Does this comply with 314?

[Octopus]

Been at a place today.......... brand new loft conversion.......... so an additional CU has been fitted for the lights and sockets ......................

Thinking specifically about 314.2 :

I would say that it doesn't............

Opinions please

and more to the point, this conversion probably cost about £45k so using RCBO's wouldn't have been noticed................

The last one I saw was where a new single RCD board had been used for the entire house and loft conversion.............. why do people do this?

 

[westward10]

I thought it was 25% so 7.5mA.
I haven't got regs book in front of me so I may be wrong

It is a new Reg in the 18th Ed draft, 10% of the rated residual operating current of the device.

 

[Octopus]

Did the loft originally have sockets and lights?
Were they on separate circuits?
Were the separate circuits protected by a single RCD?

No power in original loft

 

[Octopus]

It is a new Reg in the 18th Ed draft, 10% of the rated residual operating current of the device.

Can you please expand on that?

 

[westward10]

Can you please expand on that?

I was referring to #30.

 

[Rpa07]

And westy intended 30%rating of residual referring to -

I thought it was 25% so 7.5mA.
I haven't got regs book in front of me so I may be wrong

 

[Deleted account]

It is a new Reg in the 18th Ed draft, 10% of the rated residual operating current of the device.

Thanks for that westward. I've checked your post #30. That's interesting to know.
I've now got my books out( 17th edition that is) and I still cannot find where I've think I've seen 25% of rated residual current as a design guidance. Therefore a 30mA rcd should be designed with7.5mA as its max.
I know I've seen it somewhere.

I'm wandering where the 30% 9mA came from.

 

[westward10]

I believe some guide books may quote this figure as it is some "rule of thumb" rcbos are prone to unwanted tripping once a 25% threshold of their rating tripping current is reached.

 

[Dave OCD]

I believe some guide books may quote this figure as it is some "rule of thumb" rcbos are prone to unwanted tripping once a 25% threshold of their rating tripping current is reached.

Are you sure, all RCBOs ? If that were the case they'd all fail the half rated current 'no trip' test and therefore be no use at all.

 

[Octopus]

I believe some guide books may quote this figure as it is some "rule of thumb" rcbos are prone to unwanted tripping once a 25% threshold of their rating tripping current is reached.

Really .............. not sure I believe that.

So how do you estimate the anticipated earth leakage of any device then?

 

[Octopus]

So if we can just slap in single up front RCD boards, what is the point of the reg in question AND why did we all start putting in dual RCD boards

Just wondering ?

Anyone?

 

[westward10]

Are you sure, all RCBOs ? If that were the case they'd all fail the half rated current 'no trip' test and therefore be no use at all.

I am only quoting a rule of thumb I believe may be quoted in a commentary/guide book which is what Paignton Pete has probably seen and stuck in his mind. 25% equates to 7.5ma for a 30ma device and it does ring a bell in my head that this should be used as a basis for circuit design. It may have some substance with the proposed 18th Ed quoting 30%.

Edit, see #57.

 

[westward10]

Thanks for that westward. I've checked your post #30. That's interesting to know.
I've now got my books out( 17th edition that is) and I still cannot find where I've think I've seen 25% of rated residual current as a design guidance. Therefore a 30mA rcd should be designed with7.5mA as its max.
I know I've seen it somewhere.

I'm wandering where the 30% 9mA came from.

Okay this is bugging me so if you have a 16th Ed copy with Section 607 in it check out Regulation 607-02-03 there you will find it.

 

[Dave OCD]

I'm sceptical about that much leakage current flowing in a healthy circuit too, unless there's a heck of a lot of I.T. equipment all going at once.

 

[westward10]

Are you sure, all RCBOs ? If that were the case they'd all fail the half rated current 'no trip' test and therefore be no use at all.

The aim here is to keep the currents at a happy level to prevent unwanted tripping, ideally an rcd/rcbo should trip under fault conditions and not excessive leakage when there is no fault. By quoting a percentage level you allow some leeway for further accumulated current and all should be good. Design a circuit where levels are excessive then any further accumulated current may result in unwanted tripping.

 

[Dave OCD]

Makes sense to me, I do think that a lot of this accumulated current can be a bit of a myth though.