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Old 10-05-2011, 07:39   #1
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Converting from 30 amp Shorepower to 50 amp

Hello All, I have a 1987, 50 ft. Marine Trader Widebody. The present shorepower service is one 30 amp for the house and one 30 amp for the AC. It also has a 15KW and 5KW generators. When running off the 15 KW the entire boat and all 5 ACs can be energized. On shorepower only 1 large or 2 small ACs can be energized and I think the house side is not allowing full power to the various appliance compressors. Thoughts on upgrading to more shorepower.

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Old 12-05-2011, 20:43   #2
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Re: Converting from 30 amp Shorepower to 50 amp

Hey Captain Rich,

Up grading your shorepower would not be much of a problem if you changed up from 30amp 125V to 50amp 125V shorepower connection. this could be a direct switch as they are both single phase connections.

Your system is already set up for 30amp feed so the main parts you would need to look at are upgrading your main feed wiring and breaker from 30amp to 50amps and the feed cable from the shore power inlet to the distribution box from 10AWG to 6AWG. If you have an isolation transformer fitted this also would need to be upgraded. your distribution panel should be fine, your problem with only a few feeds on shorepower maybe all AC's are not connected to the shorepower line to avoid over loading your wiring.

I bought a new Furrion shore power 125v 50amp cable last fall which had a reverse polarity indicator and great storage bag for 100 bucks less that a marinco one, might ease the decision for the upgrade.

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Old 13-05-2011, 07:48   #3
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Re: Converting from 30 amp Shorepower to 50 amp

A few small details:
1. Ensure that the two neutrals currently used with the two 30A services are tied together to form a single neutral for the 50A/250V shore power input.
2. Reconfigure the gensets to provide 250V power.

Hope this helps.
Charlie Johnson
JTB Marine Corporation
"The Devil is in the details and so is salvation."
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Old 13-05-2011, 09:21   #4
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Re: Converting from 30 amp Shorepower to 50 amp

I'd really advice having a qualified electrician look at the situation. You are dealing with a lot of watts.


It sounds like you have two 30amp 120 volt shore power outlets with a parallel switch to let the genset supply 120 volt to both. Your air conditioners are also 120v (not 240v?). Are all 5 (!) air conditioners connected to the AC shore power outlet? Do you currently use two 30amp cords connected to two 30 amp marina outlets or do you use a "Y" adapter?

If you upgrade the AC outlet to 50 amp 120v (6000 watts instead of 3600 watts now) you would be able to run more air conditioners than now but still not as many as you run with the 15000 watt genset. This is a simple upgrade as mentioned by Birdseye. You would typically plug into a 50amp 240v marina outlet and then use an adapter to use just one leg to have 50amp 120v. You could also use a "Y" to provide 30amp 120v to your house side and 50amp 120v to the AC (using two cords).

While there are ways to use two cords to get more than 50amps 120v to your AC this is quite tricky (for starters you have to use more than one marina power outlet).

Also, be aware that air conditioners draw about 2x their normal power when the compressor motor kicks on. This can cause a shore power breaker to pop, especially if more than one compressor turns on a the same time. Many air conditioner companies offer an optional control box that has the compressors turn on one at a time. Unfortunately, this box really needs to be installed by a pro.

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