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Thread: Converting steam radiators to hot water

  1. #1

    Default Converting steam radiators to hot water

    I'm converting my heating system from good old fashion steam heat to radiant heat. In the interim, until I open the ceilings and floors, I'd like to use my old steam radiators for hot water. The research I've done concludes that I can use a single entry valve for the conversion. If you don't know what it is, I didnít, it's a valve that has both the HW input and output running through the one-pipe steam input. I'm trying to put a price on these valves but I'm having trouble locating these on the internet. Anyone have any leads or done this before?

  2. #2


    Do you have one pipe or two pipe steam presently?
    "Nothing is foolproof to a sufficiently talented fool"

  3. #3


    They are one pipe radiators.

  4. #4


    I do not think it is possible to convert a one pipe (rising steam and returning condensate through same pipe) steam radiator system to hydronic or FHW usage (other than by adding a second pipe). Meanwhile it appears to me to be a no-brainer to so convert a two pipe (separate condensate returns) steam radiator system.

    Now I can imagine a concentric arrangement, channels, not a valve, (with a horizontal "dip tube" to distribute the water inside) so the same opening in the radiator can be used for both incoming and outgoing hot water, but once outside each radiator you need to string a second pipe back to the furnace.

    Since you said the arrangement is temporary, you might get away with using the radiator air valve opening for the second pipe you are adding. The diameter is small so the flow rate of FHW is going to be low, possibly made up for by a longer duty cycle for the circulator pump and higher water temperature.
    Last edited by AllanJ; September 18th, 2006 at 12:05 AM.

  5. #5


    I've never heard of the special valve you're writing about, and I make it a point to know about weird stuff.

    The typical conversion method for one pipe is to tap the end column for a return line. This is often done in radiant pex.

    You might not have enough heat anyhow. You get about 250 btu's per square foot of steam EDR versus 150 btu's per square foot of hot water EDR. That means you will basically have 40% less radiation.

    Plus, your steam system operated at about 1/2 to 2 psi. Your hot water system will operate at about 12 or 16 psi. You will have leaks all over the place to fix, many of them being between the radiator column sections.

    Your system will also be crazy hard to balance. You'll definately need the valves left in place to throttle the radiators.

    It's not a conversion I'd happily make. There's not a darned thing wrong with steam heat. People just don't understand it. If you're replacing the old boiler, go ahead and buy the extra parts (low water cutoff, sight glass, etc.), and keep your steam setup.
    "Nothing is foolproof to a sufficiently talented fool"

  6. #6


    Quote Originally Posted by AllanJ View Post
    Meanwhile it appears to me to be a no-brainer to so convert a two pipe (separate condensate returns) steam radiator system.
    Yeah, you'd think so, huh? Well, lots of people have gotten themselves in trouble during such conversions when they don't take certain parts out of the supply valves and return ells at each radiator. Plus, the increased system operating pressure always bites you in the arse.
    "Nothing is foolproof to a sufficiently talented fool"

  7. #7


    We bought this house as a live-in fixer-upper. Keeping steam is not an option. The boiler is old, inefficient, and needs to be replaced. Our local NG supplier (Keyspan) has a deal where they will sell you the furnace for $199 if you convert to NG.
    In addition, I really want to make use of the space that all these rads take up, it makes furniture placement difficult in some cases. I nearly scraped the idea of hot water in favor of hot air when I learned that replacing all the radiators, for a temporary solution, would cost about $3500. A little more research I found that "single entry valves" could be employed to use my existing radiators for the conversion. After 1920, a lot of the old radiators had a duel use, either steam or HW. Some of the really old radiator are not connected at the top and can only be used with steam.
    Anyway, here's a pic of the valve I'm looking for.

    Found on this website:
    Last edited by Clutchcargo; September 18th, 2006 at 12:14 AM.

  8. #8


    Who's the manufacturer of that particular valve? It looks like it could be Watts.

    In any event, they're called 'twin entry valves'. They work okay, but you'll have a darned hard time finding them in the US. They are used in the UK quite a bit.

    Here's one that might work: http://store.irawoodinc.com/myhvtwenbypa1.html
    "Nothing is foolproof to a sufficiently talented fool"

  9. #9


    I'm not really familiar with valve manufacturers, I think it's Stadler-Viega.

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