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Peter Kennedy has been in  business since 1991 designing, installing and servicing marine electrical systems. The purpose of this blog is to offer support to both professional installers and  do-it-yourself boat owners who wish to undertake this work themselves.
Peter Kennedy has been in  business since 1991 designing, installing and servicing marine electrical systems. The purpose of this blog is to offer support to both professional installers and  do-it-yourself boat owners who wish to undertake this work themselves.

Duplex and Triplex wire versus using Single Conductors

Posted by Peter Kennedy on 8/4/2018 to Electrical Standards
Production boat builders usually use single conductor wires.  These wires are assembled off site into wire harnesses and laid into the boat at a stage of construction where access is most available, usually before the deck is attached.  By doing it this way boat builders are doing their best to automate the process.  Wire harnesses made up of single conductors are physically more compact, lighter and also less expensive.  So it makes total sense for boatbuilders to do it this way.

Compare that with the boat owner doing a rewiring project later in the life of the boat and you will quickly see why single conductor wires don't make as much sense for that application.  The wires have to be dragged through holes and conduits, often where they don't easily fit, and in the process they get subjected to a lot of abrasion and potential damage to the insulation.  Having an extra jacket is one way to minimize the potential damage to the insulation.  So in most cases it makes much more sense to use duplex or triplex wire for rewiring.  The only case where single conductor wires usually works out is areas with very confined access like ceiling voids.

There is one other point to consider:  The ABYC standards require for AC and DC wires to be bundled separately.  The outer sheathing of duplex and triplex wires counts as sheathing, so when using these wires you can run them in the same conduit.  If using single conductor wires then AC and DC wires have to be bundled separately.

Comments

1 Comments

Chris
Date: 12/30/2018
Is there not a greater risk of a short using duplex cable since positive and negative are side by side for the entire run?
Peter Kennedy
1/4/2019
The greatest risk of shorts are when the wires pass through openings or where they chafe against a sharp edge, or where vibration can cause physical damage. The advantage of duplex or triplex wires is that they are double insulated so are a bit more resistant to this kind of wear and tear. There isnt much chafing between the conductors inside the sheath, its more with the outside environment. The ABYC standards are quite particular about routing of wires to try and avoid this kind of damage and of course the reason we have circuit protection is to avoid disaster if it does occur. Overall I would say duplex or triplex wire has a bit more protection.

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