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...

Bump....

wrote:
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...

answered my own question.....
Seems the boiler temperature control was turned down to minimum temp
which meant the water wasn't hot enough to bring the cylinder water up
to 60C as per the tank stat. Because the boiler temp was so low there
was little heat loss across the flow and return hence the boiler
appeared not to be firing when I was checking - but the pump still ran
as the tank was still calling for heat. In fact I think the boiler was
heating the water till practically the 60C on the tank stat as the hot
water was plenty hot enough and it seemed as though the stat was
turning off.

Since turning up the boiler temp the tank stat now clicks off and the
boiler stops firing and the pump finally stops running.

wrote:
Bump....

wrote:
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...