Wiring up replacement Satchwell TLX2259 Thermostat

[TomD1947]

My existing 25 year old Satchwell TLX 2259 room stat is playing up (no complaints after this length of service) and I ordered and received what I thought was a direct replacement. What arrived was a new Satchwell TLX 2356. At first glance it looks identical except the wiring inside is slightly different. I feel it should work but I don't know which terminals to connect the existing wiring. Can anyone help please?

The existing wires are Red to terminal 3, Blue to terminal 4 and Yellow to terminal 1. There is also a yellow/green earth wire connected to the backplate.

 

[jeff the gasman]

The numbers should be the same on your new one. If not then red is coming in to the stat, yellow is the switch going out from stat and blue is neutral.
Have a look at the wiring diagram. If it makes a loud pop when you switch it back on you did it wrong

 

[TomD1947]

Thanks Jeff. That was my initial thought except when I examined the inside of new stat, terminal 4 is not used. Following your simple logic and tracing through the wiring, I suspect blue (neutral) goes on terminal 2. Just wanted to be certain and avoid the 'pop'.

 

[TomD1947]

I'm afraid it was the 'pop' alternative well, not quite. It blew the 3amp fuse in the main heating isolating switch. I don't feel inclined to experiment any further instead, I'm about to buy the correct stat, they're only £7.50 plus postage. Thanks for help anyway.