Loop test

[Carlosfandango]

I encountered a strange one the other day, new armoured supply to a shed, Ze at the Rcd main switch in the shed was 0.40, R1+R2 was 0.24 on the supply armour. When I did a earth loop on one if the sockets I got 1.09 which was high considering the run so I did a no trip test on the outgoing terminals of the Rcd incomer and got 0.96?. Swapped the Rcd and tried again, 0.90. I've just checked my tester at home and its working fine as I thought it could be the no trip function playing up. It was a BG board. Any explanations?? Could it be dodgy Rcd main switches? The second one was a new replacement from wholesalers.

 

[Pete999]

What size OCPD are the sockets on and what is the max ZS for that particular OCPD Have you calculated or measured the R1+R2 of the socket circuit?

 

[Carlosfandango]

They are well within the limits, just the fact that from the incoming side to the outgoing side is a difference of 0.50 ohms. Just curious really. The R1R2 for the socket circuit was 0.18.

 

[sammyshooter]

Never got on with BG boards; brand new RCD's returned under warranty as failing to pass basic RCD function tests.

 

[Pete999]

They are well within the limits, just the fact that from the incoming side to the outgoing side is a difference of 0.50 ohms. Just curious really. The R1R2 for the socket circuit was 0.18.

You could prove your point by swapping the RCD for an isolator only temporarily of course

 

[Andy78]

Never got on with BG boards; brand new RCD's returned under warranty as failing to pass basic RCD function tests.

You're not the only one.
I'll happily pay more for a better brand any day of the week.

 

[KFH]

Some RCDs can give high results with the no trip Zs test particularly on the Megger MFTs. I was at a Megger presentation where they said if you get this happening test at the input of the RCD, test at the output and subtract the difference from your Zs. If you do a google on it you should find some explanations.

I have put in a few BG boards and found them OK, prefer Hagar or Eaton now I can get there RCBOs at a more sensible price.

 

[Engineer54]

Never got on with BG boards; brand new RCD's returned under warranty as failing to pass basic RCD function tests.

What makes you think that premium brand RCD devices are that much better than the budget brands??

You wouldn't believe the amount of RCD devices that gets sent back for replacement by our contractor on a regular basis, from RCD's being defective straight out of the box or fail during service. It's been the same on virtually all the projects i've worked on over the years. Who is the manufacturer of all those RCD devices, probably the most respected name in electrical protection products whose recommended retail prices for standard RCD protective devices are around 3 to 4 X times that of the budget brands.

More often than not the budget label brands are made on exactly the same production lines in the same factories as some of the premium brands. ...Most won't admit it here, but they are paying premium prices for what can be bought at budget prices... lol!!