RCBO’s ? ? ? ?

[Knobhead]

Time for one of Tony’s hypothetical questions again.
But first I need something confirmed. Are RCBO’s SP or DP?
I say it’s hypothetical, my recommendation to a friend regarding a new build he’s having done will be influenced by your first answers.

 

[Paul.M]

You can buy single or double pole Tony. Whats it for?

 

[Knobhead]

Ha! Thanks Paul, you've just added to my confusion.

Got a few drawings to do so will post the main thing tomorrow. Sorry :nopity:

 

[Richard Burns]

I think most domestic RCBOs are single pole as they have a solid neutral.
I have tried to find double pole RCBOs without much success and was told that they were no longer made at the wholesalers, but...I am sure I have seen some since.

 

[Adam]

As far as I know, all RCBO's are SP. Only RCD's are DP.

 

[SPARTYKUS]

Hi

as stated most RCBO's you buy for domestic & commercial work are SP with a Neutral lead.

However DP are available, they are the same width as SP RCBOs with two small terminals for L-N on the top side by side, much the same look as a SP Contactor.

They are rife in motor home dist boards- the ones I have worked with were french I think.

Another point to mention is that DP rcbos are actually specified somewhere in the regs for TT. I had a brain trauma a few years ago trying to work out what was being asked and if every TT install I'd done up to that point was wrong!

Hope that helps

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Ps

Only 791 posts to go

 

[snowhead]

Loads of DP available but not used very often.
I come across them in Petrol filling Stations for use on Pumps.

Buy Crabtree RCBO, Polestar, Type C, 20A, DP, 240V AC...602C/203 Online

 

[malcolmsanford]

Hi

as stated most RCBO's you buy for domestic & commercial work are SP with a Neutral lead.

However DP are available, they are the same width as SP RCBOs with two small terminals for L-N on the top side by side, much the same look as a SP Contactor.

They are rife in motor home dist boards- the ones I have worked with were french I think.

Another point to mention is that DP rcbos are actually specified somewhere in the regs for TT. I had a brain trauma a few years ago trying to work out what was being asked and if every TT install I'd done up to that point was wrong!

Hope that helps

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Ps

Only 791 posts to go

Sparty you may be referring to regulation 537.1.2 with concern for isolation and switching where for a TT system the neutral should have to be disconnected. If your using your RCBO for that then yes it should be double pole, but normally it is considered that your main switch in a CU can adhere to this regulation

There is actually no mention to protection in the regulations concerning double pole protection devices with regards to TT systems. The reasons I prefer as I expect you do is that a double pole device with isolate the neutral and will clear a N-E fault, where a single pole device might not

 

[Richard Burns]

Now If only I could find type B DP RCBOs caravan parks and TT installations would be much easier to plan. I must have a look for motor home electric suppliers.

 

[snowhead]

Now If only I could find type B DP RCBOs caravan parks and TT installations would be much easier to plan. I must have a look for motor home electric suppliers.

any more wishes;

Europa RCBO DP B Curve


[url]http://uk.rs-online.com/web/p/residential-rcbos/3414430/
[/URL]

 

[Paul.M]

Haggar and Merlin are the only two makes I have used. Do a flee bay search on double pole rcbo's and you can easily get hold of whatever ratting single mod, DP rcbo.

 

[Knobhead]

OK this is the bit that is puzzling me.

How in the name of all that is holy can a single pole RCBO claim to meet the requirements of earth fault disconnection. They don’t! Yes it can and does detect a neutral earth fault. What does it do? it breaks the LIVE feed only. The neutral is still conducting and quite happily frying the cable with the minor implication of the house going up in flames.

They’ve gone from being a brilliant idea to the biggest pile of dog poo in my estimation!

Or have I missed something glaringly obvious.

The reason I mentioned my mates new house is he’s determined to go down the all RCBO route. OK if he picks the right make, a disaster in the making if he doesn’t.

 

[Knobhead]

Time for an off the wall solution.
An S type RCD protecting the CU that shouldn’t need protecting in the first place, because it’s supposed to be supper safe on it’s own!

 

[HandySparks]

Not saying you're wrong, Tony, but what scenario can you think of that would continue to give a large fault current with a neutral-earth fault and the line disconnected? (Large enough to "fry the cable".)

 

[Knobhead]

The fault that occured in my house many years back started me thinking about it. A neutral / earth fault next door but one and a high resistance line tap on the supply neutral.
I'd got 40A flowing through my house due to that.