RCD problem

[stidge]

Hi all, scenario is , Fitted new dual rcd MK Cu today. Testing rcd one ( next to main sw) all fine. Rcd two doesn't trip on x1 at all ( mft says 310ms)it trips on x5 but high reading approx 30 ms. Have tested with no loads connected. Changed rcd same results! Swapped rcd 1 & 2 round , works fine next to main sw but same problem on other end ! Have triple checked all connections on everything but to no avail????? Any ideas lads ?? Help

 

[bertt]

Hi,

May be you already solved the problem.
Whatever, even if you triple checked all connections.

At the second RCD because you tighten the screws but without wires or busbar inside you got this problem. The Cu busbar at IN of RCD remained behind of terminal block. Check properly the connections. Good luck.
Thank you.

Bertt.

 

[stidge]

Thanks burrt have tried that but cheers for reply

 

[shocking_eg]

both faulty RCD's

i personally hate the new MK boards, so cheap and flimsy its unreal !

 

[Marvo]

This thread is like deja vu, there's another thread also with failed RCD's on a brand new board. Maybe there's a widerspread problem.

 

[stidge]

both faulty RCD's

i personally hate the new MK boards, so cheap and flimsy its unreal !

I know what you men mate but I have now swapped 4rcds and still same problem but when I swap left to right all ok ???

 

[Des 56]

I may have my memory playing tricks on me but,I seeem to recall a debate about rcbos, (its not a problem I have encountered but it may have relevance)

The jist of the talk was that some Rcbos failed to operate on test at the consumer unit,but operated correctly at a circuit accessory
The rcbos in question were thought to be faulty,they were changed but still failed on test

The solution if I recall correctly,was that a short length of wire was required(maybe a bit of test resistance or similar) in order for them to operate correctly
Maybe try testing the Rcd in this manner,you never know because it is a bit of a weird problem

 

[Deleted member 9648]

I may have my memory playing tricks on me but,I seeem to recall a debate about rcbos, (its not a problem I have encountered but it may have relevance)

The jist of the talk was that some Rcbos failed to operate on test at the consumer unit,but operated correctly at a circuit accessory
The rcbos in question were thought to be faulty,they were changed but still failed on test

The solution if I recall correctly,was that a short length of wire was required(maybe a bit of test resistance or similar) in order for them to operate correctly
Maybe try testing the Rcd in this manner,you never know because it is a bit of a weird problem

+1
Not your memory failing...was a real issue....explanation unknown.

 

[nickblake]

have you tried a ramp test

 

[stidge]

I may have my memory playing tricks on me but,I seeem to recall a debate about rcbos, (its not a problem I have encountered but it may have relevance)

The jist of the talk was that some Rcbos failed to operate on test at the consumer unit,but operated correctly at a circuit accessory
The rcbos in question were thought to be faulty,they were changed but still failed on test

The solution if I recall correctly,was that a short length of wire was required(maybe a bit of test resistance or similar) in order for them to operate correctly
Maybe try testing the Rcd in this manner,you never know because it is a bit of a weird problem

Thanks des but not quite sure about length of wire where ? Between what ? Have also tried to test at accessory but no good . Thanks for input

 

[stidge]

have you tried a ramp test

Yes mate no good cheers

 

[GLENNSPARK]

View attachment 17690Hi,

May be you already solved the problem.
Whatever, even if you triple checked all connections.

At the second RCD because you tighten the screws but without wires or busbar inside you got this problem. The Cu busbar at IN of RCD remained behind of terminal block. Check properly the connections. Good luck.
Thank you.

Bertt.

yes...i`v come across this quite a bit on ECRs ....
like evidence of overheating

 

[hasel5]

Prob a N-E fault somewhere so do a IR test on outgoing circuits and will give you an idea of problem believe me especially if an PME supply

 

[Engineer54]

I may have my memory playing tricks on me but,I seeem to recall a debate about rcbos, (its not a problem I have encountered but it may have relevance)

The jist of the talk was that some Rcbos failed to operate on test at the consumer unit,but operated correctly at a circuit accessory
The rcbos in question were thought to be faulty,they were changed but still failed on test

The solution if I recall correctly,was that a short length of wire was required(maybe a bit of test resistance or similar) in order for them to operate correctly
Maybe try testing the Rcd in this manner,you never know because it is a bit of a weird problem

That was as i remember it, only applied to MEM RCBO's. The manufacturer advised the OP to connect a few inches of conductor to the terminals and testing from the ends of these short conductors!! As stated above, no explanation as to Why!! lol!!

 

[bertt]

Hi,

Please see for update for MCB safe guard connections - new pics.
There are relatively often into electricians practice this mistake.
Thank you and sorry if I was too persistent.
bertt. :sunny:

 

[stidge]

Thanks to all sorted,was an outside light I had missed with a L-E fault. Rcd working fine now thanks again

 

[stidge]

Sorry meant N-E fault

 

[bertt]

you welcome stidge.

 

[Pete999]

Are both RCDs 30ma? is the farthest one a time delay easy to miss