450 btu going?

The boiler only produced 40960  btu's
There is no missing, 20450 btu's.
The 20,450 is' not "going" anywhere, because is was never produced.

Peter

?

it ran at 32%(40960) the whole time.......and had to reduce /increase a couple times but ran 95 % of the time at 35% and that extra is going somewhere and i think i just found out. 1 1/2 header/manifold /other parts like seperator /pumps/exchanger/parts/etc...... 10% up thu flu (depending)) all release heat and also the dusty/painted baseboard all lending a hand was not accounted for in my findings. time to clean some base board/add some baseboard which i planned to do anyway for lower temps plus a buffer should do the trick.

Actually

Because of significant restriction in the boiler itself, the 0014 is pumping at around 12.1 GPM, and the 008 running at max is around 15.Which means it's taking just under 3gals of return water back. 25%

Don't Think So

The 008 at 0' of head may move 15 but not on a zone call. I've read the Ultra manuals and cannot find one missing piece of info. Why you cannot run a 40 delta across the boiler. Reducing the flow rate on the boiler side will enable you to pull out the btus on the secondary side running on a 20. The secondary side is just pulling btus made on the primary side it doesn't care how they are made. Still think the LLH is the way to go with a smaller boiler pump moving 7gpm out to the LLH. Seems to me 7gpm takes care of your needs. The colder boiler return water temps will be an asset.

maybe but

maybe your right but i and most of you guys who install would/should be worried to not follow manual. it says that the 0014 supplied with the boiler must be used in a primary / secondary install .......page 10 NOTICE and page 10 uder notice it specs the pump to be used for each model in the circulators notes.

Manual Also

Gives you boiler head loss at different flow rates and I'm not pri/sec piping using a LLH. The 0014 is given to move the needed gpm using a 20 degree delta which is just about all you'll see using pri/sec. At that gpm the 0014 is required to overcome the boiler head. Slow down the flow rate you reduce boiler head. Not a Weil user or fan but a good question for the tech dept. Still feel LLH, larger boiler delta is the way to go.

Wouldn't installing a buffer tank also defy the manuals stance for primary/secondary?

new math

"and that extra"

Do we  agree there was only 40, 960 but produced?
Yes or no?

Do we agree that you have radiation that can remove up to 62,000 btu's hr +/-
Yes or no?

If only 40,960 btu's were produced, and all of it radiated, how can there be
20,000 btu's missing?
Sorry, i'm missing something, as i didn't learn "New" math, so i need to take this one step at a time.


Peter

better

Hey Pete check my last post at 451pm.....it explains what I missed.  I run much lower temps today and stay stable after some tweaks to the delta pump and new testing.....had 132 target going today mod @ 25% with no problems (I had high @165 and low at 110)but that's with the house as one zone.....will shoot for lower temps tommorrow. Is there a way I can wire my thermostats to come on when called upon by only one locations thermostat  but shut off when each of the others hit there desired marks at their individual locations?
meaning all come on when location 3 calls for 70 but if 3 is not yet there
 1,2,4 will still all shut off when they each hit 70
this will start them off as a team but end each on there own

ouch

Tekmar has network thermostats that "talk" to each other and will hold off some zones from starting to enable more than one zone to start at the same time.
Only one problem.
Ouch $$$$
There is likely a way to do it with relays, but it would be quite a project.

Peter

Only one problem.

Only one problem.
Ouch $$$$

I guess so, but how much more fun it will be with a really interesting control system! My guess, since we do not discuss pricing explicitly here, is that it would be less than a good model railroad setup, and some people willingly pay for those.

MRR

Yes Jean,
Far, far, far, far, less. Trust me, i know all to well.
One could have one of every Tekmar device, in the catalog, and still miss it by a mile or two.

Peter

one more thought

By running all the zones as one am i risking damage to my 008 with more head?
also one more thought on a buffer idea. If I ran all the 3/4 returns to a tank then ran 1 1/2  from tank to the 1 1/2 return on boiler that would keep only my last used return temp in tank(more than likely close to the same temp for next usage) and ready to roll and add mass. this would let me use a cheaper tank and retro fit fittings. Would this also add more head? LOL that's my last crazy idea of the day...i promise. PS dang jets stink! Ty again my brain really hurts from all this.

Be more specific

Do you mean all zones in series, or just running all the zones at the same time?

If all in series, you would need to recalculate the head requirement of the pump.

If just running all the zones at one time, the head is the longest zone.

Forget about the buffer tank.

Focus on settings, and adding and cleaning baseboard.

PS add the baseboard in series with base board that already exists, not in parallel.

