Thermostat Problem

[Avo Mk8]

Thank you for your reply.

We have always thought the flame symbol showed the thermostat was communicating with the boiler. The fact that we have not seen it at all since this started was very confusing.

'So in normal operation, when the temperature is at 13 degrees first thing in the morning and you up the target temperature to say 20 degrees then you should see a radio signal briefly flash up and then the flame symbol should remain on. When 20 degrees is reached, the flame symbol will go off (and the green light on the relay box should go off as well).' That is exactly what happened before but as described above we are seeing no flame symbol now.

To be honest I have not noticed if the green light was always on before but if pressed I would say it wasn't on all the time.

So to summarise:
The green light on the BDR91 is on all the time. That is not normal behaviour.
The green light (which indicates demand for CH) should only come on when the thermostat demands heat (showing the flame symbol) and should otherwise be off.

My understanding is that there should be two way communication between BDR91 and DT92, ie that both receive and transmit, when one transmits an instruction the other acknowledges it.

So one hypothesis is that the BDR91 is 'stuck' with the light on. And is not acknowledging a command, so the DT92 is showing a communication failure. You might try power cycling the BDR91 (turning off, wait a minute, turn on).
If that doesn't do anything, changing the BDR91module would prove if that's faulty. But that is stooping to the 'swapping parts' method of fault finding, which I don't encourage.

All I can suggest is:
Power cycle the BDR91. See if you can get the green light to turn off, and if you succeed, check that the CH stops accordingly.
Take the DT92 up to the BDR91 location and see if you can get the two of them talking to each other, by pairing or factory reset etc.
If that proves impossible, replace the BDR91 module.
If that doesn't fix it, replace both the BDR and DT pair with another solution!

All this assumes the boiler is not at fault in any way!

 

[Alk]

I agree with Avo Mk8 that it seems that the relay box has got stuck and the 2 way communication is no longer working. I was also going to suggest to power cycle both the thermostat (remove the batteries for at least 15+ minutes) and relay box.
However, my concern with power cycling the relay box is that you have a system boiler/gravity hot water setup and so you may have an old boiler with a pilot? Do you have an old boiler with a pilot or a modern boiler without a pilot?
In order to cut power to the relay box, you are also switching power off to the boiler and if you have an old boiler with a pilot, then you have to re-light the boiler pilot and there is a risk with this that you then don't have heating if the boiler won't re-light. However, if you have a modern boiler that does not have a pilot, then you don't have this risk and turning the power off to the boiler and relay box is less risky. I hope that makes sense?

Depending on the outcome of how you proceed and how things pan out, I would also suggest that you reach out to Honeywell (now renamed Resideo) support on 03001301299 (freephone number). Also have a look over the installation manual for your thermostat which you can have in front of you at the same time to know what Honeywell might direct you to do: Honeywell DT92E Wireless Room Thermostat Installation Manual - thermostat.guide - https://thermostat.guide/honeywell/honeywell-dt92e-wireless-room-thermostat-installation-manual/ (this is the "advanced" guide for installers - not the consumer guide!).

Finally, again, depending on the outcome of what you find and/or what Honeywell support help you to troubleshoot as to the exact fault, should you need a tradesmen to replace parts, I would recommend that you reach out to your local Age UK branch who should be able to put you in touch with a relevant tradesmen at discounted rates. Be it an electrician, heating engineer or even a multiskilled handyman that is proficient in basic plumbing and electrics.

Bear in mind that the relay box and thermostat are paired together at the factory. So should you replace individual components they will need to be rebound, which you have already explained is inaccessible for you to do.

 

[Chewy56]

Thank you very much again for both your replies. We are going out this morning so I will digest what you have said and reply in more detail later on today.

My OH is happy what we have at the moment and has asked me to ensure that boiler keeps working at all costs!

We moved here a couple of years ago. One of the attractions was it had a new boiler with a ten year guarantee so we thought we wouldn't have any trouble with the Central Heating. How wrong we were! I have learnt more about three way valves, power flushing and the electric side of central heating than I would have ever thought possible.

 

[Chewy56]

Thank you very much again for both your replies. We are going out this morning so I will digest what you have said and reply in more detail later on today.

My OH is happy what we have at the moment and has asked me to ensure that boiler keeps working at all costs!

