BDR91 relay wiring help needed.

10 Mar 2023
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United Kingdom
Hi everyone, i need some help with the Honeywell BDR91 relay wiring that i am trying to get working but have no idea what to do.

This was originally paired with a CM921 thermostat but the screen on it stopped working. An engineer came out and said he has "disconnected it" so the boiler has been used manually ever since.

What do i need to do to get the relay working again so i can pair a T3R thermostat to it?

The relay has power but once i pair the relay and thermostat it doesnt have a solid green light.

Any help is appreciated.

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An engineer came out and said he has "disconnected it" so the boiler has been used manually ever since.
The engineer has added a yellow link wire between A and B on the backplate.
Just remove the link wire and see if that works.
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I think the solid green light only appears when there is a demand for heat.
I removed the yellow link wire and it still didnt work so i think this relay box isnt compatible with the T3R and i need to change it to a newer honeywell home relay.
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Yep did exactly that a few times but still no luck. There was no wireless signal logo on the thermostat once i did the binding steps and the relay didnt go solid green. The relay red flashing light turns off and doesnt do anything when i increase the temp on the thermostat. I've ordered this new relay that is meant to go with the T3R now so i will try that and see if it works. I'm sure i read online somewhere that you can't actually use the T3R with the BDR91 relay but it was worth a shot.
Strange, as Honeywell struggled to get the bigger receiver out (microchip shortage), so they sent bdr91’s, unless they were changed inside on the circuitry to allow it? :unsure:
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Whether true or not, web folklore suggests that newer T3R had a firmware version that added encryption to the wireless link, and killed compatibility with the BDR91....
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The T3R Relay should be arriving tomorrow and then I can report back with the outcome.
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There is something in the back of my mind the the 466 licence free handy radios went from 8 channels to 16 channels and used a part of spectrum used by some thermostats so they had to move, but where I live rare to hear any use of the handles, so the old stuff works OK.

But in my mothers house the thermostat seemed to have drifted, and slowly lost range. As to if reciver or transmitter went out I have no idea, but best to replace as a pair.
I bought a pair of radios to use when cycling, better if one does not need to stop to hear what is being said which is the case with a phone before we had watches connected to our phones, however not a clue where these were designed to be used, but they were not using UK permitted frequencies, I bought the programming lead and changed to the UK permitted 466, as a radio ham there was no way I wanted to risk my licence, so made sure they complied with UK rules.

However although I may have realised these aAofeng radios needed reprogramming, it is unlikely that most people would realise these radios could not without reprogramming be used in the UK. And so could cause interference with other spectrum users.

I know some firms were marketing devices which used the 70 cm ham part of the spectrum, and when a ham uses 400 watt, the 0.5 watt device is unlikely to work on the same frequency. I have renewed my licence, but today hardly use radios, seems I have one other radio ham which I could talk to, but easier to use a mobile. But that's in Mid Wales, in the less hilly areas of the UK I am sure there are still some radio hams using their radios, not all have moved to internet from packet.

With my mothers old house in North Wales I had a problem, this thermostat IMGP8037.jpg would loose connection and the heating would fail to switch off, I tried to find the frequency used and to see what was causing the interference, I failed, unlike the other thermostat there was no safety system to turn off heating if signal was lost.

Our homes today have so many radio devices, and we need to expect the spectrum to become flooded. So we need to buy devices as a pair, and not try to use old with new.

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