correct boiler size?

Erik_M

Hello,



I'm looking to replace our 20+-year-old oil fired steam boiler with a gas fired unit in the spring.  Our current boiler is running just fine, but I'd like to make the switch to gas (already have it at the house) before I'm facing a problem with the boiler, and more importantly to take advantage of the cost savings.



We've been in our home (circa 1917) for 7 months and I've only recently begun educating myself about steam heat.  Received two of Dan's books for Christmas and I've learned a bunch from them.  Overall, our single pipe system is running quite well.  No loud noises, no spitting vents, rooms heating evenly.  The two biggest problems I’ve discovered are 1) a main vent that leaks steam at the end of long heating cycles (and only at the end of the longest cycles - any ideas why?) and 2) our pipes in the basement are not insulated.  Needless to say I'll be replacing that main vent and insulating the pipes very soon.



So far I’ve met with two local plumbers/HVAC guys to give us estimates for replacing the boiler.  The first gentleman spent a good 30 minutes sizing up all of our radiators (he only counted the # of sections on each though – took no measurements) and checking out the specs on our existing boiler.  He was very personable, spent a lot of time talking with me, and his outfit comes highly recommended by neighbors and by Angie’s List.  Said he only uses Utica brand steam boilers, and he would mail us an estimate after doing some calculations.  His estimate arrived a few days later and it calls for a Utica PEG-C Series Model PEG150C boiler.  This unit is rated for 375 sq. ft. of steam, and has a heating capacity of 120,000 BTU/hr.



The second gentleman was here this morning and took one look at the boiler (didn't even look at the specs on it), asked me the square footage of the house, and said that was all he needed.  Nice guy, but I won’t be giving his estimate much consideration.  He was here no longer than 10 minutes.



Using the E.D.R. rating charts in one of Dan’s books, I calculated the total E.D.R. rating for all of the radiators in our house to be 333.1 sq. ft.  Using a pickup factor of 1.33, my total square feet jumps to 443 sq. ft.  Our existing boiler has a rating of 465 sq. ft. of steam, and a heating capacity of 149,000 BTU/hr.  Based on these numbers and calculations, (and clearly I’m no expert) the boiler spec’d out by the first guy would be undersized.  What do you all think?



I should point out that in the 20+ years since our current boiler was installed, the house has been insulated (blown in insulation in the exterior walls and attic) and all original windows have been replaced with thermal pane windows.  There was also one radiator removed on the first floor, which I don’t plan to replace.  Are all of these factors enough to consider downsizing to a smaller boiler?



Thank you in advance.



Erik

JohnNY

No.

Changes in building envelope are not a factor in determining replacement boiler size.



I also don't always measure a radiator. By now I've come to know a radiator's dimensions by the manufacturer and style. Counting sections is a must.

Charlie from wmass

Pick up factor included

If the edr is correct that you came up with you use that with no additional amount against the manufacturer's size. They have the 1.33 figure in that number, as in the boiler will produce 498 edr if they say 375 edr.

kcopp

Charlie is correct....

unless your basement supply piping is UN-insulated you should be fine. The p/u factor is in the ibr #.

Erik_M

thank you

Thanks for your replies!  Didn't realize the pickup factor was "built in" to the manufacturer's number.  Makes sense to me now.  Also makes me feel better knowing this guy's calculations were correct.



One more question:  I think I recall reading somewhere that the return line (mine is buried about 8" below the concrete floor) should be flushed out when installing a new boiler.  Am I correct?  I asked the gentleman who was here and he said as long as the water in the glass is clear and we've been maintaining the system like we're supposed to, it isn't necessary.



Thanks again.



Erik

Jamie Hall

You may get some debate on that return line...

but I'd go with the man who was there -- so long as the condensate returns reasonably quickly, and so long as the glass is reasonably clear, in my book it comes under the heading of "if it ain't broke, don't fix it" and I'd leave it alone.