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One radiator won't come on

Mark Eatherton
Mark Eatherton Member Posts: 5,853
18 to 20 PSI of water pressure in your system, unless you are looking for the spouting waterfall effect and puddles at every radiator :-)

Try this. Take the air vent completely off the dead radiator. Feel any air coming out? Is it panting like a dog?

If there is air coming out, and eventually steam, you need a new vent.

If its panting like a dog, the steam is collapsing before it gets up there. Could be due to a lack of insulation, or a lack of BTU's... Try shutting off other radiators. If you get steam, your boiler could be undersized. Now is a good time to consider installing non electric TRV's on the air vents to spread the BTU's out to those areas that need it. I have used this methodology to correct boiler under-sizing issues in the past.

It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.


  • Kevin Blair
    Kevin Blair Member Posts: 62
    one radiator won't come on

    The background:

    This is a two flat with a finished attic. There are three radiators total in the attic.

    The lower apartment radiators all work fine and this lower apartment controls one of the attic radiators. This attic radiator comes on and heats fine.

    All radiators in the upper apartment come on and this apartment controls 2 radiators in the attic. One of the two radiators controlled by this apartment comes on and heats fine, but the other radiator doesn't come on.

    This is the only radiator in the house that isn't working.

    Boilers work fine and were cleaned this year.

    All air vents in all radiators are new.

    This radiator worked fine last year.

    I have disconnected the radiator and using an air compressor, blown air through it. Air travels through it fine. I put in a brand new air vent just in case the one that I put in last year had somehow gone bad.

    The valve appears fine and I cannot see anything obstructing the pipe.

    I am out of ideas! Any thoughts??
  • Maynard
    Maynard Member Posts: 74
    Boiler Pressure

    Make Sure No Valves Are Closed At Radiator. You Might need To Raise Water Pressure In Boiler To 18-20 Lbs To Get The Correct Amount Of Water At Radiator To Heat.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    What if..

    it's a STEAM boiler....

    To quote the original poster, "All radiators have new air vents"

    Can't say as I've seen a HOT WATER heating system with air vents on each radiator.

    Is it steam or is it hot water??

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Kevin Blair
    Kevin Blair Member Posts: 62
    One pipe steam

    Ooops, I thought I had included all of the important information, but I forgot to mention it is a one-pipe steam system for each apartment. There are separate boilers, both are fairly new and were cleaned this year.
  • Maynard
    Maynard Member Posts: 74

    Oil Or Gas?
  • missafossa
    missafossa Member Posts: 3

    one more thing to consider is do you have a diminished input? dirty nozzle or gas burners. i know you said you had it cleaned. or, can you raise the firing rate slightly.
    has the boiler been installed in the last few years. has it ever been skimmed? are the main vents working. you can also double up on the vents if need be. or as previously posted, may be just a bad vent.
  • Kevin Blair
    Kevin Blair Member Posts: 62
    nothing so far

    I turned the heat up in both apartments and the two attic radiators that work heated up quickly and well. In fact, the two rooms they heat got too hot to be comfortable.

    So, it appears that the boilers can deliver steam w/o problem to these areas of the house.

    I pulled the brand new air vent and let the radiator sit for about 5 minutes; nothing happened. No sounds, no sign of heat.

    It behaves more like the valve is stuck closed, but I have already pulled the radiator (during a fairly warm day last week, while the system was off) and I can see that the valve is open and I cannot see any sign that the pipe is in any obstructed.

    If I pull the radiator while the system in turned on, I may get some information. However, I don't know if it safe or wise to pull the radiator while steam is traveling through the pipes?

    BTW, all of the main vents were replaced last fall. When we first bought this house I had no clue about one-pipe steam heat. After living with hammering, no heat in many rooms, phone calls to heating repair companies who had no idea what a one-pipe steam system was all about, I found this site and eventually figured out that we needed to get the boilers properly cleaned (done last November); insulate a lot of new piping that had been installed some years ago; and replaced all of the vents throughout the entire systems for both apartments. After that was done everything ran perfectly.

    This fall I started to renovate the attic space: a bathroom, two bedrooms and hallway/sitting area. It looks like they stopped using the attic as living space 50-75 years ago. Insulation, new electric, new dry wall (still taping and plastering that), new floors to come (tile in the bath, laminate in the other areas, skylights this next summer and soon it will be done.

    This radiator is the only glitch/mystery so far.

This discussion has been closed.