replacing room stat

[carl11112002]

hi

after damaging the room stat casing moving furniture i decided to change the old 1 for a new 1 i thought this would be as simple as just a simple exchange old for new (how wrong can you be)

the new unit is a sunvic tlx 4101 and on the box says it is a 2 wire design

after taking of the old casing i discovered that it has 4 wires coming from the wall into the unit

1 - red
2 - yellow
3 - earth (green/yellow)
4 - blue



i asked a friend to help out he said to wire the sunvic

1 - blue
2 - red
3 - yellow



and to just tape up the earth wire as it was no longer needed

i tried to do this and it is fine with the water on but as soon as the heating goes on it blows the fuse



please can someone help me with this

thanx

carl11112002

[Robbo]

I think the blue may be neutral, so when the thermostat makes the connection, it is shorting out your live to neutral, thus blowing the fuse.

I think you need to put the red on pin2, the yellow on 1, and not use the blue.

[carl11112002]

thanks

robbo

i will give it a go when i get a day off

[smoggy]

it is a 2 wire design so should have only 2 wires connected

you need to see which wire is permanently live most likely the red wire and wire it to COM (2)
then you need to find the switched live probably blue and wire that to 1 (to find switched live operate thermostat to switch to require heat and one of the wires will become live)
the other 2 wires need to be disconnected at the boiler end or securely taped off seperately.

be extra careful when messing with electrics.

[lucus]

you need to find the neutral and connector block this so its not connected then tape up the earth and ur left with the perm live and switch live these are the 2 cables required for the new stat if you need any more advise just ask
regards

[Rick]

More than likely the wiring will be as follows if it was installed by someone competant.

Red = Live
Yellow = Switched Live
Blue = Neutral
yellow/green = Earth

Connect the Red to terminal 2 and the yellow to terminal 3. Tape off the others incase you need them in the future.

[lucus]

Originally Posted by Rick

More than likely the wiring will be as follows if it was installed by someone competant.

Red = Live
Yellow = Switched Live
Blue = Neutral
yellow/green = Earth

Connect the Red to terminal 2 and the yellow to terminal 3. Tape off the others incase you need them in the future.

The problem is that blue as neutral is the new colours and red as live is the old colours so i wouldnt be suprised if its completely different, being a sparky i have seen all kinds of combinations in the past, as its old colours it should be sleeved using red and black sleeving. if it is the way you said then happy days if not you need to establish which conductors are what.
regards

[Rick]

Yes but a while back there was some wiring about with Red and Blue, and if it was wired according to the instructions that came with the boiler, thats how it will have been done. Hence why I said "if it's been wired by a competant person". Being a Plumber I also see loads of weird combinations also. My personal favourite is always where some arse has used earth as a live