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replacing copper steam radiator with cast iron?

jim_14 Member Posts: 268
I have one pipe steam system and all the radiators are recessed and have a three copper pipe with fins setup.

I am looking to replace 2 of them (on the first floor in living and dining room areas) with cast iron. Note: the thermostat is located in the living room. Right now its basically gives off heat while the boiler is running but it quickly cools down... I like the idea of cast holding its heat for a long time, and keeping us feeling warmer longer.

The bedroom rads I plan on leaving alone. There is a total of 6 radiators in the house. 2 of them were changed to baseboard type (i know its wrong it was before I owned the home) and they are both cast iron.

The pic is of the smaller dining room radiator and the living room rad is about twice this size -these are the 2 that I plan to replace with cast.

My questions are:

Can a retro-fit like this be done?

How expensive would it be?

Would it affect the performance of my boiler since I assume the EDR ratings of cast iron would be higher then the copper its replacing?


  • Jamie Hall
    Jamie Hall Member Posts: 22,897

    it can be done.  In fact, it really shouldn't be that much of a hassle, all told; you can probably re-use the vents and valves, and the piping shouldn't be too much heartache.  You will want to match the EDR pretty closely; not only will this help by not changing the load on the boiler, but it will help in keeping the room temps more or less as they are.

    Cast iron is not inexpensive.  You may be able to find used (maybe someone will chime in on this!) -- most areas there are always nit-wits ripping out steam.  Or there are a couple of good manufacturers of new ones.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • jim_14
    jim_14 Member Posts: 268
    let me clarify

    What I mean is can i put the cast iron in the same place where the copper fin is and still snap that cover back on??
  • Steamhead
    Steamhead Member Posts: 16,718
    You could do it

    but if all the other radiation in the house is fin-tube, the different thermal behavior would unbalance the system.

    If the steam pipes in your system are not insulated, they can pull a vacuum from steam condensing in them when the boiler shuts off. This can pull the steam out of your convectors and make them cool faster.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • jim_14
    jim_14 Member Posts: 268
    2 others are cast iron

    they are baseboard radiators that someone replaced in my bathroom and kitchen and never worked right until i pitched them properly and replaced the vents on. In fact they didnt work at all until I learned of this site years back and found out what to do.

    In fact the kitchen rad is on the same floor as the 2 rads I want to convert.

    I hadnt thought of the vacuum effect, but my steam pipes are all insulated. Its a one pipe system with one main pipe across the basement, with risers tapped off the front and rear of the run.

    The only pipes that arent insulated is the near boiler piping which is 2 drop headers into the steam main!
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