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Old 10-22-2020, 09:54 AM   #1
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Victron Multiplus installation question

My installer, installed a Multiplus 12/3000/120-50 on a 20amp breaker. So now I can only run 20amps on a 50amp line. The line coming in is rated at 50amps. so the question is can I change out the 20amp to a 30amp or 50amp?. As I understand this unit, it can supply 30amp on inverter mode but should pass thru 50 amps when it's plugged into shore power.

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Old 10-22-2020, 10:11 AM   #2
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Your question is difficult to answer without know exactly where the 50 amp, 120V input is going after it passes through the inverter's transfer switch. What size is the wire that you say is rated for 50 amps. Is it the same wire size on the output of the transfer switch?

Is this one leg of a 50A 240 shore power circuit?

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Old 10-22-2020, 10:43 AM   #3
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David,
Yep a little short on details, so here we go. Laying out the detail has made me answer the question probably :-) ! The 50 amp coming in is one leg of a 125/250 shore power circuit. I do not have any 240 volt appliance or usage on the boat. Each 120v line coming in feeds a line of breakers. Line 2 feeds things like 2 - ACs, hot water, Range(120v), battery charger. Line 1 feeds - 1 AC unit and Washer Dryer and the Inverter. The Inverter feeds all the 120v sockets of the boat. The Sockets of concern would be the Microwave, coffee pot, toaster oven, refrigerator. The rest of the sockets are a few lights, 1 TV. Wire in and out of the inverter is 10awg/3. All wire in the boat is 10awg/3. I'm guessing that is all they had when it was time to wire this boat.10/3 in a electrical box to a socket that runs the lamp at your bedside seems overkill. Thinking this through it seems a 30amp is all that should go there, given that an AC unit and washer/dryer are on the line but not going through the Inverter.

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Old 10-22-2020, 10:45 AM   #4
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10/3 is safe to upgrade to a 30A breaker. If you want to go up to 50A, you'll have to upgrade the wiring.

When I add an inverter, it'll be a Multiplus 2000 most likely, handling part of the loads on one of my 50A / 125V legs. But I'll give it a 50A breaker (and appropriate wiring), as it has a 50A transfer switch. Then when I'm on shore / gen power, I'm not restricted as far as what the outlets and such can draw when other loads on that 50A leg are light.
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Old 10-22-2020, 02:04 PM   #5
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Quote:
Originally Posted by rslifkin View Post
10/3 is safe to upgrade to a 30A breaker. If you want to go up to 50A, you'll have to upgrade the wiring.
But it is not safe to power 15A or 20A household outlets with 30 or 50 amp service. The right way to do it is to put a small subpanel with a couple of 15A or 20A breakers to feed the outlets and power the subpanel with your 30 or 50A inverter output.

Even though NEC code doesn't allow more than 30A with #10 wire, #10 with normal insulation is good for up to 60A. NEC specifies 30A max more for voltage drop considerations than ampacity of the wire. So it won't meet NEC code to go up to 50A, it will be safe if the runs are short as they are in a boat.

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Old 10-22-2020, 02:40 PM   #6
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Whether 10ga can handle 50 amps or not depends on the insulation temperature rating of the wire in question. And yes, a sub panel would be necessary.
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Old 10-23-2020, 05:15 AM   #7
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Instead of a subpanel, you can split one leg of your existing panel. There is an article that discusses how to do this in the Library section of this forum- click the icon on the upper right of the page.

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Old 10-23-2020, 07:55 AM   #8
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David,
Thanks for the "Library" pointer. I came from the Gemini Cat forum where we had an extensive "Library" of those boats. I should have looked harder for the same thing here instead of just doing searches.
Yes, I've split one leg of my existing panel and powered that with the Inverter so each socket has it's own 15/20 amp breaker.

Heading to the Library now...

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