Problem with room thermostat .....Any help would be great

[retrosimon]

Hi!
I hope you make be able to help me with a problem with the central heating in a house that we moved into a few months ago. This problem has only just come to my attention, and I believe that it has been like this since we moved in.
The problem is that the Room Thermostat will enable water to be pumped around the radiators whatever the Programmer's setting is. This means that by turning up the Thermostat the circulating pump cuts in, even if the 'Hot Water' & 'Central Heating' are off. The Thermostat seems to react to temperature exactly as it should. I have traced the wires up to the Backplate from the Thermostat and they are connected to the section marked "Roomstat". The programmer works as it should i.e the timer controls for the boiler etc apart from this problem. I have looked around on the internet for info about this Backplate-Programmer combination but have had no success.

The Thermostat is a "Honeywell T40"
The Backplate is a "Wirerite Octopus" (which has a 'Pump-Overun')
The Programmer is a "LP241"

I do have electrical experience in the automotive trade and feel confident enough to tackle this if I could have some advice. If anyone has any ideas or information it would be very much appreciated.

Thanks

Regards.

Simon

 

[stem]

The Drayton LP241 terminal 4 is the connection for the room thermostat. This terminal only becomes live when the heating is set to on and should be the live supply to your room thermostat.

You could test this by wiring a lamp between terminal 4 and the neutral then check that the programmer does switch it on and off, if it does the programmer is OK and you should then check the wiring to the thermostat.

Never come across as Wireright Octopus, but here's the wiring for the Drayton LP241

LP241 Data Sheet

 

[WDIK]

the pumps wired off the stat via P-ve its wrong call an electrician