New Boiler + EDR Sizing - Looking to Properly Downsize the Mistakes of Old

Mike_Rofone

After combing through this excellent forum and reading Dan's books I've learned a ton about single pipe steam since moving into my 1925 house in Queens NY last year.
Unfortunately my 36 year old Weil Mclain EG-45 was improperly cared for over its life and is now rusting out at the tank. My HVAC guy in part blames our chimney for being uncapped and terracotta which introduced backdraft into the system causing deteriorating it quicker than it should have. I am also suspicious of the previous owners doing any form of yearly maintenance. The chimney was already a known issue to us moving in and in the process of addressing but seems the damage has already been done.

Since were now at the juncture of replacing the boiler I want to make sure we're approaching this the correct way and not continuing mistakes.

Our home is about 1400sqft 2 story single family which in its current state is an non-insulated balloon frame. The only insulation to speak of right now is from 1"obs foam under our new siding which was added to encapsulate asbestos shingles. I have been working towards opening up access to the rim joist to air seal that with CC spray foam and eventually intend on insulating our attic as a hot roof to finish air sealing and add an additional room of space. Due to the size of our rafters this will only net us an R 27.

Across the house we have 5 x Column style radiators, 1 x Tube style radiator, and 1 x fin style.
Excluding the 20" fin style, since I haven't figured out the right way to calculate EDR on that although I know its nothing huge, the total EDR of the current radiators is 197sqft.

Our main pipe is currently uninsulated and lacks a main vent of any kind. I absolutely intend on having the main pipe tapped for a main vent have been advised to leave the mains uninsulated because its our only heat source to the basement. I know that this is contrary to everything I've read from Dan and this forum so I'm open to hearing ideas on navigating basement heat.

Since the EG-45 has a net EDR of 388sqft this feels significantly oversized for our ~200sqft even when calculating a 1.33 or even 1.5 pickup factor.
I brought this up to my HVAC tech and he said since the house isn't insulated and the basement is using the heat of the main, that this isn't as far off as it looks on paper and having the extra headroom would also allow us to add a radiator to the attic when we eventually make it a room. He said we could size down to an EG-40 but wouldn't advise going any lower and the cost and sizing wouldn't offer much in the way of performance/efficiency so it wouldn't matter too much.

I still haven't figured out how to calculate the heat loss of the house so I don't have any numbers to counter his assessment.

So my first question is would we be making a mistake replacing our EG-45 with an identical unit? By my calculations an EG-35 (258sqft) makes more sense when factoring in the 1.3x pickup or potentially even an EG-40 (321sqft) if we want to add another rad.

Also, and this is a larger picture question, since all of these systems have been historically and repeatedly oversized would the ideal world path forward be changing out all radiators and boiler to properly size to the house? I'm guessing that this would be cost prohibitive but since were no longer running these with windows open in the dead of winter it seems like the radiators themselves must be inherently oversized by virtue of history.

Any and all advice here would be deeply appreciated, of the multiple HVAC people I've met with few seem to know Dan's work and it makes me deeply skeptical of letting them work on my system.

Thanks in advance
Mike

hadeone

I am not a pro, don't know much so this could be a case of the blind leading the blind, but I was in a very similar situation to you, had an EG-45 on approx 280sf of EDR in 1700sf house. I did learn that the EDR rating of the boiler already includes the pickup factor so you should just calculate your total EDR of your radiators and match it as close as possible to the new boiler rating. It's what I did, went to a smaller 300 EDR boiler and it worked out great. No noticeable downgrade in heating performance and the system seems to be quieter. It should be cheaper to run but I'll see that in the upcoming bills.

Also, everything I read said to go by the radiation (EDR) only and not heat loss of the house, and if you believe there are too many, or too large, radiators then getting a boiler than can fill them with steam (match the EDR) should be enough. I've read posts on this site of people running boilers smaller than their calculated EDR and being fine due to the pickup factor and proper balancing I guess.

