1

This question already has an answer here:

Recently a home inspector flagged the panel box in a boathouse for having a ground wire attached to the neutral bus bar. The ground came from a jet ski lift attached to the boathouse. This 10 yr old house was in sale process so it had been that way for 10 yrs. I moved the wire to the ground bar. Is that ok?

marked as duplicate by isherwood, Daniel Griscom, Machavity, Retired Master Electrician, Tyson Mar 13 at 22:47

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • Hello, and welcome to Home Improvement. Would you post a picture of the inside of the panel box? Bonus points for highlighting the moved wire. (Thanks.) – Daniel Griscom Mar 7 at 14:13
  • 1
    Is the boathouse a subpanel that comes off of the house main panel? If so, grounds & neutrals are connected together in the house panel, so in that panel you can mix up grounds & neutrals with no real problem. But in a subpanel grounds & neutrals normally need to be separate - it could be that whoever installed the jet ski lift didn't understand the difference between subpanel and main panel. – manassehkatz Mar 7 at 15:02
3

This is a special situation.

Don't fool around with grounds around water

Electrical drownings are some of the most tragic fatalities around electrical. Current that is nowhere near lethal can stun a person to where they cannot keep their head above water, and they drown. Far worse, when someone goes to rescue them, they too suffer the same fate, like these four girls and nearly, several more rescuers.

Or it may be mistaken for a plain drowning, and only discovered after an unusual string of drownings (and more).

In fact, the death of more than one person (victim and rescuer) is the hallmark of an electrical drowning.

There are literally hundreds of these incidents.

Using Earth as a "ground wire" actually causes this

The whole point of the ground wire is to return fault current back to source. Current wants to return to source, not earth, and artificial current's source is your electrical service (i.e. neutral). If current leaks, you want to efficiently return it via the grounding wires back to the main panel and back to the power company.

Current flows down every available path in proportion to its conductance (1/resistance) - you can't do anything about that, but you can provide an extremely high-conductance path so that proportionately very little (almost no) current flows any other way. That's what a ground wire does.

Anyway, earth - even wet earth - is a terrible conductor. That's why we go to all the trouble to mine copper :) It's low enough conductance that if it's in parallel with a human, some fraction of total current will flow through the human. And that will drown them.

So we definitely do not want to go to earth as our current return, because that will cause current to try to return via earth, water and anyone in the way.

Tying ground and neutral causes a single point of failure

If your neutral-ground wire breaks, and that is a common enough problem, it means that normal current tries to return to neutral (but can't) so it floats the neutral up toward 120V. Neutral is tied to ground at the boathouse, so ground also floats to 120V. And ground is tied to equipment in contact with water, so it also floats the water and earth up to 120V.

Now if you have separate neutral and ground back to the house, it may seem clever to bond them to halve your chances of a wire break. Actually, not so much. Many things which would sever neutral would also sever ground, and you're back to this situation.

Whereas if neutral and ground are kept separate and severed, the equipment just won't work. It will not electrify the grounds/water unless it also has a ground fault. So it requires a double failure to have a problem. It's true that second failure could happen first and lurk until the first failure happens, but if you are using GFCI protection, it won't be likely.

  • 1
    @manassehkatz Sorry, I confused it with another question. – Harper Mar 7 at 19:30

Not the answer you're looking for? Browse other questions tagged or ask your own question.