Want to change my old Honeywell thermostat

[Nik0967]

Hi

Forgive me for sounding a bit dumb but I am a newbie at all this

I take it you mean a mid position valve? ( little silver box with motor arm on the side that you can move and it springs back) If that is right I only have the 1 of them.

Thanks
Nik

 

[vicvapour]

and is the 3 pipes going to the valve?

 

[Nik0967]

Hi

There is 3 pipes on the valve. Here is a pic just to confirm

Thanks
Nik

 

[Nik0967]

Hi

There is 3 pipes on the valve. Here is a pic just to confirm

Thanks
Nik

For some strange reason it won't let me put a pic on here.

It does have 3 pipes attached to it though

 

[D_Hailsham]

There is 3 pipes on the valve.

Then you have a Y Plan system.

Follow the valve cable and it will probably go into a junction box. Take the lid off.

The cable has five wires: blue, grey, orange, white and yellow/green. It's the white wire we are interested in. There will be another wire connected to the same terminal. It should be green/yellow as it is the same wire as connected to terminal 3 of the old thermostat.

Disconnect g/y wire and make it safe, e.g connect to a terminal block.

This green/yellow wire is part of a cable (brown, blue, g/y). Locate the blue wire and disconnect it.

Wrap the end of the blue wire in red insulating tape or sleeving and connect to the same terminal as the white wire.

At the new stat
Connect brown to A
Wrap blue in red tape/sleeving and connect to B
Connect green/yellow to a terminal block

 

[Nik0967]

Hi

I did the wiring as suggested and all appeared to be fine.

I have a little problem though

Once I installed the thermostat it gave me a room tempreture of 16.5c so I tested the heating by setting the thermostat to 18c. The heating came on and the tempreture went up slowly on the thermostat but when it reached 17c it cut off. so that was 1c below what I had set it to

Any ideas please
Thanks
Nik

 

[D_Hailsham]

Once I installed the thermostat it gave me a room temperature of 16.5c so I tested the heating by setting the thermostat to 18c. The heating came on and the temperature went up slowly on the thermostat but when it reached 17c it cut off. so that was 1c below what I had set it to

Did the boiler stay off permanently (over 10 minutes) when it reached 17C?

Was the flame indicator still visible (top right of screen) when the boiler stopped?

 

[matt1e]

The cable has five wires: blue, grey, orange, white and yellow/green. It's the white wire we are interested in. There will be another wire connected to the same terminal. It should be green/yellow as it is the same wire as connected to terminal 3 of the old thermostat.

Disconnect g/y wire and make it safe, e.g connect to a terminal block.

that should be connected to the earth terminal nowadays dave, not "made safe"

At the new stat
Connect green/yellow to a terminal block

but thats ok this end if no earth req

Matt

 

[D_Hailsham]

Disconnect g/y wire and make it safe, e.g connect to a terminal block.

that should be connected to the earth terminal nowadays dave, not "made safe"

So it's acceptable to have one end of an earth wire attached and the other end "floating"? How long has this been going on?

 

[matt1e]

Disconnect g/y wire and make it safe, e.g connect to a terminal block.

that should be connected to the earth terminal nowadays dave, not "made safe"

So it's acceptable to have one end of an earth wire attached and the other end "floating"? How long has this been going on?

a few years now mate. its for testing purposes and good practice
as there is the fact that someone may fit an accessory (room stat etc) that reqs an earth at a later date and just connects the earth without knowing (or testing) it was disconected upstream.
I was caught out myself once when I extended A double insulated smoke alarm system, I had connected My cpc's through (habit) but the original ones had not had theirs connected
got snagged by Building control and I had to work through the building connecting them all back up and back to earth terminal
that served me right for not keeping up with changes in the regs!
It was a bummer, Even Though It does make sense when you think about it so can't complain!

Matt

 

[Nik0967]

Hi

Just an update for you everything seems to be working fine

Thanks to everyone for there advice

Nik