Why is split RCD not appropriate for TT?

[JBW175]

No spark worth his salt is fitting split load boards these days IMO.

RCBO & SP is all I quote for.

 

[mainline]

I know that but OSG is supposed to be a bite-sized, easy reference for whats in the big brown book. Seems like the OSG talks a lot of gibberish.

Here's another one.

OSG page 61.

'Other than at the origin of the installation, every circuit...that may have to be isolated without interrupting the supply to other circuits should be provided with its own isolating device. The device must switch all live conductors in a TT system and all line conductors in a TN system.'

This basically says all breakers have to be double pole in a TT, no?

Yet you go to 132.15.201 which the OSG references and it says absolutely nothing about this.

The DP main switch makes it compliant.

 

[swaRRR]

Regulations now require residential to be rcbos.

Which reg is that?

 

[swaRRR]

The DP main switch makes it compliant.

That quote though says that all individual circuits must have their own DP isolating device. Yet the regs don't mention it.

 

[cireland]

The DP main switch makes it compliant.

It does mention 'without interrupting the supply to other circuits'.

 

[swaRRR]

Think it stems from
Regulation 531.3.5.3.2.201

But that reg says supply side of the incoming device eg main switch. **** me these books are confusing. Someone should rewrite them in normal language, they'd make millions.

 

[cireland]

But that reg says supply side of the incoming device eg main switch. **** me these books are confusing. Someone should rewrite them in normal language, they'd make millions.

It does also mention the internal wiring I think. Says something about them being double insulated or
reinforced.

 

[swaRRR]

It does also mention the internal wiring I think. Says something about them being double insulated or
reinforced.

Only as it pertains to a pre-assembled board's link cables as far as i can see.

 

[westward10]

Which reg is that?

531.3.2 (ii)
It does say 'considered'.

 

[cireland]

Only as it pertains to a pre-assembled board's link cables as far as i can see.

'Regulation 531.3.5.3.2.201 requires that where Class I enclosures are installed in installations forming part of a TT system and RCD protection is used on outgoing circuits, all live conductors on the supply side of the incoming device must have double or reinforced insulation'.

Taken from NICEIC website.

 

[mainline]

That quote though says that all individual circuits must have their own DP isolating device. Yet the regs don't mention it.

It does mention 'without interrupting the supply to other circuits'.

I'm sure it says somewhere “that provision may be made for isolation of a group of circuits by a common means”

 

[swaRRR]

531.3.2 (ii)
It does say 'considered'.

The same reg also mentions split RCD though so i don't think it means RCBO's are required in residential premises.

'Regulation 531.3.5.3.2.201 requires that where Class I enclosures are installed in installations forming part of a TT system and RCD protection is used on outgoing circuits, all live conductors on the supply side of the incoming device must have double or reinforced insulation'.

Taken from NICEIC website.

For Class I enclosures in TT systems where RCD protection is used on outgoing circuits, double
or reinforced insulation of all live conductors (incoming cables, extension terminals, etc.) on the supply side of the
incoming device, e.g. main switch, shall be used. Insulated and non-metallic sheathed cables are deemed to meet the
requirements of double or reinforced insulation.

NOTE 1: When selecting equipment, consideration should be given to the assembly manufacturer's internal line interconnecting
cable links on the supply side of an RCD being insulated and non-metallic sheathed, or having reinforced insulation
or equivalent mechanical protection.

From the book.

Supply side of eg main switch is massively ambiguous imo.

 

[swaRRR]

I'm sure it says somewhere “that provision may be made for isolation of a group of circuits by a common means”

It doesn't, not in that quote from the OSG anyway.

 

[mainline]

It doesn't, not in that quote from the OSG anyway.

Welcome to the world of interpretation.

 

[swaRRR]

Welcome to the world of interpretation.

It's all terribly confusing.

 

[cireland]

The same reg also mentions split RCD though so i don't think it means RCBO's are required in residential premises.

For Class I enclosures in TT systems where RCD protection is used on outgoing circuits, double
or reinforced insulation of all live conductors (incoming cables, extension terminals, etc.) on the supply side of the
incoming device, e.g. main switch, shall be used. Insulated and non-metallic sheathed cables are deemed to meet the
requirements of double or reinforced insulation.

NOTE 1: When selecting equipment, consideration should be given to the assembly manufacturer's internal line interconnecting
cable links on the supply side of an RCD being insulated and non-metallic sheathed, or having reinforced insulation
or equivalent mechanical protection.

From the book.

Supply side of eg main switch is massively ambiguous imo.

You were asking about the main tails and argued that :-

Only as it pertains to a pre-assembled board's link cables as far as i can see.

I was merely pointing out that it does mention DI tails or reinforced insulation.

 

[mainline]

That quote though says that all individual circuits must have their own DP isolating device. Yet the regs don't mention it.

If that were the case would it mean that all the 1000s of consumer units that use mcbs are not compliant ?

 

[westward10]

The same reg also mentions split RCD though so i don't think it means RCBO's are required in residential premises.

For Class I enclosures in TT systems where RCD protection is used on outgoing circuits, double
or reinforced insulation of all live conductors (incoming cables, extension terminals, etc.) on the supply side of the
incoming device, e.g. main switch, shall be used. Insulated and non-metallic sheathed cables are deemed to meet the
requirements of double or reinforced insulation.

NOTE 1: When selecting equipment, consideration should be given to the assembly manufacturer's internal line interconnecting
cable links on the supply side of an RCD being insulated and non-metallic sheathed, or having reinforced insulation
or equivalent mechanical protection.

From the book.

Supply side of eg main switch is massively ambiguous imo.

It doesn't say required it suggests them.

 

[swaRRR]

You were asking about the main tails and argued that :-

I was merely pointing out that it does mention DI tails or reinforced insulation.

Nah i'm on about the load side of the main switch to the supply of the RCD's which is what the picture in OSG shows.

 

[swaRRR]

It doesn't say required it suggests them.

You said RCBO's were now required in residential installations.