Is My Lightning Protection System Undersized?
The ABYC calls for 4-AWG wire to provide a ground path in the event of a lightning strike.
April 25, 2014
Question: I’m in the process of getting my new boat (bought last fall at a boat show) ready for the upcoming summer sailing season.
A wire between the base of an aluminum mast and a keel bolt can provide a ground path in case of a lightning strike -- but the wire should be a beefy 4 AWG.
Although nobody said anything about having a lightning protection system installed when I bought the boat, I do notice a green and yellow wire jumper. It is connected to the mast step and runs over to one of my keel boats. After doing some reading about this over the winter, the wire seems to me to be too small for this application. It looks to be 8 AWG. What’s your take?
Answer: Since your mast appears to be a standard aluminum spar, you are quite right; you do have the makings of a reasonable lightning ground system. But since the wire you are referring to would be considered part of the “down” conductor system, it needs to be sized at least to 4 AWG to comply with the recommendations in ABYC’s TE-4 Lightning Protection Technical Information Report. You should replace the existing wire with a new 4 AWG cable as part of your make-ready.
Incidentally, most boat sales people I’ve spoken with over the last ten or so years really don’t want to discuss lightning protection with customers. They are afraid of any implied liability that might get associated with such a system. Understand that there are no guarantees with such a set-up, but if your mast is hit by lightning, there's no harm in having a proper-sized cable that could help provide a ground path through your boat’s keel.
