Help on New Boiler Size Please

Paul48

I have a gravity conversion with a triple aquastat. Once hot, the radiators stay hot until the t-stat is satisfied. It does shut the circ off at low limit, to allow the boiler temp to come up, but that isn't noticable at the rads. The same thing would apply with a hi limit only aquastat. It just makes me have more questions.

Gordy

Gotta weed out the variables.

Chainreaction

Last night's results:

Water temperature control has settings 1 to 6. It was on about 2. We raised it to about 4. PSI is over 15. Set house thermostat to 65 over night. This had some effect. House temperature reached 63. The third floor bedroom reached a balmy 62. This room has typically been at 57-58. (at least we have a down blanket). This morning water temperature was 150. Since it just went overnight (9PM-7AM), we didn't get to observe for sure if it cycled.

No one is home until Sunday but we will try upping water temperate setting again to see if temperature can get to 180.

We are going to do the heat loss calculation ourselves just for fun. A few questions for the experts. Rooms seem fairly straight forward, but how do you do hallways? Our house has lots that turn 90 degree corners. Do you calculate as two rooms? Also fairly large stair landings. How do you figure stair wells? Ours is pretty big. Any suggestions on important parameters?

Thanks to all

bmwpowere36m3

Chainreaction said:

We are going to do the heat loss calculation ourselves just for fun. A few questions for the experts. Rooms seem fairly straight forward, but how do you do hallways? Our house has lots that turn 90 degree corners. Do you calculate as two rooms? Also fairly large stair landings. How do you figure stair wells? Ours is pretty big. Any suggestions on important parameters?

Thanks to all

Start with the whole house first, just model it as 1 big room and include all the exterior windows and doors. Do that for each floor. That'll give you an idea to the boiler size. Then you can do it room by room.

Gordy

Slant fin is room by room. Enter each hall, or stair well as a room. Skip[ doing the whole house first. That will be the end result of a room by room.

Raise boiler temp more between 5 and 6.

Another task if you are up to it. Is calculating the EDR of each radiator correlated to the room it serves to heat.

You will need to know type of Radiator (column or thin tube) number of columns, or thin tubes, and radiator height.

Pics will help us help you.

Also what were the outdoor temps last night?

Gordy

May I ask is Chainreaction an occupation related handle? Partical collider, or nuclear fission?

Gordy

One important parameter is design day temp value for your area.

Chainreaction

Gordy: Username. I got idea from Polymerase Chain Reaction (PCR) My wife and I are molecular biologists. This technique is the one used to amplify small amounts of DNA. What they use for "DNA evidence" in crimes. Nuclear fission ( and HVAC), way beyond me. Wife is the smart one.

We will raise boiler temp as suggested.

Overnight temps in Philadelphia dropped below 20, so a good test.

Might give EDR a try too. Here are some pictures of typical radiators in house. I will say that we have some pretty big radiators. I think they overbuilt if anything.

<<img src="https://us.v-cdn.net/5021738/uploads/FileUpload/f7/655416e3b8f72422e8622b2be5be1b.jpg" />

Gordy

Those are column type rads. Nice!

Rich_49

Do not perform block load calculation as suggested above . Treat hallways and stairwells as rooms . These rooms may attach with other rooms . Once you have determined the area that they best interact with you can begin to dissect what to do in reality . Stairwells can also be part of the room in which they originate at the lower floor and average ceiling height can be adjusted to show that relationship , they sometimes require a small emitter of their own . Hallways sometimes have no outside walls and thus very little heat loss , depending on what type of heat emitters you have you may or may not require heat at all for these areas . Funny thing about an area within all heated space is it gets heated also since no cold air makes it there .

Gordy

So you count number of sections. Then number of columns in each section. Then the height. EDR stands for,equivalent direct radiation.

So do a spread sheet listing rad size for each room. This will end up correlating to the btu output of the radiator to the heat loss of the room.

Gordy

Rich said:

Do not perform block load calculation as suggested above .

I hope I did not suggest that..............Not intended

Rich_49

Not you Gordy . You suggested room by room , imagine that . BMW said " Start with the whole house first, just model it as 1 big room and include all the exterior windows and doors. Do that for each floor. That'll give you an idea to the boiler size. Then you can do it room by room.

Gordy

I agree. On top of that why run around the house doing things twice. Big house alot of steps. Room by room ipad in hand much easier.

