Pump on constantly

[saintinexile]

I was wondering if anyone could help with my ch system.The room stat has to be turned down to 5c or below to turn off the radiator circulating pump.If this isn`t done the pump is on constantly.Is the wiring incorrect?We have an oil boiler with a gravity hot water and pumped rads.
The stat on the hot water cylinder is set to 20c,i know this should be 60c but the water and rads are always very hot,so struggling to understand what difference this would make.
Thanks for any help in advance

 

[warmadmax]

by the sounds of it you have a C plan layout,

where the room stat can call the boiler and pump, and the cylinder stat call the boiler and controls a 28mm zone valve.

have you got 4 sets of pipework from the boiler, 2 in 22mm and 2 in 28mm (inch+ pipe)

can you check on the pipework between the boiler and cylinder for a zone valve (box with wire coming out of it)


if you've not got the above then you should be on a more modern Y or S plan, where the pump circulates for both the heating and hot water tank.


it may be you've got faulty thermostats that are out of calibration?

 

[saintinexile]

Thanks for reply Yes it has four sets of pipes,22mm and 28mm as you say.The only wires are the ones from the hot cylinder stat so no i don`t think there is a zone value.I think maybe it`s time for a more modern set up right enough.Do you think the hot water cylinder stat is a problem set at 20c?
Sometimes the boiler seems to be on continuously and the fuel consumption ain`t that good.

 

[warmadmax]

if there is no zone valve on the 28mm pipe, there isn't anything to stop the water thermosyphing up to the cylinder, pointless exercise having a thermostat on it!

is any of the 28mm pipe hidden?
i doubt a thermostat would have been fitted to it without any control

Pictures say a thousand words,
if you can get some images up, i'm sure the guys can help

 

[saintinexile]

No theres no 28mm hidden,it`s in the loft.The wire from the cylinder stat heads towards the boiler but disappears behind plasterboard so can`t be 100% sure where it goes.
In the summertime we put the boiler on for an hour to get hot water but we turn the room stat to zero so the pump is off.That way we get hot water but no heat in rads.Is an inherited system that seems a bit inefficient and out dated

 

[cozzmic]

Frost stat keeping pump on?

 

[saintinexile]

Pump does switch off if you turn room stat to between 0-5c but otherwise runs constantly