Is it possible to test a bonding system for unwanted electrical current while the boat is out of the water? If so how? The bonding system contains several seacocks and the rudder skeg. Thanks! SC
Bonding blues
- Thread starter sailcruiser
- Start date
Theoretically, yes BUT you can't replicate conditions when the boat is in use where the insidious causes occur.
Step one is an accurate diagram.
As you make the diagram, one hopes you will not find lightning protection system, nor separate DC bonding system nor any remnants. If you do - put them in the diagram.
Otherwise - there should be no wire connection to anything except underwater fittings. There are two exceptions - the wire that runs between fittings must eventually end at an external zinc and/or they must lead to the motor block.
An accurate as built diagram will (almost always) reveal any path where damaging current can introduce itself. Further testing may not add anything, but only if your as built diagram is accurate.
As you move through the boat, test to verify each wire to underwater fitting attachment point is less than 1 ohm, no corrosion, spiffy clean.
So - diagram first, then test. Testing goes faster in water, but doable out of the water provided you have accurate as built diagram.
If all you want is a test to see if stray vulture current (AC or DC you did not mention which) is around then you need normal water level inside the boat, and the boat needs to be in the water. Water is absolutely required if the source is from a neighbor boat or marina wiring, and - absent normal bilge water levels - may not show up on your boat from a visual inspection.
Charles
As you make the diagram, one hopes you will not find lightning protection system, nor separate DC bonding system nor any remnants. If you do - put them in the diagram.
Otherwise - there should be no wire connection to anything except underwater fittings. There are two exceptions - the wire that runs between fittings must eventually end at an external zinc and/or they must lead to the motor block.
An accurate as built diagram will (almost always) reveal any path where damaging current can introduce itself. Further testing may not add anything, but only if your as built diagram is accurate.
As you move through the boat, test to verify each wire to underwater fitting attachment point is less than 1 ohm, no corrosion, spiffy clean.
So - diagram first, then test. Testing goes faster in water, but doable out of the water provided you have accurate as built diagram.
If all you want is a test to see if stray vulture current (AC or DC you did not mention which) is around then you need normal water level inside the boat, and the boat needs to be in the water. Water is absolutely required if the source is from a neighbor boat or marina wiring, and - absent normal bilge water levels - may not show up on your boat from a visual inspection.
Charles
Yes you can....My Marina Harbor Master has a neat yellow box about the size of a small suite case. It plugs into your dock side shore power outlet then you plug your shore power cord into it. Then a sensor is then dropped into the water around your boat. You shut down all systems down 12 dc as well as 120 ac breakers below. And then one by one you engage each system. As you engage each system a meter reading is taken and recorded.
When he did my boat I found out that even my s.s. rub rail was bonded as well as all stanchions and arch.
BTW...Was relieved to find out that all my systems checked out good. :dance:
I believe you still can check for continuity ....All you have to do is connect the sensor to your thru hole fittings and the rigging ....In this case I would do each fitting separately recording each fitting. This should give you a good idea of how well all the bonding connections are made.
I don't see how that would give an accurate picture of what happens when the boat is in and all the myriad underwater metals are at different potential. It's the interactions that drive the causes.
The short answer is you can test for some things, but not anything related to being in the water in a marina and plugged into shore power...
My questions would be;
*What is the actual concern?
*Do you have an issue when in the water?
*What are you trying to solve or fix?
Hi MaineSail! The concern has been these areas are all showing signs of corrosion. There is a circular pattern around the through hulls in the bottom paint (VC-17) which appears to be galvanic corrosion. I'm trying to locate the source of this current. I have been through the electrical system a few times but I'm obviously missing something. I'm wondering if a PO decided to use it as a ground or something. The corrosion is limited to these points only. My hope is to figure out a way to locate this issue before we splash for the Spring. If its impossible then it will wait. Shore power passes through an isolation transformer so right now I'm focused on my electrical system. SC
Here is an idea .... So boat is on the hard right? Try this get your shore power cord out and plug into the boats outside shore power connection on the boat. Now with the free end of the cord and an Olms meter . Check the ground side first to all your thru hull fittings then check the white neutral and then the black. Start with everything on board in the off position first . Then just go down the line turning breakers on and off until you get a hit. Next then try the 12vdc side.sailcruiser said:
I once found I had a low amp 12vdc reading at the base of my mast and chain plates.... Traced it to a bad anchor light fixture at top of mast.
Hey guys, I'm not trying to steal the thread, but this is kind of relevant I think. We touched on this a few months back, and as I recall, I made a wise-ass synopsis, and the w/a wasn't really intentional.
Anyway, I notice where it's stated that the thru-hulls should be bonded to the engine. OK fine. Mine are. The engine is also however grounded. It has to be. So what's the difference? In the phone business, the techs always referred to the bonds, which was a metal outer sheath of the cable, but in effect, it was grounded.
I recall earlier where I said that bonding and grounding were different, and in retrospect, I'm now under the semi-assumption that they are one and the same.
True? Crazy? Stupid?
I really stand to be corrected. Or at the very least informed..
