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CH rads hot when they shouldn't be

Discuss CH rads hot when they shouldn't be in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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Sah911

Hello, I am trying to diagnose the cause of a weird issue.

CH system in 5 year old house, main symptoms high heatng bills and radiators on "all the time"

most controls are drayton TA5 rads, LPSi241 prog timeswitch, ZA05 motorised actuator on the CH side not sure what the model of the HW actuator is but it isnt drayton ( has a red gear wheel rather than the black lever that draytons have )

My suspicion is that the CH actuator is either not fully closing and that hot water is leaking back through this valve when the HW system is active. The motor powers up when CH demand and the spring appears to return the actuator to closed. However this answer doesnt explain late night hot radiators when both HW and CH are in stnadby.

I have verified that the programed settings of CH and HW are ok and that there should be no call for HW or CH I have also observed the gas coming on during off cycle although only for small bursts giving what appears to be top up heat to combat circulating losses.

The CH pump is not running during the so called CH off rad hot period, nor is it running when HW only is selected on the over ride at the time switch.

At this stage any and all comments and suggestions short of start replacing everything until the issue dissapears are welcome. Things I could usefully hear about are how to set and check that the CH actuator valve is working and shutting of for example what the range of opening ought to be on a ZA05 it appears to be giving about 30degrees of movement from closed A to open B positions.

Thanks guys ..

Steve
 
try turning CH off for the 3-4 hours with only HW on, and feel the pipe after the CH motorised valve, if its hot then the valve is passing and will need replaced, if not then you have ruled out the motorised valve.
 
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