Chainreaction

It has been a while since I commented here. I hope someone is still out there. My wife and I finally got time to do a room by room heat loss calculation. We used the slant fin program, low temperature of 10, house temperature of 70 and water temperature of 180. The result was 138,000 btu. Hopefully this is pretty close to right. We are not experts.

In my first post I said we had two designs one 220 btu and the other 360 btu (some details are in that post). Our heat loss calculation was close to what the guy who gave us the 220 design came up with.

So my question for the unbiased panel is "does 220 total btu make sense?" This would be two hi efficiency 110 boilers. Do we need additional information or is it time to pull the trigger?

We have also contacted references for this contractor. All seems in order there.

As always I really appreciate the help.

SWEI

Chainreaction said:

So my question for the unbiased panel is "does 220 total btu make sense?"

The short answer is no.

This would be two hi efficiency 110 boilers.

Did the contractor explain why he proposed this configuration?

Paul48

Now, you survey the radiators to determine their output against the rooms heat loss. With big old windows, and no insulation added, I doubt 138k.

Gordy

Figure the EDR on the radiators for each room like I told you how. Do a little spread sheet nothing fancy that correlates the radiator with its EDR to the room it serves, and the heat loss you calculated for that particular room.

This will tell you how the original design of radiator size matches the heat load of each room.

I would not make a choice as of yet there are more things you can do to be assured your getting a correct system.

We still are not sure if the old boiler was adequate to heat the structure, or if it suffers from some maintenance issues that may affect its original peak performance. Did you ever turn it up enough to get to a set point of 70?

Chainreaction

Here is a little additional information.

We finally got the water temp to 180. We have not tried to get the house to 70 yet. High temp in Philadelphia today was 10. We tried to get house to 65 when outside temp was in 20s. Highest we have gotten the house is 63 or so.

The current boiler has an input of 225 and an output of
180 listed. (80% efficient?) I suspect that it has problems but I don't want to fix it and then replace it anyway.

The contractor who proposed the two 110 system calculated heat loss at 130k considering the house as a whole. ( I should note that this is an end unit of a larger building so only three exposed walls. ) The same contractor measured all the radiators and calculated the total radiator output as 217000. We have not yet done the individual room EDR.

The idea for the two boilers was that when weather is warmer only one boiler comes on saving money. Also there is a backup if one boiler has issues. Also said cost was more if you use one higher btu boiler of 220K.

Question: Is the idea of calculating the room EDR to see if the radiators are up to the job?

Gordy

Yes calculating EDR is to see if the radiation is ample for the rooms heat loss, and to see if it's over radiated which would mean lower operating water temps which in turn would increase your new boilers efficiency being its a modulating condensing boiler variety you are leaning twords.

Comparing over all radiation to over all heat loss is not the same all though it does give an idea of what the over all capacity of radiation to the over all heat loss is. But you want to see if there is problem areas of inadequate radiation. So do it room by room. At least then you know a room has enough, more than enough both good. Or not enough which will have to be rectified.

Gordy

Hatterasguy said:

If the contractor calculated the heat loss at 130K and is proposing 220K to be installed, you should fire him. Not the one you want.

A contractor that proposes two boilers when one mod-con would do the job perfectly (with 217K of radiation) should be fired. No way to justify that expense on fuel savings.

How often does a new boiler have "issues" that cannot be solved quickly?

Of course the cost is more if you use a 220K boiler when you have a requirement for 130K.

BTW, here's your new boiler:

http://www.htproducts.com/literature/versahydrobrochure.pdf

The 199K unit puts out 135K for space heating at 160F............exactly what you need. And, it will give you practically unlimited hot water to boot. And, it has a 12 year warranty. And, it is far less costly than the two boilers your infamous contractor is proposing.

I agree but would like to see how the room by room EDR balances out to see if 160 is doable. I believe the EDR is sufficient provided no rads have been removed, and or rooms have not been reconfigured, partitioned off etc., and the dead men who piped it did it right there were knuckle heads back then too just not as many.

Reality check if you will.

Gordy

Does that not have you wonder if the contractor is sizing the boiler (s) to the radiation?

Rich_49

Sizing 2 boilers to the radiation might I add Gordy . I can see advantages of installing 2 such as lower turndown in shoulder seasons , redundancy and increased longevity by sharing the duty . But if you're gonna use 2 on this job would 2 <=80Ks not have been a better choice ?

