Originally Posted by transmitterdan
Measuring the total cord is a valid test and if all is well it will read zero. St. Elsewhere has the right plan of attack.
This is correct. In a properly operating shore power
cord there would be equal current
on the black and white wires. With say 7.9A on black and 7.9A of white you would read 0A by clamping around the shore power cord.
With 7.9A on black and a resistance issue on white causing it to only pass 7.2A you would see a reading on .7A when clamped around the entire cord set. This means .7A would be flowing back to the source on the green wire or some could be leaking back through the water
path. It always gets back to Earth somehow..
If you want to use a clamp meter, rather than building your own 30A and 50A test leads, you'll need one that has low current
accuracy something most AC/DC clamps lack. You can always test your clamp meter against a standard DVM on the 10A scale with a known load low amperage load, preferably below .5A, and compare the two.
If you don't have a clamp meter than you'd need to insert a standard DVM into the green/ground wire on the 10A scale. There should be no current on this wire. Remember you are dealing with AC so if you are skittish with this leave it to a competent technician...
Shock Drowning is real and most often caused by improper wiring
, home made plugs, adapters, lack of safety
ground etc. etc...
ESD is far more common in fresh water
than in salt
but there is still a potential for it to occur in salt
. At last check there were over 40 documented cases of ESD in the US. Because an autopsy won't show anything other than drowning these documented cases need to have someone witness the paralysis in order to be considered a documentable ESD death. It is likely the issue is a lot more common but attributed to drowning not ESD.
In fresh water 12 - 20 THOUSANDTHS of an an amp or 12-20 mA of leakage is enough to cause paralysis leading to an ESD. For this to happen there is either an undetected AC leakage fault with faulty grounding energizing the boats external metals or the docks metals. The problem can also be with the marina itself and they are technically required (in the US) under NFPA & NEC standards to conduct and keep on file annual inspections of the marinas wiring
If your boat does not have an ELCI (basically a whole boat GFCI) or RCD main breaker then one should be considered.
Very often the issue is with bad or corroded connections in the dock pedestal
, shore cord, shore cord inlet or at the AC panel on your boat. If this is the case the issue will get worse as you increase current demand on-board the boat. If it is a single
source leak on an appliance the leak current won't change much as you increase loads.
These are two suitable clamps for measuring corrosion
level/low amperage leaks
on boats. Meter in this class are NOT inexpensive...
380942 - 30A True RMS AC/DC Mini Clamp Meter
Amprobe (A Fluke Company)
LH41A AC/DC Low Current On Clamp Ammeter | Amprobe
Either way the OP's situation is serious enough that it should be reported to marina management so they can enure they have a safe marina for everyone. The offending boat should be UNPLUGGED IMMEDIATELY!
I would urge everyone to look up Kevin Ritz and Electric
Shock Drowning. He has done tons of work on this having had his own son killed by ESD.
There is a good webinar out there done by Kevin and the ABYC that is worth looking up. Perhaps on YouTube? I did it live about 6-8 months ago, IIRC, and have attended other seminars by Kevin & the ABYC on ESD.
Getting shocked touching a prop is 150% unacceptable!!!