1 zone heat goes crazy

docjone5

I have a 6 zone hot water heat setup with a lochinvar knight boiler using Grundfos pumps.
I have 1 zone that no matter what I do the heat goes to 75 degrees. I set the thermo to 67, still goes to 75. I changed batteries in thermo and switched thermostats with other zones with same results.
I changed out the check valve in the Grundfos for that zone and still no luck.
Any ideas?

Brewbeer

Is their a valve on that zone you can close to see what happens?

docjone5

Hi, there is a valve before and after the Grundfos pump. I could close them.

bmwpowere36m3

Close them and see what happens… just don't leave them closed too long. As in don't keep them closed when that room/zone calls for heat as the circulator will be dead-headed.

Big Ed_4

Shut down the thermostat and see if the supply or return leading up stay warm . If so add another flow check

docjone5

I closed the valves before and after the Grundfos and the temp in that zone went down. Not sure what dead headed is...I thought that was my brother who loved the Grateful Dead!

Brewbeer

Sounds like one or more of the other zones is inducing flow in the overheating zone.

docjone5

When I turn off the thermostat the temp will eventually come down. So is it safe to guess for some reason when everything is on the hot water just flows through that particular zone regardless of what the thermostat is set at?

bmwpowere36m3

docjone5 said:

When I turn off the thermostat the temp will eventually come down. So is it safe to guess for some reason when everything is on the hot water just flows through that particular zone regardless of what the thermostat is set at?

Does the temp come down at the same rate, whether the thermostat is off OR the pump closed. Or does it drop much faster when the valves are closed?

Sounds like there's flow in the loop regardless of whether the thermostat (an thus circ) are ON. It's possible the IFC is bad or stuck in the circ, but depending on your piping you might be getting "ghost" flow on the other side. Are the circs on the return or supply side?

unclejohn

Post some pictures of the piping if you can. Get some shots that show all the pumps if you can.

docjone5

Here is a picture of the pump setup

docjone5

Also when the thermostat is turned off the temp comes down slower than when the valves before and after the pump is shut off

4Johnpipe

You have ghosts...as in flow. I would venture a guess that the returns may actually be hotter then the supply when this condition occurs...