Generator / inverter shock risk

[Drake]

This may be a stupid question, but is there a shock risk swimming around a boat when the generator and/or inverter is running? We all know about the risk of swimming in a marina, but what about swimming around a boat in open water?

Paul

 

[caltexflanc]

Depends on if the boat has ground leakage. We've never had an issue on boats we've chartered or owned, out away from other boats in a big anchorage or just drifting in the Gulf. You want to be cognizant of the generators exhaust.

 

[Lou_tribal]

Send your wife in the water first, if she is fine everything is ok, you can go too

L

 

[fastinated]

Salt water no worries unless you grab a shaft or something in the boat that's electrified. We are basically a little less conductive than the salt water so It'll go around you on it's way to ground. Fresh water well it's totally different. It's milliamps that can kill here. Some sad stories of kids passing due to dock leakage. Something not to mess around. If you have leakage I'd imagine your zincs may be bubbling.

 

[kchace]

IF there was significant leakage and IF a person completed a circuit then yes. The problem is much more prevalent in fresh water because people conduct electricity better than fresh water so the electricity takes the path of least resistance through the person. If the boat is not connected to grounded shore power then even in fresh water it is much more difficult (but not impossible) to become part of a circuit. The person would have to complete a circuit between 2 parts of the same boat through the water. So for example, one through hull would need to be energized to one side of the circuit and another though hull or maybe engine shaft would have to be connected to the other side of the circuit. If the electricity was trying to use the water to complete that circuit and the person came in between then yes. If all underwater metal was PROPERLY connected to a grounded system, then this could not happen. Of course, wires do fail.

Ken

 

[diver dave]

Seems like u would need to set up an electric field with a couple of underwater fittings at a high differential voltage. Prolly possible if u tried.

 

[Maerin]

Generators and inverters should both be grounded to the boat's ground when they're producing power, as well as the neutral-ground conductors bonded. This doesn't occur during shore power operation, the ground then is through the shore power cord and back to the source (the pedestal). There's probably less risk from the on-board generated power by virtue of the circuit being more contained to the vessel, but there's still risk. Not all inverters provide that bonding, marine inverters must meet UL 458, which has to do with the bonding. Many DIY boaters use inexpensive inverters that don't meet that standard, and the risk of leakage & electrical current exposure in the water is more likely. As others have posted, freshwater presents the greatest potential risk. The danger is not so much from electrocution, but from electric shock drowning. If you become part of the circuit, current passing through the body won't kill you, but it causes muscle paralysis, so you can't swim, you can't breathe, and you can't call for help. You drown. Still, a moot point. Dead is dead. But think twice about jumping in the water to rescue someone who is in trouble and appears paralyzed.


The new ground fault protection that NEC requires on new marina wiring is intended to reduce the risk. If you ever plug into one and it trips, your boat has an electrical leak or fault that should be corrected. Soon. If you have an inverter installed, your potential for a fault is higher. An ABYC electrician or corrosion control tech has the skills to test your boat for leakage and correct it. Leakage problems can exist undetected. There may be no indications of a problem at all until you either have it tested or plug into a shore power pedestal with the updated wiring and the ground fault breakers. Either way, a marina is not someplace to go for a swim.

 

[FF]

"Many DIY boaters use inexpensive inverters that don't meet that standard, and the risk of leakage & electrical current exposure in the water is more likely."


A proper setup ,usually the source selection switch, regardless of the price of the inverter is about as safe as can be done..

 

[caltexflanc]

Great post Steve. Add battery chargers in there too. Probably also cheap freestanding gas generators.

 

[twistedtree]

Power from any generation source returns back to the source to complete the circuit. That's what creates the shock drowning risk when on shore power, and greatly reduces it with on-board generated power.


With shore power, the source is on shore. If there is a fault in the power return path, the power seeks alternate paths back to the source. When that path is through the water, you get current flowing through the water radiating out from the boat in unpredictable patterns. Swimming through that current is what gets you into trouble.


With power generated on-board, it's returning back to the generator or inverter. As a result, there is much less risk of any of that current radiating out from the boat. There is still plenty of risk, but very little of ESD in the form we are all becoming aware of.

 

[firstbase]

Send your wife in the water first, if she is fine everything is ok, you can go too

L

We always take a couple of Nutria with us in a cage and then throw one in to check for danger before we.....never mind. Wrong thread.

 

[sdowney717]

Think many are missing the obvious fix, use a GFCI on the inverter and generator output.

I use a GFCI outlet direct on the MSW inverter.
Shore- gen- inverter can feed the entire boat's electrical panel, selectable by switched 4 pole DT power relays.
I had to use 4PDT relays since I have twin 30 amp power and they switch together hots and neutrals.

My distribution panel is made by Square-D with spaces for 8 breakers.
Which made it easy to do.
I have added five AFCI-GFCI combo breakers to it.

So all

outlets
Cruisair heat pump - AC
Water heater
Pool pump
Microwave

are all AFCI-GFCI protected circuits.

Years before I made the AFCI-GFCI changes, I had a wet wire in the cruisair which electrified the pumped water outlet. I reached down to feel the temp of the water coming out and got shocked. That wet wire connection, an unsealed but joint enabled enough leakage current to feel a hefty shock. Of course I fixed it immediately but immediately is too late if someone had been swimming nearby. Now that it is AFCI-GFCI protected, not likely to kill anyone if the wire has another issue..

