Discussions about "bonding" and "grounding" usually go off track because of terminology and lack of understanding regarding the terms.
I am in the process of rewiring my CSY 44. In regards to the bonding of the AC systems, I have read that you bond them to any wet surface (engine block/ thru hull).
The bold sentence shows some popular misconceptions. OK, here goes. Shoreside. "bonding" of AC systems as covered in the National Electrical
Code (NEC) covers many, many pages. Essentially it entails connecting all the metal, non-current carrying, components in the electrical system
together "...to establish electrical continuity and conductivity." The bonding system is then connected to the service
Aboard a vessel that is in compliance with the ABYC Standards we have:
E-184.108.40.206 All exposed, electrically conductive, non-current carrying parts of fixed AC electrical equipment and appliances intended to be grounded shall be connected to the grounding conductor.
The subtle difference is that this grounding conductor is connected at one place on board to the vessel ground (B-) AND it is connected to the neutral at the transformer that supplies the marina/dock. (I am not considering an isolation transformer and its ramifications in this, already, confusing discussion.)
But isn't that where the D/C is grounded to? Shouldn't I keep the two separate?
Gord has cited the proper section from E-11; the AC safety
ground (green wire) bus is to be connected ("bonded") to the vessel ground (B-) at one and only place to provide safety
should an AC hot (Line) ever come in contact with the DC system. This connection will provide a redundant path back to ground and cause a circuit breaker in the AC circuit to open. Galvanic corrosion
issues are handled with a galvanic isolator
I have a 10'X 2''X .250'' copper bar stock on my hull near the keel for lightning protection. Can I use that for an isolated bonding system, or should I use it only for lightning protection?
Again, the bold phrase is unclear. The following diagram from E-11 shows that there are several "grounds" that serve different purposes. These grounds are all tied together. They are separated because many of them are there to provide an equipotential connection and are not intended to carry appreciable current
; e.g., the "bonding system" that bonds all of the underwater fittings on a vessel and then connects them to a sacrificial anode to provide cathodic protection. The battery
negative return (B-), on the other hand, is designed to carry significant current
I hope this has helped
E-11; Fig. 18; Grounding Systems.pdf