We moved here a couple of years ago. One of the attractions was it had a new boiler with a ten year guarantee so we thought we wouldn't have any trouble with the Central Heating. How wrong we were! I have learnt more about three way valves, power flushing and the electric side of central heating than I would have ever thought possible.

I telephoned Honeywell and proved in their eyes that the BDR91 and the DT92 were both working correctly . I went into loft with the thermostat and followed directions. The green light on the relay box went off and then on, at the right times. This proved to Honeywell that there was not a problem with either the BDR91 or the DT92. Therefore, they said it must be with the Potterton programmer which they couldn't help me with.

 

[Alk]

I telephoned Honeywell and proved in their eyes that the BDR91 and the DT92 were both working correctly . I went into loft with the thermostat and followed directions. The green light on the relay box went off and then on, at the right times. This proved to Honeywell that there was not a problem with either the BDR91 or the DT92. Therefore, they said it must be with the Potterton programmer which they couldn't help me with.

Could you please detail what Honeywell made you do exactly?
For example, was it an RF communication test, as detailed here: Honeywell DT92E Wireless Room Thermostat Installation Manual - thermostat.guide - https://thermostat.guide/honeywell/honeywell-dt92e-wireless-room-thermostat-installation-manual/#installing-the-dt92-room-thermostat
OR was it proving normal operation of the thermostat, by turning the temperature up and down and watching for the green light on the relay box? If so, did you see the flame symbol come on the thermostat?

 

[Chewy56]

Could you please detail what Honeywell made you do exactly?
For example, was it an RF communication test, as detailed here: Honeywell DT92E Wireless Room Thermostat Installation Manual - thermostat.guide - https://thermostat.guide/honeywell/honeywell-dt92e-wireless-room-thermostat-installation-manual/#installing-the-dt92-room-thermostat
OR was it proving normal operation of the thermostat, by turning the temperature up and down and watching for the green light on the relay box? If so, did you see the flame symbol come on the thermostat?

It was 'proving normal operation of the thermostat' but as far as I recall I did not see the flame symbol come on. In fact I have not seen that since this started.

 

[Alk]

It was 'proving normal operation of the thermostat' but as far as I recall I did not see the flame symbol come on. In fact I have not seen that since this started.

....and you presumably did that with the Potterton Programmer CH switch set to ON?
Which would mean that the programmer ignores any scheduling and runs the CH 24/7 according to the thermostat.
I understand that the way you use your CH is that in the morning you get up, and switch the slider on the programmer from the OFF to the ON and then when you are satisfied with the temperature, you then slide it on the programmer back to OFF.
Until you feel chilly again, you will then slide the programmer back to the ON again.
Is that correct? Please correct me if I am wrong.

Assuming still that this is the way that you use the programmer, then the programmer won't be faulty, so long as the CH red light goes on when switched to ON, which I am sure it is doing so as shown in your earlier photo.

Did the boiler also fire up and go off when the green light when on and off during the testing?

Have you had your boiler serviced this year?

 

[Chewy56]

....and you presumably did that with the Potterton Programmer CH switch set to ON?
Which would mean that the programmer ignores any scheduling and runs the CH 24/7 according to the thermostat.
I understand that the way you use your CH is that in the morning you get up, and switch the slider on the programmer from the OFF to the ON and then when you are satisfied with the temperature, you then slide it on the programmer back to OFF.
Until you feel chilly again, you will then slide the programmer back to the ON again.
Is that correct? Please correct me if I am wrong.

Assuming still that this is the way that you use the programmer, then the programmer won't be faulty, so long as the CH red light goes on when switched to ON, which I am sure it is doing so as shown in your earlier photo.

Did the boiler also fire up and go off when the green light when on and off during the testing?
I understand that the way you use your CH is that in the morning you get up, and switch the slider on the programmer from the OFF to the ON and then when you are satisfied with the temperature, you then slide it on the programmer back to OFF.
Until you feel chilly again, you will then slide the programmer back to the ON again.
Is that correct?

Have you had your boiler serviced this year?

'you presumably did that with the Potterton Programmer CH switch set to ON?'......Yes

'I understand that the way you use your CH is that in the morning you get up, and switch the slider on the programmer from the OFF to the ON and then when you are satisfied with the temperature, you then slide it on the programmer back to OFF.
Until you feel chilly again, you will then slide the programmer back to the ON again.
Is that correct?'. Yes

' Did the boiler also fire up and go off when the green light when on and off during the testing' I am not sure about that because I was in the loft.

