Replacing Honeywell CM67 with CM707

21 Oct 2013
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United Kingdom

How difficult would it be to replace a Honeywell CM67 with a CM707? From the installation guides it appears that the wiring should be the same - just move the wires across to the same lettered terminals.

I don't mind paying for an electrician if I have to but assuming that Honeywell haven't redesigned everything it seems silly to pay for a straightforward like-for-like swap.

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Thanks for that. I'm giving the CM67 one last chance as it's been a faithful servant for many years. But it seems to let the house get warmer in the evening despite it showing the same temperature. Another thermostat on the opposite side of the room claims 1c warmer.

It does only run for half an hour in the morning compared to several hours in the evening but given it has optimum start that shouldn't be an issue. It also seems to do it at the weekends when it's set to run most of the day.

I'm wondering if perhaps it's starting to lose accuracy :-/
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