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Steam to Hot Water Conversion

Helping my brother in law convert his steam heat to hot water... the current system is a one pipe gravity steam with a condensate main return...it's installed in a 900 sq ft single floor house...uses six radiators (from their configuration, I believe they are designed for either staem or hot water).  I want to convert to a two pipe, direct return hot water system by adding a return line from each radiator to a manifold, then to the boiler. I want to use the current feed system.... we'd remove the current condensate return line.....I think it's a 2 1/2 inch supply header with either 1 or 1 1/4 take-off to each radiator. We've done heat loss calculations and between that and the way the current steam system overheats the house, I think we'll be OK with Hot Water from a BTU perspective.  I've done some research (including reading a lot on this site) but can't seem to get a handle on what I believe are critical questions...

1. Each of the radiators has a bottom inlet with a valve.  Can that valve be used in the hot water system or do we need to modify or replace it? 

2. We plan to put the exit of the radiator on the bottom opposite the inlet... any problems with that?  will the hot water circulate within the radiator or just pass thru?

3. We have been unable to remove the plugs (3/8"?) for the bleed valves at the top of the radiator.  Can we install bleed valve in the larger plugs in the top end of the radiators?  OR any hints on how to extract the plugs in the bleed valve tap?

4. We plan to balance the system with valve on the return manifold.  However I'm concerned that if he shuts off 50% of his radiators that the higher velocity in the remaining lines may cause a noise issue... I believe I saw a bypass device that diverts some of the flow based on pressure back to the boiler...can't seem to find any info on such a device now.  What is this thing called? ... and what kind of turndown can it handle?

5. Any advice re: the location of the recirc pump?  on the supply side of the boiler?  or the return side?

Thanx for any assistance you can provide.....and if you see any other issues that we've overlooked, pls don't hesitate to let us know...


  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666

    I am not a professional, but let me ask what I believe to be a very important question:

    Why would you want to do this?

    I infer you are not a professional either. But in my opinion, you desparately need one. However, I suggest you get a steam pro in there to put your existing system into top-top operating order instead of converting it to hot water.

    Steam systems can work to quite high levels of efficiency if properly designed and maintained. It is my impression that many steam systems were well designed and then messed up beyond the recognition of their original designers by knuckle-dragging incompetents.

    If you insist on converting to hot water, you will be given a lot of opportunities in the sense of Pogo's remark, HELP! We iz surrounded by insurmountable opportunities.

    1.) The pressure of most steam systems should be under 2 psi. A hot water system is usually run at about 13 psi. So you will have a leak opportunity.

    2.) The temperature of steam in the radiators is a little over 212F. The temperature of hot water in the radiators is rarely over 180F. So if the steam radiators are just the right size for the home, you wll not get enough heat with the hot water unless you put larger radiators in. A chilling opportunity.

    3.) Steam radiators are often not connected across the top, so the circulating hot water will only go across the bottom, greatly reducing the effective heating area. Another opportunity to get insufficient heat.
  • Ya`know,,, JD is right,,,,,

    people spend "megabucks" to obligate themselves to new car payments,, but few dollars are spent-on the home heating system(other than fuel costs).

    If the steam system(and I suspect it has), been neglected for years,,, get a good steam pro to tune-it up!
  • gimme_shelter
    gimme_shelter Member Posts: 2
    That horse is already out of the gate.....

    Thanx for comments/suggestions  re: the wisdom of doing the conversion but not doing is not an option.... old oil fired boiler was dead...and has been removed... new gas boiler (hot water) is being installed as I write this.... so .... back to original questions.....

  • Charlie from wmass
    Charlie from wmass Member Posts: 4,311
    no easy way to remove plugs

    some guys heat them others use PB blaster oil on them. some drill them and use easy outs. I did one of these 18 years ago and it went less than well for me. customer was happy , I taught myself new curse words not known to man yet. the radiator valves should be replaced and the radiators need to be checked throughly as they are going from gas pressure of a few pounds to water pressure of 12- 20 pounds. Also each radiator that has been sitting quietly with the weight of steam pressing down on it now has water filling it at just over 60 pounds per cubic foot depending on temperature. Hydronic Alternatives has a valve made to use the one side of a radiator to get the water in and out. Otherwise you need to remove the other plug. ALso the piping and radiators are full of 50 or more years of sludge from being an open air system. get a dirt seperator if you are going to reuse the radiators and if you are using a mod con boiler check the warranty for disclaimers.

    In short go buy some base board and pull out the iron pipe. Sell the radiators to someone who can use them and move on I think you will have a more peaceful life if you do not get buried too deep in the radiators.

    Be careful, by JB weld and PB Blaster and best of luck.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,311
    Pump as per the boiler piping

    Diagram. What boiler are you using by the way?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
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