RCD descrimination

[ccam108]

See 314 'Division of installation'

I have done.

It neither says nor implies that a CU with 2 RCDs is not allowed.

bump

Who's going to contradict me?

I am.

314.1 (i) Every installation shall be divided into circuits, as necessary, to avoid hazards and minimize inconvenience in the event of a fault

314.2 Separate circuits shall be provided for parts of the installation which need to be separately controlled, in such a way that those circuits are not affected by the failure of other circuits..........

I suppose you would also argue that today is Monday the 25 October, talk about stand on your head.

Now, I'm no electrician, but surely they both refer to separate CIRCUITS - as in on different MCBs.

I don't see the words "RCD", "earth leakage" or even "protection" mentioned anywhere there.

Colin C

 

[holmslaw]

Now, I'm no electrician, but surely they both refer to separate CIRCUITS - as in on different MCBs.

I don't see the words "RCD", "earth leakage" or even "protection" mentioned anywhere there.

Colin C

I don't see the words fuse or mcb.

On a dual RCD board a fault on one circuit can trip the main RCD and thereby kill all the other circuits connected to that RCD.

 

[ban-all-sheds]

314.1 (i) Every installation shall be divided into circuits, as necessary, to avoid hazards and minimize inconvenience in the event of a fault

Yup.

AS NECESSARY

There is nothing in 314 which says or implies that a CU with 2 RCDs cannot provide the division of circuits which is necessary to avoid hazards and minimize inconvenience in the event of a fault.

314.2 Separate circuits shall be provided for parts of the installation which need to be separately controlled, in such a way that those circuits are not affected by the failure of other circuits..........

Yup.

NEED TO BE

There is nothing in 314 which says or implies that a CU with 2 RCDs cannot be used where 2 RCDs does provide sufficient granularity of the parts of the installation which need to be separately controlled.

I suppose you would also argue that today is Monday the 25 October, talk about stand on your head.

Holmslaw - if you aren't prepared to debate this like a mature and intelligent adult will you please just go away and stop bothering this forum.

 

[plugwash]

Separate circuits shall be provided for parts of the installation which need to be separately controlled, in such a way that those circuits are not affected by the failure of other circuits..........

I have to agree with holmslaw on this one.

If you share a RCD between circuits there is a good chance that those circuits will be affected by failures of other circuits.

 

[ccam108]

OK taking your argument further - what about the single service head fuse? It's uncommon, but they do blow. Maybe every house should be supplied from at least two incomers?

Wait, better make that two substations, in case one goes down.

How far do you take it?

 

[holmslaw]

Holmslaw - if you aren't prepared to debate this like a mature and intelligent adult will you please just go away and stop bothering this forum.

You don't make the rules around here, you're just another nobody and you resent my superior electrical knowledge.

 

[ban-all-sheds]

On a dual RCD board a fault on one circuit can trip the main RCD and thereby kill all the other circuits connected to that RCD.

1) That's not the type of board you described:

Thats why split cu's with two main RCD's

Having one RCD downstream of another cannot accurately be termed two MAIN RCDs.

2) Even if we do proceed on the basis that you were inaccurate in your description, and you did mean a CU with one RCD upstream of everything else there is still nothing in 314 which says or implies that such a CU cannot comply with the regulations.

 

[ban-all-sheds]

If you share a RCD between circuits there is a good chance that those circuits will be affected by failures of other circuits.

That is not necessarily a contravention of the regulations.

"As necessary" .... "take account of" ... "which need to be" ... "due account shall be taken of"....

All these terms mean that you have to put thought into your design, you have to consider failure modes, risks, and risk mitigation.

They do not mean that you cannot use a CU with 2 RCDs in it, even of the design where one of them is upstream of everything else.

 

[ban-all-sheds]

You don't make the rules around here, you're just another nobody and you resent my superior electrical knowledge.

Holmslaw - if you aren't prepared to debate this like a mature and intelligent adult will you please just go away and stop bothering this forum.