Honeywell CM927 - Thermostat only alternative

[steptoeUK]

Hi,

We have a next to useless Honeywell CM927, very old no longer available, the temperature buttons no longer work so adjusting temperature is impossible as they got harder and harder to press to make changesand finally gave up.

The thermostat still turns the boiler on/off but cannot change temperature so stuck at 21c, unless you make it think its colder than the room temperature by putting the unit somewhere colder then it works fine.

Are there just the head unit alternatives without changing the receiver box that turns the boiler on/off.

I've found a few, they all claim to replace it but appear to have to replace the thermostat sender and receiver next to the boiler.

Not bothered about setting timers, as heating would only be on if we are in as at work most days, just a simple replacement unit for the CM927 to control room temperature is enough.

Seems the CM927 operates only on 868 frequency, so I'm assuming any thermostat that operates on that frequency should work

Came across this under different brand names but appear to be the same model that suggests it may be a drop-in replacement but not 100% sure

https://www.amazon.co.uk/TotalHome-Thermostat-Honeywell-CMS927B1049-Replacement/dp/B0FDKXBJ53

or a Salus thermostat only as they appear to also operate on 868 frequency that the CM927 but much simpler/basic functions which all we need

Thanks for any help

 

[ericmark]

I know there was a frequency removed so old replaced with new, often fails to work.

I had problems with discharged batteries, so now have two hubs in parallel so either can fire the boiler.

 

[steptoeUK]

Not batteries, the buttons simply don't work no matter how hard you press them to change temperature. Known fault with the earlier CM927 thermostat. It has to be at least 10 years old by now. The display gradually packed up on first one and the current one was a replacement by Honeywell as it was another known fault with a batch

There is a fix but means taking it apart and if it breaks we have no thermostat at all unless its turned on manually by the box next to the boiler

 

[endecotp]

Seems the CM927 operates only on 868 frequency, so I'm assuming any thermostat that operates on that frequency should work

No I don’t think you should assume that. There is more to the radio communication than just the frequency used.

 

[CountryFan]

Your linked one may bind up, but it may be easier to change the receiver too if it will click in. The bdr91 is the receiver. Total home are part of Honeywell. A Honeywell T2R may work as well. Wiring should also be a doddle if you wanted a completely different stat.