Retrofitting a Honeywell CM927 wireless thermostat to system

[Phlebas]

Hello folks

I have been thinking about replacing my wall thermostat with a Honeywell CM927 wireless thermostat and would like some advice please.

My current system is an open vented and consist of an Ideal Classic boiler, Honeywell 3-way valve, Drayton Tempus Three programmer and Drayton wall thermostat.

Drayton Tempus Three

• Phlebas
• 17 Jan 2013
• 2

Central heating and hot water programmer

The current thermostat is in the entrance hall. It was originally in the living room but was located near the kitchen door. Heat from cooking in the kitchen would switch it off when the door was opened, so the house-builder moved it to the hall. The house was built in 1998. It is not possible to fit a wall stat anywhere else in the living room due to proximity of radiators.

Is it possible to retrofit the wireless stat to the current system?

I think the Honeywell CM927 will only control the central heating, so a separate programmer will be needed to control the hot water. Is this right? What is a good one to use?

Thanks in advance.

 

[Whitespirit66]

What are you tring to achieve by replacing stat/programmer? More flexibility with timings on programmer? More accurate temp control for ch?

The CM927 is single channel, so will only control the ch. If you are happy with the current controller, but want to change the stat, you can update without going wireless. This presumes that you will keep the new stat in same position as old one. If you have the wiring already, always better to use that rather than wireless.

Something like the wired DT90e will replace your stat.

http://www.heatingcontrolsonline.co.uk/honeywell-dt90e-digital-room-thermostat-p-481.html

Or, the wired CM907 will replace your stat and control timings for the ch. You can then set ch to constant on the old programmer and control the ch timings from the new stat. Hw timings will continue to be controlled from old controller.

http://www.heatingcontrolsonline.co.uk/honeywell-cm907-day-programmable-thermostat-p-271.html

 

[Phlebas]

Hi, thanks for replying.

What are you tring to achieve by replacing stat/programmer? More flexibility with timings on programmer? More accurate temp control for ch?l

I felt that I could keep the wireless stat on the coffee table in the middle of the living room to set an accurate temperature in the living space. I hoped it may also reduce gas use if it can control the heating more efficiently.

The current position of the stat in the entrance hall isn't good as it's affected when opening the front door. I don't think a wall mounted stat could be put anywhere in the livinng room because all the internal walls are near doors or radiators.

 

[Whitespirit66]

In that case, yes you can retrofit the 927 to your system.

If you have TRVs on the rads in the room where the stat will be, ideally they should be removed. Practically, you can just leave them turned up to max, otherwise the stat and the TRVs will work against each other.

If you don't have TRVs on the rads in your house, consider fitting them. They help control individual room temps and should help reduce your bill.

 

[Phlebas]

So I can install the Honeywell RF relay box where the old thermostat is utilising the existing wiring?

Also set the Drayton Tempus Three heating to permanently on and let it control the HW as normal?

I intend to fit TRVs in the bedrooms and there is already one in the bathroom.

Thanks.

 

[Whitespirit66]

So I can install the Honeywell RF relay box where the old thermostat is utilising the existing wiring?

Also set the Drayton Tempus Three heating to permanently on and let it control the HW as normal?

The receiver needs a permanent live feed, which you probably won't have where the old room stat is located. Best to install either next to programmer or near the system wiring centre.

Yes, Tempus ch to permanently on and normal control for hw through Tempus.

 

[Phlebas]

Thanks for the advice.