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James, Developer
Category: HVAC
Satisfied Customers: 9484
Experience:  I have a portfolio of renovated houses, including DIY projects from installing bathrooms and new heating systems to rewiring.
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I have a CM927 thermostat that keeps losing connection with

Customer Question

Hi - i have a CM927 thermostat that keeps losing connection with the boiler and consequently we find the heating blaring out even when the boiler is not officially supposed to be on. is this a boiler issue or thermostat issue?
JA: Who makes your thermostat? How old is it?
Customer: its a honeywell bull
JA: How long has this been going on with your Honeywell thermostat? What have you tried so far?
Customer: been off and on s- so to speak - since we turned the heating back on in october - we usually just go through the reconnection protocal and then it works for a bit but then doesn't
JA: Anything else we should know to help you best?
Customer: we've only had the system for about 5 years
Submitted: 21 days ago.
Category: HVAC
Expert:  James replied 21 days ago.

Wlecome to Just Answer sorry to hear you are having issues with your heating.

Is your CM927 wired to the boiler or wireless with a small square receiver next to the boiler which looks like the one here?

Customer: replied 21 days ago.
it is wireless and the receiver is like that
Expert:  James replied 21 days ago.

Understood, when the fault occurs does the thermostat show a flame symbol or is it showing no demand but boiling keeps running?

Customer: replied 21 days ago.
the flame is out so assume it has met our target but the boiler is still going so consequently temp just keeps going up
Expert:  James replied 21 days ago.

Understood, and what lights are showing on the receiver when the boiler is showing demand but thermostat is satisfied?

Customer: replied 21 days ago.
i think there is a green light
Expert:  James replied 21 days ago.

Ok then that suggests the receiver is getting demand, more often than not the receiver is faulty. I would go back through the binding process and if the green light is still on 30 seconds after the thermostat is showing no demand then consider replacing the receiver, a new one can be sourced here.

It was a pleasure to assist you today. I hope the above answers the question. If you have any follow up questions then please let me know.

Customer: replied 21 days ago.
many thanks