Another benefit to GFCI protecting the AC compressor, is diagnostic, determining shorted windings in the motor to ground. Sometimes compressor motor winding fail internally and leak current into the ground, probably another source of potentially getting shocked in a wet boat environment from a failing compressor motor . So if the AFCI-GFCI breaker for the compressor does not trip off, you know the motor itself is ok.

In our house, had an old attic fan from 1965, worked sort of ok, but when going to an AFCI-GFCI breaker circuit, that fan kept tripping off the breaker. Getting a new attic fan and no more tripping off. I honestly think with that one, it was the old fan thermostat, the AFCI breaker detected to much internal arcing in the switch and shut it down. bypassing the thermostat, the fan motor ran ok.

AFCI breaker detects electric arcing which causes fires.
GFCI breaker detects ground faults which keeps you from being electrocuted.
The combo breaker combines both features into one beaker.

 

[Lepke]

Send your wife in the water first, if she is fine everything is ok, you can go too

L

Unless you have a mother-in-law.

 

[Boat]

Thanks to all of you who posted in this thread. This is a great thread. It got me to review some electricity and learn some new material.

My seismograph boat trailed a sparker in the water that was powered by a 671 generator. We had two 671 generators aboard and operated both when we were running lines. I was told that if someone went overboard with the sparker running that they were dead, no question. Also told that if we ran the sparker when a diver flag was flying that we would be arrested for murder. The sparker was a metal frame with electrodes and at night you could see, hear and feel the sparks jump. Sparks were several inches or a foot long.

I am going to have to think some more about this. I wonder if that boat is still around or if the stern corroded off of it?

Thanks again - leaning toward a metal hull trawler … maybe.


I ordered some good books from mentions on this forum. Any outstanding marine electrical recommendations?

 

[firstbase]

The books suggested to me, a marine electrical newbie, were

Boatowner's Mechanical and Electrical Manual - Nigel Calder
Powerboater's Guide to Electrical Systems - Ed Sherman
The 12 Volt Bible for Boats- Ed Sherman
Boatowner's Illustrated Electrical Handbook - Charlie Wing

 

[CharlieJ]

FF #8:

A proper setup ,usually the source selection switch, regardless of the price of the inverter is about as safe as can be done..

This is not precisely correct.

As previously noted in this thread, inverters and inverter/chargers are required to be UL 458 Listed to be in compliance with ABYC Standards that surveyors and insurance companies use to evaluate a vessel. More importantly, is the need for a true neutral to ground bond within the inverter or within the inverter/charger when inverting. The safety ground (green) wire is a redundant, low impedance path back to the source so that a ground fault will trip an over current protection device.

 

[Maerin]

My distribution panel is made by Square-D with spaces for 8 breakers.
Which made it easy to do.
I have added five AFCI-GFCI combo breakers to it.

So all

outlets
Cruisair heat pump - AC
Water heater
Pool pump
Microwave

are all AFCI-GFCI protected circuits.

While that may work in a land-based application, the difference is in the grounding . The Sq-D panel will have a neutral bonding screw. On land, that screw will probably be in place, since the panel is the source. Common practice in land-based wiring also ties ground and neutral to the same buss. In a marine application, the source is the marina's distribution panel on shore, and that's the only place the ground and neutral are bonded. So in a marine application, if the panel is fed via a shore power cable, and the bonding screw is in place and the grounds and neutrals are commingled, then the safety features of the GFI breakers are compromised, since the GFI is comparing a part of the circuit that's improperly connected. It's an invitation for leakage that the GFI is intended to avoid. A fine point, admittedly, but one that can have significant consequences for the objective of protection.

 

[sdowney717]

While that may work in a land-based application, the difference is in the grounding . The Sq-D panel will have a neutral bonding screw. On land, that screw will probably be in place, since the panel is the source. Common practice in land-based wiring also ties ground and neutral to the same buss. In a marine application, the source is the marina's distribution panel on shore, and that's the only place the ground and neutral are bonded. So in a marine application, if the panel is fed via a shore power cable, and the bonding screw is in place and the grounds and neutrals are commingled, then the safety features of the GFI breakers are compromised, since the GFI is comparing a part of the circuit that's improperly connected. It's an invitation for leakage that the GFI is intended to avoid. A fine point, admittedly, but one that can have significant consequences for the objective of protection.

Ground is not bonded in the panel, in fact all distribution panels can be unbonded by simply removing the green bonding screw. Last year I put in a GE panel in the house we just sold, and that one could also have the neutrals split from the other neutral by unscrewing a connecting buss bar. I was impressed with seeing that.

Believe me, I am not ignorant, I know all about this panel and all the AC wiring on my boat having been through every bit of it. The small QO panel is original to the boat from 1970. But I did disassemble it and sealed it in some epoxy the metal and painted it. It even came with metal strips to prevent the neutral and ground screws from touching the copper wires.

The generator must have the neutral ground bond and of course mine does.
But the distribution panel does not.
All the GFCI circuits function as they should when tested.
I must have one of the safest boat AC systems you can have.
Well you don't have to believe me, but I am just telling you!