Galvanic Isolator

[boatpoker]

Well, that's true sometimes, but it totally depends on the AMOUNT of current. The corrosion rate is dictated by the current that is produced.

Yes, the amount of current dictates the corrosion. In galvanic current you are talking about milliamps and stray current you are talking about amps, sometime very high amperage. I've never seen stray (leaking) current in the milli range.This is a clearly recognized difference in any corrosion analysis course you may take.

PS. I'm an ABYC Certified Corrosion Analyst.

 

[OFB]

Haven't seen isolation transformers in the thread. But did just take a quick look through..

Still, heavy and noisy.? Always talked about one as a dock box. Being a liveaboard.

Kinda small amps for my needs but sure changes the game.

Random thoughts

 

[tpbrady]

Newer isolation transformers from Magnum Energy are light 7-8 lbs for 30A and quiet from what I hear.

Tom

 

[Arctic Traveller]

Yes, the amount of current dictates the corrosion. In galvanic current you are talking about milliamps and stray current you are talking about amps, sometime very high amperage. I've never seen stray (leaking) current in the milli range.This is a clearly recognized difference in any corrosion analysis course you may take.

PS. I'm an ABYC Certified Corrosion Analyst.

That's good to know. Since the OP wants to know if his zinc usage is abnormal, measurement of the current would tell us if it was Galvanic or stray current leakage. Thanks...................

 

[Insequent]

Not long after I bought my boat the marina advised that they had investigated a complaint about rapid zinc loss. The guy was several boats away from me. They checked each boat on the finger arm and said I was the problem, and asked that I get it fixed.

The issue turned out to be a jumper from ground to neutral on the switch that changed from shore power to gennies (2). Hard to find as the short wire jumper was only visible when using a mirror to see the top-rear of the switch.

During troubleshooting and testing we found that 50% of the AC was being returned via the water. Yes, we measured up to 15A going back when I was drawing 30A from shore power! Very glad to have found that problem and fixed it! During boat refit a Charles isolation transformer was installed....

 

[angus99]

Newer isolation transformers from Magnum Energy are light 7-8 lbs for 30A and quiet from what I hear.

Tom

Where are you seeing these, Tom? A quick Google search isn't turning up anything from ME. Thnx.

 

[boatpoker]

That's good to know. Since the OP wants to know if his zinc usage is abnormal, measurement of the current would tell us if it was Galvanic or stray current leakage. Thanks...................

Only takes a minute with a clamp meter.

 

[boatpoker]

Not long after I bought my boat the marina advised that they had investigated a complaint about rapid zinc loss. The guy was several boats away from me. They checked each boat on the finger arm and said I was the problem, and asked that I get it fixed.

The issue turned out to be a jumper from ground to neutral on the switch that changed from shore power to gennies (2). Hard to find as the short wire jumper was only visible when using a mirror to see the top-rear of the switch.

During troubleshooting and testing we found that 50% of the AC was being returned via the water. Yes, we measured up to 15A going back when I was drawing 30A from shore power! Very glad to have found that problem and fixed it! During boat refit a Charles isolation transformer was installed....

Neutral/ground connections are the cause of ESD (electric shock drowning) and is the very first electrical check I make when doing a survey. Very easy .....
- disconnect shore power
- turn off inverter
- turn off generator breaker
- turn on all AC breakers
- set multi meter at ohms
- measure resistance between neutral (widest prong) and ground ( prong with hook)

you should see O.L. (open line) on the meter if you see numbers and the ohms symbol, call a marine electrician.
-

 

[boatpoker]

got some info and a a lot of photos of electrical problems on this web page.

 

[Steve DAntonio]

Newer isolation transformers from Magnum Energy are light 7-8 lbs for 30A and quiet from what I hear.

Tom

As far as I know Magnum does not offer a shore power transformer (transformers can be wired as isolation or polarization, it's the same transformer, only the wiring method differs, only when wired in isolation mode does it eliminates corrosion induced from other vessels, bulkheads, docks etc). Charles is the only iso xfmr manufacturer whose product meets current ABYC standards (which includes a UL Marine Listing) in E-11. They are heavy, by necessity there's no way around that as long as it's a transformer, and they generate heat and therefore need ventilation, however, I don't find them particularity noisy especially if soft mounted.

