Honeywell CM927 thermostat not coming on!

6 Apr 2016
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United Kingdom
Our 6 year old Honeywell CM927 thermostat screen is dead.We tried changing batteries but it doesnt come on at all.
It is paired to a BDR91 which now shows red solid light(loss of communication).
How do I sort this out?
Any chance of fixing the thermostat?I tried opening and using a hairdryer-but no change in screen.
Worse case scenario can I get some replacement thermostat and will it pair with BDR91?
Does it have to be Honeywell?
I dont want to buy an expensive Honeywell only then to be told it could be fault of BDR91
Many Thanks
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If the screen is dead, it’s highly unlikely that the BDR91 has failed. I believe there are YouTube videos on how to repair these. On the bdr91 there’s a grey button - this is a manual override for the heating to work. There are some Honeywell’s that might link up with the bdr91, but not all do, however if you bought one with a receiver then it would just be a case of swapping over. Alternatively, you could opt for a different thermostat altogether, I don’t rate Honeywell much anymore.
I read some where about thermostats changing the frequency being used, so would buy as a pair.

As to make and model hard to say which is best, there is a problem where the thermostat has no fail safe, from memory the BDR91 would auto close down if not signal in ½ hour so one the the better type.

However it also had from memory anti-hysteresis software, which is really good with an old oil boiler, it stops the temperature over shooting, but with a modulating gas boiler designed to extract the latent heat from flue gases not a good idea, as every time the boiler is switched off/on it often does so at maximum output rather than the reduced output appropriate when the home is nearly to temperature.

So a wall thermostat is selected to suit your home, which may be very different to my home. Now is the time to select which best suits your home.

Basic idea is normally that the TRV (thermostatic radiator valve) controls the room temperature, and if the lock shield is set up well, then can do a very good job, but they have a problem, the basic TRV can turn boiler down, but not off, so we want a device which when the weather is warm, will turn off boiler, this could be a hub collecting info from electronic TRV heads, or a wall thermostat, but it needs to work with the TRV, not against the TRV.

Add to this we often want the home cooler over night, or when out at work, so often we need some timer built into the TRV or the wall thermostat to switch off or down rooms or complete systems when not required.

There are some very clever systems on the market, but in the main a couple of linked TRV heads to a master hub/wall thermostat is enough, the rest can be unlinked so much cheaper. You can set it up with no links, just careful setting and positions, so often it is a case of the more you pay the easier to set up, but given time to set up even the cheap systems can work well.

So it is a balance money paid against time to set up to work well, there are some thermostats which are analogue, a far better system, it turns the boiler up/down rather than on/off, but not all boilers can use them, also some makes one needs to either have analogue control or linking, the boiler will not allow both, so selecting a replacement thermostat depends on boiler as well as home.

Sons house (my old one) is open plan, and one centrally placed thermostat can control the whole house, the house I had before that was hot air central heating, again one thermostat could control whole house, but this house has things called doors, with no vents in the doors, so each room is controlled independent.

So we select controls to suit boiler and home, there is no one type suits all. So what is your home and boiler like?

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