I have a twist on the zone valve threads--

I have a Honeywell 8043 zone valve that appears to stick open. After reading the threads here, I've already tried a few things: 1. manual override switch had no resistance, and I couldn't solve the problem by turning off the thermostat, 2. other zone valves are working fine, 3. when I turned off power to the boiler the zone valve seemed to close (felt resistance on the override). So, I figured the motor was shot. Got a new one and replaced it last night, but got the same problem-- heat won't turn off. Does this mean the valve assembly needs to be replaced? or could it be something else? Thanks for any help.

 

If the valve closes with power off but opens with power on you most likely have a wiring issue. If the problem is with the power head it'll stay open with or without power.

 

What heatpro said... wiring... OR... possible thermostat problem. Maybe even bad batteries. Thermostats have 'latching' type relays and they can stick on if there isn't enough battery power to turn them off... so first put fresh batts in the t'stat.

If that don't work, pull the stat and disconnect one of the wires. Valve should close. If it does, t'stat is bad...

If not, disconnect one of the yellow wires from the zone valve. That should absolutely work, and if you've gotten this far it means the problem is a short in the wiring between the valve and the t'stat... set some mouse traps.

 

OK-- this makes sense. I assume this isn't something I can tackle myself?? Also, how would a wiring issue just occur spontaneously? Is there some component in the thermostat itself that could fail? This seemed logical to me, except for the fact that when I turn off the thermostat the zone valve stays powered on and open.

 

I posted my last reply before I saw your tips. Will try and let you know how it works out. Thanks!

 

Ok-- here's the update after trying out the suggestions. I started from scratch. Put in new batteries in tstat. I reconnected the zone valve wires and turned on the thermostat. Turned tstat up and the zone valve opened normally. Turned tstat way down and zone valve shut off as it should. So-- I thought I must be crazy ... until turned the tstat to normal temp and then watched as the room temp reached the tstat setting and then kept going up. I took the tstat off the wall disconnected the wires--- zone valve was still open. Went down in the basement, disconnected the yellow wire from the zone valve and watched it close normally.

So... from your posts I take it that my next step is to pull and replace the tstat wire???

Thanks again--Jon

 

It sure does seem that way... that troubleshooting pretty much narrowed the culprit down to a problem with the wiring. Before you pull a new wire though, do a thorough visual inpection and make sure that it's not something visible that you could easily fix with a hunk of electrical tape. Check that all the wire nuts are in place, etc ...

Are there any 'free' wires in the thermostat wire? Sometimes there are extra conductors that you can use.

 

OK--
A question about the wiring. When the tstat wire comes down to the boiler one of the two wires goes to the zone valve, but the other goes to the boiler. In each case, the wires are joined with others from the other zone valves, as if they were wired together in parallel (sorry, but an electrician I am not). So, could an wiring issue somewhere else be affecting this zone valve?? This might be a stupid question, but I'd rather rule that out before pulling a new wire in from the 2nd floor.

Cheers--Jon

 

Let's see how to essplane this best...

There is a 24VAC source, and it's probably a transformer inside the boiler cabinet. There are two connections to this 24V source.

The zone valves have two yellow wires connected to the motor inside.

The thermostat is also of course two wires, and is very basically a 'switch'.

So, one of the connections from the transformer will go to one of the yellow wires on ALL the zone valves.

One of the connections from the transformer will go to one of the wires on ALL the thermostats.

The other thermostat wire will go to the other yellow wire on EACH zone valve.

Hope this makes sense!

 

Realized that I never posted the final answer. Turned out to be the thermostat wire, as suggested. Some critter had chewed through and caused a short. After running new wire, problem solved.

Thanks for all the help

 

Thanks for stopping back to let us know Jon... I hate's them meeces to peeces!

 

I'll second that notion NJT.
Been there had it happen, lucky no short, just "chewed" open.
Was able to get around it with a spare wire in the cable.

Peter