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Grid switch ratings enquiry

Had an interesting chat with a tech dept this afternoon after coming across some grid switches in a domestic kitchen.

Four grid switches (sharing a common backbox) are each fed via their own 16A cb's, and each feeds 1G sockets (for a cooker hood, fridge freezer, etc). Ignoring the cable sizes (the focus being on the grid switches), given the 13A plug fuses limits the loads in each cct, would you have the current rating of the grid switches equal to or higher than the 16A cb's (e.g. 20A), or lower (but equal to or higher than the socket rating e.g. 13A/14A)?

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0 gkenyon over 5 years ago

Chris Pearson:

BS1363-2:2016+A1:2018

<snip>

Section 6: classification and rating

6.1 The rated current of all socket-outlets shall be 13 A

<snip>

That's the bit that the manufacturers use to determine the rating, which is marked on the back of each double socket-outlet, e.g.:

I'm sure many older socket-outlets were marked "20 A", but this stopped quite a while back.

Section 16 specifies 14 A + 6 A for temperature testing.

That's a "type test", not an "in-use test".

It must be that every BS1363 socket can safely supply 13 A indefinitely because that is what users are entitled to expect of them. Nowhere does it say that the total of a multiple socket-outlet is limited to 13 A. It is not expressly stated, but if a twin socket-outlet may safely supply 14 A + 6 A for at least 4 hours with a stable temperature, it may be inferred that it is safe to do so.

I disagree, the type test is only carried out on samples, for a 1-off occasion. Just because a sample socket-outlet lasts a single exposure of 4 hours to 20 A, doesn't mean production socket-outlets are capable of repeated use at the "overstress" current !

So, regardless of how you personally interpret the snippets you posted, the manufacturer has stated the rating, and we shouldn't exceed that.

Whether a user would know, as you say, is another issue, but I guess the manufacturer would class it as misuse if it were to cause a problem.
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0 gkenyon over 5 years ago

Chris Pearson:

BS1363-2:2016+A1:2018

<snip>

Section 6: classification and rating

6.1 The rated current of all socket-outlets shall be 13 A

<snip>

That's the bit that the manufacturers use to determine the rating, which is marked on the back of each double socket-outlet, e.g.:

I'm sure many older socket-outlets were marked "20 A", but this stopped quite a while back.

Section 16 specifies 14 A + 6 A for temperature testing.

That's a "type test", not an "in-use test".

It must be that every BS1363 socket can safely supply 13 A indefinitely because that is what users are entitled to expect of them. Nowhere does it say that the total of a multiple socket-outlet is limited to 13 A. It is not expressly stated, but if a twin socket-outlet may safely supply 14 A + 6 A for at least 4 hours with a stable temperature, it may be inferred that it is safe to do so.

I disagree, the type test is only carried out on samples, for a 1-off occasion. Just because a sample socket-outlet lasts a single exposure of 4 hours to 20 A, doesn't mean production socket-outlets are capable of repeated use at the "overstress" current !

So, regardless of how you personally interpret the snippets you posted, the manufacturer has stated the rating, and we shouldn't exceed that.

Whether a user would know, as you say, is another issue, but I guess the manufacturer would class it as misuse if it were to cause a problem.
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