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Old 26-05-2016, 09:10   #1
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Question On Twin 30 Amp Shore Power Service

i currently have single 30 amp service and so am going to add a second 30 amp receptacle and panel and split the loads.

my question is: can the neutrals from both inputs still be connected together, or should they be isolated from each other?

(the grounds will of course be connected.)

thanks
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Old 26-05-2016, 10:48   #2
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Re: question on twin 30 amp shore power service

I would run the neutral legs separately due to you don't know how bad the wiring you are plugging into is. It's very possible some marina guy swapped your hot and neutral leads.

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Old 26-05-2016, 14:11   #3
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Re: question on twin 30 amp shore power service

And if the two 30A circuits are in phase then then current in a common neutral would be additive and might overload wiring that is otherwise expected to be limited to 30A.
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Old 26-05-2016, 15:32   #4
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Re: question on twin 30 amp shore power service

Keep them separate doing different jobs. And, while you're at it, invest in an isolation (1:1) transformer for each (Triad Magnetics $95 each). Then, you never need worry about stray voltage in the water or wrong polarity at your equipment. Your boat's AC is completely isolated from the big bad world. Or, at least, purchase a receptacle tester ($5.97 at Home Depot) for each that will tell you if someone has reversed hot and neutral as mentioned in a post above.
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Old 26-05-2016, 20:42   #5
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Re: question on twin 30 amp shore power service

separate. as each will be running through it's own double pull breaker as it enters the boat. if you combined them after you can end up with false tripping.

if you are using ELCI's then you'll definably have tripping.
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Old 26-05-2016, 20:54   #6
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Re: question on twin 30 amp shore power service

ABYC requires they be separate. It is potentially lethal to do otherwise.
Don't even consider the Triad isolation transformer, it does not come close to meeting ABYC Standards. Real marine transformers such as the Charles units will cost you 2k each and you can achieve close to the same protection with a couple of $350 failsafe galvanic isolators.
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Old 27-05-2016, 08:42   #7
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Re: Question On Twin 30 Amp Shore Power Service

the Yandina galvanic isolator is around $100 at Defender. Worked for me over the years although it isn't ABYC any more due to lack of a test light.
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Old 27-05-2016, 09:51   #8
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Re: Question On Twin 30 Amp Shore Power Service

You are about to electrocute yourself. Buy life insurance before fussing with your electrical system. The question you poised indicates you need a licensed electrician to do your electrical work . A lot of folks have gone to heaven from bravado in the face of ignorance. Our condolences.
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Old 27-05-2016, 10:12   #9
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Re: Question On Twin 30 Amp Shore Power Service

so, why are you adding a 2nd 30 amp service? unless your adding an AC unit or some large current device.
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Old 27-05-2016, 10:45   #10
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Re: question on twin 30 amp shore power service

Quote:
Originally Posted by tkeithlu View Post
Keep them separate doing different jobs. And, while you're at it, invest in an isolation (1:1) transformer for each (Triad Magnetics $95 each). Then, you never need worry about stray voltage in the water or wrong polarity at your equipment. Your boat's AC is completely isolated from the big bad world. Or, at least, purchase a receptacle tester ($5.97 at Home Depot) for each that will tell you if someone has reversed hot and neutral as mentioned in a post above.
$95 for a 3.6kva isolation transformer? Really? Could sell it for scrap copper for more than that.
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Old 27-05-2016, 11:39   #11
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Re: Question On Twin 30 Amp Shore Power Service

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Originally Posted by BluegillBoy View Post
i currently have single 30 amp service and so am going to add a second 30 amp receptacle and panel and split the loads.

my question is: can the neutrals from both inputs still be connected together, or should they be isolated from each other?

(the grounds will of course be connected.)

thanks

Is there a reason not to upgrade your system to a single 50A service?

You could then use just one shore power cord. [Albeit a larger gauge for 50A]

Our 50A inlet is split into 2- 110VAC feeds at the distribution panel.

This also allows us to use a 30A shore power cord with a 50A boat-side socket on it [with the single 30A hot jumped to the 2nd hot on the 50A plug on the cord] for feeding both sides of the distribution with the 30A service when that is all that is available or needed, or when all we want to schlep is the 'smaller' cord...

If twin 30A services are all that are available, and you need the extra amperage, you can use a 'smart reverse Y' adapter with your 50A cord. [e.g., Marinco RY504-2-30

This is a safe and very flexible set-up, and only requires one shore power.

You can also use the 50A cord to a 30A service with the right adapter. [e.g., Marinco 111A]

In case this is helpful.

Best wishes with your project.

Cheers!

Bill

PS: If you go the 50A route, [or even stay with twin 30A inlets] may I recommend upgrading to the Smart Plug on your boat? [If you haven't already... Here is our blog post explaining why we chose this upgrade...]
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Old 27-05-2016, 12:25   #12
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Re: Question On Twin 30 Amp Shore Power Service

10s of thousands of 125/250, 50 amp services use a single neutral, split at the panels for 125 vac. As do just as many generators.
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Old 27-05-2016, 12:46   #13
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Re: Question On Twin 30 Amp Shore Power Service

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10s of thousands of 125/250, 50 amp services use a single neutral, split at the panels for 125 vac. As do just as many generators.
A generator is a power source, a panel is not. That is the difference.
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Old 27-05-2016, 13:02   #14
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Re: Question On Twin 30 Amp Shore Power Service

A simple rule of thumb....whenever possible, isolate!
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Old 27-05-2016, 21:05   #15
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Re: Question On Twin 30 Amp Shore Power Service

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Originally Posted by wrwakefield View Post
Is there a reason not to upgrade your system to a single 50A service?
it is much easier and cheaper to add a 2nd small 30a panel and plug to the boat, then to redo the whole existing panel to 240v

depends what he is trying to get. and what's available at the marinas he uses.
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