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Old 02-10-2014, 16:52   #1
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Electrolysis Problem

[ I just bought a 1988 Morgan classic a little over 2 months ago. I have had it in a marina for that time. Last month month I had the bottom cleaned and was told that the zinc was almost completely gone. During the survey 2 months ago it looked ok. I replaced the zinc and this month it was gone again. Obviously I have an electrolysis problem. I have asked my neighbor boats to check their zinc to make sure that I am not messing them up or they me.
I guess the question is how do I run down the source of the "leak" I am pretty new to boat electrical stuff so any pointing me in a direction would be great.
I have shore power and my AC is running a lot (summer in Florida) that is the biggest electrical draw by far. Besides that I have an inverter, hot water heater port and starboard 110 receptacles and a small Microwave.
The A/C (16000 Btu unit) draws about 13 amps. The A/C breaker does switch off when the Microwave is turned on. I don't know if that means anything, but I thought I would put it in here just in case that indicates a possible problem.
Thanks for any advice or guidance you could give on this problem. If I can't find the source of the problem, I will get a marine engineer or mechanic to fix it. But I do think that I will need to know this stuff before heading out for a 18 month cruise.

Lynne
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Old 02-10-2014, 17:13   #2
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Re: electrolysis problem

Hey Lynne,

Welcome to CF! Congrats on the boat, and total bummer on your problem... There are TONS of guys more well versed in this than I... BUT...

Look up galvanic isolators, and isolation transformers to gain some background info/knowledge...

Something's definitely hot in your marina, and I would start with the dockmaster, and let him/her know what's going on...

This could be a very bad and dangerous situation if not rectified...
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Old 02-10-2014, 18:07   #3
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Re: Electrolysis Problem

you need to find someone with a silver silver chloride cell and the knowledge on how to properly use it. the 2nd will be rare.

this stuff can be hard to find and may never find anything. sometimes is something easy. normaly it's the dc side causing issues. ac current doesn't corrode stuff. however you may have dc current flowing on your ac wires to the dock if you don't have a galvanic isolator or isolation transformer. or a problem may be bypassing it.

the breaker thing is probably separate but should also be looked at. the microwave and a/c should be completely separate circuits and not effected by each other. unless it's an ac main you are blowing. which is simply just overload on the boat.
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Old 03-10-2014, 00:06   #4
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Re: Electrolysis Problem

If the marina is hot where it shouldn't be, you can lose your prop to electrolysis, Lynne, so Happy Md Sailor's warning should be heeded.

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Old 03-10-2014, 00:28   #5
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Re: Electrolysis Problem

Check to see if your AC ground is connected to the DC ground. Even if it's the battery charger. See if your prop shaft is also grounded to the motor. Current can pass thru the prop/shaft and up thru the motor to the AC ground. And if the marina is hot you'll have a path for it to go thru. Isolate your AC from your DC.

With all that AC running thru your boat you could be producing it yourself. And microwaves are power hungry. If you use it, shut down other AC systems first. Notice the size of the cord on a microwave. It's just like the aircon.
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Old 03-10-2014, 09:52   #6
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Re: Electrolysis Problem

A galvanic isolator can be installed for under $100 and will pay for itself within 12 months or less. It is the first line of defense if you are using shore power.
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Old 03-10-2014, 18:12   #7
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Re: Electrolysis Problem

I have talked to the marina people and it looks like the power line into the boat is not the problem. It is probably a 110/12 V problem. People are telling me that it is usually where 110 and 12 come together. That is what most of the replies to my query have stated. I am beginning to suspect my 12 volt battery charger. is both old and pretty loud.
I got the number of a marine electrician from the dock master. I think this is a problem that I should let a professional help me with.
I will be sure to ask him to put a galvanic isolator. I will also watch and ask questions, since I have to start figuring out this stuff sooner rather than later.
Thanks to all of you who have replied. It has been helpful and has me pointed in the right direction to get the problem fixed.
I will not be leaving the marina until the 2015/16 cruising season. so I have time to fix the myriad of problems that the boat has (nothing really major). So I have to get this problem fixed first. Once cruising I don't plan to be in a marina much. So hopefully, I will have to deal with this problem only once.

Again thanks

Lynne
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Old 03-10-2014, 18:46   #8
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Re: Electrolysis Problem

Correct, the 110/12V ground/negative connection is the cause of over 90% of electrolytic problems on boats. If it were not for that connection the systems would be isolated and current in the shore power ground could not get to the underwater metal.

Unfortunately that connection is REQUIRED for safety. If the connection is missing and anywhere on the boat there is an accidental connection from 110 volts to the 12 volt system that would put 110 volts on the underwater metal and electrocute any swimmers in the vicinity.

With the connection correctly in place, the accidental 110 volt short would just blow a breaker or fuse and swimmers would be safe.

