Hi all, would appreciate any advice on what the cause could be.
Worcester Bosch Highflow 440 (older non-CDI version), CH connected to a wireless Honeywell thermostat (BDR91 relay), works fine when it calls for heat, CH duly kicks in. However whilst the CH is on and there is a demand for DHW it doesn't override the heating and serves cold water.
Also when the heating is switched off via the thermostat and some time after the relay light goes out/clicks off, the boiler pump still continues to run and doesn't stop (even after 10 mins, I understand it usually runs for a few mins after the wireless relay has flipped off)... during the whole time the DHW still fails to deliver hot water, even when the built-in hot water tank is ready and heated.
After I turn the boiler off and on (but keep the thermostat off) it immediately serves hot water from the tank as normal, like a "reboot" temporarily fixes it.
So the boiler is ignoring the demand during CH and failing to override. Since DHW works ok when the heating is off I suspect this is not a diverter problem (unless the motor is to blame?) - could it be the PCB or maybe also a dodgy thermister?
Worcester Bosch Highflow 440 (older non-CDI version), CH connected to a wireless Honeywell thermostat (BDR91 relay), works fine when it calls for heat, CH duly kicks in. However whilst the CH is on and there is a demand for DHW it doesn't override the heating and serves cold water.
Also when the heating is switched off via the thermostat and some time after the relay light goes out/clicks off, the boiler pump still continues to run and doesn't stop (even after 10 mins, I understand it usually runs for a few mins after the wireless relay has flipped off)... during the whole time the DHW still fails to deliver hot water, even when the built-in hot water tank is ready and heated.
After I turn the boiler off and on (but keep the thermostat off) it immediately serves hot water from the tank as normal, like a "reboot" temporarily fixes it.
So the boiler is ignoring the demand during CH and failing to override. Since DHW works ok when the heating is off I suspect this is not a diverter problem (unless the motor is to blame?) - could it be the PCB or maybe also a dodgy thermister?
