Honeywell T3 thermostat operation question.

[Mister Banks]

I have a Honeywell T3 programmable thermostat which has been installed for 3 weeks as a replacement for an older mechanical thermostat. I understand that the T3 is a TPI thermostat and I understand how that works but this particular thermostats operation makes no sense. In the morning the T3 calls for heat, the boiler fires up and the house warms up fine, the T3 goes into TPI mode when it detects its getting close to the required temperature so all good.

In the late afternoon the house is normally already at the required temperature so the boiler doesn't fire up however as the house cools the T3 still thinks the temperature is OK so we adjust the target temperature from 22 to 23 resulting in the boiler firing up but only for 1 minute or so before we hear the T3 click and the boiler goes off. The T3 does this boiler on, boiler off cycle every 10 mins or so but never gives the boiler the chance to heat the water as the radiators are still cold. This seems to me to be a waste of energy and doesn't result in the house warming up. What am I missing?

 

[Mister Banks]

Bit of an update.......

The target temperature is 22 and the T3 states the room temp is 22 so I adjust the target temperature to 23 and the T3 then tells me the room temp is 23! If I adjust the target temp to 24 the T3 immediately tells me the room temp is 22.5! I think this thermostat could be faulty.

 

[CBW]

It could be. Those go up to 35 degrees, try setting it to approx 30, and see what happens.

 

[Mister Banks]

It could be. Those go up to 35 degrees, try setting it to approx 30, and see what happens.

Tested this today. If I set target to 26 the T3 detects the temp is 24! If I set target to 30 the T3 detects temp is still 24 but if I drop the temp to 24 the T3 says room temp is 22! Clearly this T3 has a problem so I will return it for a refund.