Replacement Cylinder Thermostat

[Redhotferrari]

Need to replace a cylinder thermostat but a little confused with the wires!

The one coming off is a Satchwell, (Very old) and the wiring to it 1,2,3, and an earth cable to the metal casing. The replacment I have bought is a Honeywell and any has connections for three wires, named 1,2, and C

I am assuming that wires 1 and 2 from the original should go in 1 and 2 on the new one, and 3 is the C (common) on the new one? What about the Earth though Or do these new type not require an earth?

If not should I simply isolate the Earth on the old cable?

Thanks in advance for your replys

 

[Newboy]

under NO circumstances fit it without an earth - there is an earth clamp on the heater head.

If you are not sure then get somebody competent in - electricity and water do not mix!

 

[Redhotferrari]

Not sure if we are both talking about the same thing. Its not the Immersion stat, I am talking about the stat 1/3rd up from bottom of cylinder controlling the boiler.

 

[seco services]

c = h/w on from programmer.
1 = h/w calling.
2 = h/w satisfied.

 

[Redhotferrari]

Thanks Seco, so would it be right to assume that 1 and 2 would be the same with the 2 on the old stat being c on the new one?

What about the Earth wire from the existing cable?

 

[seco services]

is it a y plan ?

 

[Redhotferrari]

Yep!

 

[seco services]

2 gos to grey, hw off
1 gos to orange, boiler ,pump live.

 

[Redhotferrari]

Seco, thanks for your replies and please bear with me, I have a headache

The existing 'electric' cable is 4 core, one going to earth on the metal casing of the thermostat.

The other three go to numbered terminals on the stat 1, 2 & 3

The new stat has no Earth terminal, Can I just isolate this core on the cable? Other than that there are three terminals 1, 2 & C

Do the numbers 1 & 2 correpond to 1 & 2 on the Honeywell?

If so '3' on the old stat must go to 'c' on the new stat.

Hope this makes semse?

 

[seco services]

easyest way forget the earth.
put h/w only on constant find the wire that becomes live and dead with h/w off

 

[Redhotferrari]

easyest way forget the earth.
put h/w only on constant find the wire that becomes live and dead with h/w off

Earth, fine will just isolate.

Are you saying put the HW on constant then swith on and off to see which wire becomes live and dead?

Once i know this which wire do i put where on the new stat? and what the 'c' about?

 

[seco services]

c is common
when you have got the live from the programmer, live when calling for heat place tha in the c
the wire that gos to the grey on the mid position valve put in 2
the wire that gos to the orange on mid position valve put in 1

 

[JohnD]

Point of information:

Does a modern Cylinder Stat need T&E or 3-core and earth to the programmer? Or more?

 

[twgas]

most modern cyl stats dont need earth as they are double insulated. Yplan needs 3core (common, call, satisfied). Splan only 2 (no satisfied reqd)

 

[Newboy]

apologies for 1st reply - didn't read your post properly!