# question

## Grounding Victron isolation transformer, wire size

Installing Victron isolation transformer on my boat. Which wire size should i use for grounding to AC grounding bus aka “all metal parts in the boat”. The wires I use for input/output 230v is 2,5 mm2 wire. Should I use the same size or only one size smaller?

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You should use a larger wire size for grounding.
The idea is that the ground wire will reliably carry the full fault current.
You local wsiring regulations will help you decide the reqired wire size.

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Thanks for the answer WKirby, to my knowledge we do not have pleasure crafts regulated in terms of electrical installations here in Denmark.

The regulation on shore demands at least 6 mm2 for potential equalization due to mechanical wear.

What should be the reason behind a thicker wire than the input wire to the isolation transformer, that complies with the specification from Victron?

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Seems i got the answer from ISO 13297

10.6 The protective conductor shall have a cross-sectional area equal to that of the live conductors.

a) For earth continuity conductors (protective conductors) in flexible cables or flexible cords:

1) a cross-section equal to that of the current-carrying conductor if the latter is less than or equal to 16 mm2; or

2) a cross-section equal to 50 % of that of the current-carrying conductor if the latter is greater than 16 mm2, subject to a minimum of 16 mm2;

b) for earth continuity conductors (protective conductors) incorporated in fixed multicore cables:

1) a cross-section equal to that of the main conductors if the latter is less than or equal to 16mm2 subject to a minimum of 1,5 mm2; or

2) a cross-section of not less than 50 % of the cross-section of the main conductor if the latter is more than 16mm2, subject to a minimum of 16 mm2.

meaning I should use 2,5 mm2 same as the conducting wire.

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