Does anyone else have an issue with the explantion of use of a clamp on meter in this

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"Once you have established that the dock's electrical system is sound, take the clamp meter and put it around your shore power cord. Most electricians use a clamp meter to measure the current flowing through the neutral, hot, and ground wires separately, but we are interested in whether or not all of the current entering the boat is leaving it. If that is the case, the current passing through all of the wires will sum to zero, and that's what the meter will show when the clamp is put around the entire shore power cord. If the clamp meter shows anything but zero, either some of the current going to your boat is entering the water, or current leaking from the dock or another boat is returning to its source ashore through the metal fittings on your boat. "
 
I thought it was a good article. The side bar was clear about hiring a qualified electrician who knows about boats and marinas. The zero sequence test is legitimate. If there really was seven amps stray current like the photo showed that would be huge.

I don't live near a dock but if I get around one I am not allowing anyone from my family in the water until we are out of sight of it.
 
exoticmagneto said:
http://www.boatus.com/seaworthy/magazine/2013/july/electric-shock-drowning-explained.asp

Scroll down to the part of the article that shows the clamp on meter usage . . . (7 amp difference)

I know you can get readings off individual conductors, but clamping over the whole cable is not proper, typically no reading ?

If you read the whole article are there any other improper facts stated ?
Click to expand...
Pretty much how a GFCI works...CT around the hot and neutral expecting to see a sum of zero. With the GFCI where the sum exceeds ~5mA the device trips, with a clamp on meter it shows you that you have a leakage current problem. In this case a very serious one.
 
Hmmmm, I guess if there is no leakage it reads zero with clamp on around all c . . .

Hmmmm, I guess if there is no leakage it reads zero with clamp on around all c . . .

don_resqcapt19 said:
Pretty much how a GFCI works...CT around the hot and neutral expecting to see a sum of zero. With the GFCI where the sum exceeds ~5mA the device trips, with a clamp on meter it shows you that you have a leakage current problem. In this case a very serious one.
Click to expand...

Yes, tried a clamp on meter before on power cord and got zero, had to cut jacket of cord lengthwise to separate hot from the neutral and ground to get a amperes reading on the hot - - - so if there is a leakage then you should get a reading when clamp on is around all the conductors ?

Hmmmm.
 
2017 NEC

2017 NEC

Sierrasparky said:
Is shore power required to be GFCI?
Click to expand...

ESD and the 2017 NEC
It appears virtually certain now that the 2017 National Electrical Code will include some significant changes affecting electrical safety around the water.
1. Article 555 Marinas and Boatyards will have a new name:
"Article 555 Marinas, Boatyards, and Commercial and Noncommercial Docking Facilities"
2. The new Article 555 will apply to ALL docking facilities, including those at private residences, condos, apartments, etc.
3. Shore power ground-fault protection will be reduced from the current 100 mA to 30 mA.
4. A requirement to post warning signs where electricity is used in or on docks.
The language from the 2nd draft of the proposed 2017 NEC reads:
[FONT=&quot]555.24 Precautionary Signage for Electric Shock Hazard in Water.

(A) Permanent safety signs shall be installed to give adequate notice of electrical shock hazard risks to persons using or swimming near a boat dock or marina.

(B) The signage shall comply with 110.21(B)(1) and be of sufficient durability to withstand the environment.

(C) The signs shall be clearly visible from all approaches to a marina or boatyard facility.

(D) The signs shall state "WARNING - POTENTIAL SHOCK HAZARD - ELECTRICAL CURRENTS MAY BE PRESENT IN THE WATER."[/FONT]
[FONT=&quot]This specific language from the proposed NEC is included in the warning signs currently being promoted to marina facilities by District 10 of the US Power Squadrons.[/FONT]
 
exoticmagneto said:
Yes, tried a clamp on meter before on power cord and got zero, had to cut jacket of cord lengthwise to separate hot from the neutral and ground to get a amperes reading on the hot - - - so if there is a leakage then you should get a reading when clamp on is around all the conductors ?
Click to expand...

Basic electrical theory- current goes out on one wire and comes back on the other. If you meter each wire, you'll read that current; read both at once and one cancels the other (add plus 5 to minus 5 and get zero). That's what's happening when you meter a multi-conductor cable. Now, if some of the current isn't coming back where it should (leakage) the plus 5 and the minus 4.5 will give you an 0.5 reading. Bad.
 
exoticmagneto said:
Yes, tried a clamp on meter before on power cord and got zero,
Click to expand...

That is good, that is the expected reading of a correctly operating circuit

had to cut jacket of cord lengthwise to separate hot from the neutral and ground to get a amperes reading on the hot
Click to expand...

Correct, to get the individual current readings for each conductor you must clamp them individually.

- - - so if there is a leakage then you should get a reading when clamp on is around all the conductors ?
Click to expand...

Yes, if you had 5 amps of current 'leaking' from the circuit downstream of your clamp meter you would see a 5 amp reading on your meter.
 
So, as the article suggests, is it a reliable methodology

So, as the article suggests, is it a reliable methodology

iwire said:
That is good, that is the expected reading of a correctly operating circuit



Correct, to get the individual current readings for each conductor you must clamp them individually.



Yes, if you had 5 amps of current 'leaking' from the circuit downstream of your clamp meter you would see a 5 amp reading on your meter.
Click to expand...


So, as the article suggests, is it a reliable methodology to go up and down a marina or dock with a clamp on meter testing cables to see if you get a reading on any of them (leakage) ?
 
exoticmagneto said:
So, as the article suggests, is it a reliable methodology to go up and down a marina or dock with a clamp on meter testing cables to see if you get a reading on any of them (leakage) ?
Click to expand...

It all depends on the sensitivity of the clamp meter. You are not likely to be able to measure leakage in the 6ma range of a standard GFCI, nor even the 100ma range of a less sensitive GFP.
But you could detect several amps of leakage, which could well cause hazardous voltages (and currents) in the water as well as providing a touch hazard.
To sum that up, a high reading definitely suggests a safety issue while a zero (within the sensitivity of the amp-clamp) reading would not insure that the circuit is safe.

If you have a measurable current at any point, going along the feeder and branch circuit tree might help you zero in on the location of the fault.
 
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