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Old 06-23-2018, 05:28 PM   #1
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Easy Conversion from 30A/120V to 50A/120V

For those of you with 30Amp/120V Shore Power RV's, the below is a relatively easy conversion to a 50Amp/120V system. Your available wattage goes from 3,600 to 6,000. It will require a new main AC breaker and wiring upgrades and possibly additions to your AC Branch Panel.


RV and Marine 50A pedestal service is actually 120/240V which produces 12,000 Watts of power with a four wire cable. Converting from 30A service is complex and costly. So how do we get to 120V/50A/6,000W with a three wire cable?


The components required, starting from the pedestal, are:


1. A 50A 120/240V pigtail that outputs 50A of 120V power. These are available from Marinco and other manfacturers.


2. A 50A rated, three wire shore power cable. Also available from Marinco and others.


3. Upgrading your main AC breaker from 30A to 50A.


4. Modifying your existing AC branch panel, if necessary.


5. Upgrading the wiring from your shore power inlet, including a new socket, to handle the additional power.


6. Upgrading your branch panel wiring as required.


The beauty of this is that nothing else changes. Also, if only 30A power is available, there is a cable converter that will allow you to plug into a standard 30A pedestal connection. Just have to remember you don't have as much available wattage.


Would like to hear your comments and/or criticisms.
Thanks,
Pat
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Old 06-25-2018, 06:01 PM   #2
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I would change step 2, by adding a comment about if a cable upgrade is needed then consider going to the four wire solution.



In the 80's the power panel is likely a Square D 100 amp panel, at least mine is. Some users might like to have the higher wattage of the four wires.
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Old 06-25-2018, 07:16 PM   #3
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I wish all 30 amp AS's were offered at 50 amps. Never made sense to me that buying an AS with two AC's got you '50' amp service. I use the apostrophes since the 50 amps are really at 240V so you get 100 amps of 120V current. Over 3x the power. So why??
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Old 06-25-2018, 07:21 PM   #4
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I wish all 30 amp AS's were offered at 50 amps. Never made sense to me that buying an AS with two AC's got you '50' amp service. I use the apostrophes since the 50 amps are really at 240V so you get 100 amps of 120V current. Over 3x the power. So why??
That's the point. What I propose above is a pure 120V solution, without having to worry about the 120/240, split phase complexity.

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Old 06-25-2018, 07:58 PM   #5
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It makes a lot of sense, except it is not allowed by NEC 551.42.

Not saying you shouldn't do it, but it may impair trade-in or resale if you ever decide to upgrade to a new trailer.
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Old 06-25-2018, 08:12 PM   #6
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It makes a lot of sense, except it is not allowed by NEC 551.42.

Not saying you shouldn't do it, but it may impair trade-in or resale if you ever decide to upgrade to a new trailer.
Maybe, but it doesn't seem to be a problem with boats. Marinas are starting to offer 120/50amp service at their pedestals. Boaters are having the same problems as RV owners. More power needed in today's world. I honestly believe that the 30 amp service days are numbered.
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Old 06-26-2018, 03:13 PM   #7
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Aside from the fact that airstreams don't normally dock at the marina, and NEC standards are different for boats and RVs, wouldn't it make more sense to go to 30a 120v/240v split phase?

Wiring would be lighter gauge, cable would be more flexible, and load balancing between phases would simplify wiring at the campground power distribution end.
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Old 06-26-2018, 05:02 PM   #8
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Aside from the fact that airstreams don't normally dock at the marina, and NEC standards are different for boats and RVs, wouldn't it make more sense to go to 30a 120v/240v split phase?

Wiring would be lighter gauge, cable would be more flexible, and load balancing between phases would simplify wiring at the campground power distribution end.

Mark,


This power transformation modification is happening outside the RV not in it. I would be surprised if anything in the NEC prohibits modifying your RV's AC Main Breaker and wiring to deal with a higher amperage incoming shore power. How do you think RV parks provide both 120/240 50A and 120V/30A power from the same pedestal? At the pedestal they pick either L1 or L2 hot legs and breaker them down to 30A for the service. Standard practice is to alternate L1 and L2 feeds so you end up with an equal number of each. The only issue at an RV Park is that the L1/L2 feeds are relatively balanced at the main transformer feeding the park.


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Old 06-26-2018, 07:53 PM   #9
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Easy Conversion from 30A/120V to 50A/120V

Sounds like a fine solution if you only need 50A total - which is certainly a lot more overhead than 30A.

Personally I enjoy a split panel / split phase operation with 2 hot 50A/120 lines. It’s really not all that complicated from a panel wiring perspective.

2 ACs + microwave + electric hot water heater would trip a single 50A supply. I regular draw north of 50A total when on shore power.

If you have a single AC then 50A on a single line would be plenty. I was always annoyed on 30A service when the microwave and AC combo would trip the main 30A breaker. Then I discovered the world of 12,000 available watts with 50A / 240 service
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Old 06-30-2018, 06:02 PM   #10
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I guess I read you listing incorrectly. It sounds like you wanted to install a four wire replacement connector onto a three wire cable to obtain one single phase 50 amp feed.


Electrically this would work, but consider the application of the shore power being an outside connection it really should be done with waterproof connector body. That would mean to obtain the "50 AMP" you would need to upgrade to the plug cable assembly which is: 4‐wire, grounding type for 125/250V.

In addition the source breaker in the pedestal needs to match the application. That will be a ganged breaker. To use it properly "which is required by the fire code" you would need to balance the loads over both sides of the ganged breaker.

There really shouldn't be a trailer wiring issue once the branch circuits are connected to the panel. As I stated before my trailer has a 100 amp panel that would accept the installation of a 50 amp ganged main breaker. Perhaps other years have something else.
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Old 07-01-2018, 07:36 AM   #11
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The NEC stops at the pedestal, but is law only if the governing body references it in their building codes. You can make any changes you want to your RV, the law doesn't apply. If it is wise to do your own electrical modifications is a different question.
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