Question: I just had an insurance survey done on my boat and one of the items in the report has me questioning the surveyor’s knowledge. The picture I sent shows the case ground cable and terminal on the back of my inverter.

Crushing cable ends in a connection like this risks cutting cable strands and reducing amperage-handling capacity.

Crushing cable ends in a connection like this risks cutting cable strands and reducing amperage-handling capacity.



The survey says that the termination does not comply with ABYC requirements because the screws you see in the picture are in direct contact with the wire strands. My surveyor says this can be damaging to the individual strands and affect the amperage-handling capability of the cable. I should point out that the boat is 12 years old and has never exhibited any problems whatsoever during the 12 years I’ve owned it. What gives here? Is this really a problem or is my surveyor just nitpicking?

Answer: Your surveyor is quite correct that the ABYC E-11 standard does in fact say that this sort of terminal shall not be used  -- for the reasons your surveyor mentions. The problem is that as the screws get tightened they can damage the fine strands of the cabling and effectively reduce the amperage-handling capability of the wire. However, the truth is that this particular wire is rarely if ever going to actually carry any current, which explains why you have never noticed any bad effect from this.

The grounding lug on a battery charger or inverter/charger case is there in the event of an electrical short circuit to the case on the DC side of the inverter. ABYC requires a case ground that is no smaller than one size under that of the DC positive feed from the supplying battery(s) to the inverter. In the event such an event occurs this wire has to be large enough to carry a considerable amount of fault current back to the source to ensure that the requisite fuse blows, mitigating a possible fire.

To make this compliant, all you really need are copper tube ferrules that can slip over the cable and then slide into the holes where the cable is now. Tighten the screws onto the copper tube ferrules and let them crush onto the fine strands of the cable. This will prevent cutting of the small strands. Usually you can find copper tubing that will be close enough in diameter to slide over the strands, or half of the strands as you see in your picture, and then slid into the fitting on the inverter. For smaller cable sizes, crimp-on pin-type connectors are available.

In any event, I wouldn’t lose sleep over this. First it would take a DC positive short circuit to the inverter case to create any threat of a problem and as it appears in your photo, it doesn’t look like any significant number of the fine strands are missing or damaged, so odds are quite good the cable will do the job.

The bottom line here is that your surveyor is right this particular installation does not comply with standards. Is disaster imminent because of this? I don’t think so.

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