The EG-40 and EG-45 are the same boiler, same number of sections, but the 40 has fewer burners. Other manufacturers also do this, if you check the specs on their boilers you'll often see pairs of boilers that have the same dimensions but different BTU / EDR ratings due to different burner configurations. I'm telling you this because you have an option to up/down-grade the burner, to a degree, after the install.

IMO if you really have just 200 SF of EDR, double check your calcs, then you most likely need the smallest boiler available.

ethicalpaul

Your boiler was 36 years old and you think it died prematurely? That boiler owed you nothing There are people on this forum whose boilers lasted 7 years. I think your HVAC guy must be sort of insane, or he's some kind of Boiler Whisperer if he thinks 36 years is premature failure.

If you have 200sq ft of steam you will be buying the smallest steam boiler that any of the manufacturers make. That's how much radiation I have and I love my Peerless 63-03L.

Do not let anyone install anything larger!

It's fine to leave your mains uninsulated, no harm whatsoever. Definitely add a main vent.

Edit: I will retroactively reply to @Jamie Hall 's point about insulating the mains. Insulated mains will sometimes result in slightly faster appearance of steam to the rest of the house, but we are talking a few minutes at most (and no faster at all if the pipes have cooled since the last heating cycle--even insulated pipes cool off). As for "much more even" heat distribution I can think of nothing about insulated main pipes that would increase the even-ness of heating (I'm not sure what that term means in terms of steam)...the steam doesn't know the pipes are insulated once they are hot. As Jamie says, the pipes don't radiate much anyway so during a heating cycle there's almost no difference.

hadeone

ethicalpaul said:

There are people on this forum whose boilers lasted 7 years.

That's me.

ethicalpaul

hadeone said:

ethicalpaul said:

There are people on this forum whose boilers lasted 7 years.

That's me.

You're not alone!

Jamie Hall

I'd disagree with one point. The basement mains should be insulated. If you still need extra heat in the basement -- you are using it as a family room or something of the sort -- it would be better to install baseboard hot water radiation, also powered by the boiler.

The reason for insulating mains is not just the heat loss from them. Even a fairly large main is a remarkably poor radiator (around 140 BTUh per foot of main for a 2.5 inch main -- the EDR of a 2.5 inch main is about 0.5 per foot), but the steam distribution to the rest of the system will be much more even and much quicker if they are insulated.

STEAM DOCTOR

How much do you trust this HVAC guy?? Did he insinuate that house insulation plays a role in steam boiler sizing?

KC_Jones

Your HVAC person is wrong, factually. You got 196, you do nothing to that number and compare directly to the rating on the boiler. You need the smallest boiler Weil makes for steam and be happy.

DO NOT LET THEM INSTALL ANYTHING BIGGER.

Yes I am yelling, all the contractors (like yours) need to hear this.

Let's address the heat in the basement thing. The pick up factor already built into your boiler rating. So the small Weil that you need (EG-30) has about 64 EDR built in. The EDR of a typical 2" main in a basement is .622 per foot. So that pick up that's built into the EG-30 can support 102' of uninsulated main pipes in a basement. I'm not in your house, but I'm pretty sure you don't have that much.

Now, if you are really sure you are going to add load, and it's going to be significant then maybe put in the EG-35, but honestly I wouldn't.

The EG-40 in your house is literal insanity.

To help understand how the 1.3 is already calculated by the manufacturer I'll do the math on the EG-30 and EG-35 for you based on the table from their website.

EG-30
Gross input 75,000
Efficiency 82%
Net output 75,000*.82=61,500 (they round to 62,000)
Gross steam Sq./Ft. 61,500/240=256
Net Steam Sq./Ft. 256/1.3=196

EG-35
Gross input 100,000
Efficiency 82%
Net output 100,000*.82=82,000
Gross steam Sq./Ft. 82,000/240=342
Net Steam Sq./Ft. 342/1.3=262 (They list 258, not sure why, but you get the idea)

EBEBRATT-Ed

@hadeone

Follow the above advise about sizing the boiler. With steam a heat loss and insulation do not come into play with sizing the boiler but insulation on the piping will help a little. Insulation in the house & windows and doors will affect comfort but not boiler sizing.


