Thermostat not switching off boiler

[BelfastGuy82]

The housing association put in a whole new heating system for me two days ago. (Boiler, two new thermostats to replace a single old one, new radiators and pipework)

The two thermostats are EPH CM3 models. I heated the room to 20 degrees last night and then decided to turn the thermostat down to 18 degrees. Nothing happened - thermostat light remained lit. So I turned it all the way down to 15 degrees and still nothing changed. The only way to get the thermostat / boiler to knock off was to turn the thermostat down to the bottom of the 'lockable range', which appears to be 14 degrees.

The 'Switching Differential' on this range of thermostats appears to be plus or minus 1 degree, not 6 degrees... https://www.ephcontrols.com/wp-content/uploads/2017/05/20221103_CM_-_DS_PK_Email.pdf

Not sure what is going on, and it's Saturday, so I probably won't get anyone on the phone, and certainly won't get anyone out to look at it. Hopefully it's a minor issue that I can solve myself with someone's help here.

The boiler is an Ideal Heating - Logic Combi2 - C30.

 

[Harry Bloomfield]

Not sure what is going on, and it's Saturday, so I probably won't get anyone on the phone, and certainly won't get anyone out to look at it. Hopefully it's a minor issue that I can solve myself with someone's help here.

Likely, the installer has accidentally left the 24v link in place, in the boiler. The 24v allows the boiler to ignore the controls, and just run on the boilers own stat. Best not to interfere with it at all, just turn the boiler temperature setting down to a level which provides some background heat, plus turning the boiler off at the isolator. Leave it then until Monday.