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SWEI

SWEI

Joined on November 26, 2011

Last Post on August 30, 2014

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Excel

@ March 19, 2013 7:01 PM in Need some info.

will not open .exe files.  Try double-clicking on setup.exe and see what that does.

You really need

@ March 19, 2013 6:58 PM in Delta T issue

a full system analysis.  This starts with a room-by-room heat loss calculation, a room-by-room radiation survey, and a table of all the distribution piping.  From this, you will determine what water temperatures and flows will be required at design conditions.  Then each segment of pipe is evaluated to see if it will carry what is required of it.  After all that is done, the appropriate system circulator is chosen (possibly more than one.)

If this process led you to an undersized manifold feeder, the best answer would be to increase the size of the pipe.  Barring that, you might consider using a dedicated circulator for that manifold, since it differed from the other piping enough to warrant a different pump curve.  The point is that you need to deconstruct the original design and then reconstruct it properly before you start buying parts.

heat flux

@ March 19, 2013 6:37 PM in Indirect DHW tank Delta T?

http://en.wikipedia.org/wiki/Heat_flux will give you the engineering school version.  Across a heat exchanger, heat flow is proportional to surface area, conductivity of the HX material, and the difference in temperature.  The first two don't change appreciably, so it really comes down to the difference in temperatures.  As ∆T increases, more heat will move during each unit of time.  The hotter the average boiler water temperature and the colder the incoming water, the faster heat will move into the DHW.  As the DHW gets close to the setpoint, the rate of heat transfer slows down.  A smart boiler control will "see" this coming using a thermistor in the DHW tank, and stop before the tank overshoots too much.  Keeping the tank at 140F prevents legionella growth but requires a thermostatic mixing valve at the tank output to protect occupants from scald injury.  Raising the tank temp to 150F or 160F has the effect of making the tank "larger" from a thermal capacity standpoint.  Speeding up or slowing down the DHW circulator without also changing the DHW target temp will simply move the average boiler water temp up or down a bit.  This will affect DHW recovery rate, but not anywhere near as much as changing the tank setpoint, boiler water target temp, undershoot and overshoot temps, etc.

looks

@ March 19, 2013 9:47 AM in Delta T issue

may not be the best standard for determining complex flow mathematics.  Nothing personal, but you really need to step back and look at the whole system design.  Where are these manifolds located?  Is there any way to either increase or supplement a supply/return line or lines?   I think we mentioned splitting manifolds earlier.

deltas T

@ March 19, 2013 9:42 AM in Indirect DHW tank Delta T?

There are two different numbers at work here.  The first, which you have described, is the difference between water leaving and returning to the boiler.  The second, which the manufacturer quotes as 65F, is the difference between the incoming cold domestic water and the desired hot water temp or tank limit.  The greater this difference, the faster heat will transfer from the boiler to the DHW, but the water still has to get up to the target temp, which will take longer with colder incoming water, assuming the boiler water stays at a fixed temperature (which of course it doesn't.)  The nominal boiler water temperature is an average of supply and return temps.  If the circulator runs slower, this average will drop, but that can be remedied by increasing the supply temp (assuming the boiler can still keep up.)

Does your indirect have a mixing valve at its output?  Do you have hard water?  How long has it been since the boiler was inspected and cleaned?   Assuming you want more hot water, these are the areas I'd be looking at first.

the ultimate goal

@ March 18, 2013 10:04 PM in Adding a secondary pump to my radiant heating system

is to make you system work properly.  If we don't understand how it was designed and installed, we stand precious little chance of improving it.

Photos of the boiler and associated piping, valves, etc. would help.

The Series 100 is a wonderful high flow low head pump.  I've never used one on floor loops so I'd really like to understand the rest of the design.

Unfortunately,

@ March 18, 2013 9:24 PM in MONO FLOW SYSTEM NOISE

"same btu rating" won't ensure the correct replacement is installed.  You can pretty much count on the opposite.

Outdoor reset control of system water temp along with constant circulation on those loops should remedy your expansion issue, but we need to take a look at the rest of the design before we propose changing anything.

loads

@ March 18, 2013 8:12 PM in Looking for small combi boiler / AC unit

Am I correct in reading that the total space heat load is180K at design conditions?

Have you done a DHW load calc?

Where is this project located?  Design temps?  Is this a new install?  If not, what is being replaced?

radiant, radiators, and pumps

@ March 18, 2013 7:57 PM in Adding a secondary pump to my radiant heating system

Radiant floors and radiators generally need rather different water temperatures.

Do floor loops and radiators share the same manifold port, or are there specific ports used for each type of radiation?

Looks like the boiler probably has an internal circulator, but just in case -- is there only one pump in the system?

Can we assume the two crosses shown in your drawing are do not represent four pipes connected together?

a drawing will help

@ March 18, 2013 2:57 PM in Adding a secondary pump to my radiant heating system

Pretty sure JPG, GIF, PNG, and PDF all will work.

Depending on the current layout and pump, there are several possible solutions.  Why do you feel you need more flow?

If electricity cost less than LPG

@ March 18, 2013 11:08 AM in Electric boiler for Radiant heat monthly cost

I'd be looking at a heat pump for that climate.

http://www.eia.gov/neic/experts/heatcalc.xls will tell you the rest of the story.

Estimating annual costs would require a heat loss calculation and some degree-day data, preferably with a bit of local knowledge.  Paul Pollets might be able to help there http://www.heatinghelp.com/professional/95/Advanced-Radiant-Technology-LLc

improving ∆T

@ March 18, 2013 11:02 AM in Delta T issue

means different things in different situations, as Gordy pointed out.  Condensing boilers run most efficiently with a large ∆T.  Most throw an alarm or shutdown when it hits 40F, so we like to run them at 35F when possible.

