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Adding-on to 110v shore power system.
mortond wrote:
Hi, Sorry, I guess I wasn't as clear as I thought! The marina only has a 50 amp receptacle. I wanted to avoid the cost of buying a second 30 amp or a single 50 amp isolation transformer. Basically, I wnted to hook-up the convection oven and fridge to the 50 amp shore power receptacle, like an extension cord, except, the extension cord would be routed via a 30amp breaker on the boat (revised that from a 50 amp) to one leg of the 'Y' branch of the shore power cord. The appliance grounds would not be connected to the boat at all. I assume the shore power ground would be isolated from the boat by the existing isolation transformer on one leg of the "Y" and because there is no boat connection on the other "Y" leg. It is true that with what you are considering, the shore power ground would be isolated from the boat. Partly true, anyway. Problem is that unless you electrically insulate your steel boat from the water, it will make a connection of sorts through the water back to the shore power ground. At least near the dock, which is where your shore power connection will be. Here's the problem. Suppose you have a conventional (i.e., NEC/ABYC approved) system and there is a short from the hot wire to the fridge case (which is most probably connected to your hull). Normally, such a short will trip a breaker instantly, giving protection as well as notice that something potentially serious is amiss. If the shore power ground is not attached to the hull, as you are considering, that same short will probably not trip the breaker. The path through the water will limit the current through the short, but not enough to avoid possible electrocution. If the fridge case is not grounded to the hull (as you are also considering) it is now at 120 volts relative to the hull! If the boat is at the dock in sal****er, you have a potentially lethal situation. It will work electrically, but unfortunately will introduce serious hazards that include fire and electric shock. The safe solutions are 1) isolation transformer(s), properly installed; 2) shore power ground connected to the hull (hopefully with a galvanic isolator); and 3) a plastic boat. I don't recommend #3 as a way around #1 or #2. Hope that helps. Chuck Thanks for the interest. David ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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