Room Thermostat problems please help

[Zebsport]

Hi guys fitted a new 3 port motorised valve a few months ago, inc with it was a new room themostat. Today i fitted it as the old Honeywell one didn't look to pretty and i'm currently decorating.
The room thermostat is a Horstmann HRT2 (very cheap!!) unfortuantely the only way to keep the heating on is to have it turned up very high ie 25c plus even when i know the room is not that hot. At settings around the 15 - 20c mark it will turn the boiler on, which then turns of a few minutes later. Is it just a dodgy bi-metallic sensor? or something more serious? I've checked the wiring which i'm sure is right, it turns on and off but the temp just seems way out.
Any help would be much appreciated.

Cheers Zeb

 

[Diyisfun]

If the t/stat is switching boiler on + off & cycling, so the wiring sounds ok, then I reckon the stat is not working.

 

[echoes]

I also had a Horstmann room stat and it was rubbish. Had same problem as you described. I replaced it with a Drayton that I had spare, and this works fine.

Richard

 

[mikely]

I fitted an HRT2 and also found that it was way out on temperature. As your's, it had to be set to 25 to achieve 18. I took it apart and there appears to be an adjustment screw on the back of the metallic assembly (locked with red paint) that should adjust the set temperature - haven't tried it yet though.

 

[stevesey]

As suggested it could just be poorly calibrated. Listen for the stat clicking on and off as you turn the dial and compare the click points with a thermometer reading.