Paul48

Chain.....Your place is 4500 sq/ft plus a full basement? Or including the full basement?

SWEI

Hatterasguy said:

Gordy said:

Does that not have you wonder if the contractor is sizing the boiler (s) to the radiation?

Typical.

And yet, we see worse. 40-60% more than the radiation can dissipate at 190°F is not all that unusual. Dan had an article on this awhile back. Two or three boiler replacements over the course of a century, each done "with a little extra just in case" will get you there.

Gordy

If the contractor that measured the EDR did it correctly the heat loss calc may be close considering.

217 k of EDR is 1446 SF of radiation at 150 btu's SF.

138k heat loss for 4500 SF is a little over 30 btus SF.

Remember Paul their design day is a little warmer 10*. Yes there are some big windows.

icesailor

I think this application needs a serious "Look-See" by someone that knows what they are looking at, first.

Because the OP posted that this is a:

""" The contractor who proposed the two 110 system calculated heat loss at 130k considering the house as a whole. ( I should note that this is an end unit of a larger building so only three exposed walls. ) """

What's with the "End Unit"? Is this some sort of a large home that was split up by developers in a nice area? Because the house was too big to sell as one and worth more cut up? How was it heated originally. IMO, these things can matter.

There's some really nice finish work in what is shown on the OP's photo's. In one photo, it shows the neighbor's house with nice red station wagon in the yard. No old mattresses, no dead refrigerators or washing machines in the yard, which makes me think that this is a better part of town.

Like Paul Harvey used to say. Here's the rest of the story.

There's an interesting history here that should be made note of. How many inches of stone and a 1" air space for a loss factor?

I once measured a house that was wire lathe and stucco. With Eel Grass for insulation. Sandwiched between two layers of Kraft Paper. What insulation factor do you use for that?

Gordy

Rich said:

Sizing 2 boilers to the radiation might I add Gordy . I can see advantages of installing 2 such as lower turndown in shoulder seasons , redundancy and increased longevity by sharing the duty . But if you're gonna use 2 on this job would 2 <=80Ks not have been a better choice ? </p>

Yes to 80s better choice

Chainreaction

Paul48: House is just under 4500 sq ft without the basement. Basement is unheated and extends under all but one heated room. Ceilings average 10 ft all the way up (there is a lot is variation)

My wife and I got a room by room heat loss of 138K. We had to make some guesses because the slant fin program we used wasn't set up for our older construction and variation of window type. For example part of house is thick stone walls. Some rooms have large windows with storms but also some smaller windows without storms. We did our best considering our lack of experience.

220K total btu is input. I guess that means at 95% efficiency output is 209K which seems a lot like the calculated radiator size of 217.

Question: If radiators are big enough to handle 209K is it always bad to have more potential heat? Since temps haven't been above 15 in Philly recently a little over kill sounds pretty good right now.

Gordy

Only to your wallet with bigger boiler costing more, and fuel usage. Having a boiler output of more than radiation can handle is useless, and again costs you more.

The key is everyone is geared to tight design parameters which in the end saves the client money, and decreases carbon foot prints by saving fuel usage.

Using a modulating condensing boiler to rely on its modulation component to compensate for its oversizing, and having the extra btus for 2% of the heating season is not a good habit to have.

No one here has anything to gain or lose by trying to save you money short, and long term.

The key here is seeing if lower than 180 water temps can be used to increase boiler efficiency. That's what we look for if radiation is oversized for the heat loss it serves.

With out knowing if your present boiler is putting out as it should hard to tell with out running the numbers. If your boiler could be set at 150 or 160 and heat the space it would be a yes. But we don't know what the water temps are out in the system.

Paul48

Over-radiating is a good thing. Especially for a mod/con. You just want to make sure the radiators can put out enough heat, at 160* max, to account for the heat loss. Take your time with this. There's no reason to make any commitments yet. You want this right, or you'll pay for the mistake, year after year.

Gordy

It concerns me that the contractor is sizing to the radiation you do that for steam not hot water. If he is stumbling on this step makes me wonder about the rest of the steps boiler piping, pump sizing, control setup etc.