'Have you had your boiler serviced this year' Yes, it's part of the guarantee to have it serviced every year although we have never needed it! Everything else to do with CH but not the boiler!!!

 

[Alk]

To be clear, when the Potterton programmer is in the OFF position, the thermostat won't work. Only when the programmer slider is in the ON position, will the thermostat work. I'm sure that you have already realised this.
It is my opinion from what you have described that if you have the programmer set to OFF, but the relay box green light is ON, then the relay box has theoretically received a signal from the thermostat (a flame symbol) because it wants the boiler to be firing as the room temperature is too low. However, because you have the programmer OFF, the boiler is unable to fire and the boiler is OFF. You have overridden the thermostat with the programmer. Therefore, nothing happens and the thermostat is unable to reach the target temperature of the thermostat and it is stuck like this with the green light on, trying in vain. This is my explanation as to why you are seeing the green light on the relay box "permanently" and why it tests out OK with Honeywell on the telephone when testing simply increasing and decreasing the temperature explained earlier (whilst the programmer is ON).

So, it is my belief now that the green light on the relay box is a red herring as the correct operation has been proved. The only thing that has not been proved indefinitely is with the thermostat in the normal room location whether the signal is OK, but again, if there were an issue with that, then the red light would be lit on the relay box. The red light lights up if a signal has not been received in the last hour. You also say that the thermostat is in the room below the loft and used to work OK. So I doubt that this is a problem.

So, your house goes through swings of cold periods losing heat. Your original question actually was....the thermostat works to bring the temperature up to the target room temperature. However, the thermostat does not seem to be triggering again when the thermostat drops by a few degrees.

So lets focus on troubleshooting that fault and ignore the relay box green light: Where is the boiler located? You need to be looking out for what happens when the target room temperature is reached and then when the temperature drops by a few degrees (still keeping the programmer ON during this period), does the flame symbol on the thermostat come on again? does the boiler fire up? at what temperature does the boiler eventually fire up? and what is the target temperature set to?

 

[Chewy56]

To be clear, when the Potterton programmer is in the OFF position, the thermostat won't work. Only when the programmer slider is in the ON position, will the thermostat work. I'm sure that you have already realised this.
It is my opinion from what you have described that if you have the programmer set to OFF, but the relay box green light is ON, then the relay box has theoretically received a signal from the thermostat (a flame symbol) because it wants the boiler to be firing as the room temperature is too low. However, because you have the programmer OFF, the boiler is unable to fire and the boiler is OFF. You have overridden the thermostat with the programmer. Therefore, nothing happens and the thermostat is unable to reach the target temperature of the thermostat and it is stuck like this with the green light on, trying in vain. This is my explanation as to why you are seeing the green light on the relay box "permanently" and why it tests out OK with Honeywell on the telephone when testing simply increasing and decreasing the temperature explained earlier (whilst the programmer is ON).

So, it is my belief now that the green light on the relay box is a red herring as the correct operation has been proved. The only thing that has not been proved indefinitely is with the thermostat in the normal room location whether the signal is OK, but again, if there were an issue with that, then the red light would be lit on the relay box. The red light lights up if a signal has not been received in the last hour. You also say that the thermostat is in the room below the loft and used to work OK. So I doubt that this is a problem.

So, your house goes through swings of cold periods losing heat. Your original question actually was....the thermostat works to bring the temperature up to the target room temperature. However, the thermostat does not seem to be triggering again when the thermostat drops by a few degrees.

So lets focus on troubleshooting that fault and ignore the relay box green light: Where is the boiler located? You need to be looking out for what happens when the target room temperature is reached and then when the temperature drops by a few degrees (still keeping the programmer ON during this period), does the flame symbol on the thermostat come on again? does the boiler fire up? at what temperature does the boiler eventually fire up? and what is the target temperature set to?

 

[Chewy56]

I would like to thank everyone for their help but it appears this can go no further.

I think the only way forward is either to leave it as it is or get a Hive or similar system to replace the programmer ,thermostat and relay.

I will ring the people who service the boiler and see what they can offer.