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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Fitting Honeywell digital thermostat. We have 3 wires; grey

Customer Question

Fitting Honeywell digital thermostat. We have 3 wires; grey with brown sleeve, black with blue sleeve and brown. Can't work out which goes to terminal a,b or c.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.


I will be referring to the diagrams in the manual.

I need a clear, well focused close up photo of the wiring diagram on the boiler, and also of the wire ABC wire connections themselves, you can use the paper clip icon at the right end of the tool bar for that, or the '+attach files'... link to the left of your send button.

I also need the brand and model number of the oil burner if that is what you have.

We can go from there.

Customer: replied 1 year ago.
We have a valiant exotic plus combo boiler. Where would the diagram you refer to be? Have attached photo of connectors. Thanks
Customer: replied 1 year ago.
Sorry should read eco tec plus !
Expert:  Phil replied 1 year ago.

Hello again.

that is the diagram for the model you gave, but it does now show that terminal block..the company changes the configuration of the models each year or so, and assigns a new model **number** with that *i might be able to pull up a diagram.

Usually however the diagram is glued inside the very large front cover of the have to remove that to get to it.

Customer: replied 1 year ago.
I'm just clarifying that the photo I sent you is of the inside of the Honeywell thermostat? We can't do anymore tonight so will try to get the cover off the boiler in the morning and photgragh that diagram for you then.
Expert:  Phil replied 1 year ago.

OK, that will work.

Customer: replied 1 year ago.
Good morning Phil,
There is no diagram behind the boiler cover but we have found the installation guide. I have attached pictures of the cover and 2 diagrams fro. M inside. Is this what you need?
Expert:  Phil replied 1 year ago.
Customer: replied 1 year ago.
See photo of control box. 3 brown, 4 brown and white, nothing in 5! Won't let me send photo as file is too large. Is there another way?
Expert:  Phil replied 1 year ago.

You can post the photo to then post the URL to that photo here.

However the documentation on what you have there is not making a lot of sense, there is a fairly good chance that we will have to give up on it, and call in a local technician... or I can opt out... the odds are slim that anyone else here will want to try to sort this out either.

If you do want to call in a local technician, tell me which direction you are from the center of the nearest city and I will see if I can get you a short list of some well rated ones.


Customer: replied 1 year ago.
My thoughts exactly, you've done you're best. Does this mean I still get charged? Thanks anyway, I'll get the guys that service it in. Bye
Expert:  Phil replied 1 year ago.

Hello again, I am just a customer here as you are, except I answer questions. You can question the site management about charges by clicking the 'report question', or 'contact us' link.