Troubleshoot a zone valve

Randy_9

Got a homeowner question.  My home is hot water baseboard heating with 3 zones (2 downstairs and 1 upstairs).  Lately, the upstairs zone has been on even though the thermostat is set lower than the room temp.  I am trying to troubleshoot the zone valve.  How to determine if it is the wiring, the motor or the valve itself?  If I move the lever to the manual open position, and then release it back to auto, shouldn't that close the valve?  It feels like the valve arm (the assembly that the manual/auto lever moves) is in the closed position, and yet I still have flow through the valve.  Could the valve itself be bad?  I can check the wiring, but nothing has been changed there lately.  Apologies if the parts descriptions are vague or confusing. 



Thanks for the help,



Randy 

Al Letellier_21

zone valve problem

Your very problem is why I always advocate installing a valve before the zone valve. It would be easy to just close the valve. IF the heat stopped coming with the zone valve closed...problem found. If you zone has valves on the return, close the one on the trouble zone with the stat turned down to keep the ZV closed. You didn't say what kind of valve you have, but with a Taco, taking off the head will close the valve and you shouldn't have any heat. It's not uncommon for a valve to fail, so that may be your problem.

Good luck.

Randy_9

Next step?

Al, thanks for the reply.  There is a shutoff valve before the zone valve.  When I close the shutoff, the flow stops.  But when the shutoff valve is open, the t-stat if OFF and the zone valve is in normal operation, water flows and the rooms heat up.  It seems like the heat is on when the other zones are calling for heat, which is why I think it is either a defective zone valve or bad wiring.  By the way, the ZV is a Penn V70MB-1 (they are old).

hot_rod

what brand

there are some types that need power to close. If the thermostat fails, or the power goes out they "open". Or it could have some crud lodged in the valve holding it open a bit. Or stuck in the open position.



hrb