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Radiator - can I use for FHW?

RekonnRekonn Member Posts: 15
My house currently has steam radiators pictured below. Can these be converted to work with a forced hot water system? How can you tell?


  • JStarJStar Member Posts: 2,668

    Yes, and maybe.

    They can be used for hot water. The question is whether they will be sized correctly or not. Are you converting to hot water from steam? A well functioning steam system will be just as efficient as forced water, and cost a lot less upfront, too.
    - Joe Starosielec
    [email protected]
  • RekonnRekonn Member Posts: 15
    considering options

    I'm considering switching to a hot water system, yes. I just bought a house in Arlington MA with steam radiators fed by an oil fired boiler. I'd like to convert to natural gas, and I like the idea of getting a newer, more efficient, smaller boiler. What I've read so far has led me to believe that forced hot water would be better than steam.
  • SteamheadSteamhead Member Posts: 11,321
    edited May 2013
    What they don't tell you

    is that if you try to run those radiators on hot-water, some things can go wrong:

    1- a steam system normally runs at ounces, rather than pounds of pressure. Hot-water in a 2-story building needs 12 pounds, in a 3-story 18 pounds etc. If there are any weak spots in the radiators or piping, they WILL leak, damaging your house.

    2- as JStar posted, they may not be big enough to heat the house on hot-water. A steam radiator will give off 240 BTU per hour per square foot, but a hot-water one only 150 and that's when the entering water is at 180°F. That's why older hot-water rads are bigger than steam rads would be for the same heat output.

    3- those 90%+ condensing boilers rely on low water temperatures (below 140°F) to condense the flue gases. If you try to run steam-sized rads on hot-water, you will have to run them at higher temperatures, so the boiler won't be able to condense. Above 140°F these units act like standard boilers, negating their touted higher efficiency.

    It's far more cost-effective to install a good steam boiler and tune up the steam system.

    What make and model boiler do you have now? It might be possible to put a gas conversion burner in it. On a well-designed boiler this would offer better efficiency than the usual atmospheric gas boiler, and cost less too.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • HenryHenry Member Posts: 696
    In flew enza

    Converting to hot water is something we have done many a time with tremendous energy savings. The large luxury apartment building we did last fall, had one leak!

    Those rads can be converted.

    The radiator sizing in the old days was to provide heat with the windows open. So no problem with lower BTU output. Remember INFLUENZA 1917!

    Here we use 1050 hours of burner operation of which 100 is for -20F plus weather. So again, most of the time the systems run much lower temperatures than even 140F. So the boiler condense for around 900 Hours.

    The physical facts are that it takes more energy to transform water into steam than heat the water to a lower temperature! You just need to do the math!

    Here were it is much colder than Mas, energy savings when converting are over 50%! We did a cathedral in downtown Montreal:

    Before 175,808 cubic meters of natural gas

    After 68,892 cubic meters of natural gas!

    I have the actual copies of the gas bills.

    We do perform a lot of repairs on existing steam systems including one pipe vacuum systems. We are about the only ones in the region that can repair this type of system and others. BTW, I first started working on steam heating in 1977 at my dentist house that had a one pipe wet return system. Since then, I have designed and installed systems and boiler rooms for industrial applications where steam is put to good use! 
  • HenryHenry Member Posts: 696

    BTW, Burnham even has a section in their website about converting steam systems to hot water!
  • SteamheadSteamhead Member Posts: 11,321
    edited May 2013
    The last time this came up

    in this thread:

    you claimed you saved Notre Dame 1/3 of their fuel consumption, with a frightfully expensive hot-water conversion. We never could make out what was on those utility bills you posted, they were so blurry.

    But once again, you haven't done anything we could not match by fixing the steam, for a lot less money. 

    And you don't cover the increased electrical usage for all those pumps, or the increased level of maintenance your mod-cons will need. These obviously add to the total operating costs, making your percentages look a lot less impressive.

    But we all admire your perseverance.

    Oh, and I could not find anything about converting steam to hot-water on Burnham's site- do you have a link?
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • Jamie HallJamie Hall Member Posts: 6,653
    Rekonn --

    Converting a steam system to hot water is, as you can perhaps tell, a contentious topic.

    The questions you need to ask, though, are fairly simple, and an honest contractor (or more likely, contractors, so you don't get a man with a bias) will be able to answer them.

    At what temperature hot water would I need to run the system to provide enough heat with the existing radiators?

    What will be the efficiency of the recommended hot water boiler (modcon or whatever) at that temperature?

    What would be the efficiency of a new steam boiler for the system?

    What would be the efficiency of a gas conversion for the existing boiler?

    In the event the piping develops leaks when used for hot water (some do, some don't, and you can't tell ahead of time), what will be the cost of repiping?

    What will a new hot water boiler (modcon?) cost, fully installed?

    What will a gas conversion for the existing boiler cost, fully installedt?

    What will a new steam boiler cost, fully installed?

    What will a tune up (traps and vents checked, etc.) for the existing steam system cost?

