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sizing for new boiler

4Barrel Member Posts: 125
first, thanks to many of you out there that helped me nurse an aging steamer through last winter. so now it's replacement time, and i am checking the size, and i'm hoping for some help checking my rationale/math. i measured and used LAOSH to calc my EDR. i have a total of 14 radiators (divided up among four apartments in a converted victorian in Buffalo, NY) with a total load of 532 EDR. multiplying by pick up of 1.33 and converting to btu, i get 170,000.


1) the current boiler is 225,000 btu. should i consider a smaller boiler?

2) one of my challenges has ben uneven distribution of heat in the apartments (first floor cold, second floor hot). i tried managing this via radiator venting, and relocation of the the thermostat, with only marginal improvement. so now i am thinking i may may add another radiator on 1st floor, and/or retire one on the second floor. is there an appropriate rule of thumb to use for amount of EDR per square foot of living space?


  • aging steamer

    i don't suppose the original owner of the building would have tolerated any heating imbalance in his new building when it was built, therefore i assume this system worked well at some long ago point, with properly sized [and working]  radiators in every area.

    check your main vents, as it seems as if the steam is not arriving at all radiators simultaneously, and a new boiler will be no better until this is corrected. are there sags in the piping keeping the steam from flowing freely?

    when you put in the new boiler, don't waste any money on a pressuretrol, get a vaporstat. if a pressuretrol comes with the new boiler, it can be used to hold open the manufacturers installation book, while you follow  them without deviation. afterwards, when painted with gold paint, the pressuretrol makes a unique christmas tree decoration for one of your "favorite" relations.

    others will be better quailified to advise on boiler size [all i can say is that it matters]. this may be an application for 2-stage firing controlled by a second vaporstat.--nbc
  • 4Barrel
    4Barrel Member Posts: 125
    old design

    thanks! great input!

    i do believe that the system was altered when the building was converted into apartments in the 1950's. so, i would be speculating on the original design. some alterations are obvious, and there is at least one dead end line, but it appears to me that most extraneous lines (if any) were removed, and the lines in place (other than the one i mentioned) all run to specific, operational radiators. they don't sag, but they've got old insulation (the nasty stuff) which i am making arrangements for removal, and will be installing new fiberglass insulation. if you are referring to the radiator vents, yes, i plan on replacing all of them with new 1As, as well as the main vent.

    i've read about the benefit of using a vaporstat... can you provide a recommendation on the type/brand I should use?
  • vaporstat selection

    i think that having a vaporstat is not merely an advantage but almost a necessity, as these systems only work really well at low pressures [with generous main venting].

    do a search here for "vaporstat" and the correct honeywell part number will be found. i think the key is "break on rise" 0-16 oz.--nbc
  • Jamie Hall
    Jamie Hall Member Posts: 21,546
    Dead end line

    Make sure that dead end line, assuming it's in use, has a jolly good big vent on it.  The radiator vent just won't do it...

    As for a rule of thumb on EDR vs. square feet, no... not really.  If you want to find out whether certain rooms have less radiation than they should, or more, it's a little tedious but can be done.  Step one is to make a list of rooms and note the EDR installed in each room.  Step two is the hard part: for each room you will need to compute the heat loss at your design temperature.  Fortunately, there are nifty programs around here somewhere to help do that.  Step three is to figure the btu put out by the radiator in each room -- multiply the EDR by 240 --  and compare that to the heat loss for the room.  Do this as a ratio (heat available -- EDR in the room times 240 -- divided by heat loss).  Ideally they should all be greater than one, but if some are considerably larger than others, those rooms will be too warm assuming all else is equal.  If you have some which are considerably smaller than others, that may be where you can put a new radiator.  Or the one you take from upstairs!

