Thermostat Problem

[Chewy56]

Is this as far as I can take this post Thermostat Problem | on ElectriciansForums - https://www.electriciansforums.net/threads/thermostat-problem.215331/

I have no intention of doing any electrical work myself.

 

[Alk]

Hi @Chewy56
I cannot reply to your original thread - it says that I have insufficient privileges to do so - I cannot post anywhere in that forum/start a new thread (what's up with that? - have you got the same problem, hence why you started this new thread?).

I just wanted to say that if there is a green light on your BDR91 receiving box (which is next to the boiler) then it means that either: 1. you have pressed the little grey button on the receiving box manually yourself (you only ever do this in a situation when there is a lack of communication) or 2. The receiver is communicating with the DT92E Thermostat correctly.
The green light indicates that the receiving box has switched the boiler on to operate, so if the light is on, then it is communicating with the thermostat if you otherwise haven't touched it.

If the thermostat is in the room directly below the BDR91 receiving box then there should be no issues with wireless communication.
When you change the batteries, there is no need to re-link the devices.

In summary, you changed the batteries (it sounds like it needed new ones) and it is working again.
To confirm that everything is working correctly:
First make sure that the green light on your BDR91 is off.
Then on the DT92E thermostat, increase the temperature to 30 degrees Celsius (for testing, it must be way way above your normal set room temperature).
At this point you should see that the thermostat display pops up with a "radio" signal of dashes, along the bottom. This means that the thermostat is transmitting a signal to the BDR91 box.
At this point, your BDR91 receiving box light will go green and the boiler will switch on and your radiators will heat up.
Be aware that sometimes there is a slight delay between the BDR91 light going green and the boiler switching on, even though there is a radio signal on the thermostat display. This is due to the way that the Honeywell thermostats work to achieve energy efficiency - it is not a fault.
If all is in order, on the DT92E thermostat, decrease the set temperature back to your normal room temperature that you are comfortable with.
The green light on the BDR91 box should now go off.

 

[Chewy56]

Hi @Chewy56
I cannot reply to your original thread - it says that I have insufficient privileges to do so - I cannot post anywhere in that forum/start a new thread (what's up with that? - have you got the same problem, hence why you started this new thread?).

I just wanted to say that if there is a green light on your BDR91 receiving box (which is next to the boiler) then it means that either: 1. you have pressed the little grey button on the receiving box manually yourself (you only ever do this in a situation when there is a lack of communication) or 2. The receiver is communicating with the DT92E Thermostat correctly.
The green light indicates that the receiving box has switched the boiler on to operate, so if the light is on, then it is communicating with the thermostat if you otherwise haven't touched it.

If the thermostat is in the room directly below the BDR91 receiving box then there should be no issues with wireless communication.
When you change the batteries, there is no need to re-link the devices.

In summary, you changed the batteries (it sounds like it needed new ones) and it is working again.
To confirm that everything is working correctly:
First make sure that the green light on your BDR91 is off.
Then on the DT92E thermostat, increase the temperature to 30 degrees Celsius (for testing, it must be way way above your normal set room temperature).
At this point you should see that the thermostat display pops up with a "radio" signal of dashes, along the bottom. This means that the thermostat is transmitting a signal to the BDR91 box.
At this point, your BDR91 receiving box light will go green and the boiler will switch on and your radiators will heat up.
Be aware that sometimes there is a slight delay between the BDR91 light going green and the boiler switching on, even though there is a radio signal on the thermostat display. This is due to the way that the Honeywell thermostats work to achieve energy efficiency - it is not a fault.
If all is in order, on the DT92E thermostat, decrease the set temperature back to your normal room temperature that you are comfortable with.
The green light on the BDR91 box should now go off.

Many thanks for your reply. My original question on the other board was:
Hi, First post and would be very grateful for any help.

I have a Honeywell DT92E Thermostat that is only intermittently communicating with the wireless relay box BDR91.

There is a full green light on the BDR91 and if I switch the Potterton programmer on HW and CH the radiators come on and switch off when it it reaches the temperature on the DT92E after that any communication stops. The BDR91 is in a very inaccessible place. Is there any way I can sort the problem out on the DT92?. I have seen a video showing how to rebind the two but I don't think I will be able to get to it!'

I will go through your reply today and let you know how I can on.

 

[Chewy56]

Many thanks for your reply. My original question on the other board was:
Hi, First post and would be very grateful for any help.

