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Cast Iron Radiators cold when boiler is on

I've got an older house with cast iron radiators & a boiler system. Turned it on last night, I could hear it running but the radiators throughout the house were all cold, not warm like usual after the system is started.

A few years back I had to replace the damper & relay & things were working good.

I didn't bleed the radiators before I started the system up this year & I don't enough to diagnose the problem.

I'm living on a pretty low budget and need help figuring this out.  I'd certainly appreciate any ideas you'd have helping lead me to some answers.



  • mikeapolis
    mikeapolis Member Posts: 46
    I'd start by seeing how much water you have in the boiler. Hot water or steam? If you could take some pictures of the pressure/temp gauge that'd be great.
  • Jamie Hall
    Jamie Hall Member Posts: 19,156
    Well, for starters, is this a hot water system or a steam system? Possible reasons for the radiators not heating are very different between the two.

    Also, I presume that the boiler is, actually, firing? You've gone to look and see and it has a good flame? Hearing isn't necessarily helpful, as there are often big blowers which are what you actually hear.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Robert_25
    Robert_25 Member Posts: 410
    If the boiler comes up to temperature as expected, you have a circulation problem.  The system may be air bound, or the circulator may be stuck.