When you come up with the total calculated EDR go to the boiler you want to use and select a boiler that is close to that #. Like the others have pointed out that will be the smallest boiler available.

Use the "sq feet of steam" rating to compare to your EDR. Forget the other ratings. Add nothing for pick-up it is already included.

Now come to installation.

Yor are going to get pushback from installers. A lot of them are "know it all's" they have been doing this for 40 years and know everything.... they don't.

I did it for 46 years and am still learning.

Insist the installer gets city/town permits if needed.
insist the installer READS & follows the MFG piping diagram for the new boiler. This is CRITICAL if the boiler is to work right.
Insist that the boiler has a skim tapping piped installed & that he skims the boiler after installation.

You should also insist on black pipe and fitting and no copper on any steam lines or dry returns. Wet returns can use copper. You should also have any venting issues addressed.

The boiler mfgs do not insist on black pipe but they should.

RTW

" My HVAC guy in part blames our chimney for being uncapped and terracotta which introduced backdraft into the system causing deteriorating it quicker than it should have. I am also suspicious of the previous owners doing any form of yearly maintenance. The chimney was already a known issue to us moving in and in the process of addressing but seems the damage has already been done."

Would anyone/ expert care to respond to this comment above in original post and, if true: whats this preventive fix? I too have an uncapped chimney with terracotta liner with an older cast iron American Standard boiler that seems fine so far. Best regards

jesmed1

We also have not one but two oil boilers venting into a 100-yr-old terra cotta chimney with no cap. The boilers are 25-yr-old cast iron Weil McLains in good condition, and we've never had any chimney-related problems. We even had a reputable, experienced local chimney sweep inspect the chimney recently to assess the chimney condition for a possible swap to gas burners. The sweep said the chimney was in good condition, but that we would need a metal liner if we switched to gas. I asked him if we needed a cap if we decided to stick with oil, and to my surprise he said it wasn't really necessary. So we still have an uncapped terra cotta chimney, and our oil boilers soldier on with no problem.

So I don't understand the OP's "problem" with his chimney either.

ChrisJ

With the information you provided,
If it was me, I'd use an EG-30. This would give you roughly 14,000 btu/h to waste with piping which is a lot.

Bigger is not better.
Bigger is headaches, noise, problems and wasted fuel. Don't do it.


Make sure it's piped as per the instructions or better.
This is very important and once it's piped wrong it's going to be very hard to get them to change it. All they need to do is follow the basic layout in the book and you'll be happy. If you have more than one steam main they should all come down into the header (horizontal pipe above the boiler) separately.

The equalizer (vertical pipe that drains the header) should be after all of the mains. Just as shown.

dabrakeman

Agree with everything said, EG30 piped per the manual. I have a WM that is 16 years old now and doing fine with its uncapped terracotta chimney. I do have an auto damper on the boiler flue. Not sure if that helps in your described situation or not and some here like them and some don't. I have had no issue with it. To me it is just a little less heat escaping and cold air returning between cycles.

Jamie Hall

According to my chimney sweep -- a very competent chap -- terra cotta lining for an oil burner flue is fine. I suspect he's right, as Cedric fires into a flue which was installed and has not been touched except for routine cleaning since 1930. It has no cap, though it does have a screen to keep birds out (we have chimney swifts...). The trick is that the oil burner exhaust is hotter and isn't as corrosive as gas.

Steamhead

RTW said:

" My HVAC guy in part blames our chimney for being uncapped and terracotta which introduced backdraft into the system causing deteriorating it quicker than it should have. I am also suspicious of the previous owners doing any form of yearly maintenance. The chimney was already a known issue to us moving in and in the process of addressing but seems the damage has already been done."

Would anyone/ expert care to respond to this comment above in original post and, if true: whats this preventive fix? I too have an uncapped chimney with terracotta liner with an older cast iron American Standard boiler that seems fine so far. Best regards

The chimney is not the problem. You probably have some leaking vent, packing nuts or other things. This means the system must take on extra water to keep going. Fresh water is more corrosive than water that's been boiled and condensed, so it accelerates corrosion.

Whoever handles the replacement needs to check the system for leaks.