Ground conductor on a boat lift

[sailingharry]

Some background first.
Our new house (almost 3 years now -- time flies!) came with a boatlift (a cantilever type with a huge steel track that goes down along a piling). The boatlift had one completely rotted track. I replaced it for several hundred dollars and a day's work. The manufacture (Magnum Boat Lifts) stated that this was caused by the plug not being removed after each use, and their instructions clearly state to unplug after each use.


I've just replaced the dock, have reinstalled the boat lift, and just rewired the dock.


The plug is a PIA, as it is hard to remember. It just got three times harder a PIA, because it now has an in-use cover.


So, I got to thinking. We boaters are very aware of galvanic corrosion instigated by stray currents on the ground wire (I don't want to get into a semantic/technical discussion on how badly I butchered those terms -- I don't see it as relevant). In fact, we install galvanic isolators to protect our precious metal parts from bad juju coming down our ground wire.


Under the NEC, a GFCI (breaker or outlet) provides such rock solid protection that you can legally install a 3 prong outlet on a 2-wire circuit (an old house, obviously) so that folks can plug in a grounded device and have all the protection that they think the 3 prong plug provides.


So.... after all that.... would it be prudent to replace my 3 prong cord to the boat lift with a 2-prong? I could then leave it plugged in 24/7. The GFCI breaker feeding the lift should provide better protection than the 3-prong plug. The in-use cover keeps all the plug stuff protected from the elements. And the lack of a ground keeps my lift from dissolving.


Could this equally apply to a boat? If I have a residual breaker (30ma) on my inlet line (I do), is there a solid reason (besides ABYC, which may be a little slow to respond to technology advances) to bring the ground aboard? I could in theory get a 30ma shock which is 6 times the limit for a GFCI breaker but still considered "moderately safe" (which is why they allow 30ma). I could improve this suggestion by adding GFCI outlets to the first outlet of each outlet circuit, making things like an A/C (I don't have one) or the hot water heater (or the breaker panel itself) as the only source of ground shocks over 5ma.


Two questions, I know. The boat lift one is the one I'm really interested in.

[dougweibel]

I think the boat lift question's answer probably depends on if the neutral and ground are bonded in the lift in any way. If so then getting rid of the ground is probably not enough as there will still be a path for stray current from the lift to earth ground.

Another possible solution: Install a three pole switch to break all three connections; hot, neutral and ground.

[sailingharry]

You have a good point, but no, they aren't bonded. If they were, you'd have an instant trip on the GFCI anyway.


I'm still trying to figure out what benefit the ground serves. Although on another thread, it was pointed out that GFCIs don't last forever (I've replaced some, but never found one to fail CLOSE -- they always seem to fail OPEN).

[GordMay]

Originally Posted by sailingharry

... on another thread, it was pointed out that GFCIs don't last forever (I've replaced some, but never found one to fail CLOSE -- they always seem to fail OPEN).

A GFCI receptacle has mechanically, spring loaded, contacts, that normally open very quickly [before the electricity can affect your heartbeat], when the GFCI trips; but, if the ungrounded side welded itself together, it could still be passing current [live], even in a tripped state [failed closed].
➥

https://www.youtube.com/watch?v=DyeijLvh-yI

[Jammer]

Originally Posted by GordMay

A GFCI receptacle has mechanically, spring loaded, contacts, that normally open very quickly [before the electricity can affect your heartbeat], when the GFCI trips; but, if the ungrounded side welded itself together, it could still be passing current [live], even in a tripped state [failed closed].

I've encountered ones where the electronics had failed that would therefore no longer trip. Also more than one that had the incoming power connected to the "load" terminals eliminating any protection.

[Jammer]

Originally Posted by sailingharry

So.... after all that.... would it be prudent to replace my 3 prong cord to the boat lift with a 2-prong? I could then leave it plugged in 24/7. The GFCI breaker feeding the lift should provide better protection than the 3-prong plug. The in-use cover keeps all the plug stuff protected from the elements. And the lack of a ground keeps my lift from dissolving.

You could start by putting an anode on it before moving on to more drastic measures.

[s/v Jedi]

A 3-pole switch is easy but needs to be remembered. An isolation transformer would be an install and forget solution but comes at a cost. You would simply wire it’s output to the outlet which galvanically isolates all three conductors.

[Statistical]

So.... after all that.... would it be prudent to replace my 3 prong cord to the boat lift with a 2-prong? I could then leave it plugged in 24/7. The GFCI breaker feeding the lift should provide better protection than the 3-prong plug. The in-use cover keeps all the plug stuff protected from the elements. And the lack of a ground keeps my lift from dissolving.

No. By code no you can't. Modifying device to go from grounded plug to ungrounded plug violates UL and NEC standards.

Outside of the standards there are two reasons why this may be a very bad idea
1) There may be parts which are connected to ground but not neutral. For example any exposed metal surfaces are likely only connected to the ground. If they were connected to neutral and ground that would mean it would trip GFCI and also would violate code standards.

Why does that matter? Well imagine inside the line (hot) wire comes into contact with metal case. The case is now energized and a potential lethal shock hazard. If the case is grounded though the GFCI should trip. It will trip as soon as this happens even if you are not there. If you try to reset it, it will just trip again. It will keep tripping until the hazard is fixed or replaced.

If you have no ground wire attached then while the case is now an energized potential lethal shock hazard there is no completed circuit, there is no current flow, there is nothing for the GFCI to trip. At this point if you touch it you may complete the circuit especially if barefoot on a wet dock. The GFCI 'should' trip but you are putting yourself into an avoidable lethal situation in hopes the GFCI saves you. It is like putting the safey on a firearm and pointing it at your head and pulling the trigger. Very likely you will be fine and nothing bad will happen but why take the chance? The point of safeties like GFCI is to protect you in the rare event you end up in a hazardous situation the best scenario is you never have such a situation to begin with.

