Changing honeywell thermostat

[Earlybird]

Hi, so I'm looking at changing my thermostat from a honeywell manual to a honeywell DT90E digital thermostat and I was wondering if you could help me with where the wires should go please. First picture is the wiring of my current thermostat and the second picture is the instructions for the new one I was hoping to buy. Thank you for any advice given, its much appreciated.

 

[brianmoooore]

Use diagram 3a.

 

[Midwest]

Probably 3a, but might depend where the wires at the other end have been connected.

 

[telectrix]

be careful with 3a. that switcheds 240V to the boiler. not good if the boiler wants a 24V switch.

 

[brianmoooore]

From the OP's question, I think we can assume they're not very knowledgeable on this subject, so I said 3a to keep things simple. When I first saw the question, I was expecting the new 'stat to need a neutral which wasn't present, but no such problem.
They're swapping one 'stat for another, not rewiring the whole thing. Nothing changes at the other end of the single T&E we can see, so 3a is a simple and sufficient answer. I could have said any of the diagrams except 3e.

 

[telectrix]

you're right. I read it wrong. only saw the 230V feed, not the 24 -230.24V.

 

[Earlybird]

From the OP's question, I think we can assume they're not very knowledgeable on this subject, so I said 3a to keep things simple. When I first saw the question, I was expecting the new 'stat to need a neutral which wasn't present, but no such problem.
They're swapping one 'stat for another, not rewiring the whole thing. Nothing changes at the other end of the single T&E we can see, so 3a is a simple and sufficient answer. I could have said any of the diagrams except 3e.

Thank you for the advice. Would you be able to tell me what wire goes where please as I am a total novice when it comes to things like this. Thanks again

 

[brianmoooore]

Connect the brown and blue of the existing wires to A and B of the new 'stat. Brown should go to A and blue to B, but it doesn't actually matter for the 'stat to work.
The grey outer sheath of the cable must enter the 'stat, and there shouldn't be any bare copper showing where the wires go into the terminals.

 

[Earlybird]

Connect the brown and blue of the existing wires to A and B of the new 'stat. Brown should go to A and blue to B, but it doesn't actually matter for the 'stat to work.
The grey outer sheath of the cable must enter the 'stat, and there shouldn't be any bare copper showing where the wires go into the terminals.

Thank you so much

 

[Earlybird]

Thank you so much

New thermostat all fitted and working

Connect the brown and blue of the existing wires to A and B of the new 'stat. Brown should go to A and blue to B, but it doesn't actually matter for the 'stat to work.
The grey outer sheath of the cable must enter the 'stat, and there shouldn't be any bare copper showing where the wires go into the terminals.

New thermostat fitted and working, thanks again for your help.

 

[brianmoooore]

You're more than welcome.