One zone not working

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txiko

Member
Dec 29, 2007
62
metrowest ma
Hi:
I'm having a problem with one of the zones in my house system.
I have replaced the T-stat and the head zone valve and the boiler (oil) is not starting.
Any suggestion on what the problem can be? I didn't run that zone for a while since we have a pellet stove.
Thanks in advance
 
txiko said:
Hi:
I'm having a problem with one of the zones in my house system.
I have replaced the T-stat and the head zone valve and the boiler (oil) is not starting.
Any suggestion on what the problem can be? I didn't run that zone for a while since we have a pellet stove.
Thanks in advance
Click to expand...


Most zone valves have a lever to manually lock them open. Try that and see if you have flow going out. It should warm quickly when you lock the valve open. Make sure the pump is running, when you lock the valve open. If the valve has an end switch, on some brands it makes in manual mode, others not.

If no flow, air lock, possible a frozen line?
 
If the boiler isn't starting, I'd call that a system problem, not a zone problem.

Think you need to clarify a bit. What happens when other zones call for heat?

Do as Bob suggested for starters.

I went through a zone problem at the parents place a few days before Christmas. They got up in the morning, after a -20c something night, and their living room zone wasn't working. Coincidentally, I went thru the same thing the day before at my place - one of my zones got airlocked for some reason, and I had to purge it. So I thought that's what was their problem too as it's happened to them before also. Spent an hour trying to find the problem before I gave up & called the heating guy. He was tied up, but asked if we were sure there wasn't a pipe froze. Well, they've been living in that place for 50+ years with no frozen anything at all before. So we said pretty sure not. But after he hung up & some second thought, came to find out a seldom used closet entry way outside door hadn't been shut tight for not sure how long, at the same time the inside door was shut, on the same night of prevailing winds blowing from a direction they don't very often - so the small 2' rad inside the entry was in fact frozen. Never happened in 50+ years. Anyway, 5 minutes with the hair dryer & problem solved - so don't rule out a frozen pipe even if you do think no way.
 
I will look into the airlock or frozen pipe in the morning.
What I did so far, besides the changing of the head.
When I start to purge the system the water didn't run out till I force the city water at the pressure reduce valve, after that the water was running ok, at least that is what I think. Don't you think, that because I didn't use it for a while the valve can be clogged? I'm not taking out the frozen pipe possibility.
Thanks
 
Highly doubt a 'clogged' valve. There shouldn't be anything in the system that would 'clog' a valve. It might be possible that it might stick shut from a long period of disuse.

You're missing some basics or missed answering some points from above.

What happens when you manually open the valve?

And what do you mean by the boiler not starting?

Is the circ pump running?

What happens when a thermostat is turned up to call for heat in another zone?

You need to be very careful which way you send the water when you hook up to high pressure from your city water. And also be very careful how much city water feed you send into your system - city water can be under very high pressure, you could do some damage. Better to isolate just that one zone and send water through just that, but you have to have shut off valves & drain points in the right spots to do that. In my experience, 9 times out of 10 when it appears there's something wrong with a zone valve, there isn't. 8 times it'll be an air lock, 1 it will be a frozen pipe. In the case of my parents place, the pipe was hot before the zone valve & cold after it - so it sure looked from that like it was the valve not opening. But it wasn't. The frozen blockage was over 50' downstream from that valve, and the hot side was being warmed by convection coming the other way from where another zone T'd off. Their system didn't have valves & drains in exactly the right places, so when I thought I was forcing water though, it was actually going all the way around the zone backwards to where the drain was.
 
maple1 said:
Highly doubt a 'clogged' valve. There shouldn't be anything in the system that would 'clog' a valve. It might be possible that it might stick shut from a long period of disuse.

You're missing some basics or missed answering some points from above.

What happens when you manually open the valve?

And what do you mean by the boiler not starting?

Is the circ pump running?

What happens when a thermostat is turned up to call for heat in another zone?