I'm a high maintenance poster eh?

i just installed jumpers across the zone valves 1,3,4 and removed the existing wires to the zone valves 1and 4 , so when zone 3 thermostat calls it opens the  1,3,4 zone valves at the same time then the pump kicks on.
Ran everything for one hour at target of 130 mod @23% avg and held on tight to a 7 degree delta the last 45min......is it the low return temp (south of 130)or the higher delta that condensates more? If temps in the home are OK in each zone, I think this could work but i want to replace the tricked out (rigged)008 with a standard 008 or 007 and sell the delta 008 I have the return sensor installed on a cold water line to keep it at peak flow ,lol. The longest run is a 3/4 pex 191 ft run which includes 46 of baseboard to my addition, figure 14 elbows.....what size pump do you think?
If I have not said it enough, thank you all for your continued help with a newbie.....you all made me laugh.....cry.....wallow in self pity and rejoice,lol

condensing

, is all about low return temps, less than 130.
That's why, furnacefigher15 and others suggest adding more and arranging existing baseboard in series.


Peter

?

arrange existing in series? what do you both mean by in series.....one long loop/zone as opposed to three side by side loops? 

condensing is all about low return temps, less than 130

This is true. And while condensing starts as you get below 130F, you get only a little at that temperature. In other words, at 140F, your mod-con may run at an efficiency of 86%. At 130F, 87%. At 120F, 90%. At 100F, 94%. At 80F, 97%. At 60F, 98%. At 40F, 99%. These numbers assume you are running at maximum firing rate. Since this is unlikely, your efficiencies may be a little higher than this at lower firing rates.

delta vs 130

So high deltas are more about achieving lower return temps to get under the magic number 130. Not the fact that the return temp is a greater distance apart from the supply temp?
Also in my case, even if I can achieve a 20 degree drop from 132 to 112 return temps I am only looking at 3-5% savings max? they may not be worth the buffer trouble then. Ill add more baseboard as needed and find my curve/refine things a bit. I went from a boiler that was a 100,000 btuh all the time at 73% eff burning oil to a boiler thats 87 %and up modding at 40,000 btu that was a big jump.....my mistakes cost me 4% or so.....live /learn i guess. 

It depends. Things are not that simple.

"even if I can achieve a 20 degree drop from 132 to 112 return temps I am only looking at 3-5% savings max?"

Those savings are the ones resulting from condensing. But it seems to me that the modulation function gets you even greater savings, and an increase in comfort besides. Even though the gas probably burns at about the same temperature whether you are firing high or low, the transfer from the fire side to the water side of the heat exchanger increases as the temperature of the water decreases. So more of that heat goes into the water and less up the chimney That is why mod-con boilers need a blower to assist air flow through the burner; the exhaust is just not hot enough to get sufficient flow up the stack.

The comfort results from delivering just the right amount of heat to the house instead of delivering design day heat most of the time when it is not needed. The temperature swings are much less when you have outdoor reset controlling the boiler temperature. This is even more important if you have a radiant slab zone where my swings were sometimes close to +|- 4F that I found really unpleasant.

Idea

I havea problem with my toe kick in the kitchen not coming on with low temps ,the built in aquastate comes on at 140 and off at 110. Can it be fixed by 
1. installing a relay to the end switch of the zone valve.(the heater is 100 and the valves are 24v)
2. removing the toe kick and adding element (8' long in every other bay of the joist bays below the kitchen) this I was told is much like radiant heat and would also help with adding element to my zones. There is a drop ceiling below this area so it would be easy(but would too much heat go downward also through the drop ceiling?)

almost there

Ok so now  I have four zones running at the same time running off one therm, which  is 4 -3/4 copper returns/supplies and running 5 degree delta at 120 degree /modding at 21%. In my mind thats as low as I can go without throwing money away ( lower than 20% is fruitless yes?) 
So if I run it all in series(one pipe) to get lower temps on return and greater delta will it make sense? Does condinsate refer to the supply or return temp being lower?
1st off- 4 pipes at 4 gpm=16gpm  vs 1 pipe = 4gpm seems odd to me but I guess if  4 gpm is 20 degrees cooler vs 16gpm 5 degrees cooler
So the savings(btuh) i reap (condisatinting )goes directly toward current water heating yes? wont it just be applied to my already low of 20%? meaning to take advantage i would have to run hotter temp?

Series loop?

Ronbo,

I want to help but it's hard to understand what your saying sometimes.

If you think you can turn all of your zones into a big series loop, then this forum is doing you a big disservice, you may get a fantastic delta, but unless you have a really big pump your flow is going to be pathetic. Even if creating a giant loop didn't wreak havoc with distribution (it will), it's not going to transfer any more energy piped that way.

Is the wall is getting soft?

Trust me integrated zoning reset controls are the way to go, the problem is as much about control as sizing. You seem adventurous.. put in a 400 house control and the 527 stats you need to go with it. All the documentation a technically literate person needs will come along with hardware... If you get stuck, well it's not that cold down in jersey... and I'm sure you will be able to find a sympathetic contractor willing to sort things out without charging you service rates.

