sizing new boiler

Emeliza

I just want to make sure that I am getting the right sized steam boiler to replace the old one . My current system is a 30-40 year old Weil-McClein that is rotting out at the top and is rated at 750 SF for steam. I have 13 radiators but only 12 are installed, one is up in the attic and not in use and I am not sure if I will have it installed as it is in a pass through room. The EDR on the 13 radiators is 635, subtract the one radiator that I am not going to be using, the total comes to 618. Based on that number the contractor ordered, with my concurrence, a Megasteam 629 (rated at 629 SF of steam. Based on all I have been reading (got Dan's book "Lost Art of Steam Heating") and this web site I think I should be okay. I had to add a chimney liner, the largest they could fit was a 6" and they had to ovalize it as there were bends and an obstruction, a piece of angle iron that held the column of bricks from the second floor thru the attic and above the roof. Oh, and my system runs on oil and since I am in Vermont, it will be years before natural gas gets here.



Second scenario, I will be replacing all the vents on the radiators with Vent-rite #1's and not sure which, or how many vents on the mains. Currently I have a Vent-rite #75 on one of the mains and it looks like the other one-same kind I think- is on what one plumber said was the wet return (I called him to look at my system and give me an estimate, said he couldn't get it done in time for heating season and that it wasn't in his best interest--go figure). My mains are 2" but the first vent is on a 1-1/2" section that services the living room and my room. I think I should have a vent somewhere near the end of the 2" main, a Gorton #1 and maybe a #2 where the one is on the 1-1/2" pipe.



I am also nervous about one of the ratings on the Megasteam 629 based on what the chimney contractor said (I don't think he understands steam, but what he said makes me want to ask the question). The GPH rating for the 629 is 1.65. Does this mean I am going to use more fuel that I would with a nozzle that is say 1.2 (which the chimney guy said I should go no larger than)? Am I not understanding something here? Does this have something to do with firing rate? And if the manufacturer stipulates a 1.65 to give the optimum performance, then that's what I should use. Right?



The contractor has installed this type of boiler but before I give him money or sign a contract I am going to stipulate that he installs it as/per manufacturer's specifications. If anyone out there in steam heating land have suggestions or confirmations that I am on the right track, please let me know.



Also I am installing a GE Geospring hot water heater (it goes in heat pump, hybrid, or resistant mode depending on the temperature in the cellar- which will have some closed cell insulation to about a foot below grade) so that I don't have to use my boiler during the shoulder seasons and summertime.



I forgot to add, the house was built in 1835 and is 2700 SF. Also, I heat the family room with a wood stove and the living room with a pellet stove (which can't keep up when it is 0 degrees outside). I want my steam system running efficiently and balanced so that I can be comfortable during the winter and not cold all the time. Last winter I kept the temp at 60 degrees so that I wouldn't use so much oil.

BobC

Will work if done right

The 629 sq ft of steam should be fine but proper installation is a must. All the steam piping has to be done in threaded steel pipe. Both tappings on the boiler should be used and the header should be at least one size bigger than the pipes feeding the header. I would pay a little extra and have a drop header installed so I would get nice dry steam. All the steam piping in the cellar should be insulated with 1" fiberglass pipe insulation so the het you pay for ends up in the living space.



Make sure the slope on all the piping is adequate so water can find it's way back to the boiler. The main vents should be large enough so all the air can be expelled from the main in a minute or two, the radiators should be vented slowly with large remote units needing a bit faster venting. Ventrite makes great vents, none better.



The 1.65 gph rating is for the full 629 sq ft of steam, if you downfire it to a lower firing rate it won't heat all the radiators because it won't make enough steam. Make sure that new liner will work with the 1.65 firing rate, the Burnham manual says it needs 7".



Anything you can do to insulate and stop any drafts will help.



Bob

Emeliza

Thank you

Bob, I appreciate the advice, I really do and will print out your response for my contractor so I have it on hand if I need it.  He's a pretty good guy and willing to listen to me.

I have been told by  a couple of plumbers and the chimney liner installer that going one size down, from 7 to 6, with a special fitting, is perfectly okay so I am not too worried about that.  I am working on the insulation aspect (2" rigid XPS against the rim joists, caulking all the cracks prior to fitting the insulation and once all that is done, having someone come in and spray 2" cc foam to about a foot below grade as Efficiency Vermont specified when they did my energy audit). I have a fieldstone foundation, rubble on the wider lower part and big blocks of granite on the upper quarter.  The only way to insulate properly is spray foam which will then be painted with intumescent paint. Got my work cut out for me this fall.

And, as you suggested, I am insulating the pipes with 1" fiberglass insulation.  Expensive stuff so I am doing a portion at a time--every time I get paid.  It'll be done by the time cold weather sets in for good.  Really would have rather had a new kitchen, but being warm and comfortable is good.  If I have an even 65 degrees in my house, I will be a happy camper.  I think I will order the venting book by Gerry Gill, that is on this site.  It will be a good reference.

BTW, I love this site, even though it contains material that most women's eyes would glaze over at!

vaporvac

Maintain same water line...

In addition to the prior suggestions, I might add to be sure the installer maintains the current water line or accounts for it with a false water line. You may have to raise your new boiler since they're frequently smaller. This helps prevent your wet returns becoming dry which can lead to a slew of problem. Treat the manufacturer's specs as MINIMUMS. Install a ball valve in the skim port and ask your installer to show you how to skim it or look here for instructions. Once is NOT enough with a new boiler and piping, at least in my experience. Disclaimer: I'm another homeowner as well as another female. Glad to see you on the site!



BC, your boiler's lookin' GOOD!

Colleen

Emeliza

New concern, I think

Just measured the area that my current boiler sits in. it is 67" from the concrete to the top of the main steam lineup and maybe 6" at most to the bottom of the joists on the first floor. Did I mention that this is a cellar and a really old house! Anyway, boiler is currently sitting on concrete block (6" maybe 8") on a concrete pad. Good thing the new boilers are shorter. I haven't checked the specs yet on the new one, but will. And I will keep your comments in mind. I should probably draw up the current situation and then sketch up the proposed (to scale) so that I can see the problems before hand. Installation is happening the 29th and 30th.

Emeliza

Question of riser length

Is the recommended 30-36" length for the riser for a drop header measured from the base of the boiler to where it connects with the drop header, in other words, that distance includes the vertical and the horizontal distances, or is the measurement the vertical distance to the first bend before it goes horizontal and drops down to the header the 30"?

Fred

Vertical

The 30 to 36 inch measurement is vertical from the boiler water line up, then you turn with an elbow, horizontal 10 to 12 inches then drop down about 15 inches. The drop is not critical. It can go down almost to within a few inches of the top of the boiler if that facilitates connecting your steam mains.

Hap_Hazzard

24" minimum riser length

Most manufacturers recommend that the risers extend at least 24" above the maximum water level. This prevents carryover from reaching the header under normal conditions, so under real world conditions, the higher the better. Surging and foaming can drive water higher than 24".