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Old 06-23-2014, 12:55 PM   #1
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ReWiring Old Boat // AC Dilema...!

Morning Troops! This be my 1st post on this Blog, so be gentle...lol...

Will try to keep this query as concise as possible..!

My Background: Old retired DOD civil servant, 40+ years experience with Comms Systems & AC Distribution, SHORE BASED ONLY, NEVER worked on Boats/Ships etc

My son buys this old semi-derelict, approx 40 yr old Cheoy-Lee 55' Long Range Cruiser & I was 'volunteered' to rewire it...

The Boat will have Shore Power hookup as well as onboard Onan 12KW 2-Phase Generator...

Trying to stay within ABYC E-11 as much as possible...

E-11, as well as other specs, state that all AC Neutrals (da White wire) shall be 'bonded' to the Safety Ground (da Green wire) ONLY at the power source. That means on-shore somewhere in case of Shore Power, and at the Generator itself in case of Shipboard power..

We want a scenario where we can use both Shore Power and Generator Power at the same time.

Our single Green-Ground bus will leave the boat thru a Galvanic Isolator.

I can very easily keep the 2 Neutrals separate on the boat, but what worries me is the Green-Ground bus. It is not unusual to
have a few volts on Neutral, especially 2-phase 240/120...

Therefore you could have an AC voltage difference between the 2 Neutrals at the points where they each 'bond' with Green-Ground ,
which could result in residual AC current on the Green Bus, which is UNGOOD.....

We will also have a 'Master Ground' point on the 'Engine Block', where we will 'tie together': Green Bus, DC Negative (da Yellow wire);
'Ships Ground' (Sea Cocks, 'Zincs', Onan Frame, etc)

So I guess my question is: Has anybody out there in 'Boat Land' got any ideas or tried this before....


Signed: Frustrated Louisiana Landlubber...
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Old 06-23-2014, 01:42 PM   #2
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Greetings,
Welcome aboard. Keep boat disown son....
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Old 06-23-2014, 01:49 PM   #3
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Quote:
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We want a scenario where we can use both Shore Power and Generator Power at the same time.
I've tried and tried to come up with an instance where that would come in handy, but can't seem to find one. I'm confident that you have a good reason, though, and just wonder what it might be?
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Old 06-23-2014, 02:44 PM   #4
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I don't know why I would wan to do it but I have two AC/Shore panels. I guess I could run them independently if for instance shore power were insufficient. Never happened though.
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Old 06-23-2014, 03:04 PM   #5
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Thanx all for replying....

I shud have elaborated in my original post...

The Shore & Ship Power scenario would be if you're out cruising on a hot summer day, you tie up overnite at a small marina that can only provide single-phase 120VAC @ 30 Amps...

The C-L LRC55 will end up having a lot of 120VAC goodies, including at least 3 single-zone Air Conditioners @ 8 to 10 Amps each, which alone pretty much eats up your Shore Power... Hence its 'Onan-Time'...
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Old 06-23-2014, 03:12 PM   #6
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What's it ps current setup? 50A 125/250 ? Or dual 125 30A? Because wouldn't you just be able to get a reverse Y that takes two 30A 125 circuits and makes one 50A 125/250. (On the left is a smart why which does what I explained)Click image for larger version

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Old 06-23-2014, 03:28 PM   #7
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Quote:
Originally Posted by BigSkiff02 View Post

The Shore & Ship Power scenario would be if you're out cruising on a hot summer day, you tie up overnite at a small marina that can only provide single-phase 120VAC @ 30 Amps...

The C-L LRC55 will end up having a lot of 120VAC goodies, including at least 3 single-zone Air Conditioners @ 8 to 10 Amps each, which alone pretty much eats up your Shore Power... Hence its 'Onan-Time'...
OK, I can see that. My boat has two 30-amp shore power receptacles, one of which is dedicated to the air-conditioning (two units). I can either plug into two separate 30-amp outlets on the dock, or else use a Y and plug it into a 50-amp outlet on the dock and run the two 30-amp cords from the other end of the Y.

Which does not at all mean that I am knocking the idea that you propose. Sounds like a good fallback to have available so long as you have to rewire the boat anyway.

And by the way, welcome aboard the Forum! :-)
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Old 06-23-2014, 03:33 PM   #8
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Oliver...