    At this point, you should have enough information to make an estimate on both the installation and running costs of your four options: new steam with system brought up to par; gas conversion on old boiler with rest of system brought up to par; new hot water system without repiping; and new hot water system with repiping.

    With those estimates, you can make an intelligent decision about which way will give you the least cost for what you want to do.

    Until you do that, you can't possibly make an intelligent decision.  You can read all the threads in the world (including this one) and they will confuse you.  You can listen to contractors with various points of view and, unless you are exceedingly lucky you will find that they all have a strong preference which, naturally, they will push on you.  You can read consumer magazines or government publications and get complete raw bovine manure.

    Do your homework.  You'll be happier...

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • vaporvacvaporvac Member Posts: 1,512
    edited May 2013
    1918 Influenza epidemic/Oversized Rads?

    Hello Henry, I lived in Montreal for many years both a a grad student and prof, so i always like it when you pipe in with your work on old and familiar buildings.

    However, this post has brought up an issue I've been meaning to address for some time. So, I'm offering my apologies to rekonn in advance, for hi-jacking this post and going off topic.

    I've read many, many times that radiators were over-sized because people wanted to open their windows for health due to the influenza epidemic of 1918-1920. However, my house and many others like it, were built prior to that and also have large radiators that I presume were sized to heat the space. It has its original wooden storms and evidence of other weather-proofing so I don't think anyone was opening up any windows during heating season. Btw, this house was built by a very well-to-do family, but I've had more modest homes and have encountered the same thing. Our modern perception that energy was cheap in the past, and was not accounted for is false if my reading of the prior owner's missives are at all representative.

    So from where did this idea come and what's the proof to back it up? I've just been wondering about it. Thoughts anyone?

    P.S. Rekonn, feel free to email me concerning my experience with this exact same dilemma and what the results are thus far. Trying to avoid fisty-fights.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • SWEISWEI Member Posts: 7,356
    Excellent advice!

    I've started about two dozen replies to these "steam versus hot water" threads, sometimes spending the better part of an hour on them  Every one was ultimately discarded due to the suspicion I might not be helping to clarify what is truly a complex decision -- and might simply be "fanning the flames."

    Jamie has asked a set of questions above which, had they come from a prospective customer, would have made me smile.
  • RekonnRekonn Member Posts: 15
    edited May 2013
    boiler info

    Awesome, thanks for all the feedback! I'll get a chance to go through it later, but at least I can answer the question about my current boiler now. It's a Weil-McLain A/B-SGO-5(W). It's an oil fuel steam boiler that also has a tankless water heater built in. The whole house uses steam, except for the sunroom which has baseboards fed by the tankless.

    There are service tags on the boiler, oldest one I see is from 1999. There's an energyguide sticker also that shows an AFUE rating of 83.6. I'm surprised, that's very close to other non condensing boilers I was thinking about, like the Burnham ECS5 (85%)

    When I bought the house, the inspector told me it is missing a flame shield and that the firebox liner is damaged and should be replaced. There's also buildup of deposits of flue, said burner can be adjusted to fix that. Also, the water pressure on the forced hot water loop is 0 on the gauge and the automatic water filler is corroded and appears to be frozen. I'm not sure how urgently these things need to be fixed, or how much the fixes would cost.
  • JeffMJeffM Member Posts: 158
    I'd keep steam

    If it were me, I'd stick with steam. I've got that exact same boiler in my house, and converted it to a gas burner last year and cut my heating bills by 40-50% (balanced the radiators and added bigger main vents helped too). Your boiler doesn't sound like it's in as good a shape as mine was, so you're probably looking at a replacement anyway, but keeping the steam and switching to gas is a worthy idea to consider. I'm not far from you (Manchester, NH) in an 1890 Victorian (2400 sq. ft), and my biggest monthly gas bill this past winter was $342, where the previous winter I was getting $6-700 of oil per month in winter.

    Getting away from the tankless coil would be a good idea for you (going to a stand-alone hot water tank or an indirect). I haven't done that only because my coil is working well and it's cheaper to run it than to change the system for better efficiency.
  • SteamheadSteamhead Member Posts: 11,321
    edited May 2013

    it's not as bad as it sounds. The firebox liner is easily replaced while the boiler is being cleaned, same for the HW loop feed valve etc. They're all readily available, off-the-shelf parts. While the boiler is opened up, it should be inspected to make sure there are no leaks in the sections- typically around the normal water level.

    If the boiler is sound, the burner to use is the Carlin EZ-Gas, which will bolt right on. You'll also need a double-swing barometric and a blocked-flue switch, to meet Code. I'd also suggest getting the acoustic cover which will make it run more quietly. Once everything's done that boiler will run nicely, and give you better thermal efficiency than any atmospheric gas steamer.

    There are two contractors near you that I know of who have much expertise with these burners- Charles Garrity and David Sutton. You should be able to find them on the Find a Contractor page of this site.

