13A and 16A sockets on the same 20A radial. OK or not?

[Mark42]

I’ve just had a ‘robust exchange of views’ with a visiting engineer about the 16A sockets in my workshop. These, together with local 13A sockets, are run from radials in 2.5mm, protected by 20A RCBOs.

I say it’s fine to have say a couple of 16A interlocked sockets, and lots of 13A doubles on each radial.

See pictures below: All the sockets in each picture are on the same individual radial (Ignore the 3P socket and the drill supply).

The visitor insisted you must have a separate circuit for 16A sockets, protected at 16A.

I say that’s rubbish, as the protection in this case is rated to the cable CCA and length, and 20A max is fine for 16A sockets as 16A plugs are not fitted to equipment which draws more than this.

All is under the supervision of trained personnel. Care is taken with load balancing as the supply in this remote building is limited to 20A per phase anyway.

Who is right?

 

[Pete999]

I’ve just had a ‘robust exchange of views’ with a visiting engineer about the 16A sockets in my workshop. These, together with local 13A sockets, are run from radials in 2.5mm, protected by 20A RCBOs.

I say it’s fine to have say a couple of 16A interlocked sockets, and lots of 13A doubles on each radial.

See pictures below: All the sockets in each picture are on the same individual radial (Ignore the 3P socket and the drill supply).

The visitor insisted you must have a separate circuit for 16A sockets, protected at 16A.

I say that’s rubbish, as the protection in this case is rated to the cable CCA and length, and 20A max is fine for 16A sockets as 16A plugs are not fitted to equipment which draws more than this.

All is under the supervision of trained personnel. Care is taken with load balancing as the supply in this remote building is limited to 20A per phase anyway.

Who is right?

View attachment 56117

View attachment 56118

Stick them on a 4mm2 Radial with 32A CB

 

[Mark42]

Stick them on a 4mm2 Radial with 32A CB

Thanks, but 16A skts on 32A? Naa. Feels wrong. Too much opportunity for it to end badly.

Plus this remote building has a limited supply, it's protected at 32A upstream, so I limit local breakers to 20A for (hopefully) a bit of discrimination.

 

[SparkyChick]

The purpose of the over current protective device is to protect the installation from overload. If it's all wired in 2.5mm cable, then a 20A device will achieve this, so whilst it's not ideal, I can't think of any regulation it breaks.

 

[Andy78]

The OSG reckons that unlimited 16A sockets on a 20A radial is fine. Appx H, H3.

Whether this is at odds with reg 512.1.2 I'm not entirely sure

 

[Julie.]

It isn't strictly correct as you haven't provided protection against overcurrent (overload), whilst the cable is OK, the socket outlet is rated at 16A not 20A and is therefore unprotected.
A 16A socket outlet is unlike a 13A version because it does not have a fuse - the 13A outlet cannot be overloaded as is fused in the plug, the 16A does not.
It is normal practice though.

 

[Mark42]

It isn't strictly correct as you haven't provided protection against overcurrent (overload), whilst the cable is OK, the socket outlet is rated at 16A not 20A and is therefore unprotected.
A 16A socket outlet is unlike a 13A version because it does not have a fuse - the 13A outlet cannot be overloaded as is fused in the plug, the 16A does not.

Yes, regardless of what the regs say, that's fair, but 16A plugs tend to be fitted to equipment incapable of drawing more than 16A, and there's leeway in the specs, especially for intermittent loads, and I only fit quality plugs and sockets.
A 13A socket can most certainly be overloaded (in theory): by plugging two 3kW loads into the same double socket, which is rated at only 20A overall. No one does that though, as it would be silly

 

[Risteard]

As above, it's permissible to have more than one 16A BS EN 60309 socket-outlet protected by a 20A device. However they shouldn't really be sharing a circuit with BS 1363 socket-outlets (although admittedly not dangerous).

 

[Mark42]

As above, it's permissible to have more than one 16A BS EN 60309 socket-outlet protected by a 20A device. However they shouldn't really be sharing a circuit with BS 1363 socket-outlets (although admittedly not dangerous).

Thanks. I admit it does feel slightly wrong, but I could think of no electrical reason why it's not OK. I wanted to have multiple radials and was running out of ways on the DB. I thought this semi-lash-up was better than keeping 16A and 13A separate but then having too great a floor area served by each circuit.
Any anything is better than encouraging the use (by clients) of these horrible things:

 

[Julie.]

