Zone Valve Stays Open - Too Much Heat

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Old 01-21-08, 11:55 AM
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Zone Valve Stays Open - Too Much Heat

I have gas fired baseboard heating with 3 zones, one each for the basement, 1 st. floor, and the 2nd.floor. They all use the same Honeywell V8043 E 1012 motorized valve. The problem is that the valve for the 1st. floor does not close when the thermostat (round Honeywell old style CT87B4024) reaches the set temperature. The first floor continues to get heat when the other zones are calling for heat because the valve is staying open.

I go down to my boiler and I have to pry the contact apart with a slim screwdriver and then the spring pulls it closed and with the round cover off the motor you see the rotary part of the motor spinning as the spring retracts the contactor. I had to do this several times yesterday morning and I even moved the switch on the room thermostat to the “Off” position thinking that this is going to open the electrical circuit to the valve motor but the valve still stays in the open position and I have to pry the contact apart as explained above.

After I left that thermostat Off for a couple of hours and then put it back into the “Heat” position it started working normally in late afternoon and all night last night and today.

I am wondering if I should just leave it alone and wait and see if this happens again? I called my local plumbing supply and they have a replacement motor available but I’m not sure that’s the problem because it appears to me that once the room thermostat opens the circuit that holds the valve open, then the spring should pull the contactor open. I’m thinking that maybe there is crud or debris in hot water lines of the system that is causing the valve to stick closed and that the contactor return spring doesn’t have the power to overcome this. Also note that these valves were installed in1989 so they have been in use a long time and so maybe I should open up the pipes and replace the entire valve.

Also one final observation is that whenever this thermostat is set on 66 degrees (top scale on this thermostat) the room temperature reaches 70 degrees (on the bottom scale).

Thanks in advance for any info you can provide.
 
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Old 01-21-08, 12:47 PM
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Just for argument's sake, put the thermostat on maximum on the zone in question Take off the cover to that zone valve and look at the 2 red and 2 yellow wires.

While the zone valve is open and letting hot water flow, unscrew the wire nut and disconnect the 2 YELLOW wires that go to the clock motor. (should be YELLOW but check first to make sure that those are the ones that go to the clock motor, the red ones should go to a micro switch)

The valve should close. Touch them together again and it should open.

Make sure that the 'finger' on the top or bottom of the zone valve moves freely in the slot (automatic position).

This is 24 volts AC and UNLESS you have a pacemaker or something, will not usually harm you, BUT do not let the wires touch anything or you MAY blow the transformer.

The valve should open and close when the wires are connected and disconnected.

BTW: When the valve FULLY opens electrically, continuity is established on the red wires by way of the micro switch and signals the unit to come on, or signals another device that the valve is calling for heat.

Keep us posted!

Charlie
 
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Old 01-21-08, 04:48 PM
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Lightbulb

I did as described and when I separated the wires (opened the circuit) the valve closed and when reconnected it opened. I did this a few times and it worked fine. I also saw where the end of the cam hits the micro switch which tells the boiler to fire up.

I figured that since the valve unit is working as it should then maybe the signal isn't getting from the thermostat to the wires that are connected to the wall plate.

So I removed the three mounting screws and disconnected the thermo from the wall plate. I took a good close look at the contacts. There where a few that had been dabbed with different colors of Magic Marker this past spring to mark where each wire went -the wall plate was removed because we where painting - and we wanted to make sure to put the wires back on the right contacts. I cleaned all the contact points first with an eraser and then with alcohol. I figure that this might have been enough to block the flow of the electrical signal from the thermo to the zone valve motor. I'll keep you posted on any developments.
 
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Old 01-21-08, 08:11 PM
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Zone Valve

It sounds like the valve is operating properly. I suspect a possible short in the thermostat wiring.
Since those thermostats use a mercury switch, it is critical they be level. An out of level stat will cause overheating.
 
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Old 01-21-08, 08:24 PM
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Keep us POSTED!

We're here to help!

Not only is it a job, it's an adventure (and an education too!).

Charlie
 
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