Bottom line, however, this is the most effective means of preventing galvanic corrosion and even stray current corrosion, the latter when it originates from a neighboring vessel. It will do nothing to mitigate stray current corrosion that originates aboard your own vessel. Stray current corrosion from neighboring vessels, while far less common, does occur, I've encountered it.

 

[seadogmike]

Mastervolt also offers an Isolation transformer that is ABYC compliant.
Mastervolt Isolation Transformer

At 13 Lbs....

 

[angus99]

Thanks, Steve.

Just wondering what the consensus might be on whether it's still advisable to bond isolated through hulls on a fiberglass hull if there is an isolation transformer installed. Or have I just displayed my still-considerable ignorance on the subject?

 

[Tomas]

I'm confused, in "Understanding the Neutral-to-Ground Connection", Capt David Rifkin, USN Ret, says:

"Determining if a neutral-ground fault exists on the boat you are working on or surveying is a matter of making a simple test with a digital multimeter. With the boat unplugged from shore power (see safety note below), measure the resistance between the neutral and ground buses in the panel, or access these two points at any convenient AC receptacle on the boat (the large slot on the receptacle is the neutral). This reading should be greater than 25kohm. Typically the reading will be close to zero ohms if a neutral-ground connection exists."

Boatpoker says:

"you should see O.L. (open line) on the meter if you see numbers and the ohms symbol, call a marine electrician"

What am I missing?

Tom

 

[rwidman]

I'm confused, in "Understanding the Neutral-to-Ground Connection", Capt David Rifkin, USN Ret, says:

"Determining if a neutral-ground fault exists on the boat you are working on or surveying is a matter of making a simple test with a digital multimeter. With the boat unplugged from shore power (see safety note below), measure the resistance between the neutral and ground buses in the panel, or access these two points at any convenient AC receptacle on the boat (the large slot on the receptacle is the neutral). This reading should be greater than 25kohm. Typically the reading will be close to zero ohms if a neutral-ground connection exists."

Boatpoker says:

"you should see O.L. (open line) on the meter if you see numbers and the ohms symbol, call a marine electrician"

What am I missing?

Tom

You are not reading carefully. They are saying essentially the same thing but in a different way. 25 thousand ohms is close to an open circuit (in this case). Numbers on the meter mean some continuity. Of course it could read 25K ohms and then what do you do?

 

[boatpoker]

You are not reading carefully. They are saying essentially the same thing but in a different way. 25 thousand ohms is close to an open circuit (in this case). Numbers on the meter mean some continuity. Of course it could read 25K ohms and then what do you do?

Absolutely correct, in fact I got much of my training from Dave. I did not mention the 25koms as it tends to confuse people. I believe unless you are utterly conversant with the issue, if you see any kohms you should call in a qualified marine electrician.

 

[seadogmike]

Absolutely correct, in fact I got much of my training from Dave. I did not mention the 25koms as it tends to confuse people. I believe unless you are utterly conversant with the issue, if you see any kohms you should call in a qualified marine electrician.

If my memory serves me correctly, the reason for 25kohms is the resistance across the polarity indicator.

 

[boatpoker]

If my memory serves me correctly, the reason for 25kohms is the resistance across the polarity indicator.

thats part of it but when you get down around 10kohms you are getting too close to the electric shock drowning potential.
I repeat ... unless you are absolutely sure about what you are doing, don't take a chance as you may be dealing with a potentially lethal condition. Call someone who knows.

 

[FlyWright]

thats part of it but when you get down around 10kohms you are getting too close to the electric shock drowning potential.
I repeat ... unless you are absolutely sure about what you are doing, don't take a chance as you may be dealing with a potentially lethal condition. Call someone who knows.

That thar is some damn good advice! Cheers to that!

 

[what_barnacles]

So would a way to test the isolator be to leave the boat plugged in to the shore power and measure the boats neutral to ground?

 

[angus99]

Would love to know the answer to this question.