Yes, regardless of what the regs say, that's fair, but 16A plugs tend to be fitted to equipment incapable of drawing more than 16A, and there's leeway in the specs, especially for intermittent loads, and I only fit quality plugs and sockets.
A 13A socket can most certainly be overloaded (in theory): by plugging two 3kW loads into the same double socket, which is rated at only 20A overall. No one does that though, as it would be silly

In your own workshop, I wouldn't be too worried either way, on some sites though I would have each fed from single 16A MCB/RCBO - I have seen too many 32A welders connected via 16A plugs ('nice' 16A plug - 32A socket adaptor lead), but outwith welding shops and the like, I would consider it OK even though technically there's a discrepancy.

 

[Mark42]

... 'nice' 16A plug - 32A socket adaptor lead ...

Yup, why does this item even exist?

(I do admit to owning one though, used only occasionally and with discretion )

 

[freddo]

Multiple 16A sockets on a 20A MCB is fine, I can't see a problem with adding 13A sockets to that circuit.

My biggest concern is how clean and tidy that workshop is, that can't be healthy.

 

[davesparks]

Stick them on a 4mm2 Radial with 32A CB

That is terrible advice, the maximum ocpd for a 16A socket is 20A.
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As above, it's permissible to have more than one 16A BS EN 60309 socket-outlet protected by a 20A device. However they shouldn't really be sharing a circuit with BS 1363 socket-outlets (although admittedly not dangerous).

Why shouldn't they be on the same circuit?

I'm curious as we regularly install circuits with a 13A, 15A and 16A outlet all on the same circuit and I've never yet seen a Regulation preventing this, plus the NICEIC assessor has never had an issue with it.
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Yup, why does this item even exist?

(I do admit to owning one though, used only occasionally and with discretion )

It exists to allow something with a 32A plug to be connected to a 16A socket, we've got a few and use them all of the time.
In fact we've got adaptors from ever size of blue and red commando up to the next size in our stock.
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Any anything is better than encouraging the use (by clients) of these horrible things:
View attachment 56122

What's wrong with a 13-16 adaptor?

 

[DPG]

Nothing wrong at all. Very useful for testing equipment if you have only got a 13A socket available. And there's a 13A fuse in the plug.

 

[Pete999]

That is terrible advice, the maximum ocpd for a 16A socket is 20A.
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Why shouldn't they be on the same circuit?

I'm curious as we regularly install circuits with a 13A, 15A and 16A outlet all on the same circuit and I've never yet seen a Regulation preventing this, plus the NICEIC assessor has never had an issue with it.
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It exists to allow something with a 32A plug to be connected to a 16A socket, we've got a few and use them all of the time.
In fact we've got adaptors from ever size of blue and red commando up to the next size in our stock.
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What's wrong with a 13-16 adaptor?

There are 13 Amp sso involved 4mm2 32 Amp no worries, wire the 16Amp sso on their own 20Amp OCPD

 

[davesparks]

There are 13 Amp sso involved 4mm2 32 Amp no worries, wire the 16Amp sso on their own 20Amp OCPD

Your post certainly didn't make that clear.

So what you're suggesting here is to remove this perfectly compliant installation and install new circuits?

 

[Pete999]

Your post certainly didn't make that clear.

So what you're suggesting here is to remove this perfectly compliant installation and install new circuits?

Yep I am 4mm2 for the 13Aand 2.5 for 16A 32 and 20 OCPDs respectively

 

[radiohead]

Yep I am 4mm2 for the 13Aand 2.5 for 16A 32 and 20 OCPDs respectively

What would be the advantage over an already compliant circuit which is apparently in service without issue?
Explain please.

 

[Mark42]

... My biggest concern is how clean and tidy that workshop is, that can't be healthy.

Ha Ha! It was not always thus.

Now I'm semi-retired I rent the workshop out as a sideline. So it has to be nice and tidy, to aerospace/military standards: Mop the floor, polish the bloody sockets, clean the tops of the doors and so on ...

I used to have six work tables, all of which gradually got covered with works-in-progress in a total mess and there was never anywhere to put anything down. So to solve this, I didn't get rid of the works-in-progress, I got rid of the tables. Reduced to two. So I now have to put stuff away properly, in nicely-labelled boxes in the tool room.

Which means, of course, that I can no longer find anything!

 

[davesparks]

Yep I am 4mm2 for the 13Aand 2.5 for 16A 32 and 20 OCPDs respectively

But why? It is fully compliant and safe now, to suggest replacing the installation for no valid reason is just ridiculous