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Topic Title: Consumer unit advice, discrimination ?
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Created On: 20 January 2014 08:08 AM
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 20 January 2014 08:08 AM
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daveretired

Posts: 2
Joined: 19 January 2014

I have seen a consumer unit that has just been replaced in a sports pavilion, it only has RCD as mainswitch and four MCB's, I say it does not comply with regs as no discrimination. Fault on kettle say, would put out all lights leading to danger, conformation please that I am right.
 20 January 2014 08:48 AM
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Parsley

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314.1 and 536.1 and GN1 3.7.6

Regards
 20 January 2014 08:50 AM
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prophet

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What's the earthing system and trip rating of the RCD?

Most likely doesn't comply with Reg 314

Tom
 20 January 2014 05:40 PM
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JimGoldfinch

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It is not discrimination that is the problem, so to say it is would be wrong- see 314. More to the point is there emergency lighting fitted that may reduce the danger/inconvenience?
 20 January 2014 06:14 PM
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phantom9

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Originally posted by: daveretired

I have seen a consumer unit that has just been replaced in a sports pavilion, it only has RCD as mainswitch and four MCB's, I say it does not comply with regs as no discrimination. Fault on kettle say, would put out all lights leading to danger, conformation please that I am right.


I agree with you, Dave. I believe fuse boards with a main switch RCD do not comply with section 314. A normal main switch and all RCBO circuits would be my choice.
 20 January 2014 08:09 PM
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OMS

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This is a commercial building however - so the RCD may not be providing additional protection against carelessness of users - it may just be dealing with, as an example, a higher than usual Zs on circuits.

I've no doubt that it could be manipulated to both comply and not comply with 314 - the requirements being totally subjective both in terms of hazard and inconvenience.

It could also be argued that an RCD is not an overcurrent protective device - it only protects from EF not EF and SC.

If you take this to an illogical conclusion, then any RCD acting on more than one final circuit is non compliant - so where does that leave the so called 17th edition boards - non compliant ?

You can't say that it doesn't comply with regulation without asking the designer what the intention was ?


Regards

OMS

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Failure is always an option
 20 January 2014 08:28 PM
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alancapon

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You could also take the view that it is no worse than having a single source of supply into the premises.

Regards,

Alan.
 20 January 2014 09:14 PM
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Phillron

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Originally posted by: alancapon

You could also take the view that it is no worse than having a single source of supply into the premises.



Regards,



Alan.


Precisely
Or even no Shilling for the coin meter lol
 20 January 2014 09:38 PM
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AJJewsbury

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Fault on kettle say, would put out all lights leading to danger, conformation please that I am right.

Would a fault on the lights also put out all the lights?
- Andy.
 21 January 2014 08:36 AM
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daveretired

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There are two lighting circuits, at the moment fault on one would put both out, if RCBO's were used on all circuits and normal mainswitch, then only one would fail, the electrics are used unsupervised, the RCD is 30m/a, I just feel in the interests of safety RCBO's on all circuits would be ideal. Thanks for all your replies so far, it will help me get my point across. Dave.
 21 January 2014 10:34 AM
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OMS

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What is the purpose of the RCD (or proposed RCBO's) ?

Regards

OMS

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Failure is always an option
 21 January 2014 10:48 AM
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broadgage

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Only 4 sub circuits suggests to me that the premises are fairly small and simple and that front end RCD protection is therefore acceptable. Especialy if used only in daylight, as many sports pavilions are, or if equiped with emergency lighting.

One can "overinterprate 314" as meaning that every circuit should have its own RCD.

A large nursing home all on one RCD ? no way !
A small sports pavilion ? fine in my view.
 21 January 2014 12:35 PM
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Jaymack

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Originally posted by: daveretired
Fault on kettle say, would put out all lights leading to danger, conformation please that I am right.

Apart from the RCD protection. For a building where the public has access, what emergency lighting is present?, and is it periodically inspected?

Regards
 21 January 2014 03:22 PM
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AJJewsbury

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There are two lighting circuits, at the moment fault on one would put both out

But unless the areas served are interleaved some areas/rooms will still be left in darkness?

- Andy.
 21 January 2014 05:12 PM
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phantom9

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Originally posted by: alancapon

You could also take the view that it is no worse than having a single source of supply into the premises.



Regards,



Alan.


No, section 314 refers specifically to circuits, not incoming supplies. It is different to that entirely.
 21 January 2014 05:28 PM
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AJJewsbury

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No, section 314 refers specifically to circuits, not incoming supplies. It is different to that entirely.

I think Alan (being a supplier chap) was suggesting that if danger arose by loosing several circuits simultaneously, then that same danger would occur during a power-cut (which in some rural areas are more frequent than local earth faults). More of a practical overall risk-assessment thing rather than BS 7671/314 specific. Hence all the questions about emergency lighting - if emergency lighting isn't required from power-cut perspective, then it's unlikely that a risk assessment would think that loosing lighting due to an internal fault would produce unacceptable danger.

Fault on kettle say, would put out all lights leading to danger

Or looking at it the other way around, a fault on the lights also trips out the kettle supply - reducing the risk of scalds from boiling water in a darkened room

- Andy.
 21 January 2014 06:57 PM
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OMS

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Originally posted by: phantom9

Originally posted by: alancapon

You could also take the view that it is no worse than having a single source of supply into the premises.

Regards,


Alan.




No, section 314 refers specifically to circuits, not incoming supplies. It is different to that entirely.


Well, you could think of it then as an incoming supply, metering, installation main switch (with protection)and a remote Distribution board or consumer unit. The cabling between the installation main switch and protection, and the remote DB is most certainly a circuit by definition, and forms part of an installation covered by BS 7671 - which puts it firmly into Regulation group 314.

The regulation is basically aspirational, open to several interpretations and has no doubt been hijacked by those wishing to sell more RCD's.

If the intention is to avoid danger and minimise inconvenience then we have to look at the installation and it's source of supply in the "round" don't we ?

Regards

OMS

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Failure is always an option
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