If your battery charger is "old and pretty loud" it won't do any harm to replace it but it is unlikely that is the cause of your zinc loss problems.
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Old 04-10-2014, 06:39   #9
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Re: Electrolysis Problem

Quote:
Originally Posted by Lynnenorring View Post
I have talked to the marina people and it looks like the power line into the boat is not the problem. It is probably a 110/12 V problem. People are telling me that it is usually where 110 and 12 come together. That is what most of the replies to my query have stated. I am beginning to suspect my 12 volt battery charger. is both old and pretty loud.
I got the number of a marine electrician from the dock master. I think this is a problem that I should let a professional help me with.
I will be sure to ask him to put a galvanic isolator. I will also watch and ask questions, since I have to start figuring out this stuff sooner rather than later.
Thanks to all of you who have replied. It has been helpful and has me pointed in the right direction to get the problem fixed.
I will not be leaving the marina until the 2015/16 cruising season. so I have time to fix the myriad of problems that the boat has (nothing really major). So I have to get this problem fixed first. Once cruising I don't plan to be in a marina much. So hopefully, I will have to deal with this problem only once.

Again thanks

Lynne
Lynne,

Sounds like you have a good plan of attack... Those pesky combined grounds of AC and DC work really well until "JUST" one component goes on the fritz, or is installed incorrectly... Either of the isolators will eliminate problems originating from "your boat"...

The only thing I REALLY DON'T LIKE.... is your statement of not leaving the marina until 15/16... Imma hunt you down if you aren't stretching your new boat's legs...
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Old 04-10-2014, 09:33   #10
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Re: Electrolysis Problem

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Originally Posted by Andina Marie View Post

Unfortunately that connection is REQUIRED for safety. If the connection is missing and anywhere on the boat there is an accidental connection from 110 volts to the 12 volt system that would put 110 volts on the underwater metal and electrocute any swimmers in the vicinity.

With the connection correctly in place, the accidental 110 volt short would just blow a breaker or fuse and swimmers would be safe.
Where do you get that from? Can you quote me a code? And GFCI's are required on boats now.
If there were a short, the ground would be where the power would get to the water, if both ground systems are connected together.
The ground on an AC system is supposed to take any lost power back to the box, not redirect it to wherever.
Another reason why most marinas don't allow swimming.

I just use a car charger to charge my batteries.
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Old 04-10-2014, 09:51   #11
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Re: Electrolysis Problem

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Where do you get that from? Can you quote me a code? And GFCI's are required on boats now.
If there were a short, the ground would be where the power would get to the water, if both ground systems are connected together.
The ground on an AC system is supposed to take any lost power back to the box, not redirect it to wherever.
Another reason why most marinas don't allow swimming.

I just use a car charger to charge my batteries.
It is required by the ABYC standards. I don't have the specific reference number but the wiring diagram for galvanic isolator installation on ABYC A-28 page 7/08 Figure 1 shows the boat AC ground connected "To engine negative or its bus". I'm sure there are surveyors on this bulletin board who can give the direct reference.

If your car charger were to develop a short between the primary side and the 12 volt side, your boat would become lethal without a ground connection from the battery negative back to the AC source ground.

The probability of failure is small but the consequences can be catastrophic.
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Old 04-10-2014, 12:08   #12
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Re: Electrolysis Problem

Well the dock master came over with a tester and it showed about a two amp loss by testing the shore plug. I guess that that means that there is a problem on my boat. I have had a diver in the water cleaning the boat bottom each of the last two months. He is the one that alerted me to the zinc loss each month. He didn't seem to have any problem with stray electricity.
I do plan to have a marine electrician come on next week to figure out where the "leak" is coming from.
I don't plan on going on any long cruises for another year. I will however be taking the boat out hopefully for some west florida cruising. Once I finally take off I will be gone or two sailing seasons one down to Venezuela (if it is hospitable) and the other season coming back to Florida.
thanks for all the input.

Lynne
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Old 04-10-2014, 22:04   #13
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Re: Electrolysis Problem

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Originally Posted by Andina Marie View Post
It is required by the ABYC standards. I don't have the specific reference number but the wiring diagram for galvanic isolator installation on ABYC A-28 page 7/08 Figure 1 shows the boat AC ground connected "To engine negative or its bus". I'm sure there are surveyors on this bulletin board who can give the direct reference.

If your car charger were to develop a short between the primary side and the 12 volt side, your boat would become lethal without a ground connection from the battery negative back to the AC source ground.

The probability of failure is small but the consequences can be catastrophic.
Yeah I've got the pictures but fortunately ABYC is not law.

If you goto the USCG Title 33 CFR Sections 183.401 - 183.460 you'll not find any code requiring the ground leg of AC systems ground to the motor or any other part of a boat. All AC systems now require a GFCI, which detect a voltage between terminals and trip if out of sync. http://home.howstuffworks.com/question117.htm

What would an engineless sailboat or one with an outboard (kicked up) do? And I think ABYC is more concerned about gasoline driven boats. Just pulling the cord out of an outlet could be leathel on a gas boat.
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