The real test

FranklinD

Well, for the last 3 nights it's finally been cold enough to really 'test out' my new boiler. -22 at night with -44 wind chills, highs of -4 during the day. I did my heat loss using the design temp of -17 as advised for my area. Our old boiler was a 100,000 btu output IBR WM. New is 78k net, 68k IBR.

Average supply water temp of 145 thru the night (cast iron rads). Boiler is not running anywhere near continuously. I'll have to check and do the math after work to figure out cycle times.

Oh how I wish I had had the $ for a mod/con at the time...but I'm very happy thus so far, especially for a 100 year old house.

Stay safe and warm out there!

icesailor

#1: Wind chill has nothing to do with OAT when it comes to heat loss. Only to infiltration leaky houses.

#2: Be very glad you have some reserve in your system. There are many I see that wish they had your luxury. And not be getting blowback from cold loved ones in your under heated house.

If it makes you feel any better, the same can happen with AC/cooling. The only thing worse than trying to live in a house that won't go above 60 degrees when it is below zero out, is to be in a house that you just replaced the equipment with equal rated equipment and it won't go below 81 degrees when it is 102 degrees outside.

Just because they claim it is more "Efficient" doesn't mean it is cheaper, nor will it heat or cool better. Just do the job, good or bad, more efficiently.

Gordy

icesailor said:

#1: Wind chill has nothing to do with OAT when it comes to heat loss. Only to infiltration leaky houses.

#2: Be very glad you have some reserve in your system. There are many I see that wish they had your luxury. And not be getting blowback from cold loved ones in your under heated house.

If it makes you feel any better, the same can happen with AC/cooling. The only thing worse than trying to live in a house that won't go above 60 degrees when it is below zero out, is to be in a house that you just replaced the equipment with equal rated equipment and it won't go below 81 degrees when it is 102 degrees outside.

Just because they claim it is more "Efficient" doesn't mean it is cheaper, nor will it heat or cool better. Just do the job, good or bad, more efficiently.

So when, and what do ou oversize to Chris? I think you keep alluding to this in other posts I have read. I mean in my neck of the woods the dsign day is -5 to -9 depending on what information you use. Yearly -10 lows are not uncommon for a day or three. But then I have seen it get to -27 for a day or three seems about every decade or so.

SWEI

Given that I'm one if the most vocal Do not oversize your heating boiler types here, I think I'll weigh in. We do several runs of our heat loss calcs using different OAT and infiltration numbers. Design temps are lowered 5-10°F and wind speeds are boosted a bit just to see. Most of the time (not on a huge house or commercial building), the load jumps up something like 2,000 BTU/hr. 90% of the time that still fits with the same boiler size. If it's close, we have a conversation with the client and explain the options. Most find that a bit of envelope improvement is worth the money and we stay with the smaller boiler. Not all, but most.

Gordy

SWEI said:

Given that I'm one if the most vocal Do not oversize your heating boiler types here, I think I'll weigh in. We do several runs of our heat loss calcs using different OAT and infiltration numbers. Design temps are lowered 5-10°F and wind speeds are boosted a bit just to see. Most of the time (not on a huge house or commercial building), the load jumps up something like 2,000 BTU/hr. 90% of the time that still fits with the same boiler size. If it's close, we have a conversation with the client and explain the options. Most find that a bit of envelope improvement is worth the money and we stay with the smaller boiler. Not all, but most.

Thats the way I see it Kurt. I mean you cannt cover every scenerio. God knows what climate change could throw on us in 5 or 10 years. Those design numbers could go up, or down.

Also it seems the trouble systems that have came the way of the wall were under emittered, lacked proper control, or flat out did not understand a products limitations. Unless I'am mistaken.

FranklinD

My heat loss calc came out just shy of 68,000 btu at -17 design. We had several stretches of -20 or so last winter for 2 months...-20 to -30 is pretty common around here in the winter, with very long stretches hovering around 0.

The next size down was 54k output I believe, and that was too much of a jump down for my comfort....however, my installer initially advised to install a 91k output boiler. His concern was my intent to install an indirect WH later.

I agree on the over sizing...I probably could've gotten away with the 54k in all honestly. But I'm pleased with what I have so far.

Gordy

Another thing is DOE vs IBR if the boiler is in a conditioned space use the DOE

Gordy

And your not using 180 swt.

icesailor

That's not what I mean when I say "Oversize". "Fudge UP, NOT Down.

