How to fit a 3 wire thermostat on an existing 5 wire installation?

[ottosump]

Hi group, hope everyone is enjoying their Christmas time...

I am trying to fit a standard 3 wire thermostat to a boiler which has had a previous 5 wire installation, long story but the previous tenant has taken their thermostat with them and now I'm statless!

Can any body advise is this can be done?
I've included pictures of the thermostat I am considering buying (DRAYTON RTS1 ROOM THERMOSTAT)
and the wiring.
TIA group

 

[JohnD]

Are you the owner? Or a tenant?

You have to identify what all the existing wires do. A multimeter will be invaluable.

I expect you have a Permanent Live and a Permanent Neutral and an earth.

One of the others will be a Switched Live that set the CH running. However it's possible that two of them are for low-voltage switching. Do you have any idea what the old programmer/timer looked like? You have the option of getting your solicitor to write a stiff letter demanding the return or reinstatement of a Fitting that was included in the House Sale and was wrongly removed by the vendor, or monetary compensation.

I don't know what the other one will be, unless there was once a cooling/air conditioning circuit. Probably unused. Looking at the copper ends, do any of them look as if they have never been tightened in a terminal?

You might consider chasing out the wall to take a metal backbox, it will be easier to accomodate your wires behind the stat without being tempted to cut them short.

 

[CBW]

You need to know which is the call for heat wire, and assuming they’re all as they are (you may need to test the wires):

Line (Brown) to L on Drayton
Neutral to N on Drayton
Call for heat (grey or black) in 3 on Drayton
Park earth in designated terminal or into a connector block.

Whichever is not the call for heat (grey or black) can be safely terminated into a connector block.

Might be better with a Honeywell T6360?

 

[ottosump]

Thanks for the prompt reply, why do you think the Honeywell T6360 would be better, looks as though they do the same thing.
Regards Otto, West Cumbria

 

[CBW]

I think they’re smaller in size, and possibly more terminals, however this might confuse anyone else who works on the system, so better with the others in a terminal block, and go for either thermostat.

 

[snb]

Why on earth would you be trying to fit a thermostat below a boiler?
That wiring was in a RF thermostat receiver box.
That’s what you should be putting back in .
Get a center brand one from plumb center. About £70 inc vat and wire in. The actual stat can then be in either the lounge or a more sensible place.