Help with programming a DT90E Honeywell Thermostat

11 Mar 2015
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United Kingdom
I installed a Honeywell DT90E digital room thermostat and all is working and controlling the room temperature but when the thermostat calls for heating the boiler only cuts in for about a minute and then the stat cuts out the boiler.

The stat is positioned in the hall away from the rad and there is no TVR fitted to this radiator.

Is there a setting in the programme that will allow the boiler to remain 'on' longer until the room temperature reaches the set point?
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The stat is designed to work like this. If the boiler was kept running until the set point was reached, the boiler would go off but the room temperature would continue to rise.

The stat is programmed to keep the boiler on until the room temperature is 1.5C below the set temperature. It then reduces the amount of time the boiler runs as the temperature nears the set point. This prevents overshoot.

I would guess that you have only had the stat running for a few days. It takes a week or so to learn the characteristics of your house - how quickly it heats up and cools down. When the stat has learnt this you should find that it will go for a long time between 'on' periods.

If the problem continues, it suggests that your house needs the insulation improved.
Thanks for the reply, yes only just installed it and room temperature stated is 18 degrees. If I manually set the target temperature to 18.5 degrees, I hear the heating system kick in and the rads start getting warm and continues until temperature is reached and over runs slightly.
My problem is that my controller timer of the system is not set to come on until later in the day meaning the heating system will be on all day or until that temperature is reached. This is more of a problem if it comes on during the night when the room temperature will be lower and I do not need the heating system on.
I am struggling why it turns the system on when the timer says it should be off regardless what temperature is set to.?
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