    Also, they should inspect the system itself to see if any upgrades such as main vents are needed. There's a lot happening outside the boiler room, and we often find efficiency improvements there.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • RekonnRekonn Member Posts: 15

    Sounds like your situation is very similar to mine, glad to see that your bills are so much lower now! Conversion to natural gas is something I'll definitely do.

    I do have an indirect water heater, a 32g Amtrol. My sister in law just stayed with us, 3 long showers in a row and we still had hot water, so I'm happy with it.
  • RekonnRekonn Member Posts: 15
    converting boiler

    Very interesting! My decision is partly based on my assumption that I'd need to scrap the current boiler. Nice to know I might not have to. I like the idea of the Carlin EZ-Gas, but how can a converted boiler be more efficient than a new one built for gas/steam?

    Thanks for the recommendations too. They're both about a hundred miles away from me, so making that trip might be tough. I'll contact them though, see if they'd recommend anyone closer. The contractor search turned up other promising options too.

    Funny you should mention the main vent, mine has a large rusted hole in attic that needs to be fixed.
  • RekonnRekonn Member Posts: 15
    Jamie Hall

    Definitely saving that list of questions for later! And, I agree with you on the manure, there's a lot of useless pages out there. I'd love to find a real product comparison. Something like two identical structures close to each other - both with thermostats set to same temp, both using natural gas. But, one has a new steam boiler, the other a new hot water boiler. See which one uses more gas after a winter heating season, and by how much.
  • BobCBobC Member Posts: 4,404
    It can be done

    But should it be done?

    I see that radiator has a heat timer air vent on it and that probably means the venting on the system is screwed up. Without proper venting steam can be expensive but if the venting is correct and the system operated at low pressure (8-12 oz) steam can be very economical.

    I would get several contractors in to quote on the list Jamie gave you. One thing to be aware of is a lot of installers don't understand steam so anything you get from them is likely to be badly slanted against steam systems.

    i replaced my boiler last year and gad a gas gun installed in a wet based oil steam boiler and by fuel costs were less than half what the oil was. Most of that was because the cost of natural gas in the Boston area is a lot less than oil butb I did use about 15% less energy with the new Smith/Carlin gas setup than I did with my oil fired v75 (comparing 2012/13 against 2010/11 because 2011/12 was unusually warm).

    just do your homework so you don't get blindsided.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • RobGRobG Member Posts: 1,850
    Gas Burner

    Another thing to remember is that when you do eventualy replace the boiler, you can re-use the gas burner onthe new boiler, saving that expense.

  • SWEISWEI Member Posts: 7,356
    That's a one pipe system

    Converting to HW would be pricey.
  • Bob Gagnon plumbing and heatingBob Gagnon plumbing and heating Member Posts: 1,341
    edited June 2013
    Is The House Two Story?

    Getting the supply and return lines upstairs can be tricky, I did do a conversion on an old steam system, with steam only radiators, and it worked great, one small leak on one radiator which easily sealed with salt. The oversized radiators would get hot about 3/4s of the way up, but the woman was almost 100 years old and kept the house at 90 degrees, so there was plenty of heat coming from the radiators, houses are usually insulated much better than they used to be. Steam is a great system, just make sure you get a qualified installer, the system can be quiet, and the bills can be low, if it's installed right.

    Thanks, Bob Gagnon
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • RekonnRekonn Member Posts: 15
    yup, two story

    Yup, it's a two story house with attic and basement. The radiators on the 2nd floor are all under windows. In my parents house, I remember seeing long steam pipes going up to the 2nd floor. But this house must have them in the walls because I don't see a single one like that on the 1st floor.

    I don't know yet how the size of my radiators goes with my house. I'll need a heat loss calc and then someone to figure out the btu output of each radiator on steam and with hot water.
  • RekonnRekonn Member Posts: 15
    direct vent steam?

    Side note - is there such a thing as a direct vent steam boiler? Or a way to make my Weil-McLain into one?
  • SteamheadSteamhead Member Posts: 11,321
    A power venter

    would work- but, like anything mechanical, would add complexity and an increased possibility of trouble. The beauty of a chimney is that it has no moving parts.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • JasonJason Member Posts: 293
    Steam to water

    Western Pa has done many many steam to water conversions with virtually zero problems. I am not saying it was financially a good decision but they were one successfully. The rep estimates over one hundred.
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,535
    Sealed with salt?

    Can you elaborate on the salt treatment for leaks please.--NBC
  • JeffGuyJeffGuy Member Posts: 70
    Bob Gagnon - radiator leak sealed with salt??

    Bob, you mentioned above: "I did do a conversion on an old steam system, with steam only radiators, and it worked great, one small leak on one radiator which easily sealed with salt."

    I can't find anything about this. What is sealing with salt?
  • Bob Gagnon plumbing and heatingBob Gagnon plumbing and heating Member Posts: 1,341
    edited July 2013

    I rubbed salt in between the sections where it was leaking, on the hot water radiator I didn't even lower the pressure, an old-timer showed me this trick. I've seen it work three times now.

    Thanks, Bob Gagnon
    To learn more about this professional, click here to visit their ad in Find A Contractor.
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