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Rick Ridley
Rick Ridley, UK Heating Engineer
Category: UK Plumbing
Satisfied Customers: 1561
Experience:  30 Years on the tools, now retired, Ex CORGI
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Worcester Greenstar Ri with a Hot water cylinder water (both

Customer Question

Worcester Greenstar Ri with a Hot water cylinder for hot water (both probably fitted 2008) but had an up to date Gas Safe/servicing cert for Apr 2015 which is when we moved into this house.
I have the CH on from 0630-0930 and again from 1500-2100 with the HW coming on DURING THE CH RUN for an hour in the morning 0730-0830 and evening 1700-1800.
CH works fine no problem but Radiators go cool during the HW run and all the heat appears to be going ONLY to the HW. I think it should go to both but not the end of the world if it left the boiler running and switched back to the CH radiators when the HW hour has finished BUT IT DOESN’T.The green light goes out, the pump stops (I think) and the boiler stops its “burn” but the blue light stays on – this happens every time the the HW goes off after being on for an hour or so in the morning and in the evening and also whenever I select “Advance” for the heating and/or “Boost” for the hot water.(which I have done to “test” the system??)
HW comes on and valve moves towards boiler and it heats the water in the tank fine but when the HW period ends, it stops the boiler from carrying on with the CH settings.
The thermostat is on and is still calling for heat throughout.
Baffled.....................
Submitted: 10 months ago.
Category: UK Plumbing
Expert:  Andrew Smith replied 10 months ago.

Are you able to check the lver position on the motorised valve for HW only, ch only and both?

When the hot water is satisfied the 3 port valve should then get power from the HW off position on the cylinder thermostat or the clock - are you able to check this if I send a wiring diagram?

Customer: replied 10 months ago.
No Andrew, sorry, but that is a bit beyond my capabilities. The main concern is that once the HW period (currently set for 1 hour in the morning and 1 hour in the evening - only want HW for washing up etc, once the period is over, instead of the boiler continuing to heat the rads, it stops the burn and the green light is out but the blue one is lit - not flashing. Shouldn't it not "turn off" the boiler regardless ie switch back to rads which it does but the boiler does not run then ie the green light is out.
Expert:  Andrew Smith replied 10 months ago.

Unless the relay is faulty in the motorised valve head and is sticking, keeping the boiler on but diverting the water still to the hot water, hence no heating

Customer: replied 10 months ago.
What happens is that when the cylinder temperature is reached and the cylinder thermostat passes the info to the controller to switch off the supply to the heating OR when the period set for HW expires (whichever comes first) then the motorised valve closes to the hotwater, returns to the normal running position as though it was going back to CH and the radiators BUT THE BOILER SWITCHES OFF ie the green light goes out, the boiler ceases burning and the pump stops pumping but the blue light stays on. Then of course, the heating system is not functioning and the radiators cool down because the boiler is not running, despite the thermostat still appearing to call for heat for the radiators. Having then waited various times from 5 minutes to 3 hours, I have to go back and re set the boiler at the boiler switch.
All works ok then until the next session of HW ending................
Sorry, but I probably can't explain things any better so looks like I will have to call out the GasSafe guy who did the last safety check just before we came into the house. Sorry your reply does not seem to help me but thanks for trying to explain. Please don't spend any more time on this, it is apparent that the system will have to be physically checked ie there is no simple explanation.
Thanks anyway for your time.

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