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Adding a radiator to a running system

Because it was crucial for me to get my boiler system up and running enough to make the house withstandable to do other work, I left the shutoffs closed for two of the radiators in the system which are located in upstairs rooms.

Now I need to bring those radiators up into the system. Before I do that I wanted to see if I could solicit any advice regarding best practices, gotchas, etc. That's a fair amount of cold water to be adding to the system, and one thing I wonder about is how long it will take for the makeup water to flow in with a 12-pound regulator suppressing the full flow. I also have a bypass valve I could open to house pressure, but I've read of boiler shock and so I'm not going to do anything until I get some more knowledge about what I'm intending to do.

I greatly appreciate this resource and thank you in advance for any advice that may be offered.


  • Jamie Hall
    Jamie Hall Member Posts: 23,655
    Do you have any way to bleed air out of that radiator? I hope so... If so, I'd be inclined to let the system cool down, and then set about bleeding the air and let your regulator maintain system pressure.

    I'm not at all sure that 12 psi in the basement is going to be really adequate... but that's a different problem.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • capouch
    capouch Member Posts: 19
    There's a bleeder at the top which is how I filled the rest of the system, which seems to be working fine. I have a standard Bell and Gossett regulator at the ingress point for the makeup water.
  • PC7060
    PC7060 Member Posts: 1,240
    Id open up the valves one radiator at a time and bleed the radiator then move onto the next one.  

    it wouldn’t be the first time cooler water (ambient) has been dumped into your boiler circuit.   Pretty much happens every time a call for heat occurs.