New thermostat wireing.

[melodymaker]

I have just purchased a TH-7281B digital 250 V room thermostat but I am a bit confused and may have bought the wrong one. The instructions show terminal (1) N.O contacts for heating terminal (3) N.C contacts for cooling and terminal (5) C=Common (one wire must be connected here)

The existing thermostat (front panel broken off) which was inherited when we moved in is a Sunvic TLX 2259 220-240 V. There are 3 wires running into it but no indication of what they are. One is black, one red and one is bare. The diagram on the box shows 3 points to connect terminal (1) (N) terminal 3 (L) and terminal 4.

Can anyone throw any light on this for me?

 

[Taylortwocities]

If it has been wired properly:

Red goes to C
Black to NO
The bare wire 'should' be earth and should go to the back mounting box or other earth terminal.

Where do the three wires go on your old stat?

 

[melodymaker]

The existing thermostat (front panel broken off) which was inherited when we moved in is a Sunvic TLX 2259 220-240 V. There are 3 wires running into it but no indication of what they are. One is black, one red and one is bare. The diagram on the box shows 3 points to connect terminal (1) (N) terminal 3 (L) and terminal 4.

Does it matter they are different Voltages?

 

[Taylortwocities]

What do you mean by different voltages?

The TH-7281B runs off batteries and when the temperature falls below the set temperature there is a connection made between the C terminal and the NO terminal. This tells the boiler to fire up and then your house gets hotter.

Thats why i asked where the existing wires go on the old thermostat. That will ensure that some muppet hasnt used one of the wires for the wrong thing.
Shall i ask again? OK, here goes:

Where do the three wires go on your old stat?

 

[melodymaker]

Shall i ask again? OK

If you like.

The three wires go into 3 different screws with no indication of what they are hence why I asked in the first place.

Thankyou.

 

[Taylortwocities]

I'm struggling here.

I'll ask a bit differently.

You have three wires. Red, Black and the bare wire that should be earth.

On what terminals on the old thermostat do they connect??