Just wondering what the consensus might be on whether it's still advisable to bond isolated through hulls on a fiberglass hull if there is an isolation transformer installed.

By "isolated through hulls," I just meant THs that are not bonded together.

If the isolation transformer totally protects me from other boat's/dock's galvanic corrosion and stray current, why would it be advantageous to bond through hulls together in the first place? Wouldn't I be creating the electrical pathways between dissimilar metals that allow galvanic corrosion to exist in the first place?

 

[rwidman]

Absolutely correct, in fact I got much of my training from Dave. I did not mention the 25koms as it tends to confuse people. I believe unless you are utterly conversant with the issue, if you see any kohms you should call in a qualified marine electrician.

I'll add one thing:

With a decent digital meter, you will see some conductivity (ohms. Kohms)) if you are touching the probes with your fingers when taking measurements. Use clips on the meter probes or make sure you are not touching the metal part of the probes.

 

[rwidman]

So would a way to test the isolator be to leave the boat plugged in to the shore power and measure the boats neutral to ground?

You can find instructions for testing a galvanic isolator on the Internet. You have to disconnect it and measure across the two terminals (each way, I believe). You are actually measuring the diodes to see if they conduct in one direction and not the other.

 

[Steve DAntonio]

Thanks, Steve.

Just wondering what the consensus might be on whether it's still advisable to bond isolated through hulls on a fiberglass hull if there is an isolation transformer installed. Or have I just displayed my still-considerable ignorance on the subject?

It's a more than valid question. A transformer, isolation or polarization, does not negate the need for or value of bonding. Bonding is still needed for onboard galvanic and stray current corrosion protection, as these can still originate aboard your own vessel, as well as onboard electrocution protection. Furthermore, even a non-lightning rated (ABYC TE-4 compliant) bonding system will, in my experience, provide some level of protection for onboard gear and crew in the event of a direct or indirect strike.

From a corrosion perspective, the transformer simply isolates you from potential shore or other vessel-induced corrosion scenarios.

 

[angus99]

It's a more than valid question. A transformer, isolation or polarization, does not negate the need for or value of bonding. Bonding is still needed for onboard galvanic and stray current corrosion protection, as these can still originate aboard your own vessel, as well as onboard electrocution protection. Furthermore, even a non-lightning rated (ABYC TE-4 compliant) bonding system will, in my experience, provide some level of protection for onboard gear and crew in the event of a direct or indirect strike.

From a corrosion perspective, the transformer simply isolates you from potential shore or other vessel-induced corrosion scenarios.

Terrific.

Thanks, Steve!

 

[Steve DAntonio]

Mastervolt also offers an Isolation transformer that is ABYC compliant.
Mastervolt Isolation Transformer

At 13 Lbs....

Mike, I've seen these before and while interesting, I have dismissed them as too complex, too much circuitry, fans etc for such an important system like shore power supply. That aside, my instinct says they are not ABYC compliant, I've gone through the specs and installation manual and other than the vendor's ad nothing in MV literature mentions ABYC compliance. Not that I can find anyway.

Like a lot of MV gear, the unit is clearly originally designed for use in a 50 Hz 230 volt environment, which is why each module is only 16 amps (which makes me nervous). You'd need two for a 30 amp system.

These are high frequency switching transformers, which is why they are so light, however, traditionally these have been unable to meet the ABYC/UL requirement for shielding between primary and secondary.

Having said all that, I've contacted MV for a statement of compliance, I'll report back with my findings. If it is compliant then the 2 units needed for a 120v 30 amp system would cost $2200, and four for a 240 volt 50 amp service $4400., pretty pricey and almost certainly more than traditional xfmrs. If you had to save weight I suppose it might be worth it, they wouldn't save much in the way of space; they aren't dramatically smaller than an equivalent capacity transformer. Stand by for more.

 

[tpbrady]

Steve,

I had looked at this transformer and the literature says:

"The Mass GI features marine aluminium casing and professional connections with strain relief cable glands. All Mastervolt isolation transformers comply with the CE and ABYC (US norm) guidelines for vessels."

