Honeywell thermostat CM907 - turning optimisation off?
- Thread starter Jaffakake
- Start date
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Have a look at the installation guide, you have to go into an Engineers menu, which is beyond the user level, Why do you want to switch of Optimum start? when using optimum start correctly you should enter the time you actually want the room to be at the set temeperature, i.e. if you get up at 07:00, set the on time at 07:00, on a cold day the heating will come on at 06:00, on milder days it wont start untill say 06:45, therefore saving fuel, whilst not compromising on comfort, the CM is an expensive piece of kit, if you are not going to try and use it as intended 
To be honest I'm probably a bit confused as to how to use it and how it works! We got it as a replacement for a bog standard thermostat and I wanted one that you can set to bring the heating on later on the weekend.
I like to not have the heating on overnight. We've set it so the first temperature checkpoint is 19 degrees at 6.30am. It seems to start heating the house at about 4.45am.
The last temperature checkpoint is 19 degrees at 10.30pm - does this mean it'll stay 19 degrees throughout the night?
Basically in the week we get up at about 6.30am and would like some warmth, then we leave by 8am.
Between 8am and 5pm there's no one in and we'd like heating from 5 till 11 ish.
I probably need to reduce all the temperatures a bit as I now know it doesn't work like I thought it did and I'm just too hot (who would've thought I'd complain about that, but hey!)
Any advice as to how we need to set it to get what we want?
I like to not have the heating on overnight. We've set it so the first temperature checkpoint is 19 degrees at 6.30am. It seems to start heating the house at about 4.45am.
The last temperature checkpoint is 19 degrees at 10.30pm - does this mean it'll stay 19 degrees throughout the night?
Basically in the week we get up at about 6.30am and would like some warmth, then we leave by 8am.
Between 8am and 5pm there's no one in and we'd like heating from 5 till 11 ish.
I probably need to reduce all the temperatures a bit as I now know it doesn't work like I thought it did and I'm just too hot (who would've thought I'd complain about that, but hey!)
Any advice as to how we need to set it to get what we want?
I fitted one of these last year - for your 10.30pm setting, you want to put this at something like 10 degrees, otherwise it's going to keep your heating on all night to keep the temperature at 19. Setting it to 10 basically means that unless the room drops 9 degrees overnight (very unlikely!), the heating will stay off until the optimisation kicks in to get your room upto 19 by 6.30.
So I think your full set-up for Monday to Friday would look like this:
6.30am - 19 deg (or whatever temp you want to set it to)
7.30am - 10 degrees (so it stays off through the day - no point leaving it on until 8.00am as there will still be risidual heat in the radiators to keep it warm enough til 8.00am)
5pm - 19 degrees (heating will kick in some time before if you keep optimisation on)
10.30om - 10 degrees
I personally have turned optimisation off - instead I set it to come on half an hour before we get up. I found it was a bit of overkill to have it coming on an hour and half before we got up.
Hope that helps
So I think your full set-up for Monday to Friday would look like this:
6.30am - 19 deg (or whatever temp you want to set it to)
7.30am - 10 degrees (so it stays off through the day - no point leaving it on until 8.00am as there will still be risidual heat in the radiators to keep it warm enough til 8.00am)
5pm - 19 degrees (heating will kick in some time before if you keep optimisation on)
10.30om - 10 degrees
I personally have turned optimisation off - instead I set it to come on half an hour before we get up. I found it was a bit of overkill to have it coming on an hour and half before we got up.
Hope that helps
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That's easy. There are separate settings for each day of the week.
That's the optimization working. When you set the temperature to 19°C at 0630, you were telling the stat that you wanted the house to be up to 19°C by 0630, so it has to come on earlier to achieve this. How much earlier will depend on how low the house temperature has dropped overnight.
Yes. So what you are hearing at 0430 is just the boiler coming on to maintain a temperature of 19°C. As the overnight temperature is the same as the daytime temperature, the optimization never works. I would drop the 2230 temperature to 5-10°C. The optimization will then work.
So set time 1 to 19°C at 0630; time 2 to 5-10°c at 0800; time 3 to 19°C at 1700; time 4 to 5-10°C at 2300. Times 5 and 6 can be disabled.
You may find that you have to set time 3 to earlier than 1700, to make sure the house is up to temperature by 1700, as optimization only works on time 1.
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