How easy to swap from a Honeywell CM907 to a wireless CM927?

[dnute]

Looking for some advice on changing from our existing CM907 thermostat to a 927 wireless version.

Curently the 907 thermostat is on the 2nd floor and controls the 1st and 2nd floor heating. What I want to do is replace the 907 thermostat with the receiver for the 927 to control the temperature in the 1st floor bedromm better.

Is it as simple as re-using the wiring that is already running to the 907 thermostat or does the wireless receiver require different wiring?

 

[simond]

The wireless receiver requires a permanent live and neutral in addition to the cables already present at the CM907.

If you go to the wiring centre for the system you can locate the receiver there.

 

[dnute]

The wireless receiver requires a permanent live and neutral in addition to the cables already present at the CM907.

If you go to the wiring centre for the system you can locate the receiver there.

Sorry-not too clued up on central heating... Which wiring centre do you mean? Down by the boiler or by the hot water tank?

 

[D_Hailsham]

What are you trying to achieve by replacing the 907 with the 927?

Do you have a wiring centre (junction box) near the hot water cylinder?

What other components do you have near the hot water tank?

 

[dnute]

The problem I have is that the thermostat is on the top floor in a room we don't use much. So a number of issues:

1 Heating a room which is usually empty
2 Heat rises so top floor is warmest anyway and you end up turing the thermostat up to warm the middle floor - which just makes it worse.

So what I want to achieve is to actually control the temperature of the middle floor from the same floor.

Looking at prices of the wireless system it may be easier just to re-locate teh existing thermostat down a floor. Was trying to avoid having to cut holes in the walls etc though....

 

[D_Hailsham]

The problem I have is that the thermostat is on the top floor in a room we don't use much.

So what I want to achieve is to actually control the temperature of the middle floor from the same floor.

That seems sensible.

it may be easier just to re-locate the existing thermostat down a floor. Was trying to avoid having to cut holes in the walls etc though....

Where does the cable to the exisiting stat on the top floor come from? Probably a wiring centre (junction box) near the hot water cylinder on the first floor. If so you just have to run a new cable to the preferred location on the first floor landing - it could be just outside the cupboard with the HW tank.

 

[simond]

It will commonly be in the airing cupboard but could be anywhere. It marshalls the cables from the cylinder stat, motorised valve, boiler, thermostat etc.

There is a number of different ways of approaching the wiring of a CH system and those of us in the know will use the most appropriate methods for the situation. In other words, we may use a multicore to amalgamate a couple of nearby components.

As such it can be very confusing for a DIY person to interpret the cabling correctly and potentially dangerous to take advice from a forum where the participants cannot confirm what can only be assumptions.

 

[tamz]

If you have a 3 core cable to the existing stat you can fit the receiver there without disturbing anything, just change the wiring around at the junction box. It will probably only be a twin and earth though as the 907 does not need a neutral. Why would you want (or need) to put the receiver there?
Easiest solution: disconnect the 907 wiring (remember to make safe) and leave 907 in position until you are next decorating.
Site the new receiver next to the junction box. Wire as MI then put the new stat wherever you like.