When I measure a room, all outside doors are 21 sq.ft. 3' wide X 7' high. Although the door is usually 80" high. A mullion window may measure 26X58" (rounded to)10.5 Sq. Ft, but may measure 58" from jamb to jamb. So, each window is rounded off to 11 Sq. Ft. If a room has two mullion windows and two regular windows, so it rounds off to 55 Sq. Ft of exposed glass. Even though a first floor room may have a unconditioned knee wall for space above it, figure the whole ceiling as exposed. The whole ceiling is usually insulated anyway. If you find that room needs 8.2' of baseboard, you use 9', a 5' and a 4'. (They don't make 9' baseboards). If you run 170 degree SWT water use 160 or 155' water because it will be closer to the RWT at the end of a loop. There's all kinds of ways to figure UP. Never average down.

When you get the final total, use the IBR number. If the total is close DOWN, go to the next one above. Especially with oil. Because Downfired oil boilers always run better and are more efficient in cost to operate when Downfired. Not maximum fired. Which is the maximum amount they can (dis)honestly het for a rating to sell the boiler to the person looking for the closest smaller boiler. Any system I ever did was not cold. And I was heavily bad mouthed for putting systems that were too small. Even though I never had any issues, no matter how long the systems stayed in place.

What difference does it make. Someone else will "give" the boiler away at "cost" (whatever that undisclosed number is anyway) and it takes time to do a proper heat loss. Especially in an old building with no heat. Anyone that can do a accurate heatless in a building in 1/2 hour is just guestimating. And also, measure the existing radiation in each and every room to compare one room to another. Compare and understand how the old dead guys did it.

Like I said, I never had a cold one, and I was often accused in the beginning of installing systems that were too small.

Oh yeah.

The IBR rating adds (or subtracts) 15% for piping and Pick-up. You disregard that 15% for a system all piped with spaghetti pipe that needs mining pumps to push the water around?

People never complain when they are warm. People get grumpy when they are cold.

Jamie Hall

The REAL test is: will the "automatic oil delivery" actually get here before the oil runs out... I'm on the list for delivery, but I don't think that they have quite figures out that this place can use 30 gallons a day in this weather.

bmwpowere36m3

Gordy said:

And your not using 180 swt.

Can a boiler supply 180, 190, 200* water at DOE?

For example: Lochinvar WHN55, Max Input 55 and DOE 51 MBH

That would be 93% efficient, right? I thought most boilers are only 87% efficient at 100% firing rate or DOE.

This chart seems to show that 93% is possible, but the return water temp would have to be below 80*

If you need 180* SWT, then likely you'll only get 150* RWT at best, no? And that's about 87% efficient. If your max input is 55 MBH, with 87% efficiency you'll only get ~48 MBH output, right?

Jamie Hall

That is a fascinating set of curves. Never seen it before, so thank you! And does it ever show the effect of going from condensing mode to non-condensing mode. That is, I'm sure, a very fine boiler -- but I see two things: first, in non-condensing it is only slightly more efficient than my big steam boiler is in the real world (86% by the meters last time we cleaned and adjusted it)! Second, it shows that unless your mod-con is really cranked down, and your return water temps are low, why bother?

Quoth a confirmed steamhead...

bmwpowere36m3

Anything below ~130* should be condensing... I think the big takeaway is the modulating aspect of mod-cons is where they shine. If you can also lower return temps, then even better.

Don_197

"Oversize the radiation........drop the supply water temp as low as possible.........size the boiler so the smallest heating zone is no less capacity than the minimum firing rate of the boiler.......let it undershoot by 20 degrees before it cycles on......and overshoot by 20 degrees before shutting off....design it for 30-40 degree delta across the boiler (keeping the return water temp as low as possible)..................try not to ever let it cycle off" 8-) Better yet?? Use em on SNOWMELT where even the SUPPLY water temp is in the condensing range 8-)

FranklinD

Heh. 180° water temp would boil us right out of the house. The DOE vs IBR question is interesting...my basement is unheated (beyond loss from the boiler and piping) and in the winter stabilizes around 51°. That's where the boiler is located. So technically the heat isn't lost, but its not doing the living space any real good.

bmwpowere36m3

FranklinD said:

Heh. 180° water temp would boil us right out of the house. The DOE vs IBR question is interesting...my basement is unheated (beyond loss from the boiler and piping) and in the winter stabilizes around 51°. That's where the boiler is located. So technically the heat isn't lost, but its not doing the living space any real good.

Well, it does reduce the heat loss thru the floors as the temperature in the basement is likely much higher than outside.

