Room Thermostat to heater wiring

[wrighty263]

Hi there,

Whilst decorating front room, i decided to investigate an unused FCU with the intentions of replacing it.

What i have discovered is that the FCU is connected to a Sunvic TLX 2259 Thermostat by a 3 core + Earth cable.

What has thrown me is that both red and yellow cores are terminated together at the thermostat, and then terminated on both "IN" terminals on the FCU. (see pics, prob explains better than i can)

Untitled

• wrighty263
• 25 Jan 2013
• 1

Untitled

• wrighty263
• 25 Jan 2013
• 1

Something doesnt seem right about having 2 lives at the FCU and neutral boxed off.

My first question is, can someone clarify if the wiring is correct, and if not what should it be.

And if the wiring is correct,if at a later date i want to connect a heater, how should a heater be wired in?

Any help greatly appreciated[/img]

 

[Lectrician]

Larger pics, and a pic with the stat removed from the wall?

 

[stem]

Hi Wrighty263, welcome to the forum.

Whether it's correct or not would have depended upon what was connected to it, as we don't know, there's no way of telling really.

It looks to me that a mains supply comes into the thermostat from a twin and earth cable to terminal 3 (live) and terminal 4 (neutral). So far so good.

Then the red and yellow cores of the 3 core cable which you say are both connected to terminal 1 (switched live) go to the "FCU". (Except to me it looks more like a dual pole switch rather than an FCU). However, as Lectrician indicates it is difficult to see properly. The neutral is just terminated in a screw connector.

If this correct, this arrangement may be like that because:
1) It's an easy way to connect two separate appliances to the same switch.
2) Perhaps one pole wasn't connected to the fuse (if that's what is mounted at the side, can't see clearly enough to tell) and the other was, as different sized loads were connected to each
3) Maybe the FCU (or switch) was just a convenient location for a spare wire when whatever was connected was removed.
4) The three core cable was used to supply a Live, Switched Live & Neutral at some point, but the original appliance may have been replaced with one that didn't need a permanent live, so they were joined together.

You can disconnect the three core cable from the thermostat, then the FCU or switch at the other end can then be removed.

If you want to get rid of the thermostat too then you will need to find out where the mains supply to the thermostat comes from and disconnect that before removing it.

 

[securespark]

Yeah, does seem a bit odd.

It looks like the live & neutral feed comes into the stat, and the outgoing cable goes out to wherever it was going via this switch.

I don't think I've seen something like that before, but I'd need a closer look.

Looks like a grid switch. Could the thing next to the switch be a neon?