Surge protection cable length

[Buzz1980]

Hi all

question regarding the length of surge protector cables. I have read the reg 534.4.8 that states that the length should not exceed 500mm. Is that for each conductor so every conductor should be 500mm or less. So with a 3 phase surge protector all 3 phases/neutral and earth should not exceed 500mm is that correct ? Thanks in advance ?

 

[Ian1981]

The line(s) conductor and PE in total from the ocpd to the SPD or neutral conductor and PE.

 

[Buzz1980]

Not sure, my thinking is that any of the conductors should not exceed 500mm that’s what I am thinking ?

 

[Ian1981]

No, I mean that is the answer, the line conductor and PE should ideally not exceed 500 mm and in no cases exceed a meter.
Same applies to the neutral and PE.

 

[Buzz1980]

Oh sorry thanks for the reply. Is that also for 3 phase supplies ?

 

[Buzz1980]

This could be pretty much impossible to be able to install a SPD on a three phase board external as some consumer units have there earth bars at the top of the boards so defo exceeding 500mm. Could be well over a meter ?

 

[Ian1981]

This could be pretty much impossible to be able to install a SPD on a three phase board external as some consumer units have there earth bars at the top of the boards so defo exceeding 500mm. Could be well over a meter ?

The Length can be reduced by simply bolting the PE to the earthed chassis of say the DB enclosure, rather than using a separate conductor and adding to the length.
See Hager’s version

 

[Buzz1980]

Oh right yeah, they look decent no cable connections either. So to clarify on a three phase consumer unit. It’s the length of the any phase conductor and earth conductor combined that can’t be over 500mm ?

 

[Ian1981]

Oh right yeah, they look decent no cable connections either. So to clarify on a three phase consumer unit. It’s the length of the any phase conductor and earth conductor combined that can’t be over 500mm ?

Yes pretty much, it can exceed 0.5 meters but not 1meter.