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Noob question - 1 zone no heat for a day. Still frozen?

feetsdr Member Posts: 9
Thanks for a great forum! I just found this while having problems with our 25+ year old Slant Fin Gas fired hot water radiator system with 3 zones. Yesterday we had no heat / pilot light didn't stay lit. I cleaned the thermocouple and got the system back up and running.

But 1 of the 3 zones doesn't warm up. I checked the zone valve and it appears to be working (the slide lever has no resistance when that zone is calling for heat / does have resistance when not calling for heat).

I even removed the zone valve mechanicals to see that the stem turns / is reacting to the motor (maybe something broke between stem and motor?). But that looks good (although valve stem turns only 1/8 of a turn? Seems less of a turn than anything I know.

Anyway, from other threads here, it might be a frozen pipe? There IS a room that has unheated garage on 1 side, outside wall on another. But heat was out for a couple hours yesterday AM. That's a laundry room and we ran dryer with vent going into room to heat it / some heat goes into radiator?

Seems weird that after 1 day of the other 2 zones working, that 1 zone is still not working. Is there anything else to do other than wait? I don't see water from burst pipe. I felt some areas of that pipe under laundry room and they are cold, but not numbing cold.

Is there a way to flush that zone? could it be a blockage? (yeah, what are the odds - blockage right when we have no heat?!).

If that's the only zone calling for heat, does that hurt the circ pump when it is running but can't circ the water? (the other zones get up over 70 and might shut off, while that 1 zone is in the 60s...).


  • feetsdr
    feetsdr Member Posts: 9
    I was wondering about the extra wires in the zone valve.... that's the end switch? Even if that's bad, if the other zones are calling for heat, this zone would get heat also (since the motor DOES engage / open the valve). Bad end switch is only an issue when just that 1 zone wants heat?
  • DZoro
    DZoro Member Posts: 1,048
    Very good chance that it is frozen. Unheated garage area outside walls...… Get some heat on those pipes soon.
  • feetsdr
    feetsdr Member Posts: 9
    Embarrassed to say - there's another area - in a corner of the finished basement which has the electrical panel, etc in there up against the cinderblocks. It's boxed in like a closet. It gets cold in there and as much as I DID put insulation over the pipes in the basement, I slacked off there... maybe years ago I ran out of the foam tubing and figured it was still accessible so I'd get to it and never did.

    Worse, there's a sizable draft coming in there along the sill plate! And I had gone around the basement with the spray foam can years ago sealing gaps. again, can't believe this area is that bad.

    I put a heater in that closet, put in a 100w incadesent bulb rather than the LED and warmed up that area.

    Went out today and turned off that zone with the ball valve in case it defrosted and water started coming out.

    When we got home, I opened the ball valve. there was a teeny bit of water movement I heard. Then silence.

    Turned on the heat for that zone and the zone warmed up. Any way to be sure there's no leaks / busted pipe other than walk around and check for leaks? Since it's a finished basement, I can't see most of the radiator pipe to see if there's damage. Just have to feel around for wet carpet down there?

    But the 2 unfinished areas (that would get cold) show no water leaks.

    Any advice on x% of frozen pipes do / don't bust the pipes? Again, it's an occupied house, lost heat for a couple hours but it was very cold outside / likely blowing right on that bare pipe in the electrical closet...
  • Leon82
    Leon82 Member Posts: 684
    You can turn off the fill valve and monitor the pressure. It will drop if there is a leak.
  • feetsdr
    feetsdr Member Posts: 9
    AH!! Fill valve - I've wondered if there's an automatic process to keep water in there. Would you expect in a 25 year old system th the fill valve is something automatic or manual?

    I've feared draining some water to see if it's clear or not (surprised when I did it that it WAS very clear.). But have to be concerned that the system will run dry or cold makeup water will crack the boiler?

    I guess the system has to be running while you check the pressure? Even a slow leak will make a noticable drop? That gauge built into the front of the boiler seems small / not all that sensitive.
  • Leon82
    Leon82 Member Posts: 684
    Look for half inch copper line coming from your cold awter pipe. It will have a tag with the factory settings. 12 psi for example. If the expansion tank is good it should remain close to that