Rich_49

If the heat loss is 138K and the emitters can put out 220K there is an opportunity to run lower water temps which saves you money .
That being said the question is this , what outdoor temp did you design to and are you willing to sacrifice not reaching indoor design temps during periods of record cold ? Like right now . If the answer to this question is no , we are not willing to be uncomfortable . Then using the 2 110s could be beneficial to the unrefined . We know there is about 15 -20% fudge in heat load calcs and that can be considered .
Ask the contractor to put in 2 80s and if he has a problem with that insist that the boilers be set up so that when the lead boiler reaches 50% duty the second enters operation and they both operate at 25% and go up from there . You do not want one getting beat up so you have 1 beat boiler and 1 damn near new boiler . If you are making hot water with these also , you will never even think about running out .
I personally would install the 2 - 80s , use a lower water temp in those rads and call it a day . Set the cascade up the same way though for obvious reasons . It will keep you comfortable throughout even periods like now .

Chainreaction

Hi Icesailor:

I said end unit in describing house to make things easy. Yes it is in a nice area of town. The house started life as a large stone mansion in 1888. From what I can figure about half of our section dates from a 1904 expansion by the original owner. The rest of the house dates from 1914 when is was divided into 3 town houses. I think daughters of original owner lived in it. This guy had resources so construction was excellent. The person we bought it from had been there since 1969. While they "did no harm" they didn't do things to top quality from what I can tell. We are cleaning this up as best we can.

This house obviously has a fun history but I don't want to bore you with it. However if you have ever owned an old Disston wood saw this house was built by a Disston.

icesailor

When you have two different types of construction that have a wide disparity, I do it twice. Once with each type, then combine the two. I.E. if part of the house is stone and another part is wood framed, do two houses. Just make a spread sheet and put the results on and add them up. You subtract the lesser loss wood frame from the greater loss of the stone.

If you could find the original books that the Slant-Fin program is based on, you would see that with the old, you just change the factor for any room as needed. When you change a factor in the Slant Fin program, it changes the factor in the whole house.

Trust me. If you can figure out PCR and DNA, you can figure this out.

Gordy

Chainreaction said:

Hi Icesailor:

I said end unit in describing house to make things easy. Yes it is in a nice area of town. The house started life as a large stone mansion in 1888. From what I can figure about half of our section dates from a 1904 expansion by the original owner. The rest of the house dates from 1914 when is was divided into 3 town houses. I think daughters of original owner lived in it. This guy had resources so construction was excellent. The person we bought it from had been there since 1969. While they "did no harm" they didn't do things to top quality from what I can tell. We are cleaning this up as best we can.

This house obviously has a fun history but I don't want to bore you with it. However if you have ever owned an old Disston wood saw this house was built by a Disston.

Do give us history not boring at all. Yes the Disston's

Chainreaction

Just talked to Mrs Chainreaction who has been point of contact with contractor. (long story) Apparently he stated that output btu from this system would be 176K. This is two WeilMcLain ECO110N supposedly 95% efficient. Does this sound correct? If that is the correct output then design sounds pretty close?

Also this is designed to run a 45 gallon indirect water heater. I now know I probably should have mentioned this earlier. If this has caused confusion I apologize. I have already confessed to ignorance!

For those of you who have good memories this discussion started because another contractor suggested 360 btu total. If nothing else I have learned that this is way way out of line.

Rich_49

Ask the contractor what temp he is intending to use at design . This will give more of a sense of him .
Tell him to use an ECM circ and don't pump too much fluid through this system . It will really like a 30* Delta , It will also spend more of the season condensing . I would imagine DHW priority so you won't run out of hot water and priority call should be shorter in duration if set up as I described above .
I must say that 2 - 80K boilers at 95% and 161.5K is closer than 176 would certainly be better . Ya gotta love brand loyalty no matter what the reason for it .

icesailor

A 45 gallon indirect is barely speeding up to get on the interstate with your car.

You can drive from NYC to Delaware by taking 95 through Philadelphia, or take the NJ Turnpike. You get there just the same. Its just a different route.

Chainreaction

Rich: Wife and I did heat loss with 10 degree design day, room temp 70. On really cold days I'll be happy with mid 60s. 53 degrees in the third floor bedroom where we are living until other construction is finished is pushing the limit. Especially since it is costing us a fortune in energy to freeze.

Other question. Slant Fin program did not ask for fireplaces. Most of the fireplaces are closed off at flue. Two are working with functional, but old, dampers.