HW temperature too high

[squiff]

My system consists of a Suprima 40 gas boiler, with a timer (EP2002 - separate CH/HW switches), PRT2 room thermostat in lounge, PTT2 thermostat on HW tank (all Potterton).

I usually have the timer set for timed CH (twice a day) and constant HW.

This setup has been working correctly since I moved in (last October). However, since about 3 weeks ago the temperature of the HW has increased significantly (a good 15-20 degrees, if you can go by the reading on the thermostat).

Last week I turned the HW off at the timer, and it still appears to be heated when the CH is on. This could be normal (the timer manual mentions something about "simple systems"), but surely the HW thermostat should cut out at the set temperature (it is set to minimum)?

Could the HW thermostat be at fault?

Any advice would be greatly appreciated.

 

[oilman]

Could the HW thermostat be at fault?

Yes.


Does turning the stat up and down switch the boiler or pump on and off?

 

[AlanE]

If you have a motorised valve controling the DHW then this could be letting by even if the thermostat has instructed it to close.

Went to job yesterday with valve so stiff the spring return failed to close valve.

Alan

 

[squiff]

Thanks for the replies.

oilman, yes the pump does switch on and off when the thermostat is turned up and down.

Just a thought, could there be a bad connection between the thermostat sensor and the HW tank? There are in contact but it's possible the sensor could have been knocked. Should they be held in contact with some sort of adhesive?

Thanks,
squiff

 

[taydo]

they are normaly held on with a curtain wire or strap around the tank

 

[ollski]

Last week I turned the HW off at the timer, and it still appears to be heated when the CH is on. .

motorized valve. Which model valve is it?

 

[squiff]

The valve is made by Potterton, but there does not appear to be any model number on it.