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Steam to Hot Water Conversions

Lee_11 Member Posts: 6
Overall, please advise whether it is a bad idea to convert a two-pipe steam system to a hot water system.

The setting is a multi-unit apartment building, so the goal is to separate the heat to the individual units so the tenants foot the gas bill.

My main concerns are

1) I want to be sure that the larger inlet and outlet steel pipes that will be used won't create any problems, both because inlet pipe is not the same size as the outlet (do they need to be balanced? If so, how?) and also because these pipes will carry more water than if PEX were used (is there a compression tank?)

2) will the old pipes create any issues with the new boilers (e.g., because of rust)?

3) Is replacement of all of the steel inlet/outlet pipes with PEX and the associated headache/cost worth it?

Any other tips on questions to ask to make sure that the job is done right are much appreciated.


P.S., I have read Dan Holohan's article with conversion tips, but want to be sure I am not opening a can of worms. (And I have considered electric heat, but don't want to lose tenants because of its expense every month).


  • clammy
    clammy Member Posts: 3,094
    steam h2o conversion

    I personally would not try to convert unless you are going to do all the math to make sure that the existing convectors or raditors will be capable of heating the apartment with the lower btu output that a hot water system would give you ,besides the fact that those steam pipes have never seen the pressure that a hot water system will be putting on them (min 12 to 15 psi)plus all the crude that is in those pipes which will end up in your new boiler or damage to your cicrulators impella .What is a matter with the existing steam system anything or are you just tried of paying the gas bill and would rather have your tenants pay for the heating ? i personally belieev that if converting then you might as well do it once and do it right instead of trying to use all the existing piping over and installing seperate boilers and gas lines ,meters and then electric to operate these boilers ,plus will the existing chimmey sized large enough to handle multi boilers flue capacity?these are all big if 's and you may be either better off having a professinal take a look and remenber if you do a conversation and there promblems with piping ,ect who pays that repair bill ?you or are you going to stick the tenants with up keep and maintance alot of questions and with out some one who knows what they are looking at and what to do there are alot of variables peace and good luckc clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    multi unit bldg.

    if i were you, i would just get the system working as well as possible, as it now is. i would put the remote sensor for a new honeywell visionpro thermostat in the coldest apt, and the visionpro itself in a secure place, accessible only to me. i would not bother with using the setback feature, and would set it at 68 deg and leave it there.

    i would pay close attention to the steam pressure with a good low pressure gauge, and use a vaporstat to maintain that ideal pressure which might be as low as 2 ounces. i would make sure that the air can get out of the main steam pipes as quickly as possible, letting the steam in. i think that if your system is typical, or new to you, you will be pleasantly surprised by the improvement. for long term leases you could have an elevator clause to compensate for any inflation in the cost of fuel per square foot.--nbc
  • Jamie Hall
    Jamie Hall Member Posts: 22,917
    Don't do it

    As has been said, step A -- get the system properly vented, trapped and generally working properly at a nice low pressure (if it isn't already).

    Step B -- if you want your tenants to have individual thermostats, that's cool too. Two ways to go: TRVs on the radiators or thermostats controlling zoning valves, one for each unit. There are things to be said for and against both approaches. In your setup, I would probably go with the zoning valves individual thermostats and set it up so that if any valve was open, the boiler could run and would run if the steam pressure was low enough; simple enough to do with if there are auxiliary contacts on the zoning valves, a little harder if there aren't. You could probably figure out a way to bill them based on how long their zoning valve was open related to the total time any zoning valve was open and the total EDR of their system vs. the total EDR of the building.

    The conversion from steam to hot water is not one I would recommend. First, there is the little problem of heat output from the radiators, which someone mentioned. Second, the odds on the radiators and pipes NOT leaking are enormous: steam runs on a pound or less; hot water at least 15 times that. Drip drip drip drip... Third, even if the radiators don't drip, are they really suited to water? The right tappings for air release? Correct inlet and outlet locations? And so on...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Lee_11
    Lee_11 Member Posts: 6
    Steam to Hot Water COnversion

  • Lee_11
    Lee_11 Member Posts: 6

    Thanks for all of your replies. The problems of the old pipes (leaks and crud) and possibly undersized steam radiators for hot water are really holding me back from doing this job.

    My main boiler is a huge Weil McLain that is from the 60's and has only two zones of an 7-Unit apartment building (5000 sq ft total). We have it well-adjusted with vents, new traps, etc. so it is running well, but is there is no way that I can measure the heat usage by unit using just one boiler and two zones. And with two main trunk lines spanning a couple hundred feet in the basement, no easy way to add any extra zones.

    Unfortunately, it looks like I'll just have to keep raising rents to pay the ever-increasing heating bills.

    I appreciate the sanity check, though, it confirmed my fears.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,314

    Lee going with new boilers, possibly 2 units.or four units 2 for each zone would be one way to get a grip on who is using what for heat. The multiple boilers would allow for a more accurate heat load match and also provide backup if a unit should drop in January at least the building will have some heat until it can be up and running.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Lee_11
    Lee_11 Member Posts: 6
    Keep the steam with separate boilers?

