RCBO 3P+N

[Boostjunky]

I am building  a garage/ workshop it will have is own  CU  I oder a 3P +N RCBO from aliexpress but they send me  a 3P RCBO can I use this one

or better to oder  a new?  shold  I use the same earth rod from the house or fit  a new it is about  15 meters between  them?

[carlyai]

Some experts will visit shortly, but I recently built the same sort of thing about 30m from the house. I treated it as a new installation as (mine only single phase), the underground power feed is from the incoming mains. So I did put an earth rod from the new garage CU.
I haven't looked up the RCBO 3P + N, but I presume it open circuits the N as well on a trip. If this is the case I'm not sure why you require it on a garage installation.

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[Crossy]

@Boostjunky can you post a photo of the device they supplied please.

 

I would use a separate rod but do NOT link N-E in the outbuilding CU.

[Boostjunky]

here is he picture .  

[Crossy]

OK, that's a 3-P RCBO intended for operation of balanced 3-phase loads with no neutral (motors and the like).

 

I do not believe it is suitable for the application you intend where there will be significant neutral currents.

 

Time to open a dispute with the supplier I think if they definitely sold it as 3P+N.

[wayned]

I just went to the Aliexpress website. https://www.aliexpress.com/wholesale?ltype=wholesale&d=y&origin=y&isViewCP=y&catId=0&initiative_id=SB_20170222185203&SearchText=3P+%2BN+RCBO&blanktest=0&tc=af, and it seems that some of the RCBOs advertised  as 3P+N gave a neutral connection and some don't!  The picture of the EFET one looks exactly like the one you have and is obviously missing the neutral but is advertised as 3P+N, the picture of the DELIXI advertised as 3P+N has the neutral connection.  Both advertised as 3P+N. Doesn't surprise me!

[Boostjunky]

I contacted the seller  and he will send me the right one   that I oder , so abut10 days befor i get  it

[Crossy]

Don't let your option to open a dispute expire.

 

I've seen this ploy from a couple of Chinese sellers, low value stuff so they hope you'll not bother opening a dispute.

 

Item in question was a pack of 10 football adaptors. Only one arrived.

"Sorry, sorry, we'll send you the rest"

Some time later, after I'd let the dispute time out, another one adaptor arrived

 

So I have two adaptors for the price of 10 (they were really cheap mind).

 

[wayned]

I haven't had too much trouble with the sellers on Aliexpress, but always keep the dispute date in mind.  However, Lazada customer service is totally useless.  I order a lot through Lazada and the majority of the time they perform  and deliver before the committed date, but when I have a problem and have to contact customer service they have to be the worst.  Getting a refund for non delivery takes a month of Sundays! off topic!

[bankruatsteve]

Just to say... I have ordered a lot from Lazada and the one time I had issue it was resolved by their customer service immediately.  They refunded the price and I sent back the defective item.  

[carlyai]

Probably silly question, but how can you have a 3 phase RCBO without a neutral? What inbalance causes it to trip?

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[Crossy]

23 minutes ago, Arjen said:

I think Crossy gives the answer here? "operation of balanced 3-phase loads"  So an inbalance between the phases will make it trip?

 

Nearly. A simple phase imbalance won't trip a 3-phase 3-wire RCD/RCBO (with no neutral the phase voltages will go awry).

 

The RCD device performs a phasor addition of the three phase currents, this should result in zero. If it does not the difference must be going somewhere (through you) and the device operates.

 

The 3-P+N unit does the same sums on the 3 phase plus the neutral (still looking for zero).

 

[tutsiwarrior]

I always wondered about the operating principle of the RCBO...am I right in presuming that it's the same as a differential protection relay in an HV/MV installation?...a low voltage version of detecting ground faults...

 

 

[carlyai]

 
Nearly. A simple phase imbalance won't trip a 3-phase 3-wire RCD/RCBO (with no neutral the phase voltages will go awry).
 
The RCD device performs a phasor addition of the three phase currents, this should result in zero. If it does not the difference must be going somewhere (through you) and the device operates.
 
The 3-P+N unit does the same sums on the 3 phase plus the neutral (still looking for zero).
 

Ahhh, forgotten my 3 phase stuff. Thanks for the response effort.

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