EDR calculations

#1
03-03-11, 10:55 AM
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Join Date: Oct 2009
Location: USA
Posts: 13
EDR calculations

I'm replacing my oil fired steam boiler with a gas fired one. I have read over and over to properly size it. My plumber suggested a Burnham Independence model IN6. I decided to calculate the EDR values myself.
I have 6 radiators 36"tall by 9" deep, between 4-9 sections. I also have one steam Iron baseboard radiator 8' long. Through my calculations, I have determined my total sq. ft. EDR to be 191.
Looking at the spec. sheet, the IN6 steam sq. ft. rating is 450. A couple of questions:

1) Could my plumber have been that far off?
2) Does my calculation of 191 sound reasonable?
3) Am I looking at the right specs? Multiplying by 240 gives me 45,840.

The spec sheet lists:
1) Input MBH
2) DOE Heating Capacity
3) Steam MBH
I have read there's a factor of 1.3 or 1.5 to cover all the mains and risers, I'm just not sure which is the best number to try and match.
It's a simple 1920's single pipe steam system with a 40+ year old Weil-McClein boiler I can't read the model #.

#2
03-03-11, 11:19 AM
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Join Date: Aug 2009
Location: USA
Posts: 4,947
Compare the size of your old boiler to the size of the one being suggested by your plumber. He may be just matching the size to the old one. You calcs don't sound too far off to me. I have 10 radiators with a total of 571 sq ft EDR. Now mine are all tube type and yours are column type. The tube type have more surface area as well.

#3
03-03-11, 11:39 AM
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Join Date: Oct 2006
Location: USA
Posts: 23,539
1. Probably

2,3. I think so.

Sounds like the IN4 is a better fit.

disclaimer: I'm steam-stupid, so don't trust me (or your 'plumber', because my bet is he's steam-stupid too! It's real good that you are verifying this info!)

How many square feet are you heating again?

#4
03-03-11, 02:00 PM
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Join Date: Jan 2005
Location: Delaware, The First State
Posts: 14,247
This may help in calculating the existing EDR. U.S. Boiler::Sizing Obsolete Radiation - Cast Iron Radiators

#5
03-03-11, 03:03 PM
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Join Date: Jul 2007
Posts: 2,482
Always size a steam boiler on the sq ft of steam. Verify the steam mains are insulated in the basement and do not add anything for piping. It is already in there.
For more steam info see FAQ in the upper left of this link.

#6
03-04-11, 10:30 AM
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Join Date: Oct 2009
Location: USA
Posts: 13
thanks

Thanks to all for your responses. I'm feeling good about my value of 191 and getting a grip on all the other numbers.

I'm thinking the IN4 model would be sufficient:
DOE:87
Steam MBH:65
Steam sq.ft.:271
Does the fact that I have 2 10' hot water baseboards on a loop in the basement effect my needs? If so will the IN4 still cover it?

#7
03-04-11, 05:16 PM
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Join Date: Jul 2007
Posts: 2,482
If your numbers are correct you should be good. Why don't you supply me with the info on the radiators and I can double check them.
Please private message me the info.

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