I have a Honeywell DT92E Thermostat that is only intermittently communicating with the wireless relay box BDR91.

There is a full green light on the BDR91 and if I switch the Potterton programmer on HW and CH the radiators come on and switch off when it it reaches the temperature on the DT92E after that any communication stops. The BDR91 is in a very inaccessible place. Is there any way I can sort the problem out on the DT92?. I have seen a video showing how to rebind the two but I don't think I will be able to get to it!'

I will go through your reply today and let you know how I can on.

I have been through your post and the green light is showing on the BDR91 all the time. I looked at it before I put the heating on this morning and it was green. When I put the heating on it was still green and when I switched it off it was still green (as photo 1 attached). Photo 2 shows the DT92 when the heating was first switched on this morning. I had already set the temp to 30% but I knew from the intermittent problem from the past two days that although no wireless signal was showing that the radiators would heat up so I did not leave the heating on! Photo 3 shows the programmer when the heating was switched on this morning (need to reset the clock to winter time).

 

[Alk]

From everything that you have explained, I believe that the problem is with the CH scheduling on your Potterton programmer.
Here is my logic:
You have explained that when you manually switch the Potterton programmer to ON, that the room then heats up to the temperature set on the thermostat and then it switches off. If the thermostat were not communicating with the BDR91 relay box correctly, then that would not happen and you would not be able to get the heating to come on in this way.

As you no doubt know, the Potterton programmer will get in the way of the thermostat working.
So let's take an example where you have the CH set to OFF on the programmer; then it doesn't matter what is set on the thermostat, the heating just won't work. The thermostat will continue to try and reach the say 25 degrees C that you have set to be the target room temperature, but it just can't do so, because it has been overridden by the Potterton programmer and the boiler is actually off. Likewise, I think I'm right in saying that in this situation that the green light will still be on, showing that it has received the signal from the thermostat and is "calling for heat" from the boiler (attempting to reach the 25 degrees), but because it has been overridden by the OFF on the programmer, the boiler is actually off and nothing happens at your radiators - so the light continues to remains on, attempting in vain to get to 25 degrees.

So this is just the same as when you have a schedule setup on the Potterton programmer. When the programmer schedule is set for the CH to be off, the thermostat cannot work. The thermostat can only reach the target temperature when the programmer schedule is set to be ON (just the same as when you manually switch it to ON) and with sufficient time allocated on the schedule for it to reach that temperature (say you need a minimum of 2 hours to heat the house to the target temperature of X degrees? - you won't be wasting energy once it has reached the target temperature, it will just maintain the set temperature).

So in summary, please check the Potterton programmer's Central heating schedule and check it is set correctly. It would be best to have a pen and paper handy as you will have to go through and check each day.

 

[Avo Mk8]

Many thanks for your reply. My original question on the other board was:
Hi, First post and would be very grateful for any help.

I have a Honeywell DT92E Thermostat that is only intermittently communicating with the wireless relay box BDR91.

There is a full green light on the BDR91 and if I switch the Potterton programmer on HW and CH the radiators come on and switch off when it it reaches the temperature on the DT92E after that any communication stops. The BDR91 is in a very inaccessible place. Is there any way I can sort the problem out on the DT92?. I have seen a video showing how to rebind the two but I don't think I will be able to get to it!'

I will go through your reply today and let you know how I can on.

Your BDR91 doesn't seem to be behaving in the way I would expect, or I may have misunderstood your post.
The green light should not be on all the time, it should only come on when the DT92 calls for CH.
Secondly, if communication was lost the lower red light would be on/flashing.
The pen marks on the front suggest there has been some confusion in how it should be connected.

From what you say and the photos, the boiler controls seem to be solely responsible for controlling heating at the moment rather than the thermostat/BDR91. Has it ever worked properly?

I suggest it needs someone with a test instrument to check the wiring, maybe disconnect the BDR91 from the boiler and see if it will perform correctly with the DT92, ie both lights off, turn up the thermostat and the green light should come on, turn down the thermostat and the green light goes off.

 

[Chewy56]

Thank you very much for the replies.

Could someone advise the cheapest way out of this problem. We only use the Potterton Programmer to switch the water and central heating on and off. I realise the temperature is controlled by the DT92 and therefore the BDR91 is needed. I do not intend to do any electrical work myself but this problem could be in any one of three places and cost a lot of money to sort out.

