Hi, I have recently had a wireless thermostat (CM927) installed for my Vaillant combi boiler. The programmes on the thermostat are set to the times we want the heating to come on and to the correct temperature etc. However, it is telling the boiler to come on in the 'off' periods when the temperature drops below the target one. Checked the programmes several times and it is in the Auto position. Scratching my head - can anyone help?
Wireless Thermostat problems
- Thread starter jeremycolton
- Start date
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That's what it's supposed to do.
Even when the thermostat's programme is set for the heating to be off altogether? I understand that it will get the room to the desired temperature when its programmed to be 'on' .....but it's not
From a quick read of the instructions it looks as if the CM927 doesn't actually switch OFF, instead it switches to a lower setpoint. Are you sure that the temperature isn't dropping below that? During one of the times you're expecting the heating to be off, press the "i" button and that will tell what target temperature it's trying to maintain.
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Off isn't off. It is what the target is. If the ambient temperature drops below then the boiler will fire.
Also, if optimisation is enabled, the controller will fire the boiler early to reach the program time and temperature then rather than firing on the time you set.
Also, if optimisation is enabled, the controller will fire the boiler early to reach the program time and temperature then rather than firing on the time you set.
Thanks Dan, that's helpful. One more thing from someone who is obviously not the most clued up with these things! Is there much point in having the six programmes on the thermostat then?
Depends on your lifestyle. You can delete the ones you don't need.
My living room zone has a double off setpoint for when I override it to watch a film, and forget to turn the heating down again.
However, the bedrooms only have a morning and evening program.
Downstairs are on pretty much all day at a a slightly lower temp than the evening.
My living room zone has a double off setpoint for when I override it to watch a film, and forget to turn the heating down again.
However, the bedrooms only have a morning and evening program.
Downstairs are on pretty much all day at a a slightly lower temp than the evening.
Okay, I understand that bit. But as an example - our thermostat was set to come on at 6pm this evening and is due to go off at 10pm. It started getting up to temperature by firing up the boiler at 5pm though ....
It's supposed to.
Depending on how new the install is, it can take a couple of days to find its feet, however. Some rooms might take that long.
My bedroom zone and the living room zone kick in a good 90 minutes or more before the setpoint time. However, my boiler is weather compensated so the running temperature of the heating is only about 45 degrees or so at that time of the night/morning.
Depending on how new the install is, it can take a couple of days to find its feet, however. Some rooms might take that long.
My bedroom zone and the living room zone kick in a good 90 minutes or more before the setpoint time. However, my boiler is weather compensated so the running temperature of the heating is only about 45 degrees or so at that time of the night/morning.
The CMT901/920/907/927 do not do 'off'. There are (up to) 6 time periods/zones per 24 hours. They switch from one set temperature to another at the allotted start time for each zone.
'Off' will only happen if an unachievable temperature is set.
'Off' will only happen if an unachievable temperature is set.
We've started setting the ones we fit for customers so that even with the slider to off it will fire at 10 degrees.
Massive help mate. Thanks for your time
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