Date: Mon, 20 Jul 2009 15:53:26 -0700 (PDT) From: Dennis <dmcmurtr@yahoo.ca> To: trawlers <trawlers-and-trawlering@lists.samurai.com> Subject: T&T: LandApplication Equipment The post regarding neutrals connected to a CB, to me seems incorrect. I was under the assumption that on boats, all neutrals are grounded . I know on mine they are. DM?? Dennis, If you mean by, "all neutrals are grounded" that they are permanently connected together on the boat, that is INCORRECT. If your boat is wired that way - sorry to be so blunt - your boat is wired wrong. The easiest and best lay literature available to read about this is Nigel Calder's "Boatowners Electrical and Mechanical Handbook." This situation gets exactly to my point about people with passing understanding of residential installations being able to make something work, but failing to comply with basic safety tenants. This happens all over boats, in all systems. For example, do you know why shower sumps are supposed to have a cover, or why air conditioning condensate drains aren't supposed to drain into a bilge space? Basic safety stuff... but I digress... The rule is, AC neutrals and grounds should only be connected together on the boat at the frame of a genset or at the frame of an inverter/charger, and ONLY then for the time that the genset or inverter/charger is in the actual process of producing ac power for the boat's ac electrical system. All AC neutrals should be collected on a single common buss, and all AC grounds should be collected on another, separate common buss, and the two busses should be scrupulously maintained completely separate from each other. These two separate collecting busses are only SWITCHED together 1) by the generator transfer switch or 2) by interlocking manual switching or an internal relay design in some inverter/chargers. On a slightly different point, DC returns (blacks/yellows on a negative DC ground boat) and AC Grounds (green) should be bonded together, at one single place by one single large size wire only, onboard. The rest of the discussion about double pole circuit breakers emanates from this fundamental understanding. Hope this helps. Jim Peg and Jim Healy aboard Sanctuary, currently at Rondout Creek, Kingston, NY AGLCA # 3767 MTOA # 3436

"Jim Healy" <gilwellbear@gmail.com> writes: >All AC neutrals should be collected on a single common buss, and all AC >grounds should be collected on another, separate common buss, and the two >busses should be scrupulously maintained completely separate from each >other. These two separate collecting busses are only SWITCHED together 1) >by the generator transfer switch or 2) by interlocking manual switching or >an internal relay design in some inverter/chargers. Exactly what he said. It's critical to understand that the bonding of neutral to ground must take place ONLY at the source (inverter/genset/isolation trans former). There is a very good reason for this. Should you have multiple point s of bonding, if one of the bonds failed then there is a possibility that som e segment of wiring would have an unbonded neutral but you might not notice. This could lead to leathal voltage being present in a conductor (the neutral) usually at zero potential. THIS CAN KILL YOU. In addition to Nigel Calder's book, I also highly recommend Charlie Wing's "B oatowners Illustrated Handbook of Wiring". Scott Welch Product Manager, Open Text Collaboration and Social Media Group www.opentext.com 905 762 6101 "Things turn out best for people who make the best of the way things turn out ." - John Wooden

> -----Original Message----- > If you mean by, "all neutrals are grounded" that they are permanently > connected together on the boat, that is INCORRECT. If your boat is > wired that way - sorry to be so blunt - your boat is wired wrong. Jim, Very good post! For those who don't know the details about the difference between a residential and a marine electrical system - they are very difference and should not be confused! If you don't know the differences, then bring in a marine (NOT a residential) electrician before messing with the basic design. This is especially true of anything to do with bonding neutrals and/or safety grounds, as well as adding isolation transformers, galvanic isolators, generators or inverters. Residential and marine electrical systems are NOT the same!!! Kevin