HELP... Using a 2 gang 2 way switch to control power outdoor lights and sockets

[Barry Watson]

A bit of advice would be much appreciated on this one before I blow myself up.

Purchased a 2 gang 2 way outdoor IP66 light switch to provide switched power to outdoor sockets and outdoor lights. I liked the small size and most of the other multi output switch boxes had 8A maximum per output terminal and I have an outside halogen heater that is 8.4A and 2000 Watts so fuses would blow.

One gang on switch to be used to control power to outdoor sockets, the other the outdoor lights.

Power to the switch itself is provided via a 1.5mm cable run through wall and plugged into a 13a wall socket via an 30mA RCD plug.

External cable from switch to sockets is 1.5mm and to lights is 0.75mm.

The way I have it configured is:

Live wire from RCD power socket connected to COM on gang1 (for external sockets), plus a short link wire from COM on gang1 to COM on gang2 (to provide a live for the external lights).

Live wire from external sockets connected to L1 on gang1.
Live wire from external lights connected to L1 on gang2.

Earth wires from RCD power socket, external sockets and external lights connected to a single terminal block within the switch. Would have connected to the built in earth connection on the switch but too fiddly to get all cables into it.

Neutral wires from RCD power socket, external sockets and external lights connected to another single terminal block within the switch (providing a shared neutral).

That's it basically.

Now this appears to work but with one unexpected result. With the rockers in the off position power is output to the external sockets and lights. With the rockers in the on position no power is output to the sockets and lights. So I basically at the moment have turned the face plate round so that rocker up is off and rocker down is on.

So my questions:

1. Is it ok to use a 20A 2 gang 2 way switch in this way to control power to 2 external circuits.
2. Is it within regulations to use a shared neutral in this way.
3. I was expecting that if my switched live's (from external sockets and lights) were connected to L1 when the rocker was in the off position there would be no link between COM and L1 so no power would be output. And if the rocker was in the on position then link between COM and L1 would be complete and power would be output. BUT it appears to be the opposite for some reason.
4. A query on using a shared neutral. Cant remember the exact current/wattage upper limits for 0.75 and 1.5mm cable but lets say 6A/1400watts and 15A/3000watts. If I run my halogen heater on an external socket which uses 8.4A/2000watts does this return on the shared neutral cables and would it go down the 0.75mm cable used for my external lights. Cant get my head round this.

Thats all really.

Any help much appreciated.

Barry

 

[333rocky333]

It likely says in the instructions to use COM and L2 for 1 way use

 

[Barry Watson]

Thanks for reply 333rocky333 but read through instructions beforehand and it defo says L1. I assume I could just connect to L2 and it would work as expected with the faceplate the correct way up but cant get my head round why it does not work with L1.

 

[EFLImpudence]

Some places regard the 'normal' position of switches as the other way round.
You say it is smaller and unusual in its rating; where did you get it?

One gang on switch to be used to control power to outdoor sockets, the other the outdoor lights.
Power to the switch itself is provided via a 1.5mm cable run through wall and plugged into a 13a wall socket via an 30mA RCD plug.
External cable from switch to sockets is 1.5mm and to lights is 0.75mm.

The way I have it configured is:
Live wire from RCD power socket connected to COM on gang1 (for external sockets), plus a short link wire from COM on gang1 to COM on gang2 (to provide a live for the external lights).
Live wire from to external sockets connected to L1 on gang1.
Live wire from to external lights connected to L1 on gang2.
Earth wires from RCD power socket, external sockets and external lights connected to a single terminal block within the switch.

Ok so far.

Would have connected to the built in earth connection on the switch but too fiddly to get all cables into it.

I presume the switch does not require an earth.

Neutral wires from RCD power socket, external sockets and external lights connected to another single terminal block within the switch (providing a shared neutral).

Yes the problem would be if the neutral was not shared. It is all one circuit.

1. Is it ok to use a 20A 2 gang 2 way switch in this way to control power to 2 external circuits.

Yes it is all protected by a 13A fuse.

2. Is it within regulations to use a shared neutral in this way.

See above.

3. I was expecting that if my switched live's (from to external sockets and lights) were connected to L1 when the rocker was in the off position there would be no link between COM and L1 so no power would be output. And if the rocker was in the on position then link between COM and L1 would be complete and power would be output. BUT it appears to be the opposite for some reason.

See above.

4. A query on using a shared neutral.

See above.

Cant remember the exact current/wattage upper limits for 0.75 and 1.5mm cable but lets say 6A/1400watts and 15A/3000watts. If I run my halogen heater on an external socket which uses 8.4A/2000watts does this return on the shared neutral cables and would it go down the 0.75mm cable used for my external lights. Cant get my head round this.

No. Only the light demand will be on the light cable. Draw the circuit and you will see.
Anyway, as said, it is all protected by a 13A fuse. 13A might be a bit much for 0.75mm² but it will only carry the light's current.

 

[winston1]

Power to the switch itself is provided via a 1.5mm cable run through wall and plugged into a 13a wall socket via an 30mA RCD plug.

Is the circuit already RCD protected at your CU? If so you don't need the additional RCD plug.

 

[Barry Watson]

Thank EFLImpudence for your detailed reply.

Made me feel a bit happier with what I had done. My other half was not too happy with me attempting it but I read up a bit on circuits, cable specs etc and felt quite confident it would work, the only thing confusing me being the power being off when switched to L1. I assume I could connect to L2 instead of L1 and switch would then work as I expected.

Got the switch from Screwfix. It is normal size for a 2 gang switch but much smaller than using a 2 gang plug socket which was my other option. Was limited on space.

The switch is of polycarbonate construction so I dont think it should need earthed itself. I also put plastic caps on the front cover screws.

All it says in instructions is "Any earth connections MUST be made & continuity maintained". So I assumed the shared earth block although not connected to the switch itself would provide continuity for the external circuits back through the internal house circuit.

So I assume from your reply thst shared neutral used this way is within regs.

Many thanks again.

Barry

 

[Barry Watson]

Thanks winston1.

Yes I think it more than likely is. I was just being a bit over causious. Double protection.

Cheers

Barry.

 

[winston1]

Thanks winston1.

Yes I think it more than likely is. I was just being a bit over causious. Double protection.

Cheers

Barry.

Double hassle. If there is a fault both go.

 

[JohnW2]

Double hassle. If there is a fault both go.

Given that faults are so relatively rare, I would not regard that as significant hassle. This sort of misleading numerical statement is akin to many of the 'medicine scares' - doubling a risk which is extremely small still leaves one with an extremely small risk!