one zone stays hot when not calling for heat


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Old 02-22-21, 06:51 AM
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one zone stays hot when not calling for heat

I have a 2 zone hot water heating system with baseboard radiators. There are 2 Taco 007 circulator pumps, and no zone valves. I bought the house in August so I have no idea about past winters. I am not at all knowledgeable about heating systems and am not planning on doing any work on the system myself, but I'm trying to get some idea of what might be going on before I call someone out (again.) (Or to get an idea of whether it's cheaper to just pay for the excess heat rather than fix the problem.)

In November one circulator pump (the one for the 2nd floor zone) was leaking and a plumber replaced it. Shortly after that I noticed the 2nd floor would sometimes get too warm. It was inconsistent -- not like it was just churning out heat all the time and getting hotter and hotter -- but it always stayed warmer than the 1st floor and would usually be 5-10 degrees higher than the thermostat setting. Even when the thermostat was off, the radiators remained warm (more so in one room than the others.) I started keeping windows open upstairs.

I had the plumber come back because I thought it was related to the pump he replaced. He bled air out of the system, but that did not help, and he thought it was a thermostat issue. I replaced the thermostat. The new thermostat is working -- if I set it above the room temperature, the the pump kicks on. If I set it lower (or turn it off), the pump turns off, but the radiators remain warm and the room temperature does not drop. I've been keeping the thermostat off. The 2nd floor seems to get warmest when the 1st floor zone calls for heat, as if the hot water is "leaking" into the wrong zone. The 1st floor maintains the temperatures that it's set at but the 2nd floor is still 5-10 degrees higher. Any ideas?
 
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Old 02-22-21, 10:10 AM
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Welcome to the forums.

I had the plumber come back because I thought it was related to the pump he replaced.
It is more than likely a pump problem.
When you have pumps instead of zone valves you need to have flow check valves installed or pumps with check valves. These valves keep both zones from heating at the same time.

Ask your plumber if that pump has a check valve in it.
 
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Old 02-22-21, 01:43 PM
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It sounds like a Flocheck problem. The purpose of the Flocheck is to stop heating water going into unwanted areas when there are multiple zones using pumps instead of zone valves.

On your 2 zone pump system it takes the operation of the pump running to open the Flocheck to allow water to heat the zone. When the stat is satisfied the pump stops and the Flocheck closes so no more hot water flows through that zone. The same with all zones. The Flocheck only opens when the pump for the zone it is connected to is running.

You either have a Flocheck on your supply line to that zone or as PJ said they now have them incorporated into the circulator. If you had a pump with a check valve initially and the plumber replaced the pump that didn't have one,(they are optional) then every time the other zone called for heat the water would circulate through both zones. If you have a Flocheck on your supply line it will have some type of screw on top which is a way to manually open the valve if needed. Under normal conditions it should be turned all the way down so only the running pump will open it.

Check to see if the screw is open. It works just like a regular screw. Down is closed, up is open. If it's open turn clockwise to close it and if it's operating properly that should solve your problem. When the boiler is on from the working zone turn the problem zone's stat off and from the boiler follow and feel the problem pipe and see how hot it gets all the way to the return.

Pics would be helpful of the pump and supply lines to see what you have. Also the complete model number of the pump. See if it has an IFC which means it has a check valve or should have. They are removable.

Long but hopes this helps a little.
 
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Old 02-22-21, 02:12 PM
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Thanks all.
The pump is a Taco 007e - 2F2, which according to the info I found on it, has an IFC. I will check the supply line to see if there's also one there, but if it's incorporated into the pump then it seems like that wouldn't be the issue (unless it was removed from the pump, or is defective.) I'll post some pics.
 
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Old 02-22-21, 05:06 PM
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Both supply lines have those screw type valves on them, which I took a picture of. Both are closed.
Currently, the 2nd floor thermostat is off. 1st floor is on. Pipe temperatures are:

1st floor supply: very warm
1st floor return: ice cold
2nd floor supply: very warm
2nd floor return: slightly warm




 
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Old 02-23-21, 04:09 AM
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One thing that seems really odd about this is that although the 2nd floor has 3 rooms with radiators, one room is getting most of the heat. The radiators in this one room are always very hot.
 
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Old 02-23-21, 09:41 AM
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T,
So your 2nd floor zone seems to be the problem. From the pics and info provided it looks like you are getting what they call ghost heating which simply means when the boiler is on the hot water migrates into the pipes unless there is something there to stop it.

Those 2 valves you showed are your Flochecks for each zone that are suppose to stop the water from going where it's not wanted. That 2nd floor rad that gets hot is probably the first one on that 2nd floor loop so every time the boiler runs as the hot water migrates up the pipe it hits that rad and as it continues since there is nothing pulling it back to the boiler the water further the water travels the cooler it gets.

As far as the 1st floor stat being on but the return being cold I'm guessing that you mean it is set at a certain temp but is not calling at the time you checked.

As far as your problem goes my guess is your 2nd floor Flocheck may not be working and when the plumber saw you already had a Flocheck might have left the one with the new pump out.

Basically you are getting gravity flow of hot water through 2nd zone whenever boiler runs which should not be possible if flochecks were working, especially 2 of them.

I would call the plumber and ask him if he installed the one that came with the pump.
 
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Old 02-24-21, 12:52 PM
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Thanks spott, this definitely makes sense. I will check with the plumber about the flocheck.
 
 

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