Fluke 360 / testing for AC leakage.

[BAD ORCA]

my shaft zinc has replacement has gone from every 6 months to about every three months recently. It was replaced at the beggining of january and my diver just told me it needs replacing again.

My DC wiring has been recently upgraded, about 6 months ago. im confident i did it correctly but am wondering if when getting rid of or disconnecting old wiring if i disturbed or did something to any of the old AC wiring that may be causing AC leakage. the AC wiring is in poor shape and its possible something got disturbed somewhere behind the panel or elsewhere thats now causing a leak. it seems the rapid zinc loss roughly coincides with the timing of my upgrade.

im far from an expert yet but have started down the path to try and understand how to try and figure out if i have an AC leak somewhere. As far as i can tell it seems pretty easy to do. In my one evening research session it seems all i need to do is put a Fluke 360 meter over my shore power cable. if i dont have any leakage my readings should me less that 30 milliamps to be within an acceptable range. If thats the case it would mean my problem lies elsewhere.

am i correct that testing for AC leakage is that easy?

 

[sail sfbay]

I will let the forum electrical experts comment on your specific question. I will be very interested on what you find out with your test. A few questions.

1. Do you have an isolation transformer or galvanic isolator?
2. Have you ruled out stray current from shore power supply? I understand this can / should be tested my the marina on some frequency say annually.
3. Are your boat neighors having a similar issue? Could the next berth be hot?

 

[RoyS]

Is your dock pedestal circuit breaker a GFCI type?

 

[Don S/V ILLusion]

The most common cause is on the DC side and most multimeters are not precise enough to detect the small current leak when it comes to problems such as multiple ground loops. Not to say it isn’t important to also investigate the AC side but don’t omit the more likely cause.
Not to imply you did anything wrong but the chronology you described indicates your problem occurred concurrent with the upgrade to your DC system.

 

[BAD ORCA]

The most common cause is on the DC side and most multimeters are not precise enough to detect the small current leak when it comes to problems such as multiple ground loops. Not to say it isn’t important to also investigate the AC side but don’t omit the more likely cause.

Interesting. I asked a similar question on another forum and was also told the DC side would be the current that would corrode a zinc. It was mentioned an AC leak would be more likely to eat the metal.

I do not have a galvanic isolator or an isolation transformer. I was considering a galvanic isolator. I would like to understand what multiple ground loops are in more detail though. I have some homework to do.

When i upgraded my DC wiring i basically just replaced all the wiring between the charger, the batteries and the 1,2,B switch. There is still a lot of old DC wiring aboard. I did add a DC neg bus bar to try and consolidate all the DC grounds i was dealing with with my section of the upgrade but there are other grounds connected to other parts of the engine. the AC wiring has an earth ground connected to the rear of the engine (seperate location). Im assuming the very old alternators case is grounded where its attached, and there are a couple other small wires ive noticed connected to the engine at random bolts. I dont understand ground loops yet and if those multiple connection points would be relevant. I also added an earth ground from my new charger case to the DC neg bus i added.

The faster corrosion of my zincs seems to roughly coincide with the point when i completed my wiring upgrade. not precisely but close, so its possible i upset some previous electrical balance. i will ask my neighbors when i see them if they suffer the same problem. The boat next to me also arrived roughly around the same time i finished my electrical upgrade.

 

[BAD ORCA]

I will let the forum electrical experts comment on your specific question. I will be very interested on what you find out with your test. A few questions.

1. Do you have an isolation transformer or galvanic isolator?
2. Have you ruled out stray current from shore power supply? I understand this can / should be tested my the marina on some frequency say annually.
3. Are your boat neighors having a similar issue? Could the next berth be hot?

1. neither but i do want to add an isolation transformer.
2. no. im not sure how to do this yet. i found a good link on 'Trawler Forums' that has an bunch of simple tests i can do with a multi-meter. I will look at them in closer detail but plan to carry out all of them this weekend since they are easy to do with a multi-meter.
3.possibly. one of my neighbors showed up ROUGHLY around six months ago although i cant remember exactly when. i guess thats about when my problems started but it also coincides with the timing of when i began working on replacing some of my DC wiring. im going to ask my neighbors if their zincs go equally as fast.

 

[BAD ORCA]

Is your dock pedestal circuit breaker a GFCI type?

i will double check this weekend but all the pedestals are brand new and where installed about a year ago. from memory im almost 100% sure they are. All of the electrical in the entire marina im in is brand new. they did have some problems though with the installation in the beginning so who knows what they did. the mentality around here is the lowest bidder gets the job.

 

[Don S/V ILLusion]

. I would like to understand what multiple ground loops are in more detail though.


I did add a DC neg bus bar to try and consolidate all the DC grounds ... but there are other grounds connected to other parts of the engine.

You just (unintentionally) described how to create multiple ground loops. Each has a slightly different ground potential essentially creating multiple ‘batteries’ which promotes electrolysis.
While I understand your plan to diagnose with a multimeter, that isn’t the ‘right’ tool for the job and can easily mislead you.

 

[BAD ORCA]

You just (unintentionally) described how to create multiple ground loops. Each has a slightly different ground potential essentially creating multiple ‘batteries’ which promotes electrolysis.
While I understand your plan to diagnose with a multimeter, that isn’t the ‘right’ tool for the job and can easily mislead you.

Sorry if this is a lazy question. I will do more homework after work but, would it be a simple matter to just run all of the grounds connected to all the different locations on the engine to the single Neg bus bar i installed? That would be an easy thing to do and one iv'e been considering. The Neg bus bar i added, I connected to a spot on the engine that was previously being used as a ground path for the batteries.

I just realized iv'e never looked closely at the DC ground bus at the distribution panel. I think i may have some sneaker wires that probably should be connected to this bus but may actually go to the engine. There is some very old and wonky connections.

 

[Stu Jackson]

would it be a simple matter to just run all of the grounds connected to all the different locations on the engine to the single Neg bus bar i installed?

That would help, can't hurt, you're halfway there already.

May I suggest a different approach? You mentioned reading various forums and replies to your posts.

I will do more homework

Good for you! Hold off on the forums and read a few good books on the subject by experts. Nigel Calder's Boatowners Manual is one of the better ones. There are others that delve into this subject in great detail and Calder's book explains how to do these tests and measurements far better than I've read on boating forums and I read a LOT of them, daily.

Good luck. Happy Homework. You are heading in the right direction.

 

[BAD ORCA]

That would help, can't hurt, you're halfway there already.

May I suggest a different approach? You mentioned reading various forums and replies to your posts.

Good for you! Hold off on the forums and read a few good books on the subject by experts. Nigel Calder's Boatowners Manual is one of the better ones. There are others that delve into this subject in great detail and Calder's book explains how to do these tests and measurements far better than I've read on boating forums and I read a LOT of them, daily.

Good luck. Happy Homework. You are heading in the right direction.

Thanks Stu. I have his book but for some reason never think of referencing it. It got burried in a locker somewhere and i forget about it. Time to dust it off.