I want a 16 amp socket in the garage with 3 double sockets

[Julie.]

Should preface this by saying I’m not fully qualified yet - just waiting for nvq 3 from my employer!

But rcd discrimination would ensure garage trips first if there’s a fault there no? Correct me if I’m wrong !

Nope

Why would any particular rcd go?

In effect you have two devices in series, both operate at 30mA with the same time setting.

If anything, the upstream one is likely to operate first.

 

[littlespark]

RCDs trip at values below 30mA. It’s just a maximum.

The ramp test of an rcd tester gives the actual threshold.
Some are only 19mA…. So whichever “30mA” rcd has the lower threshold, will trip first.

However… if the fault is substantial… it could be both.

 

[davesparks]

I would personally add a rcd in the garage cu even if the house db has one. Saves the hassle of the entire house loosing power.

No it doesn't,

There are two reasons why the industrial 16A socket is not permitted in residential,

The regulations do not allow them for household use, but that's not the same as not being permitted in a domestic installation.

 

[brianmoooore]

553.1.201

Every outlet for household shall be shuttered and preferably bs1363

(Paraphrasing as I haven't got my book to hand)

It's the lack of shutters on a 16A outlet that is prohibited.

16A socket has a shutter - a big blue spring loaded one, albeit a manually operated one.
Depends on the exact wording of the reg.

 

[Rockingit]

16A socket has a shutter - a big blue spring loaded one, albeit a manually operated one.
Depends on the exact wording of the reg.

Having looked this up now.... 553.1.201 says "Every socket-outlet for household and similar use shall be of the shuttered type, and, for an AC installation, shall preferably be of a type complying with BS1363" - so exactly as @Julie. said (thank you....). However what I'm now finding curious is that there doesn't seem to be an exception for those with interlocks either.

That said, 553.1.5 (iii) DOES allow outlets to BS EN60309-2 for special purposes where danger would arise or it is necessary to distinguish the circuit.

 

[Intoelectrics]

Having looked this up now.... 553.1.201 says "Every socket-outlet for household and similar use shall be of the shuttered type, and, for an AC installation, shall preferably be of a type complying with BS1363" - so exactly as @Julie. said (thank you....). However what I'm now finding curious is that there doesn't seem to be an exception for those with interlocks either.

That said, 553.1.5 (iii) DOES allow outlets to BS EN60309-2 for special purposes where danger would arise or it is necessary to distinguish the circuit.

Interestingly the definition of household is as follows : a house and its occupants regarded as a unit
So if the socket outlet is in a workshop at the property separate to and not part of the "household" then does this reg apply? So would this fall under the "special purposes" definition?

 

[Julie.]

Interestingly the definition of household is as follows : a house and its occupants regarded as a unit
So if the socket outlet is in a workshop at the property separate to and not part of the "household" then does this reg apply? So would this fall under the "special purposes" definition?

It does indicate "or similar ", in principle I see it as either falling into household/residential.. or commercial/industrial.. or perhaps public.

Only commercial/industrial are regarded as having trained persons, so it's understandable that these are the only area where not having shutters or proper prevention of access to live conductors would be acceptable.

Anywhere where untrained persons can access I think implies the extent of protection described by this regulation, so sockets in a garden, garden shed/workshop/home office to me ought to be regarded as household.

In our own home workshop (husband's hobby) with lathe, Mill etc I have fitted interlocking outlets.

 

[littlespark]

All this about interlocking 16A sockets…. But caravan owners, who are mostly untrained general public type people are expected to plug into whatever socket is at hand.

There are pre-made hook up leads with no interlocking sockets, and even 13A to 16A adaptors for plugging in at home.

 

[brianmoooore]

All this about interlocking 16A sockets…. But caravan owners, who are mostly untrained general public type people are expected to plug into whatever socket is at hand.

There are pre-made hook up leads with no interlocking sockets, and even 13A to 16A adaptors for plugging in at home.

There was a change with the 18th. 16A site sockets are now required to be switched and interlocked, so any unswitched are now C3 on an EICR.

 

[Taylortwocities]

Should preface this by saying I’m not fully qualified yet - just waiting for nvq 3 from my employer!

But rcd discrimination would ensure garage trips first if there’s a fault there no? Correct me if I’m wrong !

Just going back to this. You cannot discriminate RCDs in the same way as you may be able to do with MCBs (and even this ain't easy).
Yes you could have a number of RCDs in a row with decreasing trip currents. but let's look at a simple example.
A 100mA RCD at source, and a 30mA RCD in the outbuilding.

Yes, it is true that an earth leakage of, say, 60mA would trip the 30mA but shouldn't trip the 100mA, BUT in the real World this doesnt happen. You usually get a big wolloping earth fault when you scythe through a mains cable and both RCDs trip because the instantaneous earth fault is more than several amps!!
The only reliable way to discriminate with RCDs is on the basis of TIME.
So you install a Time-delayed RCD nearer the source (they are called type S). The time-delay varies, and sometimes is adjustable. typically an S-type RCD has a time delay of between 150ms and 500ms. An earth fault of any magnitude will trip the standard RCD (typically within 40mSec). The S-type will stay in play.

This is another reason why it is better not to feed a submain (eg to a garage CU) directly from an RCD-protected MCB. Better to provide the circuit from a non-RCD protected way, or - even better - from a separate switch/fuse, then you dont trip the freezer when a mouse dies in the garage.