Room temp problem

[mordzy]

Hello, I have a ongoing problem that's really annoying and no matter what I try I don't seem to be able to rectify.

I have a remeha boiler and a remeha celcia 20 thermostat in my living room which is about a meter from the radiator. I normally set the thermostat to 20-21 degrees and leave on constant rather than timer. What I tend to notice is even when the room has hit 20-21 degrees ( in some instances 25) the LCD display shows the radiator symbol and you can here the boiler fire up.

I know the room can't be exact temp as heat still radiates after boiler has stopped. What I can't understand us why it fires up again When its already past required temp. It gets really hot sometimes. So much so that I end up turning it off. With winter approaching I'm worried about the fule bill if indeed there is a fault.

I had left it on today while at work. At 16 degrees. When I came in i could here the boiler running, I pushed the info button on the thermostat and it said current room temp was 21. I don't get it

Thanks

 

[dcawkwell]

Most likely thermostat is wrong or wired in reverse like an air con unit.
It is firing to try and cool it down but is only making it hotter.

 

[mordzy]

Most likely thermostat is wrong or wired in reverse like an air con unit.
It is firing to try and cool it down but is only making it hotter.

Kind of makes sense but in a cold house if I turn it on and increase the temp dial the heating comes on, so I don't think it's hooked up wrong.

For eg, if its on 6 degrees and I up it to 20, boiler comes on and radiators get hot.

Maybe this extract from the manual helps. Seems confusing.


"Celcia 20 is an optimising timer /room thermostat with options for inside weather compensa- tion or outside weather compensation only (factory set for room compensation)
Your installer should set the control to outside weather compensation if an outside sensor is fitted NOTE: An optimiser will check inside and outside temperatures and start the heating system be- fore the set start time to ensure the required inside temperature is achieved by the start time
The control can be programmed to provide time and temperature control over the heating and hot water system to suit the specific occupancy requirements of the property (PI). It also has a built in (non adjustable) a factory default set of times (PII) which can be used (see table 2 on page 5)
Unlike some “time” controls the Celcia 20 is set to operate to comfort temperatures during occu- pancy and economy temperatures during non occupancy periods.
So in reality the heating is never switched off just sets back to a background heat level (ECO- TEMP) or one of the other pre set temperatures (TEMP-1 to TEMP-5) to minimise heat up time when heating is actually needed"

 

[dcawkwell]

Sounds like it is too complicated for it's own good.
Take it off the wall and see if a normal on/off thermostat works.

 

[D_Hailsham]

The Celcia 20 can use either room or external compensation.

Do you know if an external sensor was fitted? It will be a small box on a north or north-west wall about 8-10 foot off the ground with a cable attached.

 

[D_Hailsham]

Take it off the wall and see if a normal on/off thermostat works.

You can't just do that! The Celcia 20 is an OpenTherm device and uses different boiler terminals from a standard 230V thermostat. However, a volt-free stat would be OK.

 

[Agile]

Folks, its only a metre from the rad in the room!

Thats far too close!

Tony

 

[mordzy]

Hi all. There is a small white dongle type thing on the north external wall literally behind the boiler. Pressing the info button on the thermostat I can get a reading for the current room temp (23) the external temp (10) and the temp I have set (16)

House was roasting when I got in from work , even though I set to the temp to 16. It Just doesn't make sense. Thermostat is probably too is close to rad for accurate room temp throughout but doesn't explain why it's at 23 when set to 16 if anything the house should bee cooler due to thermostat turning heating off as too close to rad

 

[D_Hailsham]

Hi all. There is a small white dongle type thing on the north external wall literally behind the boiler. Pressing the info button on the thermostat I can get a reading for the current room temp (23) the external temp (10) and the temp I have set (16)

The dongle is the temperature sensor, so the Celcia 20 should be set to weather compensation.

Celcia 20 Installation Manual (English starts on page 23)

House was roasting when I got in from work , even though I set to the temp to 16. It Just doesn't make sense. Thermostat is probably too is close to rad for accurate room temp throughout but doesn't explain why it's at 23 when set to 16 if anything the house should bee cooler due to thermostat turning heating off as too close to rad

If the Celcia 20 is set to weather compensation the sensor in the control unit is just used to display the room temperature, it does not turn the boiler off when the required temperature is reached, so the proximity of stat to rad is irrelevant.

The problem is that the heating curve has not been correctly set. The relevant parameters are on pages 34 and 35 of the manual. The summer settings are probably OK (20C flow when it's 20C outside), but the winter water temperature is probably too high. This could be because you have a well insulated house. Try dropping the winter flow temperature by 10C and see what effect it has. You will have to experiment.

When you change the required temperature on the control all it does is move the curve up and down parallel to the curve line.

 

[billdiy]

The Celcia 20 can use either room or external compensation.

Do you know if an external sensor was fitted? It will be a small box on a north or north-west wall about 8-10 foot off the ground with a cable attached.

a hertsman is a good controller

 

[D_Hailsham]

a hertsman is a good controller

Who said that?
Who are hertsman
How is it relevant?

 

[mordzy]

Thanks D_Hailsham.

To be honest that sounds complex for your average home user. I do notice the tap icon as well as the rad icon display all the time.

I'm not back home till mid week so will check setup then. Is this kind of advanced settings supposed to save fule?

 

[D_Hailsham]

To be honest that sounds complex for your average home user.

I agree. The installer is supposed to 'tune' the system for your specific needs. The problem, as I see it, is that they don't know how to do it as they have never been trained; they are used to just bunging in a thermostat and that's that.

I do notice the tap icon as well as the rad icon display all the time.

Which model Remeha do you have comb, system or open-vent?

Is this kind of advanced settings supposed to save fuel?

Yes.

Read Weather Compensation. It's written by Viessmann but the Remeha version works in exactly the same way.

The important thing is to get the control curve right as this determines the relationship between flow temperature and outside temperature, which will be different for each house.