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aknavy · 06-07-2019, 05:45 AM

I'm looking to add a power receptacle on the rear of my fiver for generator power. I carry the generators on a swivel wheel back there, so with this, they can stay plugged in, and even run while driving the last couple hours to keep the rig cool.

Alternatively, it could be used to plug in if the campgrounds power pedestal is in a position that works better there. Plan on running the cable from there to a automatic transfer switch and connecting both power inputs to the transfer switch.

I need about 30 feet of cable to run from the rear of the fifth wheel to the rest of the power distribution. I was under the impression that I need 6/4 cable, but looking at the specs for 50 amp RV cords, most list a 10 gauge conductor. 6/4 looks to be listed at 55 amps, 8/4 looks like 45 amps - so why are the RV cables smaller conductors? Would I have any issues running 8/4?

Finally - this cable is going to run under the fiver, along the frame, then into the "crawl" space. Can I use the flat direct burial cable, or should I be using a round portable cord, typical of the RV plug ins?

If you've added a plug in and transfer switch, please share your tips/tricks/lessons learned.

Teamfoxy · 06-07-2019, 06:14 AM

10 guage is for 30 amp chords. 6 guage is the size wire that I see listed on all of the 50 amp cords that I could find. Neither of my RV's with generators have a transfer switch. There is a plug for the generator output located in the electrical bay and the RV chord gets plugged into that whenever we disconnect from the power pedistal. Simple, foolproof and effective!

twinboat · 06-07-2019, 06:21 AM

Quote:

Originally Posted by Teamfoxy

10 guage is for 30 amp chords. 6 guage is the size wire that I see listed on all of the 50 amp cords that I could find. Neither of my RV's with generators have a transfer switch. There is a plug for the generator output located in the electrical bay and the RV chord gets plugged into that whenever we disconnect from the power pedistal. Simple, foolproof and effective!

The ATS is installed to prevent both power inlet connectors from being HOT, while one is connected.
Basicly, its a safety control in case the little one decides to open the shore cord door and stick its fingers in.

aknavy · 06-07-2019, 06:22 AM

Quote:

Originally Posted by Teamfoxy

10 guage is for 30 amp chords. 6 guage is the size wire that I see listed on all of the 50 amp cords that I could find. Neither of my RV's with generators have a transfer switch. There is a plug for the generator output located in the electrical bay and the RV chord gets plugged into that whenever we disconnect from the power pedistal. Simple, foolproof and effective!

With that setup, I'm assuming both power sources are tied to your main distribution panel? Or are they combined elsewhere? I'm using the transfer switch to bring both power sources into the RV -> Progressive Dynamics surge protectory -> breaker box/power distribution.

jacwjames · 06-07-2019, 06:24 AM

6 gauge wire for the 50 amp cord.

I would consider running a length of conduit under the frame to help protect and support the cable. I'd be concerned about road debris kicking up and damaging the cable. At least the conduit would provide some protection.

**Spdracr39** · 06-07-2019, 06:41 AM

My OEM cord for 50 amp is 6/4 and is 30'. Having said that you can size your cord based on the breaker size on the generator. I doubt your are carrying a large enough genny to put out a full 50 amps per leg. You could most likely get by with 8/4 which is good for 40 amps 10/4 is only good for 30 amp. My 7500KW has a 35amp breaker so I would use 8/4 on mine.

aknavy · 06-07-2019, 06:45 AM

Well, seems that the gauge question is settled....6/4. The power cords I was looking at had multiple options, they must not have been updating the specs when going between 30 and 50 amp.

Any other words of advice on the overall undertaking?

Beau388 · 06-07-2019, 06:53 AM

Conductors are rated by overall diameter of the conductor, the heat of the wire when conducting the rated current and by the number of strands in the conductor (cable). For example: a solid #6 wire is rated at 155 amp @ 90C where as a 23 strand #6 cable is rated at 55 amps @ 90C. Reduce the current capacity by 20% if using a 70 C degree maximum

mobilemike · 06-07-2019, 09:01 AM

In addition AC and DC cable size requirements are different.

It used to be much cheaper to go to en electrical supply store to buy components and make your own shore power cord than to buy a pre-made one. You might want to look into that.

aknavy · 06-07-2019, 09:24 AM

Quote:

Originally Posted by mobilemike

In addition AC and DC cable size requirements are different.

It used to be much cheaper to go to en electrical supply store to buy components and make your own shore power cord than to buy a pre-made one. You might want to look into that.

It is, but not much cheaper.

mobilemike · 06-07-2019, 09:40 AM

Quote:

Originally Posted by aknavy

It is, but not much cheaper.

But then you get to make it custom length, run it and attach it however you want and terminate it with several options. I would hard wire it on the transfer switch end.

I would used round cord as it is easier to route and secure. Use an outdoor weather and oil proof line and do not uses a conduit. Conduits hold the moisture and will rub the coating. Not to mention the extra work.

Solo_RV_Guy · 06-07-2019, 10:14 AM

Quote:

Originally Posted by mobilemike

But then you get to make it custom length, run it and attach it however you want and terminate it with several options. I would hard wire it on the transfer switch end.

I would used round cord as it is easier to route and secure. Use an outdoor weather and oil proof line and do not uses a conduit. Conduits hold the moisture and will rub the coating. Not to mention the extra work.

Additional info: portable cords like types S, SO, ST, SJ, SOOW, SEOOW, etc are not permitted in conduit. Cords Listed for direct burial are allowed in conduit for physical protection of the cord/conductors.

hillbilly3 · 06-07-2019, 06:16 PM

Rubber cords have a higher ampacity rating than regular wire due to the finer strands which dissipate heat better. A/C does what is called "skin effect" most of the current travels on the "skin" of the conductor, so more strands equaling the same guage carries current better.

Solo_RV_Guy · 06-07-2019, 07:38 PM

Quote:

Originally Posted by hillbilly3

Rubber cords have a higher ampacity rating than regular wire due to the finer strands which dissipate heat better. A/C does what is called "skin effect" most of the current travels on the "skin" of the conductor, so more strands equaling the same guage carries current better.

I dunno about that. The skin effect at 60Hz is pretty low. As frequency increases the effect becomes more pronounced; at RF frequencies it's one of the reasons tower transmission line center conductor is hollow.

Ampacity is a combination of resistance (conductor area and material), the ability to dissipate heat, and the heat tolerance of conductor terminations and switch gear. Portable cords (type S, SC, W, a few others) require derating when there are 3 or more current-carrying conductors (ground doesn't count, but neutral does) under that outer jacket due to heat.

The highest ampacity for a given wire size is for an open conductor in free air as heat can freely radiate.