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# Verification of boiler sizing, completed radiator survey. Am I thinking right?

Member Posts: 43
I finished my radiator survey of the museum house I’m working on (see below spreadsheet). Based on what I’ve learned about the system, I’ve been thinking the boiler is undersized. I was told that they installed this boiler as it was the largest Weil McLain made for residential use (which doesn’t seem like a good reason). The actual sq footage numbers of the basement convectors (rads 1-7) is my best guess using 10 sq ft / section, which seems about right based on conversations with a bunch of different people. The DOE Heating capacity of the boiler (is this the number I should use?) is 247,000 BTU, where my radiator survey shows a total capacity of 454,000 BTU. Does this look right?

Unidentified convectors estimated at 10 sq ft / section

• Member Posts: 8,266
how does the system work? Are you getting any heat at all? looks like the NET AHRI output is 770 Sq. Ft. that is the number you need to use in your calculation. At the estimated 1865 Sq ft of EDR, I'll concur with your assumption that the boiler is undersized by more that half. Are you sure someone didn't hide another boiler behind a secret wall?

Edward Young Retired

After you make that expensive repair and you still have the same problem, What will you check next?

• Member Posts: 23,889
You should be comparing the EDR of the boiler, which is listed on the nameplate as "square feet of steam" to the total EDR of your radiators -- skip the BTUh bit. And I see from your spreadsheet -- which is entirely plausible, by the way, that your total EDR is 1895 (for comparison, the museum house I care for -- Cedric's home -- is 1230/ Museum houses tend to be on the large size...). Your boiler is only rated for 770 square feet.

Problem...

Your installer may well be right and there may not be a residential boiler much larger than what you have, but that's no excuse for not installing a correctly sized boiler, since commercial boilers exist which are considerably larger. Cedric, for instance, is a Weil-McClain 580. The next size up -- the 680 --would be just about right.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 43

how does the system work? Are you getting any heat at all? looks like the NET AHRI output is 770 Sq. Ft. that is the number you need to use in your calculation. At the estimated 1865 Sq ft of EDR, I'll concur with your assumption that the boiler is undersized by more that half. Are you sure someone didn't hide another boiler behind a secret wall?

Most of the radiators do not get heat all the way to the outlet end. With zero pressure showing on a 0-3psi gauge, it appears that steam is condensing before getting to the end of the radiators & there isn’t enough steam to replace it. I also have about 500 sq ft EDR valved out or cut out, which improves the numbers a bit (but I want to get most of these back in service). There are a couple of run outs that tap into the bottom of the Main that take forever to get any steam & even then, it might take 30 minutes to get these convectors to get halfway hot. It just seems that there isn’t enough steam, which is what got me looking at this.
• Member Posts: 8,266
@NealJ, How old is that boiler install? and do you have a good lawyer? The original installer needs to give you all the money you spent on that job so you can use it for a down payment for the correct boiler.

Edward Young Retired

After you make that expensive repair and you still have the same problem, What will you check next?

• Member Posts: 1,009
first clock the gas meter while just the boiler is running to make sure that your getting the proper amount of gas. If it's supplying the input then i would just confirm your sizing numbers. a second eg-75 might need to be added. 2 steamers is not ideal but better than trashing a good boiler that can work. it might be the best option or not.
• Member Posts: 43

@NealJ, How old is that boiler install? and do you have a good lawyer? The original installer needs to give you all the money you spent on that job so you can use it for a down payment for the correct boiler.

Boiler is only 4 years old. Near boiler piping is copper, with one take off between the risers, one take off after the two risers. The boiler is 1/2” out of level. Installation manual for boiler shows threaded joints that we don’t have, plus they have a tech bulletin for locations of threaded connections when using welded pipe (which I equate to soldered copper). I was thinking that I would repipe the near boiler piping this summer before the boiler stressed too much, but there is so much other stuff going on.
• Member Posts: 8,266
The Weil-McLain LGB 7 section is also the correct size for your location based on the numbers you posted

Edward Young Retired

After you make that expensive repair and you still have the same problem, What will you check next?

• Member Posts: 2,722
NealJ said:

There are a couple of run outs that tap into the bottom of the Main that take forever to get any steam & even then, it might take 30 minutes to get these convectors to get halfway hot. It just seems that there isn’t enough steam, which is what got me looking at this.

that doesn't sound right, unless they feed down to basement rads,
post a picture or 2,
• Member Posts: 11,157
Just for your information, I know this is not your situation but FWIW.

There is a 1953 church of 7,530 sq feet with serious cathedral ceiling, limited insulation from that era.
From the print there is 2689 EDR connected. All 2 pipe convectors.

The boiler was changed in 2002, two Burnham Independence IN8's were installed for the replacement.
By their name plate they put out 1266 EDR, together....633 EDR each.

(The boiler sizes were selected by retired gas co man who is "never wrong"!)

I picked up the service work in 2018.

The pressure seldoms gets over 1/2 PSI.

There are 2 3" mains, 150' and 210'.

Perhaps the saving grace is that the near boiler piping is excellent: 2 2" risers on each going into 2" headers which then do a tall drop header into the existing 6" header that feeds the 2 3" mains.

The building can maintain about 65 degrees, no set back is done.

If you have to redo your NBP you could add another boiler as a twin.

Do you need much heat in the basement? Everything was oversized years ago.

Granted all churchgoers are dressed for winter.

But if it was too cold, there would be some comments. Not a poor church, something would be done.

There are maybe 2-3 convectors shut off.
• Member Posts: 43
neilc said:

NealJ said:

There are a couple of run outs that tap into the bottom of the Main that take forever to get any steam & even then, it might take 30 minutes to get these convectors to get halfway hot. It just seems that there isn’t enough steam, which is what got me looking at this.

that doesn't sound right, unless they feed down to basement rads,
post a picture or 2,
See photos below. Yes, this line goes to basement ceiling mounted convectors. This is the first tap off of this main. It drops straight down off the main and then goes over to two convectors. The first convector (you can see drops off to the right) was cut out of the system and capped off. You will see in the second photo the convector at the end of the line. I have replaced two of the condensate returns (& flushed out the rest of the piping to the return header). The drain off of the end of the steam line was fully plugged off (third photo) & when I unscrewed it, I drained 10+ gallons of water out of the steam line. I also replaced a small section of the radiator drain & flushed that line as well. The steam drain now gets hot pretty quickly when the boiler starts running, as I believe this is the first real drain in the Main. But even when I remove the radiator vent, the first few sections of the radiator (only) will get hot after 30 minutes of boiler run time. I originally thought this was because the drains were plugged or restricted. But now with the drains working and no water in the steam line, still little or no heat from the convector. Now I know it’s because the boiler is 50% undersized and there’s little or no motive force to send steam down this line.

This is a 4” main coming through the wall towards you, with the 2” take-off dropping down and coming towards the viewer. There is another take-off you can see (on the right), but it is valved out and capped.

This is a continuation of the takeoff coming through the wall above the doorway. You can see the new copper drain at the end of the steam line and the new copper drain off of the left convector.

This is the top end of the condensate return pipe, after unscrewing from the end of the steam takeoff. 10+ gallons of water drained out as soon as this pipe was removed…
• Member Posts: 5,877
Most of the radiators do not get heat all the way to the outlet end.

Forget where the heat goes in the radiators. It's not directly relevant. Use room comfort to determine success.

NJ Steam Homeowner.
Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
See my sight glass boiler videos: https://bit.ly/3sZW1el