Boat will be wired internally to accept one 240VAC Shore Connection at up to 50A per leg/phase (Black/Red/White/Green). If Shore can only provide Single-Phase 120VAC, that will be solved with adapter cable between Ship & Boat, and any on-board 240 large loads (WaterMaker, Water-Heater, Clothes Dryer, Etc) fed by Onan. Will be using Blue Sea 8496 (No Longer Made) as main AC Panel. The 8496 can accept 240, and 'divide' into separate 120 legs. Will have separate Power Panel for 240 loads, plus a 240 Selector Switch, Blue Sea 8361, to select 240 from Shore or Onan. I know it sounds a little complicated, but hopefully should work, not counting my concerns in original post.

Currently 'Cutting & Crimping' lots of AWG8...!
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Old 06-23-2014, 03:36 PM   #9
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John..

Just got your reply after my posting to Oliver...

Admittedly my scenario/approach is a 'worst case'..

//
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Old 06-23-2014, 04:10 PM   #10
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Quote:
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Admittedly my scenario/approach is a 'worst case'..

//
Perhaps. But you are on the Gulf Coast, a/k/a "The Godforsaken Coast," and so preparing for worst case marinas is not a bad idea at all. Some of them along our stretch of the woods are in a time warp and only offer 1950's accommodations to travelers. :-)

Anyway, I have made all the comments I am going to make on your thread. Time to step aside and let the experts (of which I am definitely not one) comment. You have come to the right place to get good advice --on everything from alka-seltzer to ultralights.
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Old 06-23-2014, 04:18 PM   #11
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John:

Appreciate Replies // Stay Safe // Hurricane Season Just Starting...!
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Old 06-23-2014, 04:19 PM   #12
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Why bother to go through all that split panel stuff. You're running the genny, so why not just run it all. don't want to start a genny load debate but they typically do better with a load, and are quieter(from what I've noticed from ours). 12kw sounds like more then enough.
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Old 06-23-2014, 04:31 PM   #13
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Oliver...

Thanx, that's what we will probably end up doing. Trying to 'cover all bases' contingency-wise is turning into a wiring/switching headache...
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Old 06-23-2014, 04:31 PM   #14
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If the genny woun't run it all...each buss of AC could have it's own ship/shore switch or covered CB's allowing you to chose source.

For that boat...I'd be running 2 50A 125/250 shore cords and have a 10kW genset or if a smaller genset...maybe a large inverter for house loads and let the genny recharge batts when demand is low.
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Old 06-23-2014, 04:40 PM   #15
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Quote:
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If the genny woun't run it all...each buss of AC could have it's own ship/shore switch or covered CB's allowing you to chose source.

For that boat...I'd be running 2 50A 125/250 shore cords and have a 10kW genset or if a smaller genset...maybe a large inverter for house loads and let the genny recharge batts when demand is low.

Yes, this is how were setup. We have two 240v 50A Inlets, one for the ship (water heater, davit, oven, dryer, etc) and one for HVAC or AC whatever you wish to call it. We can have the AC run of the ship (which we do most of the time) or have it on it's totally separate cord. It really works out good when you're at the dock in the Bahamas for extended period of time you can run all AC's, make water, wash and dry clothes, cook in the oven and hey even put the dink in!
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Old 06-23-2014, 04:47 PM   #16
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Some shots of our panel if you need ideas.Click image for larger version

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Old 06-23-2014, 07:38 PM   #17
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Two 50a cords and a gen/shore selector switch for each leg is the way to go.
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Old 06-23-2014, 07:49 PM   #18
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I'm not sure the generator will like having only one half pulling current loaded and the other side doing nothing or unloaded.
So you want AC Mains #1 for the shore or genny and AC Mains #2 for shore or genny. Either leg can get power from either source or the genny can run both mains or shore power can run both legs. Is that what you are looking for?
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Old 06-23-2014, 08:02 PM   #19
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Question: Will you have an inverter/Charger on board sufficient for your non-AC needs. If so you can simply do this by connecting your inverter / charger to your normal shore power and the generator by a plug. Thus you could manually switch to a totally isolated shore power 30 amp inlet that only goes to one duplex outlet. I did this when cruising areas with limited shore power. I had the charger on one shore power inlet and the refrigeration on another.

Check this but if I remember we also isolated the neutral for the separate shore power inlet from all other neutrals.
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