Honeywell DT90E help...please

Postby jimbobuk » Sun Aug 21, 2011 2:32 pm

Hi guys,
Wonder someone might be able to help me work this out...
So I've just bought the Honeywell DT90E digital thermostat to replace the old manual dial we had.
The installation instructions on the Honeywell site ( ... f/1072.pdf) are possibly the most confusing I've ever seen (as a lay-person).

I just cant work out which wires need to go where. So, I have 4 wires sticking out of the wall right now; Yellow, Brown, Red, and Yellow+Green. With the previous manual thermostat, yellow went in 3, Brown went in N, Red in L and the yellow + green was to the side Earth Ground.

However with this new DT90E there are only three places, A B C.

Does anybody know which ones go where?[/url]
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Simply Build It

Postby stoneyboy » Wed Aug 24, 2011 8:30 pm

Using your description of the original set up you will need to put red onto terminal A and yellow onto terminal B. Terminate the brown and yellow/green in the box.
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