Wired on through hull valves

MarkB

Hello Team! 

Why are there wires going to my through hull fitting isolation valves?  What are they for? 

Lifes Good

Bonding the system.... anticorrosion.

raybo3

Yerp bonding for anti-corrosion.......

LaRea

And also lightning protection.  It's a complex subject.  

TikiHut2

.... reference Chapmans.....

(frikken new image link system sux)

MarkB

Ahhhhhhhhh!  OK, all makes sense now.  What threw me really off was the two wire on the toilet (head) through hull.  I was thinking maybe it's a solenoid that I can switch from above!  NOT!

Black_Diamond

Interesting my boat has none of these bonded: A/C, toilet, nor the gen thru hulls.   wondering if it's another winter project worth doing....

edit:

I just found this researching around:

Bonding Primer

For the most part, all metals touching sea water should be bonded, including seawater pumps, strainers, and plumbing. Moreover, all electrical equipment and large metal objects should be grounded to prevent electric shock and increase lightning safety.

Fuel tanks and fills should be linked with the main DC negative bus or a battery terminal. Bronze through-hull fittings are an exception. ABYC leans toward bonding, but also allows through-hulls to be isolated. As noted above, among the issues that can arise is wood damage—the tiny amounts of current passing through bonding wires can deteriorate nearby wood, including the wooden backing blocks that are often installed beneath the flanges of through-hull fittings.

Dream_Inn

RY, you also don't have it?  I'm a bit surprised BD that yours aren't done either.  I'm not sure I've seen boats that didn't have it bonded. (well, one's built in the last 15 years or so)

LaRea

Yes, I've seen builders use two small wires instead of one large wire.  

Bonding of metal thru-hulls is interesting.  In addition to the possible wood damage that BD pointed out, I've also read that a bonded metal thru-hull is more vulnerable to catastrophic damage in a lightning strike.  

So, which risk is better for metal thru-hulls:  If you bond it, a lightning strike could destroy the thru-hull and sink the boat.  If you don't bond it, stray current could corrode the thru-hull over time, and if nobody notices, it could break and sink the boat. 

Rinker bonded all of the thru-hulls on my boat.  (My surveyor pointed out that the bonding wire on the AC intake is too small and not the right color.)

Black_Diamond

RY and I have the odd-ball 342's of the bunch.  lol  I had to upgrade the trim tab switch to the lighted type..and I noticed on some 2002 models they came with them...same for my cockpit frig that was 12VDC only..had to upgrade that to the 120VAC/12VDC with a converter and yet older 342's had this stock.  Go figure!

LaRea

No hose clamps.  The wire needs a ring terminal attached to a screw or bolt on the body of the fitting.  Most marine thru-hull fittings have a built-in bonding screw.

Black_Diamond

I'll have to look, but I do not remember seeing and screw for bonding.