My cylinder themostat turns of CH when HW temp is reached

8 Feb 2009
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United Kingdom
Hi can anyone help

I have a old potterton boiler with seperate HW tank and 3 way Honeywell diverter valve. The valve is new. I have also added new Siemens RWB29 programmer to my system.

The system runs fine with all programs until the hot water tank trips the HW thermostat and then it turns the CH off. As i said it's fine until the HW heats to 65 degrees. If i then remove the thermostat the central heating works fine again. If i turn the HW on the controller off the system immediately runs again. I thought that the HW thermostat would just cause the valve to divert the water to CH if the desired HW temp is reached - not turn off the CH.

any ideas would really be appreciated.

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Did whoever replaced the valve put the right one in - two position or mid-position valve?
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thanks for the replys. i will check wiring - the valve is a 3 way mid position valve. will post back when tried.


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