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How do I put a timer onmy Central heating?

(16 Posts)
BumWad Wed 10-Dec-14 20:27:01

I have an Edwardian property and this is our first winter. Our radiator thermostat is a scare thing with a dial by Honeywell.

I would like a timer so that the house is warm when we get in from work, is it just a case of replacing the thermostat? Only other issue is it has to be compact and around the same size as what we already have in as its squeezed in between a door and a light switch.


PigletJohn Wed 10-Dec-14 21:09:20


please measure the gap.

A Honeywell CM907 would be an excellent choice, but will it fit?

PigletJohn Wed 10-Dec-14 21:13:23

133mm wide
89mm high
26mm thick

If not, please add a photo of the gap. The cable might come at it from above, below, or through the wall.

BumWad Wed 10-Dec-14 22:20:21

Hello there Piglet John,

Many thanks for your recommendation, I like the very reasonable price too. Attached is a pic, we have approx 0.5mm gap on the door frame side and 0.8mm gap on the light socket side do you think this will be enough space?

Also will an electrician have to fit it or do you think a simpleton like myself could do it?


BumWad Wed 10-Dec-14 22:30:28

The figures I have stated are if we put the Honeywell CM907 btw

PigletJohn Wed 10-Dec-14 22:49:46

you could probably fit it yourself from the instructions, if you are reasonably handy. You can probably use the old screw holes. Avoid drilling new holes above, below or beside electrical fittings as there may be cables in the wall. It is essential to turn off the power to the boiler before you start, preferably at the main switch in the consumer unit, because mains voltage goes to the thermostat. It is best to test for dead with a multimeter. A neon screwdriver is not a safe tool and belongs in the bin.

Unpack it and identify the terminals first. You will need a medium and a small screwdriver.

Photograph the connections on the old one as you work, in case for any reason you have to put it back.

The first time you set the timings and temperatures will take you a while. Decide on them and write them down before you start.

Have it turn up the heat half an hour* before you normally get out of bed or come home; and go down half an hour before you go out or go to bed. Unlike an old timer, it does not have "on" and "off" periods, just "warm" and "cool" ones. During the cool periods it will not come on unless the temperature drops below your setting. You can turn it to12C if you like a cold house, that will be enough to prevent pipes freezing and keep it dry, for example if you are away for a winter holiday. Look at Holiday setting and you will be surprised at what it can do. I usually put mine on holiday during the summer months.

*if you have a badly insulated old house and small radiators, it may take longer. With experience you can modify the timings. A modern well insulated house is unlikely to get as low as 15C overnight if it was warm in the evening, so the heating will act as if it was off..

For example, you might like:
Monday - Friday First: 07:30, 19C, second: 09:00, 15C (if you are usually out during the day), fourth: 16:00, 20C, fifth: 22:00 21C, sixth: 23:00, 15C.

Saturday and Sunday can be different. You can program any day of the week with its own times and temperatures.

IIRC you can program it before you fit it to the wall, running on its batteries. Lithium batteries will last longer than alkaline.

PigletJohn Wed 10-Dec-14 22:53:46

if you get stuck, put the old one back (using your photos) and get an electrician or heating engineer to fit it.

PigletJohn Wed 10-Dec-14 22:58:12

There is a bad tempered and unsympathetic person I used to work with, who says "I don't mind helping, as long as they don't ask which end of the screwdriver to hold"

DelGirl Thu 11-Dec-14 06:50:45

on the same subject, I have no thermostat or timer. would either be easy to install? tia

DelGirl Thu 11-Dec-14 06:52:25

I mean no thermostat on the wall, only on the boiler which is how I put it on and off

PigletInABlanketJohn Thu 11-Dec-14 10:18:55

That's awful

It will not be difficult, but as you do not already have the wiring and connections, best to get a heating engineer to fit one. An electrician or other person could do it but might take longer to get a wiring diagram or puzzle out your particular boiler.

The Honeywell I suggested is I think the best on the market, it includes heating timer and programmable thermostat. Wireless versions are available but have more to go wrong.

DelGirl Thu 11-Dec-14 12:42:30

Thanks that's very helpful smile

FoodPorn Thu 11-Dec-14 14:53:43

I have the CM907 which we fitted ourselves and it is great. We fitted a separate switch for the hot water so that it could come on at different times to the heating.

BumWad Tue 16-Dec-14 20:39:52

Thanks Piglet John!

Nice little thermostat fsmile

sherbetpips Wed 17-Dec-14 20:31:41

I have that one too it's brill!

PigletInABlanketJohn Wed 17-Dec-14 20:41:56

best on the market IMO

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