Anyway, I notice where it's stated that the thru-hulls should be bonded to the engine. OK fine. Mine are. The engine is also however grounded. It has to be. So what's the difference? In the phone business, the techs always referred to the bonds, which was a metal outer sheath of the cable, but in effect, it was grounded.
I recall earlier where I said that bonding and grounding were different, and in retrospect, I'm now under the semi-assumption that they are one and the same.
True? Crazy? Stupid?
I really stand to be corrected. Or at the very least informed..
I am not Maine Sail but --
Are the halos white?
Are the metal through hulls painted with bottom paint?
Is the bottom paint black?
Do all the bonded items show the same halos?
Do any of the halos show bright green color (rare but if so quite significant.)
Answers will provide opportunity to give you a clincher diagnosis.
Charles
Are the halos white?
Are the metal through hulls painted with bottom paint?
Is the bottom paint black?
Do all the bonded items show the same halos?
Do any of the halos show bright green color (rare but if so quite significant.)
Answers will provide opportunity to give you a clincher diagnosis.
Charles
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Ah ha, a big piece of the puzzle has just been ruled out.... Unless your IT is installed improperly, which is probbaly unlikely, then the issue is created on-board your boat (usually is).
You are "isolated" from shore power even when plugged in. With an isolation transformer (IT) you are "creating" your own on-board AC power station via the transformer...
Some sources of DC leakage:
Bilge pumps & associated wiring
Bilge pump float switches
Corrosion resistance especially in the neg side of circuits
Wires in the bilge or close to bilge water
Open terminal strips in or near bilge level (salt can bridge across circuits)
Any wires close to bilge water with non water proof terminals
Cracked or poor wiring jackets in or near bilge level
Owner used "bonding" circuit wires to carry DC current back to batteries
Chafed mast wiring shorting to the spar then into the bonding circuit
Some bad practices that can lead to corrosion issues:
Multiple ground points on-board the vessel
Non-marine inverters or battery chargers
Corroded high resistance terminations
Poorly executed terminations
AC leakage on-board can happen, inverters, battery chargers (ALWAYS be sure they are "marine" chargers) and water heaters are the biggest culprits. However AC is unlikely to cause the issues you are seeing..
Easiest way to check and see if the bonding wires are carrying current is to insert a DVM between the battery and the bonding circuit wire. Set it to the 10A scale and begin turning on DC devices one by one. If you have motors like pumps, macerators or any device that can pull more than 10A then you need to use a DC clamp meter when testing those circuits. Start with the low draw circuits first, as pumps etc. are usually direct wired with heavier wire..
Out of the water you can check for continuity between under water metals by using the Ω setting of your DVM. Just systematically check continuity between all pieces of metal you know to be bonded. You should see good strong readings. This won't tell you much other than you have "some" continuity. best to always clean, re-terminate and treat these connections every now and then so you KNOW you have good continuity.
If there is a DC leak, the bonding system is doing its job by spreading the "load". If there was no bonding system the fitting closest to the leak would be the one to suffer and it would suffer more rapidly.
Maybe stray current is not the problem.
If the bonding wires are separate from all current carrying 12v. wires it is very unlikely you have 12v. stray current on your boat. An in tact bonding system will - nearly always - trap stray current and send it directly back to your battery thus underwater fittings will not be energized.
White halos (or no color) means a paint application goof. These are usually cosmetic.
Bright green in the halos tell you stray current is probable.
Bonding will not stop stray current from a neighbor boat but typically the decay would be only on one side of your boat. Isolation transformer is good here - but some installers wire these for polarization only - not good. Verify that safety green on the boat side is separate from safety green on the shore power side.
Halos are usually found with high copper content anti-foul paint because the copper in the paint makes it somewhat conductive. Black is more susceptible because black contains carbon. Follow the VC 17 directions (don't over copper the mix.) Bonded metals should be cleaned of anti-foul paint, epoxy coated 2 coats to isolate them from actual contact with bottom paint. Otherwise apply the anti-foul close to the fitting and non copper anti-foul on the fitting.
Zinc areas causing hull potential greater than about -700mv is needed to cause halos. If you are lower then no halos. Hull potential measurement is simple and conclusive but the boat needs to be in the water.
Charles
If the bonding wires are separate from all current carrying 12v. wires it is very unlikely you have 12v. stray current on your boat. An in tact bonding system will - nearly always - trap stray current and send it directly back to your battery thus underwater fittings will not be energized.
White halos (or no color) means a paint application goof. These are usually cosmetic.
Bright green in the halos tell you stray current is probable.
Bonding will not stop stray current from a neighbor boat but typically the decay would be only on one side of your boat. Isolation transformer is good here - but some installers wire these for polarization only - not good. Verify that safety green on the boat side is separate from safety green on the shore power side.
Halos are usually found with high copper content anti-foul paint because the copper in the paint makes it somewhat conductive. Black is more susceptible because black contains carbon. Follow the VC 17 directions (don't over copper the mix.) Bonded metals should be cleaned of anti-foul paint, epoxy coated 2 coats to isolate them from actual contact with bottom paint. Otherwise apply the anti-foul close to the fitting and non copper anti-foul on the fitting.
