Is it possible reverse polarity on a supply?

[Mikegh]

Having a brain fog on this

Is it possible to reverse polarity on a new connection or a meter swap and have it to go unnoticed ?

 

[James]

Yes it is.
Under certain circumstances

 

[Mikegh]

Can you expand on that .....

 

[James]

Almost all single phase loads will not be able to determine polarity and will work just fine.
A phase an N reversal in a 3 phase system will cause issues that are easy to spot.

However a live to E fault may not be detected by the protective devices if the polarity is wrong as the current will not be flowing through them.

 

[Tom 256]

Are you talking of the connection from the meter on the load side? If so imagine the tails without any colour marking could it happen? Whats the difference if one is brown and one blue?

The colours assist identification but don't stop reverse polarity happening.

What do you mean by 'have it go unnoticed'?

 

[pc1966]

Yes it is.
Under certain circumstances

Actually I would say under almost all circumstances for single-phase...where no testing is performed.

Even a simple socket checker woulds report a problem if anyone tested, as would any attempt to measure Zs/Ze

Would meter replacement would involve that sort of step? Not had it happen to me recently to see if anything was done beyond the actual swap.

 

[pc1966]

However a live to E fault may not be detected by the protective devices if the polarity is wrong as the current will not be flowing through them.

I would phrase it differently as in the UK almost all protection is line-only, and if supply is swapped then every circuit is only limited by the supply fuse.

If you are lucky and there is some RCD or neutral-switching RCBO then some chance of ADS, but they do not provide the sort of current/energy limiting that the normal fuse or MCB side of things offers.

 

[loz2754]

Hence why reverse polarity at the origin would be classed as C1 for an EICR.