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Electrical Grounding via thru-hull

My boat has a Balmar regulator which apparently requires a ground connection. Currently the ground connection (to the water actually) is being done via a wire run to a bronze thru-hull.

Is this acceptable? Will this cause corrosion damage (electrolysis) to the bronze thru-hull as electrons flow in the circuit?
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Re: Electrical Grounding via thru-hull

for a regulator you want to connect to the battery ground buss or the engine block not to the bonding system ground
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Re: Electrical Grounding via thru-hull

To elaborate a bit on what's already been said. Electrical terminology is (unfortunately) a bit confusing.

On a boat, "ground" usually refers to the DC negative wires. This is different from house wiring, where "ground" usually refers to the safety wiring that's ultimately connected to stake driven into the ground. In house wiring, the second power wire is often called the "nuetral" -- this is actually common terminology for much AC wiring, which can make things even more confusing when a boat has an AC electrical system in addition to the DC one.

"Bonding", "bonding system" or similar wording refers to the electrical connections to things like thru hulls that helps prevent corrosion.

I just finished installing a new Balmar alternator + regulator system ... so I can say that unless you have a radically different model than I do, there are no wires that should be connected to thru-hulls (or anywhere else on the bonding system). The wires marked as "ground" should be connected to the DC negative bus.
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Re: Electrical Grounding via thru-hull

I was advised by someone who worked at the yard, that a Balmar regulator (atleast the type I have - Digital Duo Charge), needs to connect to the System Ground (where System Ground means sea-water) or it would be damaged. The diagram from Balmar website also indicates that a ground connection is needed: Digital Duo Charge | Balmar

When I bought the boat there already was a green wire that connected the ground bus to the thru-hull. My concern is the thru-hull was covered in green-stuff (which could just be oxidation) and was leaky. It looked like the leak was coming from a bad seal, and the thru-hull was fine except for oxidation, but it is hard to know for sure, since I had the thru-hull replaced and neglected to properly examine the thru-hull for corrosion, so I cannot know for sure if the thru-hull was corrosion damaged or simply the sealant gave way.

I found this on the Balmar website, and they clearly say that you need a "System Ground" which means actual ground (on page 2 here: http://www.balmar.net/wp-content/upl...nual-REV.B.pdf ) :

Quote:
Ground Wire

The Digital Duo Charge must be properly connected to system ground, which must be shared between the house and starting battery banks, for proper operation. Failure to do so will result in non-operation and potential damage to the device. Connection to system ground can be made at one of the following: house battery negative post, starting battery negative post, or system ground bus. User-supplied 14-gauge wire is recommended. To install the ground wire:1. Select a length of 14-gauge wire long enough to extend from the Ground Terminal on the Digital Duo Charge to your intended ground source, such as a ground bus as shown at right.2. Crimp appropriately-sized ring terminal and 1/4” female spade connector to the wire ends.3. Connect the female spade terminal to the Ground Terminal on the Digital Duo Charge.4. Connect the ring terminal to the desired ground source.
Here is a good resource I found on the difference between System Ground and equipment ground (which matches what the Balmar manual states above): https://electrical-engineering-porta...-ground-system

Quote:
System grounding means the connection of earth ground to the neutral points of current carrying conductors such as the neutral point of a circuit, a transformer, rotating machinery, or a system, either solidly or with a current-limiting device.
I guess, my main question is is it safe for the ground to be connected to the thru-hull, or will that cause corrosion problems later on? It seems pretty obvious to me that a System Ground is needed in the case of my balmar regulator.
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Re: Electrical Grounding via thru-hull

Quote:
Originally Posted by hildamman View Post
I was advised by someone who worked at the yard, that a Balmar regulator (atleast the type I have - Digital Duo Charge), needs to connect to the System Ground (where System Ground means sea-water) or it would be damaged. The diagram from Balmar website also indicates that a ground connection is needed: Digital Duo Charge | Balmar

When I bought the boat there already was a green wire that connected the ground bus to the thru-hull. My concern is the thru-hull was covered in green-stuff (which could just be oxidation) and was leaky. It looked like the leak was coming from a bad seal, and the thru-hull was fine except for oxidation, but it is hard to know for sure, since I had the thru-hull replaced and neglected to properly examine the thru-hull for corrosion, so I cannot know for sure if the thru-hull was corrosion damaged or simply the sealant gave way.