Emitters are a bit more complex.  Radiators can handle 30F in many cases, but in-floor loops deliver uneven heat when ∆T gets above 15F.  Baseboard depends on the length and layout, with series loops probably being the most particular.  Remember that the quantity of heat delivered is based on the average water temperature, so if you increase the supply by 5F and decrease the return by 5F you will deliver the same amount of BTUs with a 10F greater ∆T.

Commodity infrared thermometers are in the $20 range these days.  You can't rely on them for absolute temperature indication, but if you measure consistently (black electrical tape on pipes or fittings, hold the gun at the same close distance each time) they are entirely useable for relative measurements, which is what you need here.  A handful of clip-on dial thermometers could be useful, but you would have to calibrate them at least to the point that they match each other.

Larger ∆T

@ March 17, 2013 9:12 PM in Delta T issue

Will reduce the return water temp, which both increases boiler efficiency and reduces pumping costs.

did anyone do a heat loss calc

@ March 17, 2013 9:09 PM in Home heating - Oil to gas conversion

on your house before proposing?

change the primary pump

@ March 17, 2013 7:05 PM in Delta T issue

I'd pick something that gave me 35F ∆T at maximum fire.  As usual, I'll ignore the manufacturer's pump suggestions and pick what actually delivers what I want.  99,000 BTU (DOE rating) at a ∆T of 35F will require 5.65 GPM.  If I look at their head loss curve, I see that will impose about 2.7 feet of head.  The way we pipe primary loops, there would be an additional half a foot or so of piping losses.  In Taco, that puts me somewhere between a 003 and a 006 in size.  I don't think Taco offers a VDT version of the 006, but that would be ideal.  If Laing is shipping the E10 brass that would be another good option (with ridiculously low electrical cost.)

freeze bursting

@ March 17, 2013 6:40 PM in IS THIS ENTRAN PIPING

would probably affect copper and brass long before you'd see it in PEX.

as usual, it depends

@ March 17, 2013 2:08 PM in Do you sell your GAS customers on Indirect or tankless?

mostly on DHW demand and expectations.

With a single big DHW load (rainforest shower or monster tub) I find that a hybrid design can work very well.  Indirect for the full house plus a dedicated tankless on the branch feeding the large load.  Warm water leaving the exhausted indirect decreases the rise on the tankless, but increased flow rates mean you have to watch that pressure drop.

when to buy, and what

@ March 17, 2013 1:47 PM in Retrofit/upgrade suggestions

A less expensive mod/con will quite likely cost more to install, given the requirement for primary/secondary piping and two circulators.  It will come with higher maintenance costs and bigger electric bills.

With those wonderful oversized cast-iron radiators, you can run a higher ∆T and direct pump a firetube boiler which should be condensing the entire season.  Ironman is probably right with that 40% fuel savings estimate for a properly sized, installed, and commissioned TT PST or Lochinvar WHN boiler.   Factor in historically low interest rates, a few percent per year rise in NG costs, and you may like the payback.  Borrowing money from a bank, a 401(k) or some utility program could make a lot of sense if you plan on keeping the house for awhile.

If plan to follow this route, and not modify the piping too much, an ECM circulator may make sense at this time, since a fire-tube mod/con will not have much more HX head than the old CI boiler.  If you do this, be prepared to purge and flush several times, add water treatment and a Caleffi DirtMag to protect the new circ.

buffer tank and ODR

@ March 17, 2013 12:21 PM in Retrofit/upgrade suggestions

will reduce the short cycling.

Did you use 170 BTU/sq ft for your EDR calculation?  If so, you should have measured 753 square feet, which can deliver the 65k output you need on a design day using roughly 140F water.  Any time the outdoor temp is higher, you would need cooler water to prevent overshoot.

Adding basic ODR control to the existing boiler would not help much since the highest temperature you need is at the low limit of what can be delivered safely by a conventional boiler.

If I were asked to upgrade your system, I would install an ODR-controlled mixing valve (Taco iSeries-R is usually the least expensive answer there) on the system side of tank-type electric water heater used as a buffer with an ECM system circ on constant circulation.  Then set the boiler aquastat to to keep the buffer tank at 150-160F.  The cost of all this will probably come to about half that of a new mod/con boiler.

Given the age and efficiency and oversizing of your existing boiler I'd take another hard look at ROI (and probably end up recommending the mod/con.)

135 deg at the outlet and 130 at the inlet

@ March 17, 2013 12:02 PM in Delta T issue

tells me the boiler is overpumped.  P.49 and 50 of the TFT IOM show several suggested pump sizes and the HX curve for the 110.  What kind of pump is on the boiler loop, or is the system direct pumped?

Manifolds with less head loss might be worth considering.  Is there any way to replace or supplement the supply and return piping to any of the manifolds?  Breaking a large manifold into two smaller ones with new supply/return pipes can help a lot.

is this the Q Premier?

@ March 17, 2013 12:17 AM in rinnai combi boiler

Haven't even laid eyes on one yet.  Looks like a 24 gallon indirect from what I can see. 

Unfortunately, 130k is 2-4X our typical residential design load.  I'd trade for a 65k with a 50 gallon indirect in an instant.

37 BTU/sq ft

@ March 16, 2013 10:59 PM in Retrofit/upgrade suggestions

Sounds about right for what you you described.   If that's accurate, your current boiler is twice as big as it needs to be to heat your home on the coldest ay of the year.

I'd probably be looking at a Lochinvar WHN-085 for that job...
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