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Old 16-09-2016, 11:38   #1
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Adding 2nd 30 amp shore power inlet

As I explore adding ac to my boat I'm to the realization that one 30 amp service isn't going to cut it. I would like to install a dedicated 30 amp inlet to a 3 breaker blue sea panel, and then run the legs to my ac units. I feel like it must be more complicated then that. I have done ac and dc wiring before but never added a whole system to a boat.
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Old 16-09-2016, 14:33   #2
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Adding 2nd 30 amp shore power inlet

It is not more complicated than that, unless I too am missing something, fundamentally it's not different than house wiring, you sound as if you have done some of that.
May want to consider another isolation transformer though, I assume you have one already.

On edit, consider a single 50, that would I believe be more complex as I believe it would require a new 50 amp panel, I assume your current panel can only handle 30 and the bus bars at least would I think need upsizing, or a new panel entirely.
Operative word is assume, others may correct me.

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Old 16-09-2016, 22:28   #3
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Re: Adding 2nd 30 amp shore power inlet

converting his boat to a 50a 240 would be way harder and more $$ then adding a 2nd 30.

get a panel with a douple pole main breaker. wire from new shore plug to panel. to AC units. connect a jumper from ground on new panel to old panel. do not join the neutreals or hots between panels.

have galvanic isolators or transformers on both, hopefully you already have one.
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Old 17-09-2016, 04:58   #4
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Re: Adding 2nd 30 amp shore power inlet

There are specific considerations to installing a second 30A inlet. Namely: (1) do not interconnect the neutral buses. They must remain separate for each system. (2) do interconnect the grounding (green) wires to a common bus, but make sure you have an adequately sized galvanic isolator protecting both inlets. (3) each inlet needs it's own dual pole main breaker and reverse polarity indicating equipment.
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Old 17-09-2016, 09:20   #5
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Re: Adding 2nd 30 amp shore power inlet

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Originally Posted by boatbod View Post
There are specific considerations to installing a second 30A inlet. Namely: (1) do not interconnect the neutral buses. They must remain separate for each system. (2) do interconnect the grounding (green) wires to a common bus, but make sure you have an adequately sized galvanic isolator protecting both inlets. (3) each inlet needs it's own dual pole main breaker and reverse polarity indicating equipment.

o.k. GOT IT~~ When I installed a 2nd 30amp inlet I just connected it to an economical Breaker Box with 2x 15amp beakers and run 10swg to each A.C. Unit.
Why do I need to connect anything to the main power panel? And why do I need isolation transformers on a plastic boat?
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Old 17-09-2016, 09:59   #6
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Re: Adding 2nd 30 amp shore power inlet

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o.k. GOT IT~~ When I installed a 2nd 30amp inlet I just connected it to an economical Breaker Box with 2x 15amp beakers and run 10swg to each A.C. Unit.
Why do I need to connect anything to the main power panel? And why do I need isolation transformers on a plastic boat?
Refer to ABYC E11 - AC and DC Electrical Systems On Vessels, or call a certified Marine Electrical Technician.

You can either:

A. Correct your electrical deficiencies now and be safe
B. Be unsafe now and forced to correct after your insurance renewal survey.
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Old 17-09-2016, 10:44   #7
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Re: Adding 2nd 30 amp shore power inlet

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o.k. GOT IT~~ When I installed a 2nd 30amp inlet I just connected it to an economical Breaker Box with 2x 15amp beakers and run 10swg to each A.C. Unit.
Why do I need to connect anything to the main power panel? And why do I need isolation transformers on a plastic boat?
No, you need a dual pole 30A main breaker feeding whatever distribution panel you choose (live and neutral both run through the breaker) and then you make sure the green wire from the shore inlet runs through a galvanic isolator and then to the boat's grounding bus.

All the appliance neutrals fed by the new panel must be bused separately and not interconnected to the existing shore panel.
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Old 17-09-2016, 15:56   #8
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Re: Adding 2nd 30 amp shore power inlet

Most likely you have underwater metals connected to your ground, the isolation transformer protects those underwater metals, prop and shaft most likely, some boats all thru hulls are bonded as well.


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Old 17-09-2016, 16:33   #9
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Re: Adding 2nd 30 amp shore power inlet

A 50 amp cord alone is north of $250 last I looked.
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Old 17-09-2016, 17:03   #10
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Re: Adding 2nd 30 amp shore power inlet

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A 50 amp cord alone is north of $250 last I looked.
Closer to $1000 for a 50ft long 50A 120/240 cord set.
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Old 18-09-2016, 00:57   #11
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Re: Adding 2nd 30 amp shore power inlet

You can have a 50a/125 plugset. That's what I have. You just need to make or buy pigtails cords to transfer from 50/250 (only use one leg) or 30/125(when you aren't using air conditioning) because 50/125 dock receptacles are very rare.

Follow guidelines for your system when you change it, should be without saying.
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Old 18-09-2016, 04:53   #12
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Re: Adding 2nd 30 amp shore power inlet

Nothing to add to the electrical nuances above, but a buddy added an additional 30 amps in an interesting way.

He installed the second 30 amp inlet in the anchor locker (I'm sure he dealt with making it water tight) so regardless of which end of the boat was closest to the pedestal, his power cords (I guess 25ft & 50ft) easily reached.
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Old 18-09-2016, 05:52   #13
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Re: Adding 2nd 30 amp shore power inlet

All good input, but do you really need the extra complexity of a second electrical inlet? If you don't mind juggling your load, there is no reason not to be able to run your Air conditioner, battery charger, water heater etc... When I turn on the aircondtioner, I wait on the batter charger to not be outputting anywhere near its full load. I've also installed a 750w heating element in my water heater so that this can be run simultaneously with comfort. I'm just too adverse to hauling out another 50' run of shore cable when I get to a slip when I don't have to. You may also consider going a more elegant route than installing a second inlet or "juggling" by installing a soft start module on your aircondtioner, this dampens out the huge current demand on start up and brings you down to 10 amps or less for continuous running on a less than 16k BTU unit.


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Old 18-09-2016, 07:58   #14
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Re: Adding 2nd 30 amp shore power inlet

I power manage and get by with one 30 amp cord myself, but I can see where it would be nice to be able to run everything at once, expense and having to store twice as much power cord and laziness has so far kept me to one cord.
I never though of a bow mounted shore power plug, but I can see how I would like one on both ends. It would have seemed more logical for it to be midship, right by the power panel, must be a reason it at the extreme rear of the cockpit, and on the other side of the boat than the panel is though?


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Old 18-09-2016, 09:22   #15
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Re: Adding 2nd 30 amp shore power inlet

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Originally Posted by boatbod View Post
Closer to $1000 for a 50ft long 50A 120/240 cord set.
Yes, prices are all over the map on then for sure. $400 is not uncommon for a shorter one.
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