Honeywell CM907 odd behaviour

16 Sep 2007
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United Kingdom
Has anyone experienced any odd behaviour from the CM907 with optimisation turned on? I've noticed that in the morning, the heating starts coming on far too early - on Saturday for example, it is set to reach 20°C at 09:00, but the boiler woke me up at 06:00. After going downstairs, it said the room temperature was 18°C, and the target temperature was 16°C. It definitely doesn't take 3 hours to raise the temp by 2°C! (usually takes about 30 mins at the most)

In the evening we have the temp set to 20°C at 18:00 and 16°C at 22:30
Last night, the boiler fired up about 23:30, yet the house was still 20°C as it takes a long time for this house to cool down. The target temp was still confirmed as 16°C as expected (by pressing 'i').

This is the first time anything odd has happened in the evening, but the problems in the morning are regular.

I'm going to contact Honeywell to see if they can help with this. I've now turned optimisation off as god knows what its doing during the day while we're at work...
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I have a combi.

The thermostat turned it on as it had the little flame symbol on the display.
The optimisation feature of these honeywell programmable thermostats is not as good as some may think.

I've turned optimisation off on my CM67 as it also came on far too early. When I got a CM927 for my dad a couple of weeks ago, the first thing I did was turn it off on his also.

Do a google groups search on this and you will find plenty to read.
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I've turned it off and adjusted the times to suit and everything is working a lot better. It hardly takes any time to get the house up to temperature, so heating the house for an extra 10 or 15 mins on a cold day doesn't bother me. Better than 2 hours early every day!

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