Need help determining bad zone valve or thermostat

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Old 04-07-18, 09:15 AM
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Exclamation Need help determining bad zone valve or thermostat

Of course, as soon as I went away on a trip, there was a heating issue at home. It would not turn off.

We have gas fired hot water with 3 zones: kitchen, bedrooms, basement. Since we're remodeling, the kitchen has no thermostat so the corresponding zone valve has the mechanical override enabled for that zone to be driven by either of the other two.

My wife noticed it getting way to hot in the kitchen zone so (over the phone) I told her to lower the two thermostats. It didn't stop the heat. I told her how to remove the T-stat from the base on the bedroom zone and it didn't stop the heat. She had to shut the system off from the master electrical cut-off.

Now that I'm home I know it's the bedroom zone for sure, but don't know if it's the valve or the T-stat. Turning down the T-stat does nothing nor does removing it from the wall plate. The system still runs with the basement T-stat turned way down. Also, the bedroom zone valve stays open. I even disconnected the white wire from the zone valve and the valve stays open.So is it the thermostat or the zone valve? Why won't the zone valve close and why does the system not want to shut off? How do I troubleshoot?

To be clear, the pump and boiler will not stop running unless I use the master electrical switch.

Thanks guys!
 
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Old 04-07-18, 10:20 AM
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Trouble shooting zone valve

Before I go through the steps it would help to know what zone valve you have .A picture would be even better .
 
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Old 04-07-18, 10:23 AM
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Could be the valve or control board. At the control board put your voltmeter on the zone valve wires. Let us know. Post a pic of the control board.
 
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Old 04-07-18, 10:34 AM
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Skaggsje, unless this is a newer or HE boiler there probably is no "control board'', just a "TT" connection to the boiler relay and the relays very rarely go bad. My guess would be a zone valve failed in the open position causing the end switch to constantly call for heat.
 
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Old 04-07-18, 11:35 AM
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I see no control board. What exactly should I be testing for?
FYI - I pulled the R V&W wires on the motor to troubleshoot.
 
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Old 04-07-18, 11:54 AM
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@poorplmbr If you're correct about failing in the open position, you don't mean the water portion of the valve, correct?

I know the motor is replaceable alone, so would that do it w/o draining the whole system for a valve replacement?
 
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Old 04-07-18, 12:45 PM
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If you have disconnected the yellow wires that come from the valve from the red/white wires that go to the transformer and thermostat, and the manual lever still moves freely, the valve is stuck open and the end switch is sending a signal to the boiler. If you disconnect the red wires from that zone valve the boiler will shut. Those come from the zone valve end switch. You are best off replacing the entire power head assembly instead of just the motor. If you look closely you will see two screws diagonally apart from each other in the zone valve housing, those will allow you to remove the entire head without having to drain anything at all. Probably going to be easier to get an entire zone valve and just strip out the head to change. Bring the cover to a plumbing supply or even the big box stores like Depot or Lowe's, they should have it there.
 
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Old 04-07-18, 12:50 PM
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Thanks poorplmbr.

I pulled the motor off and powered it with 24V and it does rotate.

Curious why not the motor alone? Is it because of a possible faulty end switch or gear issue?
 
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Old 04-07-18, 09:37 PM
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Check into the motor operation a little further. When power is applied.... the gear drive opens the valve and winds a spring. When the power is removed.... the spring closes the valve.
 
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Old 04-08-18, 12:37 PM
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Often brass teeth wear midway on quarter round gear and it does not fully open activating switch.

Put 24 VAC on motor and watch to see if it activates switch.

Whole valve does not have to be replaced, only the "activator motor and valve assembly". On new generation valves it can be removed without draining the zone.

https://customer.honeywell.com/resou.../95C-10655.pdf

For older valves there is an adapter plate kit that allow motor assembly to removed without draining zone. Picture in link below shows the items:

https://www.google.com/search?q=hone...hrome&ie=UTF-8
 
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Old 04-15-18, 10:22 AM
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@poorplmbr @PJmax @doughess - thank you for the great advice!

Fixed and working. I replaced the entire electrical head assembly and we're back in business.
 
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Old 04-15-18, 10:43 AM
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Good job. Just in time for our little "cold snap".
 
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