ESD-(Electric Shock Drowning)-no swimming
- Thread starter Pat T
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From the ABYC's presentation last year- it takes TWO faults together to create the conditions for an ESD hazard:
- The AC hot shorts to boat ground somehow
- The boat ground is not connected to shorepower ground
In that ABYC video, I’m going a little from memory (long video, I didn’t watch it again) but I believe that the boat involved in the presenters accident had a fault where the hot wire of the AC had come in contact with the 12 volt on the DC side in the boat. The outboard was connected to the DC ground so the AC hot was applied to the water through the low impedance of the battery. I believe they had smelled wire burning the day before (or something like that) so maybe a wire got hot (either the AC or 12V and another fusing error) and melted the insulation creating the fault.
I believe these diagrams to be correct - but since I just threw them together, could be an error.
The fault that caused the dangerous condition is shown in the picture below. There was no earth ground connected up and the current into the water wasn’t enough to blow any fuse in the system.
If the boat had only the earth ground connected up - either directly to DC ground or through a galvanic isolator - and of course correctly sized AC wires and fuses, the accident would not have happened. In the picture below, when the fault happened, a LOT of current would have flown through the battery into the DC ground, through the galvanic isolator back to AC safety ground and this would have blown the AC fuse the second the fault occurred. FYI, this is why galvanic isolators are sized to handle a lot of current.
Also, with or without the earth safety ground, if the dockside would have had ELCI, the same fault would have blown the ELCI breaker. In the picture below, some of the AC current on the hot wire would have flown into the water through the outboard. Since the fault current would not have returned on the neutral wire, the ELCI would have detected the imbalance and blown. In this case, even if the boat did not have the earth safety ground hooked up, the ELCI (or GFI) would still have blown as the earth safety ground doesn’t need to be involved for this trip.
I believe these diagrams to be correct - but since I just threw them together, could be an error.
The fault that caused the dangerous condition is shown in the picture below. There was no earth ground connected up and the current into the water wasn’t enough to blow any fuse in the system.
If the boat had only the earth ground connected up - either directly to DC ground or through a galvanic isolator - and of course correctly sized AC wires and fuses, the accident would not have happened. In the picture below, when the fault happened, a LOT of current would have flown through the battery into the DC ground, through the galvanic isolator back to AC safety ground and this would have blown the AC fuse the second the fault occurred. FYI, this is why galvanic isolators are sized to handle a lot of current.
Also, with or without the earth safety ground, if the dockside would have had ELCI, the same fault would have blown the ELCI breaker. In the picture below, some of the AC current on the hot wire would have flown into the water through the outboard. Since the fault current would not have returned on the neutral wire, the ELCI would have detected the imbalance and blown. In this case, even if the boat did not have the earth safety ground hooked up, the ELCI (or GFI) would still have blown as the earth safety ground doesn’t need to be involved for this trip.
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