    I hope I haven't confused you...!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • 4Barrel
    4Barrel Member Posts: 125
    final calcs

    i decided to add in the extra radiators in the cold apartments, and i re-did my calcs and came up with gross heating capacity of 193,000 btu (includes 1.33 pick up). If i remove one radiator in the hot apartment (which i might/might not depending on the final install) i get a gross heat capacity of just over 183,000. a direct replacement of my current dunkirk model has a gross rating of 183,000. the next model up is a gross HC of 214,000, and is of course more expensive. my supplier thinks i'll be fine with the 183,000 should i stick w/ the 183,000, or size up?
  • boiler selection

    how were those extra radiators "added in"? as far as i can see, everything connected to the boiler [whether working well or not] should be included in the EDR calcs. if the system is relatively compact and doesn't contain any excessively long pipe runs; then the sizing could be smaller.

    when you get your new boiler in, with vaporstat, and new main venting, you will probably find that those cold radiators spring back to life, so they definitely need to be part of the calc.

    double check the piping requirements for the dunkirk, as i seem to remember problems with a misprinted inst. manual, which undersized the piping.

    someone here [Boilerpro?] has argued for the benefit of undersizing, so you might want to do a search.--nbc
  • Be cautious!

    I'm an amateur at this but the immediate thing that strikes me is that you need to get your present system straightened out before thinking about moving /adding radiators. Overheating can be controlled with TRVs and do the radiators on the "cold" first floor get really hot all the way across? If they don't, I'd get them straightened out first before adding /moving any radiators.

    Since this is a 4 apartment unit rather than moving the thermostat, I'd also look into a Tekmar 279 or something similar.  I would think that in your situation it would quickly pay for itself.

    You really might want to call in a steam pro in to look at your system.  I'm sure there are some good steam pros in Buffalo so  you might try the Find a Professional above, though the new software seems to have some problems and sometimes not give a good reply. Actually Cleveland isn't that far from Buffalo (190 mi?) I'd think about contacting Gerry Gill  http://www.gwgillplumbingandheating.com/

    and if it is too far`for him maybe he'd be able to recommend a good steam man in your area to help you out.  I understand that this might not be an expense that you want to incur however there are times when a pro can save you from spending much more time and money chasing your tail!

    - Rod
  • Jamie Hall
    Jamie Hall Member Posts: 21,546
    Re: Final Calcs

    If your present and smaller proposed boiler sizes are that close to your calculated load plus pickup, you should be OK -- provided that all of the steam supply lines you can get at are insulated.  Which you should be sure of anyway.  If there are some lines you simply can't get at (risers are often a real bear this way) don't sweat it, but insulate everything you can.

    Vent like mad.  It's almost impossible to have too much venting on your mains.  Then there are other ways to control the heat to the various spaces, depending on exactly what kind of system you have.  One step at a time...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • 4Barrel
    4Barrel Member Posts: 125
    edited September 2009
    great input

    lots to think about in these responses, but let me try to summarize:

    - the "added in" radiators are, in case 1, going to a fist floor location where one existed before, i just needed to put the riser back in from the line in the basement, a foot or so beneath the floor, and in case 2, i am considering adding a short extension, tying into a location that previously existed,, again to the first floor. so in both cases, the added piping to accomplish these adds is small. i thought there was a dead line going up to the attic, but that's not in the steam loop. believe it or not, the piping is set up pretty efficiently for the apartments.

    - insulation: i am re-insulating all the lines in the basement - everything.

    - under versus over-sizing: i seem to recall from LAOSH that it's better to be a bit under than over, but wasn't sure if i misinterpreted this.

    - hot versus cold apartments: yes, I am hoping that the colder apts are better with the new boiler, but the EDR calcs per SQFT of each apt were illuminating: the cold APTS are getting 15-20% less EDR than the hot ones under present config. i kno the upper floor should get more, but this is too much it seems... open to input on this.

    - thermostat: i installed a white-rodgers with a remote sensor last winter to try and even things out using the avg function. i had just moderate success w/ this, primarily, i think, to the slow death the current boiler was undergoing.

