20 Amp DP Switch on 32 Amp Ring Main

Tabs101 · 13 Feb 2016

Hi,

I am getting a lot of conflicting information regarding my query.

Can you have a 32 amp ring main (two 2.5mm cables) into a 20 amp DP switch then to a single 2.5mm cable to a single socket?

So 20 amp DP switch - 2 cables IN (on the ring) and 1 cable OUT (to a single socket)

Thanks

flameport · 14 Feb 2016

Yes you can.
Others may disagree and spend the next 100 pages wrangling over it.

Tabs101 · 14 Feb 2016

Perfect. Thanks for your reply.

The reason for asking is because my electrician asked me to purchase 20 Amp switches (to match other sockets) and I was a little unsure because when I opened one, the tail fixings and holding screws where small. Not the usual size like the ones found in double gang sockets.

Echo the husky · 14 Feb 2016

It's fine, I did it recently with a 4 gang engraved grid to feed 2 single sockets and 2 fused outlets for appliances. What brand switches are you using, the terminals should be plenty big enough for 2x 2.5mm²?

Tabs101 · 14 Feb 2016

Hi, thanks for your reply.

I have purchased a Nexus Metal 20 Amp DP switch. The terminals look like they will fit 2 x 2.5mm tails but they are a lot smaller than terminals found on gang sockets. I don't know if the size of the terminals are rated to certain amps. See photo

Echo the husky · 14 Feb 2016

The terminals are just made smaller on some products so they can be manufactured more cheaply.

Tabs101 · 14 Feb 2016

Perfect . . . thanks for you advice

bernardgreen · 14 Feb 2016

Is there any connection between those two earth terminals ? As per the green in the image.

If there is no connection between then and the installer uses both Earth terminals then the continuity of the CPC ( Earth ) will depend on the back box being metal and BOTH the fixing screws being tight. If ALL earth wires are wired into just one of the terminals then continuity will not depened on screws and back box.

Echo the husky · 14 Feb 2016

It's a metal plate. Not that that is good manufacturing, my comment about cost cutting applies here too.

bernardgreen · 14 Feb 2016

freddo said:
It's a metal plate. Not that that is good manufacturing,

Will the connection between the rivets and the chromed front plate carry a fault current ( from the CPC ) long enough for the MCB to operate. As you say not good manufacturing due to cost cutting to save a bit of metal.

Jackrae · 14 Feb 2016

Seems a strange design if the "user contactable" outer plate is being used to form part of the CPC continuity circuit

sparkwright · 14 Feb 2016

Jackrae said:
Seems a strange design if the "user contactable" outer plate is being used to form part of the CPC continuity circuit

Assuming the back plate isn't metal, which I think you are suggesting, I would then suspect there is a metal strip on the other side of the switch, which gets covered by the cover plate.

Echo the husky · 14 Feb 2016

bernardgreen said:
Will the connection between the rivets and the chromed front plate carry a fault current ( from the CPC ) long enough for the MCB to operate. As you say not good manufacturing due to cost cutting to save a bit of metal.

I think I would probably put all 3 conductors into one terminal.

sparkwright · 14 Feb 2016

Deleted.

Tabs101 · 14 Feb 2016

There is no direct connection between the two earth terminals. It looks like it is connected via a small metal case to the front of the plate. I am assuming when the screws are in this will complete the earth circuit.

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20 Amp DP Switch on 32 Amp Ring Main

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