Honeywell MZV Zone Valve stuck in open position

jldets

I just moved into a home with zoned radiator heating. It uses MZV Series PowerTrack valve operators (like this one: https://inspectapedia.com/heat/Honeywell-MZV-Zone-Valve-Manual.pdf). One of the valve operators sticks in the open position. Does anyone know what the problem could be, and if it's possible to fix it without replacing the valve operator?

If I remove the valve operator, it goes to the closed position. When I install it, I turn the brass nut until the pointer is centered over the dot and the valve remains closed. Then, when the thermostat turns on, the valve correctly opens. However, when the thermostat turns back off, the valve stays in the open position and will not close again.

Here's what I've done to diagnose the problem so far:

* I am fairly certain it is not the valve itself. I installed an operator from a different zone onto the valve. When I turn the thermostat on/off, the valve opens and closes correctly, so I don't think it's the piston in the valve that's sticking.
* I verified that I see 24V at both the red and yellow wires when the thermostat calls for heat, and that they turn off when the thermostat is off.
* I tried to put some lubricant (WD40) around the plunger, which did not make any difference.
* I thought about replacing the valve operator. Unfortunately, they are discontinued, and I cannot find a replacement anywhere online, including on ebay and craigslist.

Any help would be very greatly appreciated!

hot_rod

It’s a rack and pinion type drive and I think they drive off the end sometimes.  They were sold as an Uponor brand also, look for that version. I have seen the green Uponor brand ones online.

jldets

That's perfect. The Uponor one looks the same except the labeling, and I see it available on ebay. Thank you!

For my understanding, I am still struggling to figure out how the operator failed. I actually have two of them that failed the same way. It looks like it closes passively - two springs pull it closed when there is no power. When the motor is powered, the operator opens by turning against the springs. So, why would it open ok when it is powered, but fail to close when the power turns off? Just a curiosity at this point, since I think I need to replace the valve operator either way.

jldets

Actually, I spoke too soon. The green Uponor one doesn't look like it's sold anymore on ebay either. Do you think this one, that's supposed to be the replacement for it, might still fit?

https://www.uponor.com/en-ca/products/controls/four-wire-thermal-actuators

EdTheHeaterMan

jldets said:

Actually, I spoke too soon. The green Uponor one doesn't look like it's sold anymore on ebay either. Do you think this one, that's supposed to be the replacement for it, might still fit?

https://www.uponor.com/en-ca/products/controls/four-wire-thermal-actuators

YES!
According to SupplyHouse.com this is the replacement for your actuator.https://www.supplyhouse.com/Uponor-Wirsbo-A3023522-Thermal-Actuator-Four-Wire
https://youtu.be/9rEIFUy2qc8
To see if the adaptors that come with the part will fit your valve, Ask Supplyhouse.com

jldets

Thank you - I will give it a try.

hot_rod

check with Uponor to see if they offer the conversion adapter to go to a thermal actuator
Usually  if the pin in the valve body gets sticky it takes out the actuator, the same happens with those “helmet head” thermal actuators

Might be time to suspect the valve assembly, replace that part with one that matches newer actuators

Im not a huge fan of those plastic adapter kits, another weak point and they need to be set up correctly or the valve may not open or close completely 

Those gear type actuators were designed by Sparco, became Honeywell/ Sparco

OEM to Wirsbo and a few other brands, Embassy, maybe early Heatway manifolds

Alan (California Radiant) Forbes

I just replaced a bunch of the older actuators on the old manifolds and needed this adapter ring:
https://www.supplyhouse.com/Uponor-Wirsbo-A3019900-Spacer-Ring-VA33-for-Thermal-Actuators

Edit: Oh, sorry. Maybe you don't have the Wirsbo manifold?

wstockman

Thanks to both of you for posting this, it worked for me. I have a Boiler with the Honeywell MZV525e zone valve which are discontinued. When it failed, I replaced this zone valve with the Uponor A3023522 thermal actuator. The only question I had was how to connect the wires. There were 2 yellow, 2 red. I cut the wires from the MZV525e and just wirenutted yellow to yellow, red to red. I didnt know if it matter which yellow to which yellow and which red to which red. I dont know if i got lucky but i just wirenutted them together and it seemed to work. The Uponor valve seemed to take a long time to work, but after about 30 mins it kicked in and works fine now. It's a workable solution for anyone that does not want to cut pipes to replace the MZV525e with the next generation Honeywell valve, V8043E1145.