Boat dock grounding and NEV

dbchamblee

dbchamblee

Member
To minimize the effects of neutral-to-earth voltage (NEV) at boat docks, I heard it suggested to install only low voltage DC equipment (lighting, boat lifts, etc.). The thinking is since you don't have AC run to the dock, you don't have to ground metal parts which prevents the neutral voltage from being transferred to the metal parts.

Would it have to be run off batteries or PV? Could you have an AC power supply as long as it was on shore?

Thoughts?
 
If the supply is totally isolated from anything with continuity to the utility neutral you shouldn't have any NEV issues. An AC to DC power supply powered by utility power has some risk of some sort of interconnection of grounded conductors especially if the DC system is grounded.
 
Elevated 'neutral-earth-voltage' can have multiple causes. The utility multi-earth-neutral wire is the cause that gets the headlines, but it isn't the only source of issues.

A big source of the problem can be on the local low voltage side of power distribution. See as just 1 example:

Poor grounding electrode???

Hi, I have a 120/240 200 amp underground service at my vacation home. The problem is there is stray voltage 30 volts on cold water sill cock outside the house. When using water and ground is wet in bare feet you get shock from fauct,not safe.The service is properly bonded and grounded.The area...
forums.mikeholt.com

Which goes to say that even if you only have local low voltage distribution you can still have problems.

Now if by low voltage you mean something like 12 or 24V DC, then you might remove even these problems, but now you are greatly reducing the functionality of the system; you are not going to provide much shore power to a boat or much power for a boat lift at 24V. If you just want a bit of decorative lighting 12V is fine. But if you want to run a half horsepower motor down the dock you are not going to do it at 24V.
 
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