2) GFCI can and do fail. Having the exterior metal surfaces grounded provides some level of shock protection in the event the GFCI fails.

Could someone design a boat lift with an ungrounded connector? Sure and they could design it to be very safe but this is a non-trivial engineering choice not something to be done by simply cutting and replacing the plug.

[sailingharry]

Originally Posted by Statistical

No. By code no you can't. Modifying device to go from grounded plug to ungrounded plug violates UL and NEC standards.

If you have no ground wire attached then while the case is now an energized potential lethal shock hazard there is no completed circuit, there is no current flow, there is nothing for the GFCI to trip. At this point if you touch it you may complete the circuit especially if barefoot on a wet dock.

Not sure NEC applies to anything plugged in. I think (but am not sure) that it only applies to hard wiring. UL applies, but who hasn't intentionally or unintentionally cut off (or broken off) a ground part of a 3 prong plug and continued to use it. But, your point is still valid.


Actually, the GFCI would trip if either the white or the black made contact with the metal boat lift, as they are exceptionally sensitive and will trip if any current makes it to ground. Curiously (I mentioned this recently, I think on this forum), my lighting system failed as soon as I upgraded to a GFCI breaker on the new panel, as there was an undetectable very high resistance connection between the hot and ground inside the switch leg cable going to the house. That connection had been leaking current to ground for years, without any ill effects, and the GFCI found it. I had another cable that I was about to abandon that allowed me to fix that without digging up 100' of my front yard.


The most compelling reason to not do this is the anecdotal reports that GFCI do fail closed. I've only seen them fail open, but that's all I have seen, not all that actually happens. New GFCI have self test circuitry, but that may not be able to detect welded contacts.


An anode is an idea, but actually my lift is fully coated on all surfaces with an anode -- it is galvanized. I'm not sure if an anode added to a galvanized structure will provide any protection. Wonder if an aluminum anode would sacrifice to protect zinc? If so, a Divers Dream anode (the big plates) would be an excellent idea.

[Jammer]

Originally Posted by sailingharry

Not sure NEC applies to anything plugged in. I think (but am not sure) that it only applies to hard wiring.

The NEC is adopted by various state/local jurisdictions that vary in how they interpret scope, and is further interpreted in different ways by individual electricians and inspectors. In Minnesota, all equipment that utilizes electricity must comply with the NEC and must be listed by UL or a similar testing agency, with certain exceptions; see https://www.revisor.mn.gov/rules/3801.3620/.


As to what the de jure and de facto situation may be where you are, I could only speculate.

The most compelling reason to not do this is the anecdotal reports that GFCI do fail closed. I've only seen them fail open, but that's all I have seen, not all that actually happens. New GFCI have self test circuitry, but that may not be able to detect welded contacts.

I like to tell people that adding a GFCI to an unsafe installation does not make it into a safe installation.

[donradcliffe]

If the lift is in fresh water, I would keep the ground.

[GordMay]

Originally Posted by sailingharry

Not sure NEC applies to anything plugged in. I think (but am not sure) that it only applies to hard wiring...

You’re correct.
Generally, the NEC applies to field installation, and wiring.
Manufactured items, that are shipped pre-wired, are generally not covered by the NEC - that is where UL comes in.

While there is some overlap in the NEC and UL standards, and the CEC and
CSA standards, these specifications generally work together, in concert, to
provide guidelines for safe design, application, and installation of electrical components and equipment, and often reference each other’s standards, in their documentation.

UL (Underwriters Laboratories) is an organization that develops standards, and test procedures, and certifies products, with a significant focus on product safety. A UL listing (certification mark) serves as a tangible testament, that a product has undergone independent testing, affirming its compliance with mandated safety standards.
UL also is a Nationally Recognized Test Lab (NRTL), under OSHA, and products certified by UL are accepted by almost all jurisdictions in the US. OSHA Safety Standards, which are US law, contain requirements for “approval” (i.e., testing and certification) of electrical equipment by an NRTL.

CSA (Canadian Standards Association) is a similar body, to UL, in Canada. CSA is also an NRTL, under OSHA.
Installations, in Canada, are covered under the (CEC) Canadian Electrical
Code.

The NEC (National Electrical Code, also known as NFPA 70) is a specification that establishes minimum standards for the safe installation, and utilization, of electrical wiring, and equipment, in the US.
The NEC was created, and is maintained by, the National Fire Protection Association (NFPA).
The NEC is frequently mandated by states, and local jurisdictions, and it is possible for different jurisdictions to adopt different revisions of NEC code.

[sailingharry]

Ha! We have this discussion with hypotheticals, and whaddayaknow, I've got real life.


My breaker feeding the boat lift is a 20A, 5ma GFCI breaker, brand new. I was doing some adjustment to the wiring, and accidentally connected the Neutral to the Ground, and the breaker tripped (expected behavior). Except, now I have no function outlet. The breaker opens and closes mechanically as expected, but the trip test button does nothing and I have no power to the outlet. A little sleuthing, and I find that the ground pigtail appears to not get into the breaker. With the breaker ON, I have 120 at the line terminal, but the neutral terminal is not neutral (open circuit). Since the pigtail is internally open, the GFCI circuitry has no power and so doesn't work. End result, I have 1/2 of a GFCI breaker (I assume that if I moved the neutral to the neutral bus bar, I'd have a functioning 20A breaker without GFCI).


While the breaker was installed (it's out now), and turned on, I had 120V line going to the lift, and no GFCI protection. Exactly an example of why the ground is important (if I also had a line-lift connection, the lift would be live).