It depends on where you are and/ or what classification society you are working with as to what rules you will need to conform to. Here in Europe the ISO norms are probably the best to comply to (up to 24metres). In particular you need to take note of the derating section referring to bundling and engine rooms. In the US you will probably need to refer to ABYC or ABS depending on the size of vessel but also I believe the coastguard have a big input in the rules there. I am sure Elnav will be able to give a better info on the subject for that area.
ISO 10133, low voltage standards
ISO 13297, AC standards
Hope this helps
Chas
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