Zinc areas causing hull potential greater than about -700mv is needed to cause halos. If you are lower then no halos. Hull potential measurement is simple and conclusive but the boat needs to be in the water.
Charles
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That would be what I referred to as "improperly" installed. Should not happen but it does...
Thanks everyone. This problem existed before the IT was installed and present when we bought the boat. The battery charger is a Victron multistage (was ferro resonant), water heater is CNG, the IT is also Victron. There isn't an inverter on board. There is a macerater, and bilge pumps of course. All wiring in the bilge is contained by both wire ties and PVC used as conduit. It is a deep bilge and and I have never seen water come near the conduit (under the sole). The pumps are not deep in the bilge (also under the sole) but have long hoses. The auto switch however is. The spar hasn't appeared to be an issue but I may not have tested correctly either time I've checked.
The bonding wire doesn't connect to the engine ground but rather the breaker panel which I found odd. Nothing is hard wired to the battery at that I have located. There are 2 12v batteries and only battery cables connected. To the best of my recollection there is one ground wire to the engine. Salt is a not a factor being in fresh water which makes this a bigger concern. I don't own a clamp on meter but may be time to invest in one. I did buy a probe that will help in the water but I'd rather fix this soon and sail while in the water. I do own a good quality DVM.
I will update when I check this out. I believe this to be a DC problem but a tough one to locate. It needs to warm up a bit yet but I'm literally writing a plan in hopes of solving this once in for all.
SC
Sailcruiser -
I added some information by editing my last post.
The additional items might help.
Bottom line -- your bonding cable needs to end at a zinc and you must make the motor block part of the bonded metal group. Make cable from motor block to bonding cables.
Charles
I added some information by editing my last post.
The additional items might help.
Bottom line -- your bonding cable needs to end at a zinc and you must make the motor block part of the bonded metal group. Make cable from motor block to bonding cables.
Charles
Hi Charles, all input is welcome. This has me VERY frustrated! A clincher DX would be um...supercalafragalisticexpealadocious! (My first choice wouldn't be appropriate for forum use.). I have spent weeks chasing this when I'd rather be sailing since the season is so short. To answer your questions:
1 The halos are sort of white looking at old pics. I remember them looking more rusty color.
2 The metal through hulls were not painted by me when touch up was done. I could sand them I suppose go make sure no remnants are there. Everything is taped off while painting.
3 The bottom paint is a dark gray to my eye. It's VC17.
4 Everything bonded including the skeg is showing symptoms.
5 No green to my recollection.
I have attached pics from our first winter haul out in 2011. We had the boat at this point about 6 weeks. They were taken in the dark with a flash on my phone. I'd need to go up with my decent camera for current pics. No idea if the PO had painted the through hulls. I don't remember.
The surveyor suggested a grounding plate which isn't a bad idea but I'm not sure it is necessary.
Thanks for any insight!
SC
Attachments
I will take a look at the edited post. The only anode on board is on the aluminum sail drive. It is magnesium collar being a fresh water boat. The PO did tell me the sail drive was pitted when he bought the boat but had a zinc anode which didn't offer much protection. He switched to magnesium which did get beat up badly. (He had the boat a year before selling to me.) The last thing I need is an out of production sail drive to be destroyed. I'm not aware of any anodes on the motor itself (Volvo md17c) but would suppose the sail drive offers some protection.
Adding a cable isn't a problem. I just don't want to compound this issue to include the sail drive. Is it possible that it is connected through the panel? I did a lot of reading and can't quite grasp why this goes to the electrical panel.
SC
OK
The fact you have a motor/saildrive propulsion changes things -- always a risk of long distance diagnosis.
Bonding the other underwater metals to the motor/saildrive will lead to accelerated wasting of the saildrive anode because the anode will be protecting the saildrive and the other underwater metals in addition. Volvo did not intend that the sail drive anode should be protecting anything except saildrive. But they claim the drive is electrically isolated from the motor.
Check any motor/drive manual to verify whether the manufacturer permits bonding of other metals to the motor bock/saildrive and if so then whether additional anodes are recommended.
Be certain to keep the saildrive anode fresh, clean, and working.
As to the paint - two questions: what is the hull made of and did the paint fall off altogether or is there still paint under the effected area ?
Charles
The fact you have a motor/saildrive propulsion changes things -- always a risk of long distance diagnosis.
Bonding the other underwater metals to the motor/saildrive will lead to accelerated wasting of the saildrive anode because the anode will be protecting the saildrive and the other underwater metals in addition. Volvo did not intend that the sail drive anode should be protecting anything except saildrive. But they claim the drive is electrically isolated from the motor.
Check any motor/drive manual to verify whether the manufacturer permits bonding of other metals to the motor bock/saildrive and if so then whether additional anodes are recommended.
Be certain to keep the saildrive anode fresh, clean, and working.
As to the paint - two questions: what is the hull made of and did the paint fall off altogether or is there still paint under the effected area ?
Charles