Stray Cur­rent

Soundings - - Workings -

When field­ing ques­tions about bond­ing and cor­ro­sion, I’m in­evitably asked where stray cur­rent comes from. The big­gest of­fender is a poorly wired bilge pump cir­cuit, as con­nec­tions have to be made only inches above wa­ter in the bilge, which acts as an elec­trolyte.

The first chal­lenge when wiring a bilge pump is find­ing the cor­rect con­nec­tor since the wiring might be a dif­fer­ent gauge — de­pend­ing upon the cal­cu­lated sizing of the man­ual and au­to­matic cir­cuits — than the of­ten smaller pump pig­tails. There are step-down butt con­nec­tors that al­low for one size dif­fer­ence in the wiring, but there also is the dif­fi­culty of hav­ing two con­duc­tors on the pos­i­tive side that con­nect with the pump pos­i­tive wire, all of which must be prop­erly sealed.

Seal­ing these con­nec­tions is vi­tal to the in­tegrity of the cir­cuit. I rec­om­mend heat­shrink con­nec­tors and tub­ing, and some method of seal­ing any ex­posed con­duc­tor. I use liq­uid neo­prene sealant. Wiring con­nec­tions should be as high as pos­si­ble in the bilge with­out strain­ing con­duc­tors.

When an en­er­gized con­duc­tor (the al­ways-on au­to­matic cir­cuit) dan­gles in bilge wa­ter, cur­rent can flow and form a path back to its source: the bat­tery. This Paul Mirto is a dig­i­tal il­lus­tra­tor, long­time boater and for­mer Coast Guards­man. mir­toart.com

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