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# Need help determining steam boiler size

Member Posts: 2
I would appreciate it if someone could help me determine the

proper size Weil-McLain steam boiler based on the supplied square feet of

radiation that I have listed.

*All six (6) radiators are FOUR-TUBE and measure 4 7/16” WIDE

Radiator 1      25”   High    22 Sections

Radiator 2     25”    High    22 Sections

Radiator 3      25”   High    34 Sections

Radiator 4      25”   High    26 Sections

Radiator 5      25”   High    22 Sections

Radiator 6      22”   High      8 Sections

Base board hot water loop = 27 feet

Based on the supplied square feet of radiation (radiators

1thru 6 and the hot water loop) what size Weil-McLain steam boiler should I use-

a 4 or 5 section?

Also, would an additional hot water loop in the basement (approximately

50 feet) require the next larger sized steam boiler?

I would like to thank one and all who contribute to the

success of this website, especially Dan Holohan. Thank you.

• Member Posts: 1,564
WM Eg-35

This is assuming that its a gas boiler and that the mains are insulated. when you refer to the 27' and 50' of baseboard is that the amount of actual baseboard or the total lenth of the loop including the pipes/tubing? Is there a reason that you are only considering WM? Good luck
• Member Posts: 212
edited August 2011
Steam Boiler Size.

Each section of those radiators, 4 tube, at 26" high has 2.75sq ft. On the 23" rad, its 2.5. Multiply that by the number of sections, then by 240 to get the btu. If the piping is well insulated, you probably dont need to add for piping loss, but if most is uninsulated, add 10-15%.

As far as adding for a wet loop off the bottom of the boiler, you will have to add those btu's in as well.
• Member Posts: 1,564
Steam boiler

Sorry to disagree Gregg. On a steam boiler there is generally a 33% pickup factor added for insulated pipes and a 50% pickup factor for uninsulated pipes. Also as long as the BTU output of the hot water loop is within the pickup factor we don't add add anything for the loop
• Member Posts: 212
PIck Up Allowance

We are in Maine, with a very cold climate, and have been doing steam for a long time, and I have never heard of anything near a 50% allowance. 25%, yes, but I believe that even that is excessive in most cases, but I sure am not averse to learning something new.
• Member Posts: 8,572
edited August 2011
what size to install

this might be a good situation for a modulating burner, controlled by pressure, since there could be some question as to what size boiler to buy.--nbc
• Member Posts: 2
Additional info and question

Thanks for the replies. I would like to add that this is an oil burner and a one-pipe steam system. I hope someone can correct me if I am wrong in my calculations. Using the book E.D.R. (Ratings for Every Darn Radiator by Dan Holohan) the six (6) Burnham radiators listed produce a total of 57,504 BTU’s times a 1.33 pick-up factor equals 76,480 BTU’s.  This figure does include the hot water baseboard loop.

Is my calculation correct?What do I have to add for the 27’ hot water baseboard loop? The baseboard loop is fed by a 25 foot supply and return line (a total of 50

additional feet of copper pipe).

Would you recommend a 3, 4, or 5 section Weil-McLain steam boiler?
This discussion has been closed.