Honeywell CMT927 Wireless 7 Day Programmable Room Thermostat

Joined
23 Nov 2011
Messages
1
Reaction score
0
Location
Berkshire
Country
United Kingdom
Hello - I am wondering if anyone can provide some advise please regarding a recently fitted Honeywell CMT927.
1. The receiver has been positioned in the airing cupboard and unless the thermostat is positioned on the landing (not the hall) the receiver doesn't seem to pick up a signal. If the airing cupboard door is open then it seems to work semi-effectively from the landing but the receiver tends to drop the signal if the door is shut. The Honeywell website refers to a set distance from metal etc - is this really correct? Where from experience should the receiver be positioned?
2. During the heating cycle the heating is continually on and off - even if the room temperature is above the target temperature. We are only talking 0.5 - 1 degrees above but I am not sure this is right. I would say sometimes it can be on and off 2 or 3 times in 15 mins. The system does maintain the temp as per the target temperature and doesn't go too far over, however it seems odd that the boiler is firing when the room temp is above the target temp. Is this how the system works as I have no experience in comparison to my old manual thermostat?
3. Every morning the heating and water start at 06:30. But 8 - 9 mins after the cycle the heating switches off even if the target temperature has not been achieved. If re-fires 3 - 5 mind later and then remains on.

Any help / guidance would be appreciated

Thanks
 
Sponsored Links
2 & 3. Yes this is normal behaviour, it's called TPI.

TPI CONTROL

TPI (Time Proportional & Integral) control is an industry standard term for an On/Off control using an advanced energy saving control method that can be used by most heating systems in the UK. The controls simply switch current supplied to the boiler on or off at different times. Unlike a traditional thermostat, these rely on digital technology that matches the boiler firing to the load on the system.

The result is that the temperature will not swing from hot-cold-hot-cold like you get with older or less accurate thermostats. You will also not get much overshoot if any at all.

I personally didn't get on with it even after reducing the cycles per hour to the minimum level and decreasing the proportional bandwidth but a lot of people like it.
 
1. The receiver has been positioned in the airing cupboard and unless the thermostat is positioned on the landing (not the hall) the receiver doesn't seem to pick up a signal. If the airing cupboard door is open then it seems to work semi-effectively from the landing but the receiver tends to drop the signal if the door is shut. The Honeywell website refers to a set distance from metal etc - is this really correct? Where from experience should the receiver be positioned?
There's a lot of metal in an airing cupboard - HW cylinder etc. It would have been better if the receiver was outside the airing cupboard. I have mine high up on the wall, above the door frame.

During the heating cycle the heating is continually on and off - even if the room temperature is above the target temperature. We are only talking 0.5 - 1 degrees above but I am not sure this is right. I would say sometimes it can be on and off 2 or 3 times in 15 mins.
If you have a gas boiler it is set to work in 10-minute cycles. The on/off periods can range from one minute on/9 minutes off to 10 minutes on. It could be that the boiler's own thermostat is turning it off.

If you have a well insulated house, the proportional bandwidth may need to be increased. This will help reduce the overshoot.

Every morning the heating and water start at 06:30. But 8 - 9 mins after the cycle the heating switches off even if the target temperature has not been achieved. If re-fires 3 - 5 mind later and then remains on.
The boiler seems to be short cycling. The heat output from the boiler is more than your rads can dissipate, so the water temperature rises very quickly, shutting the boiler off. See previous paragraph.

Which boiler do you have (make and exact model)?
Use the Boiler Size Calculator to find out what size boiler you should have.
Post the info.
 
Sponsored Links
It would be simpler to see if it's the Honeywell unit turning the boiler off in the first few minutes by checking if the green light goes off on the box. When I used to have the Honeywell CM927 it used to do this nearly every time i.e. switch off after a few minutes at the start of a time window and then come back on 3-4 minutes later and continue as normal.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Back
Top