Zone valve was stuck closed - now what

Old 12-22-19, 11:34 AM
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Zone valve was stuck closed - now what

Hi folks,

Long time lurker, first time poster.

I suddenly lost heat in one of 3 zones in my baseboard heating system. I thought it was air, so I tried to purge it, but could not get any flow at all. My first thought was that some had manual ball valve been closed somewhere, but that was not the case. I thought some section of pipe might have frozen, but it has not even been that cold yet, so that seemed unlikely. I put space heaters in all the affected rooms and kept them at 65 overnight, with no change.

On further checking, hot water seems to reach the zone valve, but not past it. I checked and it seems to be activated open, but I pulled the manual activation lever anyway. It is an old green taco (555-102) - I will try to post a pic. Still no heat appears to get past the zone valve. I swapped out the head to be sure, but no change. I ended up removing the head and opening the valve by compressing it with a C clamp. I left it that way for a while as I tried to think of other causes and the heat started working again somewhere between an hour and 2 hours later.

Since it is nearly Xmas I did not want to take a chance on losing heat again over the holidays, when a service call will be expensive and/or impossible, so I left it clamped open. The zone still calls for heat properly, but will also get heat when any zone starts the circulator. As it is the upstairs bedrooms this is not to bad a solution.

I confirmed this as the problem since I can now purge the system.

My question is does this valve need to be cut out and a new one soldered back in, or have I loosened up an rare jam scenario and it will now function normally, if I reinstall the head?

As the weather is getting colder I am not anxious to have an extended loss of great for replacing the valve and putting the system again.
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Last edited by Dmichaud; 12-22-19 at 12:09 PM.
Old 12-22-19, 03:26 PM
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. The " guts " can be replaced without cutting the old one out, but parts are not available so you would have to buy a new valve anyway. The moter probably does not have the power to open the sticky valve
Old 12-22-19, 04:40 PM
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If the valve was stuck..... it will probably get stuck again.
The only sure way to know is to replace the entire valve.
Old 12-23-19, 05:03 AM
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Hi, could have been frozen pipe, double check the pipe run, doesn’t take much for a frozen pipe, trust me, I would swap the heads as you did and keep an eye on it and see what happens.
Old 12-23-19, 09:34 AM
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My guess is you may have had a frozen pipe or restriction somewhere. The fact that there was no tension on the manual lever is telling you that the plunger on the zone valve was down and the zone valve open. If you turn the stat down and the valve closes you will see the difference with the resistance of the lever.

Next, by pressing the plunger down with the C clamp, if it was the ZV you would have got heat immediately and no 2 hrs. later.

It does not take excessively cold weather alone to freeze a pipe. A constant cold draft on a pipe would do it if the air is cold enough. Remember, hot water freezes faster than cold. If you have any pipes in outside walls possibly exposed to drafts I would insulate if possible or if it really gets cold leave it on manual as you have now so hot water will circulate when any zone calls.

The only other alternative is antifreeze which I don't recommend unless it's a last result.

Hope this helps a little.

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