 

[Avo Mk8]

Thank you very much for the replies.

Could someone advise the cheapest way out of this problem. We only use the Potterton Programmer to switch the water and central heating on and off. I realise the temperature is controlled by the DT92 and therefore the BDR91 is needed. I do not intend to do any electrical work myself but this problem could be in any one of three places and cost a lot of money to sort out.

The only way I can see to sort this out is for someone to check out the wiring and find what `i believe to be a fault somewhere. Ie 'Electrical work'.

If you understand electrics, you might turn the whole system off at the mains, and investigate what wire goes where. You could then draw out the circuit diagram of what you have, and compare that with example circuits on the web. That would at least establish if it's wired correctly.
Failing that you need an electrician familiar with central heating controls to do the investigation.

The BDR91 box is about £60 to purchase, but we don't have enough evidence to say that is what's wrong at the moment.

In the meantime if you set the programmer to switch on the CH for a period to provide the heat you need, and then switch off after say an hour or two, you might be able to arrive at an 'on' period that gets the house to the right temperature without using the thermostat

 

[Chewy56]

The only way I can see to sort this out is for someone to check out the wiring and find what `i believe to be a fault somewhere. Ie 'Electrical work'.

If you understand electrics, you might turn the whole system off at the mains, and investigate what wire goes where. You could then draw out the circuit diagram of what you have, and compare that with example circuits on the web. That would at least establish if it's wired correctly.
Failing that you need an electrician familiar with central heating controls to do the investigation.

The BDR91 box is about £60 to purchase, but we don't have enough evidence to say that is what's wrong at the moment.

In the meantime if you set the programmer to switch on the CH for a period to provide the heat you need, and then switch off after say an hour or two, you might be able to arrive at an 'on' period that gets the house to the right temperature without using the thermostat

Thank you for your reply.

I thought the problem that I have would be an easy fix. The set up with the thermostat, relay box and programmer has worked faultlessly for over 1 year. Just for the last couple of days, the connection symbol on the thermostat has not shown which has resulted in an intermittent problem when switching on the heating at the programmer, as described in my original post. Once the temperature reaches the ceiling figure input on the screen of the thermostat, the boiler switches off and will not fire up again until the system has completely cooled down. Ideally, once the temperature had dropped by a few degrees, it would switch on again, but this is not the case.

I still don't quite understand how the thermostat communicates with the relay box, as I have been told that it is not by WiFi.

From the comments I have received, it now seems that the problem could be with the relay box and /or a problem with the programmer, though the programmer was new about 18 months ago. If I get an electrician in, to have a look, it could end up a very expensive business, in which case I would rather put up with the fault. I would have no problem getting an electrician if it was a small job but this could turn out to be hundreds of pounds which I could not afford.

 

[Chewy56]

A friend has just recommended a Hive or Tado system which would cost around £100 to buy and an Electricians time to install.

If this was a solution to my problem I would certainly consider it. I would be very grateful for any comments.

 

[Avo Mk8]

Thank you for your reply.

I thought the problem that I have would be an easy fix. The set up with the thermostat, relay box and programmer has worked faultlessly for over 1 year. Just for the last couple of days, the connection symbol on the thermostat has not shown which has resulted in an intermittent problem when switching on the heating at the programmer, as described in my original post.

OK, sorry I had missed that it was working OK until a few days ago. That suggests it's not a wiring problem, so ignore my comments

Once the temperature reaches the ceiling figure input on the screen of the thermostat, the boiler switches off and will not fire up again until the system has completely cooled down.

Something wrong here. If the thermostat is showing no received signal from the BDR91 then maybe it's lost its pairing, or the BDR91 is not transmitting when it should be.
It would be worth re-binding the two units, though I appreciate the access problem.

Ideally, once the temperature had dropped by a few degrees, it would switch on again, but this is not the case.

is the green light on the BDR91 literally on all the time?

I still don't quite understand how the thermostat communicates with the relay box, as I have been told that it is not by WiFi.

The units communicate with each other on an 868MHz radio link, I think the protocol is specific to Honeywell.
It's correct that it's not WiFi, which is a higher frequency.

From the comments I have received, it now seems that the problem could be with the relay box and /or a problem with the programmer, though the programmer was new about 18 months ago. If I get an electrician in, to have a look, it could end up a very expensive business, in which case I would rather put up with the fault. I would have no problem getting an electrician if it was a small job but this could turn out to be hundreds of pounds which I could not afford.

