Why the Uninsulated Wire on My Bus Bar?

Uninsulated wire on the bus bar helps keep other connected metal components at the same electrical potential. The new standard is for stranded wire, but don't worry about a sold-wire installation by a reputable builder.

13th November 2013.
By Ed Sherman

Question: I spent some time this past weekend cleaning out my boat for winter storage and started wondering about something I’ve never seen before on any boat I’ve owned. Running to one of the electrical bus bars in my lazarette is a solid copper, totally uninsulated wire that disappears into the bilge area on the boat.

The uninsulated single-strand copper wire shown here doesn't carry a current. It's there to keep other connected metal components at the same electrical potential.

The uninsulated single-strand copper wire shown here doesn’t carry a current. It’s there to keep other connected metal components at the same electrical potential.

What’s up with this? Is this dangerous without insulation? I thought only stranded wire was allowed for use on boats.  Nobody has worked on the boat outside of the factory, and I thought the builder was pretty reputable.

Answer: I think the best answer for your question falls under the “old habits die hard” category. You didn’t say, but I’m guessing that your boat is a Tartan of some type. They have been using uninsulated single-strand copper conductors as bonding conductors for as long as I can remember. They are not the only reputable builder where I’ve seen this technique employed, either. I recall working on some older Hinckley yachts that used the same arrangement.

Basically this wire is considered not to be carrying a current. Its purpose in life is to keep all of the metal components that get connected to the boat’s bonding system at the same electrical potential. This is done to help minimize problems like stray current corrosion, and since the wire is grounded to a metallic through-hull fitting somewhere, may also help to minimize the possibility of electronic background noise, also known as RFI or radio frequency interference.

ABYC prefers the use of 8 AWG green insulated multi-strand copper wire for this application. Tartan does attempt to comply with ABYC standards in most instances that come to mind, but this method of bonding is truly an example of some legacy thinking on the part of someone at the factory. The short answer for you is, don’t worry about it! It’s not going to hurt anything. Just make sure that any of these wires you see on your boat stay connected, and that the termination points don’t get too corroded.


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About the author:

Ed Sherman

Ed Sherman is a regular contributor to boats.com, as well as to Professional Boatbuilder and Cruising World, where he previously was electronics editor. He also is the curriculum director for the American Boat and Yacht Council. Previously, Ed was chairman of the Marine Technology Department at the New England Institute of Technology. Ed’s blog posts appear courtesy of his website, EdsBoatTips.

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