    - vaporstat: yes, i am going with one, but i have questions on this and main venting that i will save for another post

    - buffalo steamers: believe it or not, there aren't many up here. def a market opportunity. scary that i seem to kno as much, usually more, just from reading LAOSH. i would love to have the cleveland guys here.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Buffalo steamers ...

    When I was a kid in the 1940s, my parents lived in Buffalo, so so did I. I was interested in things like heating. We rented two different houses and after WW-II, my dad bought a house. In those days, everyone heated with coal. For one thing, gas there was manufactured gas and too expensive to heat with. I never saw anyone who heated with oil.

    The first and third houses were heated with hot air. The first one had natural convection, with a single cold air return in the dining room downstairs. The second one heated with hot water, and the boiler even had a stoker so you put coal in it about once a day, and took the ashes out likewise. The third was hot air too. I am unaware of any steam units there. Sometime later, the city stopped picking up the ashes, so my dad had that converted to gas.

    The University of Buffalo had a lot of buildings on their main campus that were all heated by steam. They had a separate building that had the boiler or boilers in it, and the steam was delivered to the other buildings througjh underground steam lines that were mostly under the sidewalks. So they got snow melting. I do not know if that was done on purpose or by accident, but it worked pretty well, except for blizzards. My grade school was also heated by steam that must have been a two-pipe system of fairly high pressure. Each room had a pneumatic thermostat that ran the supply valve to the radiator in the room. I knew the engineer of the building at the time, and found they had three or four downdraft boilers. One was a spare. I thought downdraft boilers (coal burning) were pretty neat, but could not figure out how you would get a draft to start one. I still do not know. He told me you needed a license to run those boilers, and he certainly had one. He must have been smarter than later engineers because the chimeny did not smoke when he ran the plant. But after he retired, whoever ran the system got a lot of smoke and the neighbors hated it. So, in my limited experience, there was very little steam heating in Buffalo in the 1940s, by which time most of the buildings were built. Maybe there was some in larger buildings. I imagine the Frank Lloyd Wright house was heated by hot water radiant, but do not actually know. According to their web site, it is geothermal now.

    OTOH, my grandparents in Upper Montclair, New Jersey, had steam heat and sometime after the war, they replaced whatever they had with a GE boiler that was oil fired. I have the impression that that was a one-pipe system, but they had a big radiator on the ceiling of the basement and it had a radiator vent on it. I seem to remember another vent down there somewhere and my grandfather did not, as I recall, know what it was for. I was under the impression that the air all escaped trom the system through the radiators, but I was only about 8 years old then, so I may not have known everything I might have found out were I older.
  • 4Barrel
    4Barrel Member Posts: 125
    History & Cold Air Return Q's

    Thanks JD! This is really interesting! I've thought a lot about the history of how this house was heated in the context of it's overall history, but you give some new insight. my victorian is in a historic district, Linwood Ave, and these homes were built in the late 1800's by the second tier wealthy of, at the time, a booming industrial town. being on Linwood carried status, and many places were build with the latest technology, but it makes sense to me that this home started out with the coal-fired steam, and then later when converted to apartments in the 1950's, switched over to gas. i believe most the risers to the individual radiators are original, but the basements lines were all revised, and extra risers were removed. i believe this because the basement is laid out in a very straightforward manner to serve the present radiators. The near boiler piping was again revised, consistent with the DUnkirk installation requirements, i believe in the early 1990's when the present boiler was installed.

    One thing i am wondering about is the notion you rasie of cold air returns. i've been trying to figure out what is/was the function of this floor vent (see picture). I wondered if there was some sort of underfloor steam radiator mounted in the basement rafters. is there such a thing? or was this part of some sort of passive air circulatory system? this picture just happens to show the location of where i want to install a small radiator - against the wall. if i could find some way of mounting an appropriate steam emitting device under the floor, that would save floor space... does anyone know of such a device?
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