Honeywell T3 to Hive with Baxi

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zackaryh8

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Hi, I've just purchased a Hive Thermostat today. I originally had a Honeywell Home T3. The boiler is a Baxi Assure Combi 25.

The issue I'm facing is the wiring (seems as though this is a common theme. Anyways I've attached a picture of the wires that were in the wall.

There is a brown one, a black one with a brown sleeve, and 2 others which were not used for the Honeywell.

The black and brown cable were connected into the honeywell A and B respectively

Any help would be greatly appreciated.
 

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If you’re able to trace that grey wire, then it’s may be of use. Basically what you had was a live in and a switched live out. What you need now is both of those and a permanent live and permanent neutral, often taken from the boiler. Opening up that boiler forms part of the room seal and combustion circuit so needs to be checked for safety afterwards.
 
So would need to have someone in to do that I assume?

You said the grey cable could be of use could you elaborate please?
 
zackaryh8 said:
So would need to have someone in to do that I assume?
Click to expand...
Yes, unless you know how to do it?
zackaryh8 said:
You said the grey wire could be of use could you elaborate please?
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If it’s all mains switching (looks likely) then, yes, if it’s (grey wire) connected to a neutral (possible as it’s in a connector block),then you have a permanent neutral and the live would also be permanent, and connect up to the switch wire, link L and common and away you go.
 
So what wires would go into what numbers on the hive, sorry if it sounds like I have no idea, it's because I don't
 
zackaryh8 said:
So what wires would go into what numbers on the hive, sorry if it sounds like I have no idea, it's because I don't
Click to expand...
Once you confirm if the grey is neutral then:

Brown to L
Grey with blue tape or sleeving to indicate a neutral wire to N
Link a wire from L to Com (1)
Black wire with brown sleeving to heating on (3)
Park the earth in earth terminal or leave in connector block.
 
The grey wire is not neutral and after switching the boiler on and off, all cables went dead.

Probably going to return the hive, get a nest and get a heating engineer to come and install the correct cables for open therm.
 
Just before you do, make sure the Baxi is capable of communicating with standard opentherm, I’ve heard not all are compatible?
 
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