It shouldn't cost hundreds if someone familiar with Honeywell Home was used to diagnose the problem.

 

[Avo Mk8]

A friend has just recommended a Hive or Tado system which would cost around £100 to buy and an Electricians time to install.

If this was a solution to my problem I would certainly consider it. I would be very grateful for any comments.

Honeywell Home is generally regarded as one of the better systems, and I wouldn't personally advise changing it unless you need the additional features those others offer.
I suggest it's premature to change the hardware until you've tried re-binding the units - the BDR91 could surely be screwed to a wall as it's designed to be, and made accessible somewhere?

 

[Chewy56]

Honeywell Home is generally regarded as one of the better systems, and I wouldn't personally advise changing it unless you need the additional features those others offer.
I suggest it's premature to change the hardware until you've tried re-binding the units - the BDR91 could surely be screwed to a wall as it's designed to be, and made accessible somewhere?

Many thanks for this and the other replies above.

To answer your question above re the green light on all the time......yes it is!

The reason I have been holding of about re binding is not just because of the inaccessibility but if it goes wrong it could lose us our heating until it is fixed. We are both OAP's! If I did bite the bullet would you recommend this as a good tutorial? Honeywell Home DT2 Digital Room Thermostat not working - Recherche Google - https://www.google.com/search?client=opera&q=Honeywell+Home+DT2+Digital+Room+Thermostat+not+working&sourceid=opera&ie=UTF-8&oe=UTF-8#fpstate=ive&vld=cid:f97f43ce,vid:0sT2rc4ikO8,st:0

 

[Alk]

By the way, there is nothing wrong with your Potterton programmer. I thought that you might be using the programmer on a schedule (on TIMED) and if you were doing that, than the schedule would have been potentially preventing the thermostat from working correctly. ....but that is not the case....because you are just using the programmer to manually switch your CH ON and OFF. Which is OK. So no issues there with the programmer.

Are you seeing a flame symbol on the thermostat? A flame symbol should be showing when the green light is on the relay box.
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).

Once the temperature reaches the ceiling figure input on the screen of the thermostat, the boiler switches off and will not fire up again until the system has completely cooled down. Ideally, once the temperature had dropped by a few degrees, it would switch on again, but this is not the case.

I agree that this should happen and is presumably what used to happen. So check what the target temperature is still set to (ie. that it hasn't changed) and check whether the flame symbol is showing on the thermostat at that time.
You need to be looking out for the flame symbol and making a note of it and what else is happening with the boiler at the time - is the flame symbol showing? and if so, is the boiler firing or not when the flame symbol is showing? (ignore the green light on the relay box for now)

Have you previously noticed in the past whether the green light has been permanently lit on the relay box? I'm thinking whether it has always been like this and whether it is actually a new problem?

At this stage, I don't believe there should be a need to rebind the units - they are programmed at the factory specific to your units. Because if there was a Radio Frequency communication problem, then the relay box would have a red light on it, and the radio signal would be flashing constantly on the thermostat as well.

 

[Chewy56]

By the way, there is nothing wrong with your Potterton programmer. I thought that you might be using the programmer on a schedule (on TIMED) and if you were doing that, than the schedule would have been potentially preventing the thermostat from working correctly. ....but that is not the case....because you are just using the programmer to manually switch your CH ON and OFF. Which is OK. So no issues there with the programmer.

Are you seeing a flame symbol on the thermostat? A flame symbol should be showing when the green light is on the relay box.
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).


I agree that this should happen and is presumably what used to happen. So check what the target temperature is still set to (ie. that it hasn't changed) and check whether the flame symbol is showing on the thermostat at that time.
You need to be looking out for the flame symbol and making a note of it and what else is happening with the boiler at the time - is the flame symbol showing? and if so, is the boiler firing or not when the flame symbol is showing? (ignore the green light on the relay box for now)

Have you previously noticed in the past whether the green light has been permanently lit on the relay box? I'm thinking whether it has always been like this and whether it is actually a new problem?

At this stage, I don't believe there should be a need to rebind the units - they are programmed at the factory specific to your units. Because if there was a Radio Frequency communication problem, then the relay box would have a red light on it, and the radio signal would be flashing constantly on the thermostat as well.

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.

 

[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.