I.e. by heating the basement your reducing the heat loss on the floor above.

bmwpowere36m3

Don said:

"Oversize the radiation........drop the supply water temp as low as possible.........size the boiler so the smallest heating zone is no less capacity than the minimum firing rate of the boiler.......let it undershoot by 20 degrees before it cycles on......and overshoot by 20 degrees before shutting off....design it for 30-40 degree delta across the boiler (keeping the return water temp as low as possible)..................try not to ever let it cycle off" 8-) Better yet?? Use em on SNOWMELT where even the SUPPLY water temp is in the condensing range 8-)

a 40* range, hmmm… with a mod-con?

I was wondering how to set my boiler set points. So if you wanted 160* SWT, for example, you would set the boiler set point at 160* with a 20* offset and 20* differential set point? So the boiler would operate between 140 and 180*.

Gordy

bmwpowere36m3 said:

Gordy said:

And your not using 180 swt.

Can a boiler supply 180, 190, 200* water at DOE?

For example: Lochinvar WHN55, Max Input 55 and DOE 51 MBH

That would be 93% efficient, right? I thought most boilers are only 87% efficient at 100% firing rate or DOE.

This chart seems to show that 93% is possible, but the return water temp would have to be below 80*

If you need 180* SWT, then likely you'll only get 150* RWT at best, no? And that's about 87% efficient. If your max input is 55 MBH, with 87% efficiency you'll only get ~48 MBH output, right?

I was speaking about Frankllin's thread. We are not talking about Mod/Cons. So his best efficiency will be gained from not short cycling so a stable burn cycle happens.

Gordy

Hell I was at -12 last night, and my AWT was 104 Radiant baby over emitterized radiant.

I dont have a Mod/con according to that chart If I sized one to my design temp I would only hit 90% efficiency at 100% fire with 95* retun water. Where did you get that chart?

bmwpowere36m3

@Gordy

I understand… sorry if its OT. I'm still curious if a boiler can supply water at 180* or so at its rated DOE? I assume at DOE the boiler firing rate is 100% or MAX. So then does it depend on RWT or whether its a modulating, modulating/condensing, CI, etc…

I found it in an article regarding boiler efficiencies. Here is a chart from John Siegenthaler's book, specifically to mod/cons:

bmwpowere36m3

I assume a CI boiler would just follow the 100% input curve…

Gordy

bmwpowere36m3 said:

@Gordy

I understand… sorry if its OT. I'm still curious if a boiler can supply water at 180* or so at its rated DOE? I assume at DOE the boiler firing rate is 100% or MAX. So then does it depend on RWT or whether its a modulating, modulating/condensing, CI, etc…

I found it in an article regarding boiler efficiencies. Here is a chart from John Siegenthaler's book, specifically to mod/cons:

No problem

DOE, or IBR has no bearing on the boiler being able to achieve 180.

bmwpowere36m3

Gordy said:

bmwpowere36m3 said:

@Gordy

I understand… sorry if its OT. I'm still curious if a boiler can supply water at 180* or so at its rated DOE? I assume at DOE the boiler firing rate is 100% or MAX. So then does it depend on RWT or whether its a modulating, modulating/condensing, CI, etc…

I found it in an article regarding boiler efficiencies. Here is a chart from John Siegenthaler's book, specifically to mod/cons:

No problem

DOE, or IBR has no bearing on the boiler being able to achieve 180.

So "my" hypothesis is correct, in that a mod/con boiler cannot supply "high" water temps at DOE? If so, that makes me rethink some things… As in if the boiler is near max capacity on cold days, you might not be able to raise the supply temps in hopes increasing the BTU output of your emitters to raise the temp in the house. Which makes sense to me, BTUs are BTUs

However that raises an issue wrt mod/cons, I think, because if you size the boiler based on its DOE assuming it can output that many BTUs on design day… in reality it can only do so at very low return water temps.

If I sized my emitters for say 160* SWT and a RWT of 130* (design day) at best the boiler will only output 87% or so of its input. That WHN55 with a DOE of 51, suddenly is only a 48 MBH. I guess it comes down to how accurately the heat loss was done and how close you size the boiler to the heat loss.

Gordy

Unless you have a ridiculous amount of supply piping that is in an unconditioned space, and the btus that are lost have no effect on the load for the space before it gets to the emitters then you use the IBR rating. Most of the time that is not the case.

so no your hypothesis is not correct.

icesailor

I don't disagree with what is being said. My whole thing is that if you are going to heat, you better heat well and leave out all the BS. Because if it is cold, some will be unhappy.

Like my wife says, "A happy wife means a happy life".

Where I worked, they ran out of copper repair couplings and shark bite fittings. Those houses must ne heated. PEX blows apart at the fittings when they freeze. Hopefully, not in a wall.

It appears to me that all across cold America, there are a lot of under heated houses that people are suffering in. Come Summer, they'll be hot and can't get cool.