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Subject: Re: TWL: Alternatives to isolation transformer?
From: Bill Martin (Martin_WJ@XXX.XXX)
Date: Fri May 03 2002 - 12:56:53 EDT
>I have recently been strongly encouraged to install an isolation
>transformer on the boat. ....
There are pros and cons with isolation transformers (this is a boat after
all!). On the pro side, it's probably the best way of getting the ultimate
galvanic isolation. It doesn't do you any good though, unless you
rigorously also eliminate all other sources of grounding from boat to shore
which many people don't do. For example, do you keep a water hose
connected to shore? How about a cable TV connection? (on my boat that
grounded the whole boat until I did some rewiring) Is there a phone
connection with an unexpected ground line? You just have to scrutinize all
the connections to shore and make sure none of them are grounding something
that you don't expect them to.
The cons are the heavy weight and heavy cost -- particularly if you're
running 50amp service or larger. Noise shouldn't be an issue, but....
Galvanic Isolators are just as good as isolation transformers IMHO, for all
the "normal" cases and are in fact what I installed on my boat. They won't
work as well though in pathological cases of things miswired or a bare 12v
wire in the bilge or whatever which you shouldn't have anyhow.
My chosen solution was to install the galvanic isolators, and then check
them periodically to make sure they're not conducting due to some fault in
the system. Just check the voltage drop across them....
Good luck....
Bill Martin
Telegraph Hill
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