honeywell room stat upgrade help

Joined
28 Dec 2009
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Bedfordshire
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United Kingdom
i would like some help with upgrading my old honeywell t40 room stat to the digital dt90e as there are 4 wires on the old stat and only 3 on the new one any help would be great,John
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As the new stat is battery operated you don’t need the blue neutral wire so put it in a separate connector out the way. Same for the green earth. Then connect the red live to the A terminal and yellow switch wire to B. Job done.
 
The bare copper earth with the green/yellow sleeve is not used with new thermostat, I would fold it over and tape it up.

Same with neutral, I fold them over so there is no sharp end likely to stick out of the insulation tape.
 
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