Can Live wire runs through the Neutral side of RCBO?

[KelvinGaliny]

So I had an inquiry to make an electric panel (single phase) with RCBO, but it seems like our customer uses type C and F power plug (I live in Indonesia). This plug doesn't have a guide to ensure the Neutral would always be in Neutral side & Live to always be in Live side. Can I still use RCBO in this application?
This is the first time I'm asked to use RCBO, so I don't have any experience in using this. I apologize if the question is too basic / have been answered before.

 

[timhoward]

To clarify, do you mean your panel that contains an RCBO could be supplied with the polarity either way around?

 

[pc1966]

Can I still use RCBO in this application?

The answer is a qualified 'yes' but it really depends on the level of risk applying here.

An RCBO will detect faults to ground. Usually that is L-E as more volts present to breach insulation, etc, but if you have a N-E fault it will also trip. Indeed it trips on any current imbalance above 15-30mA typically so it also can pick up N-N faults to other circuits, etc.

However, many RCBO do not disconnect the N when they trip, they are assuming that N really is referenced to true Earth and so the "polarity" of the main supply is correct. If you have a major mistake or fault on that supply that elevated N above Earth then the RCBO will not (usually) make it safe as only L is switched. That is why, for example, in the UK the regulations for caravan supplies require both L & N to be isolated when tripped.

With a socket type that lacks polarity then you don't know if a given live pin is L or N (here "live" means current-carrying, and L=line for elevated voltage w.r.t. Earth) so you might have issues like single pole fuse or switching is in fact on the N-side and so when off an appliance is still at dangerous voltages inside.

Here having some form of RCD protection still offers you good protection against a shock to Earth or grounded metalwork.

TL;DR version is RCBO is far safer than MCB, but unless it switches N (like all RCCB, and a few types of RCBOs) you still have some risk if you can't be sure N is properly Earth-referenced.

 

[timhoward]

My understanding in slightly simpler terms is that a SP+N RCBO would be ok as current flowing from N to E would trip as an imbalance, current flowing from N to L would be measured for imbalance as usual, and overcurrent from N to L would operate the over current aspect on the way back out.
So the key seems to be making sure it disconnects the N.
Most RCBO have a diagram printed on them that show if the N is permanently connected or switched.

If it’s a typical non Uk unfused plug with fairly low overcurrent protection on the supply circuit then it may be that the overcurrent aspect of an RCBO doesn’t add any value and a simple double pole RCD is adequate?

 

[KelvinGaliny]

To clarify, do you mean your panel that contains an RCBO could be supplied with the polarity either way around?

yes

 

[davesparks]

The RCBO will need to be double pole if there is a chance of polarity reversal.

A single pole or a single pole switched neutral RCBO only detects overcurrent in one pole, a double pole RCBO detects over current in both poles.

 

[brianmoooore]

Just going to post exactly what davesparks wrote above.
Don't think it can be done with any RCBO that I know of. It would have to be a DP MCB followed by a RCD.

 

[pc1966]

You get true DP RCBO in many EU locations such France where traditionally they did not have a 'N' strongly reference to Earth, in fact some countries provided two L from a 3P supply so both lines were elevated above Earth and so always needed over-current protection on both poles.

The UK style of SP+N RCBO where the neutral is switched but lacks OCPD are not suitable if supply polarity reversal is a real risk. While they should trip on the RCD side on a fault to Earth the N-side lacks the arc chute, etc, needed to clear a high energy fault, and the relatively slow RCD trip times compared to the thermal-magnetic MCB side means your fault I2t is much higher.

You do sometimes see DP RCBO in the UK for the likes of caravan supplies, but most UK distribution board lack the dual busbar arrangement to suit those double-width module.

TL;DR Certain RCBO are suitable, but (in the UK at least) practically none that fit in to a DB.