BTW- Are you saying that even after putting all your zones on one thermostat and turning your maximum modulation to 20% your still short cycling?


Online vendor for Tekmar- http://www.pexsupply.com/Tekmar-400-tN2-House-Control

It's not that easy.

Sounds like you have it tweaked well enough.

Leave it alone.

Found a problem?

I think I found a problem. My expansion tank and auto fill is located on the flow side, not the suction side of the 008 pump. Does this not slow thee pressure/flow greatly!

still short cycling.

I am in the same boat. My modcon is chort cycling pretty much all the time. Here are some tweaks I've done to improve it.

-Turned down max fan speed for heating from 5500rpm (default) to 2000 rpm (min is 1300rpm)

-Set high/low diff to -7/+5

-Remove IHW tank priority. The tank is piped like a zone, so if the zones want to come on while I'm making hot water, let them, it just increases the load.

I'm still short cycling, but it's been a little better. My plan for the spring once heating season is over is to combined the two small zones on the first floor of my house to create one larger zone, and to replace all the multipak 80 baseboard I put in with cast iron baseboard which will provide more load. Just have to figure out how to join the sections together and hope I can find some end caps that fit.

I'm hoping the increased load of those rads will increase cycle times and provide more even heat to the rooms.

Great post.

im no pro but

i would think the hot water heater should stay on priority 1 by itself.
what temps are you running?

Heating Temps

The heating zones are on an outdoor reset. Min temp 120, max temp 160. Usually it sits around 130-135.

The IHW tank runs at 170.

If everything is piped to be equal, and the larger the load the better, then isn't it a good idea to remove the priority? I haven't had a problem with hot water so far since we only have 1 bathroom right now.

you could argue that either way

but I would stick with priority. You have a reset curve because you want one, presumably, so defeating it on a DHW call isn't ultimately that great of an idea.

Ronbo

Does the boiler still short cycle?

"1st off- 4 pipes at 4 gpm=16gpm vs 1 pipe = 4gpm seems odd to me but I guess if 4 gpm is 20 degrees cooler vs 16gpm 5 degrees cooler
So the savings(btuh) i reap (condisatinting )goes directly toward current water heating yes? wont it just be applied to my already low of 20%? meaning to take advantage i would have to run hotter temp?"

To answer this question, No don't just run them all in one loop, but I would try to match the gpm capacity of the pipe to the amount of heat emitter on that pipe.

Meaning each size pipe has a peak gpm capacity before velocity noise becomes an issue.

I'll give the common pipe sizes found in a home.
1/2 inch is good to 1.5 gpm
3/4 inch is good to 4 gpm
1 inch is good to 8 gpm
1 1/4 is good to 14 gpm for copper and 17 gpm in steel
1 1/2 is good to 22 gpm for copper and 25 gpm in steel

To find the btu limit of the pipe, multiply gpm by 10,000 (20 degree delta drop)
So on a 3/4 inch zone loop, 40,000 btu / 600 btu per foot (180 ) = 67 ft baseboard

"zone1 has 43' of baseboard and 100' coppper supply/return zig zagging about the ceiling in basement to feed it. about 18 elbows heat loss is 15,285 in this area i could add/use 2000 more btuh for this area
zone 2 = also in basement can be joined to zone 1 if needed and is 12' of base with 26' of s/r pipe copper pipe 7 elbows. heat loss calculation is 7000 in this area.
zone 3=has 68' of baseboard, 93' of s/r copper and a toe kick 5150 btu.and could use another 2000 btuh to help out. heat loss is 25,038 in this area.
zone 4 = 46' baseboard 130' s/r pex 3/4"

So like I was saying in an earlier post, Zone 2 is too small of a zone for your boiler, and should be run in series with zone 1 or zone 4, or have about 50 feet of baseboard added to it, or be eliminated all together. Zone 3 is at it's limit, and should be left alone.

better

Ty all, i am leaving them run in parallel and adding the small zone2 to zone 1. But can I throttle back 1 afterwards to reduced the BTU into that zone to even things out? That zone gets warmer than most. I know that will change the return temps a bit but I'm getting to good numbers now and ill be adding some BTU to zone 4 soon. Im hoping to add some radiant floor heat from under the floor in zone four at the end of the loop so ill get a better delta there and some much needed heat to that bath floor

Sounds like a plan

I like the idea of adding a infloor loop to the end of a existing zone loop. This is called load stacking, and is a great approach to create lower return temps.

You can throttle the btu output, by tinkering with the flow in that line, or if you put the the zone 4 in series with zone 1, but have zone 4 get the flow 1st and zone 1 get the flow from the output of zone 4, you will lower the water temp to the zone 1 loop by a few degrees, and that alone may be all you need.

reading

for someone else