Heat to radiators in two zones while thermostats are off

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Old 09-03-18, 02:24 PM
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Heat to radiators in two zones while thermostats are off

I have a seven zone radiant heating system in our house. Recently radiators in two of the zones are warm even though the thermostats are shut off and it is 90 degrees outside.
The system hat two Taco controllers and uses WILO Star S 21F circulating pumps. I troubleshooted the thermostats and they seem to be operating correctly. Then I disconnected the thermostat wire from the Taco controller and pulled the corresponding relays. I also checked the voltage to the WILO pumps. No voltage and the pumps are not running. The copper piping past the two malfunctioning zones is very hot to the touch so I am assuming that hot water is flowing from the main feed circuit from the boiler that feeds all seven zones. The last zone is the hot water tank that is warmed by a hot water coil inside.
The only solution I can come up with is that as the hot water tank calls for heat, the hot water from the boiler leaks through the WILO pumps in zone 4 and 5 and heats the corresponding radiators by conduction.
I don't know if the WILO pumps have check valves in them, although I suppose they must as the other zones are not hot.
Any thoughts would be appreciated.
Thanks,

Bert
 
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Old 09-03-18, 02:38 PM
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Welcome to the forums.

I'm not familiar with those pumps so I looked them up and it says "installable check valve".
Do you have a pump for each zone ?
 
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Old 09-04-18, 11:29 AM
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More system information may be needed such as pictures of the boiler and system boiler piping. The one thing I would check is the position and condition of any flow control device that stops the water from flowing by gravity in the 2 zones that are heating up
 
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Old 09-04-18, 11:39 AM
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BK
There are 2 ways to stop unwanted hot water flow to heating zones.

One is by the installation of individual zone valves in each zone, and the other is by the installation of flochecks in the zones.

The flochecks can be installed on the supply lines going to each zone or incorporated into the individual pumps.

If already not installed you can get a set of pump flanges that have a check valve installed or add a flocheck to your supply line to the zone.

The flocheck is only needed if you use pumps for the zones. You do not need FC's with zone valves because when closed and not calling for heat or hot water they provide a positive shutoff to the zone.


Hope this helps a little.
 
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Old 09-10-18, 03:37 PM
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Thanks to all that responded. I had called WILO to find out if the pumps had checkvalves, but was told they did not. This really puzzled me, as Steamboy and Spott are spot on and the heat to the radiator was caused by gravity, then conduction all the way up to the second floor. Not wanting to disconnect the pumps myself, I called a plumber who was most helpful. He too was stumped, then suggested removing one of the pumps Lo and behold, he spotted a small plastic checkvalve inside the body of the flow valve that is under the pump (each pump has manual valves above and below to allow pump replacement without having to drain the whole system. This valve malfunctioned and caused the hot water to go through the pump and heat up the supply circuit all the way to the radiator. After the plumber left, I found the part on the WILO website (never thought to look at the manual shut off valve section before), called them, got a part number for the checkvalve and have ordered seven of them. I'll replace three since I found one more that was leaking through and keep the rest as spares for next time. The valves lasted 9 years, so not a bad record for a piece of flimsy plastic with a spring loaded valve.

Thanks again for the help.

BK
 
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Old 09-10-18, 08:00 PM
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Wow.... what a cluster of pumps. I'm surprised that zone valves weren't used with that many zones.
 
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