Help please Pigletjohn or anyone else

[Ruhrpott]

I would like Pigletjohns ever useful advice on our central heating controls. We have the following timers, one which controls hot water and downstairs heating and one which controls upstairs heating and the pictured thermostat again one upstairs and one downstairs. We would like a better way of controlling the heating that we could program to go on and off when we wanted. Which ones do you recommend for us and do we get a plumber to fit it or an electrician (or even DIY, DH is quite good with electrics). Thanks for your help.

Honeywell CM907. You need two.

It replaces the two wired thermostats you have. An electrician or a heating engineer can fit it, or a competent DIYer.

The two programmers are no longer required, or can be set to CH=On since the CM907 includes the heating timer.

You still need a simple timer for your HW cylinder. To remove the programmers or to replace one of them with a HW timer you will need the wiring diagram for the old programmer, which you can probably get off the web, in order to identify the wires, or a heating engineer will recognise them. There might be a Wiring Centre, which is simply a junction box, where the connections can be bridged except for the ones that go to the HW control. You have two heating zones and one HW zone. Probably you have one two-port valve and one three-port valve, but you might have three two-port valves.

If you have a gravity feed to the cylinder (not pumped) it will be less trouble to get a heating engineer. It is less efficient and it would be preferable to convert it fully pumped.

Thanks for the info. So could we just replace the thermostats with the CM907 and leave the house existing ch programmers permanently on and the hot water timed on the existing programmer?

I think we have gravity feed. We have two big tanks in the loft and a shower pump (showers run off hot water) and whatever these are in the photos.

yes

those are two-port motorised valves
www.screwfix.com/p/honeywell-v4043h-2-port-motorised-valve/31480
they usually last 20 to 30 years and are replaceable when worn out.

the tanks are not what makes it gravity feed (circulation). It depends on whether the pump pushes the water through a valve to the cylinder.
www.screwfix.com/p/grundfos-ups2-15-50-60-central-heating-pump/42635

An old system with gravity circulation to the cylinder would probably have 28mm pipes circulating from the boiler to the cylinder. If pumped, more likely 22mm. As yours is controlled by a motorised valve I think it will be pumped.

Thanks that's very helpful. I will order two cm 907 and get hubby to change the thermostats and leave old programmers on on and use them to carry on timing the hot water. That sounds like a good (and relatively cheap) answer.
Any idea which out old thermostats are so we can google the wires and changing them for a cm907? It just says Honeywell on them and no numbers.

I bet you 50p you find a red and a black wire behind them, plus an earth wire which might be bare but should be sheathed green and yellow. They will be Live and Switched Live. The switched live might have a red sleeve on it.

There is a chance you will find a neutral as well, in which case the wires will be red, blue, yellow plus earth. In which case the neutral is for an accelerator heater which you will not need. Wall thermostats are (almost) all the same connections regardless of make and model.

Colours mentioned are old convention, no longer used in new work.

The wires carry mains voltage so the circuit must be isolated at consumer unit and tested for dead. A multimeter will be useful. If you have a neon screwdriver put it in the bin.

We have a multimeter and hubby is competent at electrics and has already changed all our light fittings (unlike me who won't go near them but can tile a kitchen!)

Thanks again for all your help. Hubby is off all week so will order them now and put him to work.

Thanks again for your help. We have just installed them and they are up and running.