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Old 03-31-2016, 08:05 AM   #41
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Mastervolt also offers an Isolation transformer that is ABYC compliant.
Mastervolt Isolation Transformer

At 13 Lbs....
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Old 03-31-2016, 08:50 AM   #42
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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?
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Old 03-31-2016, 12:26 PM   #43
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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
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Old 03-31-2016, 06:06 PM   #44
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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?
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Old 03-31-2016, 06:25 PM   #45
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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.
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Old 03-31-2016, 07:46 PM   #46
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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.
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Old 03-31-2016, 07:52 PM   #47
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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.
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Old 03-31-2016, 09:51 PM   #48
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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!
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Old 04-01-2016, 05:30 AM   #49
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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?
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Old 04-01-2016, 07:12 AM   #50
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Would love to know the answer to this question.


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Originally Posted by angus99 View Post
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?
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Old 04-01-2016, 07:52 AM   #51
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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.
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Old 04-01-2016, 07:55 AM   #52
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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.
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Old 04-01-2016, 08:20 AM   #53
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Originally Posted by angus99 View Post
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.
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Old 04-01-2016, 08:39 AM   #54
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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!
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Old 04-01-2016, 08:40 AM   #55
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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.
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Old 04-01-2016, 02:08 PM   #56
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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.

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Old 04-02-2016, 01:38 AM   #57
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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!
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Old 04-02-2016, 07:52 AM   #58
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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.
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Old 04-02-2016, 07:53 AM   #59
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Galvanic Isolator

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?
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Old 04-02-2016, 08:18 AM   #60
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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.
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