57v earth to neutral. yikes

[Lee321]

just been to a job main rcd tripping in 1 1ph db. all circuits off and it still trips in say 10secs.

got no testers with me other than my fluke t5.

3ph tt. a phase to each 1ph db 3 of

so possibilities?

 

[johninlondon1]

Is it possible that they have been putting nails/screws in the wall and compromised cables? Switch off each circuit one by one and try and locate which circuit is responsible I would have thought.

 

[Lee321]

told them got to go back. working mans club in full swingut the kettle on

they got power for lights, bar and disco and really needs isolating to sort.

the board effected luckily is not really essential right now

as you say need to narrow down to which db then circuit. neutral and earth faults more of a pain cus you gotta get the db open

 

[ProDave]

Well it's got to be a neutral to earth fault as it's still tripping with all circuits off.

 

[Electroglow]

Sure does but if it did how did u manage to measure 57v

 

[andy_spark]

I had a lighting rcbo tripping in about 30 to 60 seconds after reset without anything be switched on. The fault was outdoor light switch IP66 rated, 1/2 full of water which was covering the terminals. A dry out with a rag and a drain hole solved the problem.

Could be worth looking for some outdoor accessories.

Just re-read and realsised it's a club. Are there any patio heaters for the smokers?

 

[Lee321]

only had access to the db thats tripping dave. could be another circuit on the other phase / db

 

[Electroglow]

O in 10 secs I should read thing properly

 

[Lee321]

Sure does but if it did how did u manage to measure 57v

voltage tester across n - e!

 

[Phoenix]

Its quite likely that with 57v N-E on a TT system that not only is there a neutral to earth fault on one of the circuits off the DB that is tripping, but also a live to earth fault and a duff rcd elsewhere that is creating the 57v across the suppliers earth rod, this is quite likely on another property. Turn all the main switches off for your installation and then measure N-E volatage, if it persists, then call the DNO who will probably go knocking on doors and go after a bit of searching take someones service fuse away!!

 

[Lee321]

O in 10 secs I should read thing properly

you could always test live side of rcd glow if it tripped instantly

---------- Post Auto-Merged at 20:54 ---------- Previous post was made at 20:52 ----------

big thanks to all for quick replies

 

[Andy™]

Its quite likely that with 57v N-E on a TT system that not only is there a neutral to earth fault on one of the circuits off the DB that is tripping, but also a live to earth fault and a duff rcd elsewhere that is creating the 57v across the suppliers earth rod, this is quite likely on another property. Turn all the main switches off for your installation and then measure N-E volatage, if it persists, then call the DNO who will probably go knocking on doors and go after a bit of searching take someones service fuse away!!

definately a L-E fault somewhere. as above, may not even be in this property

had similar a while back - dead short L-E, no RCD. 230v N-E. didnt measure other properties, but i would have expected them to have a N-E voltage because of metallic gas pipe

 

[steptoe]

whats the 57v on?

the N or the E ?

even a basic tester would show that.

 

[Phoenix]

Its not shared services that can cause results like this andy, the fact that a current is flowing between ground, through the transformer earth electrode and back to the star point (creating the 57v volt drop across it) means that there is a fault volatage between the physical ground and the neutral star point of everything fed from that transformer! (thats why the regs call for DP isolation to TT systems)

 

[Lee321]

whats the 57v on?the N or the E ?

even a basic tester would show that.

couldn't get a connection to another reference steps

can't remember if connecting across l-e showed 173v dont think it did 230 still

 

[steptoe]

you tester on N E should show you polarity though, so you know if the potential is on the N or the E

 

[Lee321]

polarity! on ac and if you only 2 points of test! ?

 

[Andy™]

you tester on N E should show you polarity though, so you know if the potential is on the N or the E

some testers will give a live indication with only 1 probe touching, but that wont give you a voltage reading.

2 probes between N & E will give you a voltage, but not which one is 'live'. you would need another reference for that, like the line, or the ther probe stuck in the ground etc

 

[steptoe]

errmmm, mine does,

one of these

 

[Andy™]

errmmm, mine does,one of these

so does mine, but wont give you a voltage or polarity. it will buzz if the probe touches something live. to get a voltage you need another reference. simply connecting between 2 terminals will give a voltage but not tell you which of the 2 is live