Hi,

Got a question about my CH ....pretty much as per subject ...but is
this right ?

Backgroud is new house with oil fired central heating (boiler in
integral garage with frost stat). HW tank in airing cupboard (F&E tank
in loft) with pump and 3 way valve. Thermostat and heating controls
downstairs.

If HW only is set to come on AM and PM then I've noticed that I can
hear the pump running all the time ( even when say the HW has been on
and not been used..so I presume the tank is hot and I'd expect the
boiler to not be firing ).

If I have the heating on as well then I can see the 3 way valve
correctly moving and the pump runs fine ...but when the room thermostat
is turned down the pump switches off immediately.


I thought initially it was the boiler controlling the pump after it had
finished firing to help disipate residual heat....but then with the CH
and HW on when the room thermostat is turned down it cuts the pump
immediately (in this case the HW had already been fullfilled and 3 way
valve had switched over to CH only).
This implies (to me and my logic anyway ) that the pump is not
controlled by the boiler (additionally turning the HW off (from say
timed) at the programmer stops the pump straight away too ) ....and I
don't think it is a faulty tank thermostat ?( don't think so as water
doesn't feel too hot and if I turn the tank stat down when CH/HW on the
3 way valve clicks over to HW only ( implying to me that it recognises
from the stat that the HW demand has been met) ...

....so my question is why would the pump continue to run when on HW only
and the tank is hot ?...it seems to me that all this will do is
transfer some of the heat from the HW in the tank back into the CH
pipework.

Thanks...