thermostat question

givememoney

Recently had new combi boiler installed with ESI thermostat controlling the system.

I find when the boiler reaches the desired temperature it can take quite awhile before it shuts off and by the same token when the temperature drops, it can take a long time before the boiler kicks in.

Is this normal? 

Mark_d

Firstly the thermostat measures the temperature of the room.  It can take a while for the room the heat up even after the boiler has reached it target temperature.

Secondly, when you set the thermostat to 22, it might switch the boiler on if you're less than 21 and switch off at 23.  If it didn't do this then the boiler would be constantly switching on and off.

It is normal for the thermostat to keep the temperature within a range as opposed to keeping the temperature at the precise temperature you set.

FreeBear

Mark_d said:

Firstly the thermostat measures the temperature of the room.  It can take a while for the room the heat up even after the boiler has reached it target temperature.

Secondly, when you set the thermostat to 22, it might switch the boiler on if you're less than 21 and switch off at 23.  If it didn't do this then the boiler would be constantly switching on and off.

It is normal for the thermostat to keep the temperature within a range as opposed to keeping the temperature at the precise temperature you set.

With a smarter thermostat that can communicate with a boiler, it can instruct the boiler to reduce the output as the desired temperature is reached. Virtually all modern gas boilers can do this, but it does need the right sort of thermostat.

My boiler takes 10-15 minutes to get up to working temperature, and then I'm looking at a room temperature rise of around 1°C per hour - This can be made to work faster if the maximum flow temperature is increased, but it severely impacts on fuel efficiency. When I had a new boiler, I took the opportunity to fit larger radiators to maximise performance with lower flow temperatures.

givememoney

I wonder if the thermostat is faulty, it is new. Tonight for instance we have now set the stat at 19.5 as we really want 20 so when it doesn't switch off as expected at 19.5 and goes onto 20 it's what we want.  I was starting to feel a bit chilly tonight and the ambient temperature was indicating 19 so it had dropped 0.5. It stayed at 19 without the boiler kicking in for nearly an hour. 

Is this right that it takes that amount of time to switch the boiler on when the temperature has dropped along with it not switching off for ages when it has reached and past the desired temperature.

QrizB

givememoney said:

Is this right that it takes that amount of time to switch the boiler on when the temperature has dropped along with it not switching off for ages when it has reached and past the desired temperature.

There are two separate factors here; how quickly does your home cool down, and how wide is the hysteresis band on your thermostat?

It sounds like your stat has a band 1C wide, so it only shuts of when it reads 0.5C above the setpoint and only restarts when you're 0.5 below. It also seems that your house cools slowly (which is a good thing) as it takes a couple of hours to cool by that 1C.

This all sounds quite normal to me.

givememoney

Thanks for this, sort of understand what you are saying I'll leave it be.

QrizB

givememoney said:

Thanks for this, sort of understand what you are saying I'll leave it be.

For the house you've got, which heats and cools slowly, you might benefit from a thermostat with a narrower hysteresis band than 1C. Is yours adjustable at all?

givememoney

I have no idea. The model ESRTP4RF make is ESi.

QrizB

givememoney said:

I have no idea. The model ESRTP4RF make is ESi.

The installer instructions are here:
https://support.esicontrols.co.uk/wp-content/uploads/2022/05/esrtp4rf-_installation-instructions_web.pdf
See page 14 of the boolket (page 8 of the pdf) for how to adjust the "swing", although I suspect yours might already be set to 0.5 (the lowest number).

kassy64

Have a look through the instructions to see if the 'swing' can be narrowed down. Ours (Alpha) can be set to come on and off at 0.1c above or below target temperature. I have it set at 0.3c above and 0.3c below and set target at 19.5c, so in theory temp is always between 19.2c and 19.8c (in theory).

givememoney

QrizB said:

givememoney said:

I have no idea. The model ESRTP4RF make is ESi.

The installer instructions are here:
https://support.esicontrols.co.uk/wp-content/uploads/2022/05/esrtp4rf-_installation-instructions_web.pdf
See page 14 of the boolket (page 8 of the pdf) for how to adjust the "swing", although I suspect yours might already be set to 0.5 (the lowest number).

Well I've looked at the manual and as you say 0.5 is the lowest setting so we'll have to go with that. Of course we can turn it up or down manually should we want to. Thank you for your advice I had no idea to be frank.