Where is reg for singular main switch

[Foxyspark]

Hope some more knowledgeable member can educate me as to where in the BS7671 regs demands that every installation has a singular "Main Switch" if suppling 2 CUs on the same domestic meter board. (Does the internal Main Switch in each CU meet reg 537.1.3?
TIA

 

[littlespark]

Huh?

537.1.3 is about plugs and sockets for luminaires.

 

[happysteve]

The Schedule of Inspections IET model forms give you a clue: item 7.3 in the EIC Schedule of Inspections, or item 4.6 in the EICR Schedule of Inspections.

Either way, the answer is "462.1.201" as far as it goes. The Reg states:

"A main linked switch or linked circuit-breaker shall be provided as near as practicable to the origin of every installation as a means of switching the supply on load and as a means of isolation.

A main switch intended for operation by ordinary persons, e.g. of a household or similar installation shall interrupt both live conductors of a single-phase supply."

"Electrical installation" is defined in part 2 of the Regs as, "An assembly of associated electrical equipment having co-ordinated characteristics to fulfill specific purposes."

 

[Foxyspark]

Huh?

537.1.3 is about plugs and sockets for luminaires.

Aahh, perhaps I should have said; reg 462.1.201!

 

[Foxyspark]

The Schedule of Inspections IET model forms give you a clue: item 7.3 in the EIC Schedule of Inspections, or item 4.6 in the EICR Schedule of Inspections.

Either way, the answer is "462.1.201" as far as it goes. The Reg states:

"A main linked switch or linked circuit-breaker shall be provided as near as practicable to the origin of every installation as a means of switching the supply on load and as a means of isolation.

A main switch intended for operation by ordinary persons, e.g. of a household or similar installation shall interrupt both live conductors of a single-phase supply."

"Electrical installation" is defined in part 2 of the Regs as, "An assembly of associated electrical equipment having co-ordinated characteristics to fulfill specific purposes."

Thanks @happysteve for your inspiration. Would the internal main switch in each CU meet 462.1.201?

 

[cliffed]

Any definite answers on this one

 

[sinewove]

Any definite answers on this one

This has come up before and it's been said the circuits from each cu are classed as an installation so each main switch counts as an isolator for that installation.
S

 

[Lucien Nunes]

I don't like relying on the letter of the regulations without applying logic. If the circuits from each CU form a separate installation, would the circuits on each RCD in a split CU form two separate installations. Would you carry out two EICRs, one for each installation? With double-pole RCBOs, wouldn't each circuit form a separate installation each with a means of DP isolation? One EICR per circuit and no need for a main switch in the CU? It could get very arbitrary.

There are situations where there is perfect sense in declaring some parts a separate installation, for example a group of high-integrity circuits for medical equipment, supplied from a central UPS and run by themselves to special, marked points. But where there is a single source of supply and the distinction between which circuits are on which CU is neither obvious to the user nor done that way for a specific functional reason, it is only logical to call it one installation.

Imagine someone is getting an electric shock, or a building is on fire, dark and full of smoke. Ideally you want to be able to dive for a big switch marked 'main switch' and pull it, in the expectation that the entire system will be dead.

 

[pc1966]

I agree with @Lucien Nunes that there ought to be a single point of isolation. If a 2nd CU is to be fitted then putting an isolator before any Henley blocks splitting the tails to feed them would solve all of that!

 

[ipf]

But where there is a single source of supply and the distinction between which circuits are on which CU is neither obvious to the user nor done that way for a specific functional reason, it is only logical to call it one installation.

I'm with you there.
Then again, I've been working on an old farm building conversion. One 3 phase supply with two adjacent isolation switches, one singe phase for CU feeding original house and one 3 phase for switch fuse feeding remote DB.
It's all one house.....with two isolators fitted and sealed by DNO a couple of years ago.
I'm just going to label that both supplies need to be isolated in emergency.

 

[AJB Temple]

I am a DIY person, but in case it is relevant we have recently had a lengthy debate with Building Control on exactly this point. In our case we have 6 CUs distributed around the buildings doing various different things. There is a main CU that serves the main house and all of the others are fed by tails to a Henley Block and from there BC insisted on SWA to distribution box containing main switch and an individual RCBO for each of the sub consumer units AND for this to be immediately adjacent to the main CU. This was done, and signed off by Building Control as compliant in December 2021.