Hi-

I am installing an isolation transformer and want to isolate the ground
from the shoreside supply. The manual from Charles states that I need
a 2-pole GFCI circuit breaker. I have not found any marine breakers
for 30 amp 120v that are also ground fault. Anyone have any
information on a manufacturer? Or does one use residential vice marine
in this instance?

THANKS for any help.

Bud

BeenWetter wrote:
Hi-

I am installing an isolation transformer and want to isolate the ground
from the shoreside supply. The manual from Charles states that I need
a 2-pole GFCI circuit breaker.

Why?

I have not found any marine breakers
for 30 amp 120v that are also ground fault. Anyone have any
information on a manufacturer? Or does one use residential vice marine
in this instance?

Marine c'bkrs are hydraulic devices.

Shore side c'bkrs are thermal-magnetic.

The only thing they have in common is that they are both c'bkrs.

They are not interchangeable.

Lew

Lew Hodgett wrote:
BeenWetter wrote:
Hi-

I am installing an isolation transformer and want to isolate the ground
from the shoreside supply. The manual from Charles states that I need
a 2-pole GFCI circuit breaker.

Why?
Their exact language is "Main Shore Power Disconnect Circuit Breaker
with OFP" I've found no reference to "OFP" anywhere (I sent an email
to them querying the abbreviation last week, but have received no
reply). Perhap it is not a GFCI.
The reason is that the shore ground is not going to be used any further
than the power inlet connector. This eliminates current flow through
the shoreside ground wire.

I think you should go buy "Boatowner's Mechanical and Electrical Manual" by
Nigel Calder. His chapter on DC and AC power distribution covers all of
your questions.

There is some controversy on how to disconnect shore power, but for now,
note that the "common practice" is to disconnect the hot wire and the
current-carrying neutral (don't even consider a 2-wire system that uses the
bonding circuit as an AC neutral), but leave the (green) ground wire
connected. On your boat, the AC and DC grounds SHOULD be connected to each
other and don't let anybody tell you otherwise. Rather than follow bad
advice that's intended to reach the same goals, go buy a galvanic isolator
(aka 'zinc saver'), e.g. http://www.boatersworld.com/product/196902571.htm
and keep those AC and DC ground circuits a) connected to each other on the
boat, and b) connected to the shore power ground. I suspect (too lazy to
look it up right now) that the ABYC also requires that both the AC hot side
and current-carrying neutral are disconnected by the boat's disconnect
(breaker or switch). This might be because all the neutrals are connected
together on the shore side and you could accidentally become a path to
ground if you touch it and the bonding circuit at the same time AND if the
neutral-to-ground connection on the shore side is faulty. By breaking the
neutral at your boat, you reduce the amount of wiring that you might be
exposed to while on your boat, e.g. on your panel. That said, note that
some folks believe that this risk is the smaller risk and that it's more
likely that you'd have bum wiring on your boat than bum wiring in the shore
side power distribution. If so, then your boat's AC neutral provides an
alternate path to ground (additional safety onboard), noting again that the
shore side neutral and ground are connected to each other back at the shore
side transformer(s). In non-marine practices, the entire world leaves the
AC neutral connected (always) and only disconnects the hot phases with
breakers and switches ...except for a couple of backwards places that insist
on being different (like France). It's also important to note that Blue Sea
and other prime manufacturers sell only 2-pole circuit breakers for
disconnection of single phase AC shore power. I'd swim WITH the fishies
rather than against and just go buy a Blue Sea 2-pole circuit breaker and
call it done. And do follow my advice on grounds and the galvanic isolator.
Oh, and go buy Nigel's book... you only have to read about 20 pages to cover
the AC power distribution stuff. You'll want to read his advice on properly
wiring and installing your bonding (grounding) circuit as well. Good stuff,
Maynard. Stay safe. And don't go swimming near the docks.

Brian D



"BeenWetter" wrote in message
oups.com...

Lew Hodgett wrote:
BeenWetter wrote:
Hi-

I am installing an isolation transformer and want to isolate the
ground
from the shoreside supply. The manual from Charles states that I need
a 2-pole GFCI circuit breaker.

Why?
Their exact language is "Main Shore Power Disconnect Circuit Breaker
with OFP" I've found no reference to "OFP" anywhere (I sent an email
to them querying the abbreviation last week, but have received no
reply). Perhap it is not a GFCI.
The reason is that the shore ground is not going to be used any further
than the power inlet connector. This eliminates current flow through
the shoreside ground wire.

Go to http://tinyurl.com/gaxe9 . Buy Blue Sea 2-pole, 30A, circuit breaker
P/N 7365 for your main disconnect. Use GFCI breakers or receptacles on the
load side of your isolation transformer on the individual circuits that need
it. Call Blue Sea and find out which of their circuit breakers have GFC
protection built in ...the web site is not obvious, but they are obviously
aware of it. Get Charles to give advice on the GFC protection and ask them
why you can't just put GFC protection on individual circuits that need it
(on the load side of your is-xformer). Note that you can have separate line
protection on the input side for GFC-like protection, but it'll just result
in lots of nuisance trips.

Good luck,
Brian D


"BeenWetter" wrote in message
ups.com...
BeenWetter wrote:
I've found no reference to "OFP" anywhere
Mystery solved- "OFP" is a typo- should be "GFP" - Ground Fault
Protection, says the technician at Charles.

Still haven't found any such marine 2 pole 30 amp breaker, though.

BeenWetter wrote:

Mystery solved- "OFP" is a typo- should be "GFP" - Ground Fault
Protection, says the technician at Charles.

You need a GFI c'bkr for that application like a moose needs a hat rack.

Still haven't found any such marine 2 pole 30 amp breaker, though.

Don't expect you will.

Lew

Moose wear hats? I never noticed... ;-)

Brian D



"Lew Hodgett" wrote in message
ink.net...
BeenWetter wrote:

Mystery solved- "OFP" is a typo- should be "GFP" - Ground Fault
Protection, says the technician at Charles.

You need a GFI c'bkr for that application like a moose needs a hat rack.

Still haven't found any such marine 2 pole 30 amp breaker, though.

Don't expect you will.

Lew

I have a 2 pole 30 amp breaker on my boat. I installed it because
Nigel Calder recommended it in this book. I just went to the local
electrical supply house and told them what I wanted. I also took
along Nigel's book so they could see the precise wording. They had no
problem pulling it out of their inventory.

Lee Huddleston
s/v Truelove
on the hard at Bock Marine
Beaufort, NC

Lee Huddleston wrote:
I have a 2 pole 30 amp breaker on my boat. I installed it because
Nigel Calder recommended it in this book.

I don't get it. What's all this talk about GFCI on a boat with an
isolation transformer? Beyond the transformer, there is no physical
connection to any shoreside wiring, the boat's AC circuits are
isolated.

Aren't isolation transformers set up this way --

Shoreside hot and neutral wires connected to isolation transfomer input
windings. Ground wire connected to isolation transformer shield, to
protect against transformer failure. Ship's hot and neutral wires
connected to isolation transformer output windings. No AC ground wire
in ship's wiring. No connection of any AC wires to any DC wiring. No
risk of stray DC currents generated by the ship's AC wiring anywhere.
Only risk is touching the ship's hot and neutral wires simultaneously,
which is the same risk as with any AC wiring.

That being said, I also have a 2 pole 30A breaker on the shoreside of
the isolation transformer, per Calder, in case the dock breaker is
faulty.