    Thanks, Charlie. My thinking now is to keep the pipes and radiators using steam heat, but with individual boilers for each unit. Hopefully, breaking the main into separate runs tieing each apartment to a boiler will give me the best of both worlds with minimal work. Will also allow me to slowly wean off a 40+ year old boiler as I get each zone done.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    separate heating systems

    how many months of gas can you buy for the cost of 7 boilers [or how much insulating, window replacement, etc?} will this be the same cost as the replacement of 1 large common boiler? many people have had problems with their zoned steam systems, contributing to higher running cost, etc. a 5000 s. f. building should be the same temperature end to end within a couple of degrees. it is possible that your present boiler is over sized, and that the zoning was used to correct an overfired [or under vented] condition. your main boiler, if replaced with one of the correct size should need no zones.

    since you contemplate installing new separate systems, why not convert them to 1-pipe steam? or mini-split system heat pumps?--nbc
  • Tony Conner_2
    Tony Conner_2 Member Posts: 443
    The First Thing...

    ... I'd check is to see if the landlord's plan to bill the tenents is legal. I'm not aware of anyplace that allows anyone except a utility to bill individuals.
  • Lee_12
    Lee_12 Member Posts: 3
    Utilities are in tenants' names

    Thanks. By installing a meter yoke to split apart gas to each unit, tenants will be billed directly by the utility.
  • Tony Conner_2
    Tony Conner_2 Member Posts: 443

    ... every apartment will have it's own boiler?
  • Lee_12
    Lee_12 Member Posts: 3

    Yes--and they will collectively foot the $13K of heating gas a year once it is all broken off.
  • Tony Conner_2
    Tony Conner_2 Member Posts: 443
    What's The...

    ... payback on this project?
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    extreme heating cost

    here in nebraska, we are heating 10,000 s.f. with gas-fired steam for a little less than your $13K, so i would think that either your system could use a minor to major tune-up, or you must be in a very cold area!

    will your tennants have any money left over to pay the rent, after paying the gas co. $2K a year?--nbc
  • Mad Dog_2
    Mad Dog_2 Member Posts: 6,711
    Not worth the effort in most cases

    Tried it a few times. As some others said, either get the steam working optimally, or convert over entire system. Mad Dog

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  • ChrisL
    ChrisL Member Posts: 121
    Apartment Heat

    I am in a similar predicament with two older centrally heated steam heat buildings. Its a very complicated decision, and switching to individual units has its downside with much more maintenance and repair. But then you see a window open, or a complaint that its not warm enough only to measure a nice 72 inside and you reconsider. I think the best approach is to install furnaces with AC right away. While hot water or steam heat is definitely more comfortable, you can't beat cost efficiency of getting ac done as well.

  • Lee_12
    Lee_12 Member Posts: 3

    Couple of points all in one:
    $42 K cost of job / $13K per year of heat +3.2 Years payback

    Tenants will not have $2K per year because:
    1) inefficient 200 ft of insulated steam main and condensate lines running in basement will be gone (I need to crank heat to get back apartments heat)

    2) Huge 1960 vintage inefficient boiler will be updated with more efficient ones (it has been tuned up by a commercial heating contractor that services schools and commercial buildings in the area)

    3) Last but not least--tenants will have skin in the game and not crank the heat to 80 degrees (two thermostats one for each zone presently do not adequately allow me to limit and service all units without waste out windows of overheated apartments)
  • Tony Conner_2
    Tony Conner_2 Member Posts: 443
    I'll Bet...

    ... you could get a huge improvement by simply fixing the existing steam system - not just the boiler - for a fraction of the conversion cost.
  • jimmac
    jimmac Member Posts: 47

    at the cost of your quoted system new rads an pex were not included? do not think that would stop the contractor from taking on the job?the breakdown of how the apartments (rooms,walls doors ) are laid out usually dictate cost? are you going to seperate the hot water as well? would not reuse the old pipe and rads.baseboards are iffy depending on your type of tenants!! we do this type of seperation in all types of buildings nowadays.some tenants will move once they get there gas bill..but those might be the ones with the open windows :)
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    to divide or not

    i imagine you are in a similar position as the other apt. owner, also with a system you think is doing as well as it can, but is probably burning a lot more fuel than it could, and so therefore you are wondering whether to put it in good shape, with subsequent lower gas bills, or...? or the other choice would be to put in a new heating system for each unit, which may be furnaces, with their need for new filters changed each month, blower motors problems, and shorter life than boilers, more space taken up by new equiptment, etc.

    can there really be any other choice in this sort of situation, other than making what you already have, work as it was originally designed to do--that is quietly....economically....evenly.--nbc
  • Lee_11
    Lee_11 Member Posts: 6

    You are forgetting one thing. . . I am not in the heating business but am being gouged by a commercial contractor to service a large commercial boiler. I am not a school, nor am I a large commercial building but a mom and pop apartment building getting charged commercial repair rates.

    Every service call I receive cost on average $750-$1000--and there is NO ONE else in town that knows these steam boilers installed by the Dead Men. I am losing my shirt on repairs--and god forbid this unit craps out, I am sunk. I have already spent thousands (yes, thousands, venting, repiping, individual thermostating radiators, etc) to optimize this system-- but at the end of the day, it is still a beast.

    SO converting to more manageable units is another benefit that hopefully will give me peace of mind.

    P.S., I wish any of you who are replying were closer to the Lehigh Valley in PA to compete with the one commercial contractor out here in steam heat.
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    Lee, I'm in Baltimore

    which isn't so far that I couldn't come up and take a look.

    I haven't posted in this thread before, since the others have said pretty much the same as I would have regarding keeping the steam. We have documented savings of 30% and up in several medium- and large-sized steam-heated buildings like yours, just by getting the basics right.

    Where in the Valley are you located?

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  • Lee_11
    Lee_11 Member Posts: 6

    I am in Easton, PA which is on the New Jersey border, a bit east of Allentown. Do you ever get up in this area?
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