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Vitodens 100W permanently on DHW

GB1309
GB1309 Member Posts: 1
Hi everyone. I have traced out the wiring today and believe that my boiler is permanently outputting a "1" "call" to the Cylinder stat despite not being enabled by the on board programmer. This means the tank stat permanently sees a "live" and (if cold enough) holds the valve open permanently. The system is working fine apart from this anomaly. I have the DHW side of the programmer set for 3 x half hour slots per day and I would have expected the programmer to determine when the boiler (X1 L) goes live?
My major concern is that the tank valve is being held open 24/7 and may take the motor out?
Any help or advice gratefully received.
Cheers,
Graham