Hot Neutral

[mayfair]

Hi Guys
Have a 3 phase installation 3 phases plus the neutral are fed by 25mm cables into 63A circuit breaker then all split of into the 3 RCD's with 10mm cable inc the N lives are all warm but Neutral is hot checked screws for tightness etc no circuit is reading more than 41 Amps . Any ideas???????????
Cheers
Mayfair

 

[Tunnel Sparkie]

Just a shot in the dark, does the neutral pass through a metal casing by its self. say a hole in trunking.If it does you may be producing eddy currents which will produce heat or check you are getting a 3phase and neutral supply at your incommer you may have lost your incoming neutral. I hope this helps you out.

 

[Sparky Ninja]

Are the phases balanced? Have you checked for the neutral currents?

 

[Guest123]

Have you clamped the neutral conductor???

 

[mayfair]

Are the phases balanced? Have you checked for the neutral currents?

seem reasonable balanced not checked N for currents

 

[mayfair]

in a word No,

 

[Sparky Ninja]

seem reasonable balanced not checked N for currents

Then that's what you should do next, as Lenny says... Try to carry it out with load on of course.

 

[mayfair]

Then that's what you should do next, as Lenny says... Try to carry it out with load on of course.

What size cables would u use for this as ive been in Spain 20 year bit out a touch with the UK regs or do you rekon im ok on cable

 

[mayfair]

Then that's what you should do next, as Lenny says... Try to carry it out with load on of course.

got 43 on P1 38 on P2 36 on P3 but are freezer units so sometimes for example P1 may only be 10 bit concerned about cable sizes

 

[davelerave]

maybe it's harmonics- i don't know too much

 

[Sparky Ninja]

Are the 10mm cables single? Bunched? In free air? Containment?

BS7671 allows a current carrying capacity of 42amp to 59amp depending on these factors (assuming cable at the 10mm stage is non armoured single core..)

Seeing as how the over current device is 63 amp I would consider this to be a potential danger and so the best action to take may be to increase the 10mm conductors to 16mm or better still 25mm.



Need more info to be as accurate as poss, but it appears that the cable are near it's peak tolerance if the lines are warm and neutral is hot.

Are the circuits csa 10mm?



Hope this makes sense...

 

[mayfair]

maybe it's harmonics- i don't know too much

mmmmmmmmm maybe !!!!!!!!!!

 

[mayfair]

Are the 10mm cables single? Bunched? In free air? Containment?

BS7671 allows a current carrying capacity of 42amp to 59amp depending on these factors (assuming cable at the 10mm stage is non armoured single core..)

Seeing as how the over current device is 63 amp I would consider this to be a potential danger and so the best action to take may be to increase the 10mm conductors to 16mm or better still 25mm.



Need more info to be as accurate as poss, but it appears that the cable are near it's peak tolerance if the lines are warm and neutral is hot.

Are the circuits csa 10mm?



Hope this makes sense...

25 mm singles into the mcb 63A then when i split it into the 3 rcd's got 10mm singles so they are about 20cm long to the rcd's and they are warm but noting to write home about as it was 33 deg here today, the room they are in was 37deg.
But the N that has been fed into choc block and split to the two pole rcd's all on 10mm........ is notably hottish........ all csa halogen free decent quality cable make any sense m8 btw free air that is in the dis panel

 

[davelerave]

a short bit of 10sq feeding the rcds and final circuits- ya?


measure the N current anyway as already said

for harmonic currents you need 'true rms ' reading

dunno if it's an issue -any computers?

 

[mayfair]

a short bit of 10sq feeding the rcds and final circuits- ya?


measure the N current anyway as already said

for harmonic currents you need 'true rms ' reading

dunno if it's an issue -any computers?

ye computers about 8 on phase 2