Not being an expert in ABYC, I am not sure what that means.

On the specification side, it says it is rated at 16A at 230V with make power of 3500W. With my limited knowledge of electricity that would seem to translate to 32A at 115V and be within the 3500W power handling capability of the transformer.

I am interested to see what you find on this as I was considering one for my boat. We are starting to see new harbor construction in SE Alaska with the newer ELCI breakers. Almost universally boat owners are finding that they only way to reliably plug in is with an isolation transformer between shore power and the boat.

Tom

 

[FlyWright]

You guys have inspired me. Today on the boat, I checked all my AC plugs with a polarity sensor and all were good. I unplugged all AC and checked my neutral/ground resistance. Good news...open line!

I went ahead and ordered a Yandina GI for my 30A vessel. It might not be perfect but it's what I can afford and install given my space constraints. I've always been concerned about AC current leaks. Hopefully this will provide an added level of safety.

Thanks guys!

 

[Steve DAntonio]

Steve,

I had looked at this transformer and the literature says:

"The Mass GI features marine aluminium casing and professional connections with strain relief cable glands. All Mastervolt isolation transformers comply with the CE and ABYC (US norm) guidelines for vessels."

Not being an expert in ABYC, I am not sure what that means.

On the specification side, it says it is rated at 16A at 230V with make power of 3500W. With my limited knowledge of electricity that would seem to translate to 32A at 115V and be within the 3500W power handling capability of the transformer.

I am interested to see what you find on this as I was considering one for my boat. We are starting to see new harbor construction in SE Alaska with the newer ELCI breakers. Almost universally boat owners are finding that they only way to reliably plug in is with an isolation transformer between shore power and the boat.

Tom

Tom, I saw that but only in the ad (the ABYC part), not in MV's own literature. Did you see that in MV's literature?

Agreed on the 16 vs 32 amp volt part, it would seem as if one unit at 120 volts would work, however, it does't specifically say this, which concerns me, anytime you see 16 and 32 amps you know it's initially set up for a Euro environment. The instructions do show a 120 volt hook up (with Euro wire color codes, which are ABYC compliant, if not confusing to a US installer), however, I have to confess I haven't read them cover to cover, yet. I may have missed this. I will.

I did get a response from MV, they sent a deceleration of conformity doc, which is on the page with the product, which makes no mention of ABYC, nor did the person responding...and I responded...

"It complies with '11.7.1.2.1 Meet the safety requirements of IEC/UL 60950, Information Technology Equipment'.

However, I see no mention of compliance with… ABYC E-11.7.1.2.2 the environmental requirements of IEC 60945, Maritime Navigation, et al…

So the question remains, does it comply with ABYC E-11?"

The person responding said she'd look into it. I'll keep the Forum posted.

 

[Catbird]

OP here. I have been following the thread closely. Thank you for all the guidance. I also bought the Yandina unit but have not installed it yet. I had enough time at the boat to check the negative to ground at the shore power connection on board.

I used two different multimeters. One was a cheapo - the other was a decent Craftsman. Each read out a "1" . I took the readings with both high settings and low settings. The readout stayed at 1.

Never saw the OL reading. Does this confirm an AC leak problem?

 

[rwidman]

OP here. I have been following the thread closely. Thank you for all the guidance. I also bought the Yandina unit but have not installed it yet. I had enough time at the boat to check the negative to ground at the shore power connection on board.

I used two different multimeters. One was a cheapo - the other was a decent Craftsman. Each read out a "1" . I took the readings with both high settings and low settings. The readout stayed at 1.

Never saw the OL reading. Does this confirm an AC leak problem?

"1" what? Ohm, hundred ohms, thousand ohms?

I don't mean to insult you but if you don't know how to use a meter, you should not rely on the results. I suggest getting someone with at least a basic knowledge of electricity to help you.

BTW: While the Yandina galvanic isolator is the most inexpensive, it doesn't meet the ABYC requirements because it is not "fail safe". "Fail safe" in this case means that if the device fails, it will leave the ground conductor intact. It will no longer function as an isolator but people will still be protected with an intact grounding system.