I found this on the Balmar website, and they clearly say that you need a "System Ground" which means actual ground (on page 2 here: http://www.balmar.net/wp-content/upl...nual-REV.B.pdf ) :



Here is a good resource I found on the difference between System Ground and equipment ground (which matches what the Balmar manual states above): https://electrical-engineering-porta...-ground-system



I guess, my main question is is it safe for the ground to be connected to the thru-hull, or will that cause corrosion problems later on? It seems pretty obvious to me that a System Ground is needed in the case of my balmar regulator.
The “system ground” you are referring to is most likely the engine block. There should be a heavy black wire bolted to the engine block that leads to a bus bar which is where all of the ground wires from the electrical panels and equipment connect. Via the engine block the System is grounded to seawater.

Connecting to a thru hull for an electrical circuit ground is a very bad idea, as it is likely to be a source for electrolytic action and degradation of the thru hull. From your description it sounds like you have a bonding system that is also connected to your “system ground”. I would prefer not have that setup on my boat - I like the electrical systems isolated from the thru hull bonding system if there is one.
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Re: Electrical Grounding via thru-hull

The installation schematic you linked to clearly shows all negative connections as ground, connect it up as shown and all will be well, do otherwise at your peril . For what it's worth many parts of the world do not routinely adopt the bonding system that appears to be religiously applied in the US.
The use of a through hull as a negative bus is definitely not done.
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Re: Electrical Grounding via thru-hull

Thanks, I am going to move the ground to the engine block.
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Re: Electrical Grounding via thru-hull

One of the links you provide is for house wiring, and as I've already mentioned, the terminology is inconsistent between AC systems and DC systems.

The Balmar document you quote clearly states that the negative must be connected to a negative bus that is common to both battery banks. They recommend a ground bus in their diagram and in the verbiage.

The engine block is _probably_ a good place to go. However, the document clearly warns that this ground MUST be shared between both banks or the combiner will be damaged. While this is going to be true on 99% of the boats out there (since it's considered the correct way to wire things) I HIGHLY recommend that you verify that you have a common ground bus before connecting things. The description of things already makes me suspicious that other parts of the system might be wired incorrectly.

One important reason for NOT wiring things to items on the bonding system (such as thru hulls) is that it can result in stray current corrosion. This occurs when there is enough electrical potential to cause corrosion because electrical devices are putting that potential there. This might be accelerating the corrosion you're seeing on the thru hull, so getting device wiring disconnected from it is a good idea. If you have an actual bonding wire to the thru-hull, be sure to leave that intact.
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Re: Electrical Grounding via thru-hull

Quote:
Originally Posted by hildamman View Post
Thanks, I am going to move the ground to the engine block.
Hil - Bill makes some good points above...this may be a great opportunity for you to do a complete review and check of your boat’s entire grounding and bonding system to ensure that everything is wired correctly and check the integrity of the connections.

Here’s a link to a good article on the subject: https://www.westmarine.com/WestAdvis...unding-Systems

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Re: Electrical Grounding via thru-hull

I will conduct the review and post my findings here. That said, based on what I know, I am confident that there is a negative bus that connects the two negatives of the battery (house & starter) and that negative bus runs to the thru-hull.

I know this because I removed a large 225 Amp Hour House 8D House battery and replaced it with 3 x 85 Amp Hour batteries where 2 of the 85 Ah batteries where House Batteries and one of them I combined with the starter battery. During this process, I was able to complete the circuit and measure voltage on a multi-meter by connecting the positive end of the multi-meter to the positive House Battery and the negative end of the multi-meter to the negative starting bank.

I do not think that the grounded thru-hull is part of a bonding network because, if it were part of such a network, all the thru-hulls would be connected together, and I would not have just one wire running to a single thru hull.

That said, it does make sense to double check the setup just to be sure and I will check it and update this thread.
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