You need to be very careful which way you send the water when you hook up to high pressure from your city water. And also be very careful how much city water feed you send into your system - city water can be under very high pressure, you could do some damage. Better to isolate just that one zone and send water through just that, but you have to have shut off valves & drain points in the right spots to do that. In my experience, 9 times out of 10 when it appears there's something wrong with a zone valve, there isn't. 8 times it'll be an air lock, 1 it will be a frozen pipe. In the case of my parents place, the pipe was hot before the zone valve & cold after it - so it sure looked from that like it was the valve not opening. But it wasn't. The frozen blockage was over 50' downstream from that valve, and the hot side was being warmed by convection coming the other way from where another zone T'd off. Their system didn't have valves & drains in exactly the right places, so when I thought I was forcing water though, it was actually going all the way around the zone backwards to where the drain was.
Click to expand...

When I open manually the valve I can hear the water running but the boiler does not start. What I mean with "the boiler does not start" is that stays quiet, it does nothing.
The circulator pump is not running
When I use another T-stat everything works, boiler runs, pump runs and I have heat in that zone.
Hopefully, I responded all the questions.
Maple 1 is there a way to check if the valve is stick shut?
Thanks for your help and sorry if I'm bothering
 
It sounds to me like you have a bad end switch in the zone valve. I don't know exactly what kind of zone valve you have though, and if 'head zone valve' was replaced, that should have fixed it.

I have Honeywell zone valves, and the end switches in those sometimes need replacing. The last time one went bad, I didn't bother replacing it - it's an upstairs zone, and circulates OK by convection.

Although, that might not be your problem either, if manually opening the valve seems to be letting water flow, but turning up the thermostat for that zone does not. Is that the case? Manually opening the valve should also start the pump, if the end switch is OK - does that happen? Again, that's without knowing what kind of ZV you have, or exactly how your system is controlled.

So, if you turn up that thermostat - does the valve itself open? You should be able to tell by turning it up, then seeing what it feels like if you then try to manually open it. Mine manually opens by a lever - if it's already open, the lever is loose & floppy in its entire travel since the valve is already open.
 
Last edited:
txiko said:
When I open manually the valve I can hear the water running but the boiler does not start. What I mean with "the boiler does not start" is that stays quiet, it does nothing.
The circulator pump is not running
When I use another T-stat everything works, boiler runs, pump runs and I have heat in that zone.
Hopefully, I responded all the questions.
Maple 1 is there a way to check if the valve is stick shut?
Thanks for your help and sorry if I'm bothering
Click to expand...


Got a picture of the rouge zone valve?. It could be simply that the end switch is, missing, has a bad connection, or a faulty switch. Knowing the brand and model of the valve would help determine what to check next.
 
Remove the thermostat from the wall, disconnect the wires and clip them together then check to see if the circulator starts which should also trigger the boiler if the temperature is below the setpoint. If that doesn't work the problem is in your zone control. Could be something as simple as a disconnected wire or worse, a blown component. You should be able to tell which control to inspect by tracing the thermostat wire. Check to confirm that the thermostat wire has continuity all the way to the control by clipping the TT terminals together at the control.
 
You could also check the wires at the zone valve for voltage when the stat is turned up. That might be hard or easy to do - mine are wire nutted right outside the valve, so pretty easy. Make sure you check the power feed wires, and not the end switch wires. Should be 24v AC going to the ZV. To check the end switch side, you can disconnect those wires from the ZV, and cross them. That should start the circ pump.

But be very careful in doing any of that, if you cross the wrong things you might do damage. We still don't know what kind of control setup you have there.
 
Ok, it is sad to say but Maple 1 was right, after following all the suggestions from everybody one pipe was frozen. The pipes are without insulation and again the outside walls.
I was so lucky than when it burst I was right there, no damage just a little bit of the ACT and a little bit of water. All done and clean.
I have to check the basement also, for the just in case.
Thank you very much for all the help
 
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