50 AMP RV Connection Box

Topic: 50 AMP RV Connection Box (Read 2554 times) previous topic - next topic

50 AMP RV Connection Box

July 04, 2021, 11:51:24 am

Happy 4Th of July to The Collective!

I have a electrical question. I am not seeking "Professional Advice" but I know many Forum members are a lot smarter than me. I just want O-pinions cuz I know everbody got one. I trust the advice of most of you. (The Wackos I choose to ignore).

We have a 50/20 AMP Midwest brand RV power box mounted on our fence next to our driveway. It was installed by a licensed electrician who seemed (to me) competent. The box is tied into our main house breaker box (200 AMP service) with a dedicated 50 AMP circuit breaker. The wires run from the breaker box, up through the wall to the attic, down the outside wall in metal conduit to a junction box, then underground in plastic conduit about 35 feet to the fence, and up to the power box. There are 4 big wires showing in the junction box: red, black, white and green, plus a bare copper wire. I assume this means I have a "proper" RV power circuit with 2 hots plus neutral and ground.

The Power box has never given us any problem. My Progressive EMSPT50C surge protector has never had any problem with connecting to the power box. Our shore power setup doesn't break a sweat when running both roof air units plus other devices in the coach.

Photos below and in next post show details of our present setup.

We are considering moving our coach from its parking spot in the driveway to a parking pad further out behind our back yard. The exact type of spot (open pad, covered pad, enclosed RV barn) is (as yet) undecided. Regardless, the new location would be about 100' from the existing RV power box.

So here is my question. Could I connect 4 suitably sized wires (plus a bare copper wire) to the wires inside the existing power box, run them in plastic conduit underground out to the proposed parking pad, and then install a second identical power box? Our coach would be connected to one box or the other. I don't anticipate ever using both boxes at the same time.

I guess I should add that we live out in the county. Things are pretty loose here as to building codes and such. However, I don't want to do anything dangerous. If what I propose is indeed acceptable practice, then I would purchase the materials, dig the trench, lay the wires, and mount the box on a pole at the pad site. If necessary, I could hire a pro electrician to make the actual connections, just to be sure it was done correctly. Obviously, I am trying to hold the cost of the project down as much as possible.

So what say you? Don't mince words. I can take the truth - however painful (and expensive).

Re: 50 AMP RV Connection Box

Reply #1 – July 04, 2021, 11:52:31 am

More photos:

Yes, it DOES rain in desert West Texas...occasionally. I think we got our whole years worth of rain in the last week. Smells like a moldy jungle outside. Disturbing to us desert dwellers.

Re: 50 AMP RV Connection Box

Reply #2 – July 04, 2021, 11:59:53 am

I Don't see a problem with your plan. I am not an electrician so don't know what size wires to use but the info is on the web. I bought a 100' 50 amp extension cord and keep the coach end in the compartment when I use it to keep it dry. Most of the time I am using a 30' but when I park in front of the house on the street and want air conditioning I use the extension cord. I have been doing this for over 20 years without a problem.

Re: 50 AMP RV Connection Box

Reply #3 – July 04, 2021, 12:08:08 pm

Yes / no
http://www.paigewire.com/pumpWireCalc.aspx?AspxAutoDetectCookieSupport=1
Need to figure out total length and calculate size of wire needed. If your current wire is bigger in size (smaller number) your fine. If not you will be restricting the amount of power do to voltage drop. So if the calculator says you need a #6 and you have a #8 your first wire is too small to safely accommodate your needs. If you need a 8 and you have a six your fine.
Scott

Re: 50 AMP RV Connection Box

Reply #4 – July 04, 2021, 12:14:00 pm

I did the same thing at my former shop except I used just the standard 50A weather proof box instead of the fancy RV setup. I had 2 boxes on one circuit for use on either side of the shop, only using ONE box at a time. The book says 6ga wire for 50A. You could use 4ga since it's 100" but I think that would be over kill. FYI, I bought direct bury cable, no need to run it in conduit. Running 4ga in conduit is a major PITB, don't ask how I know!

Even if you did use both boxes at once, anything over 50A load (from both boxes combined) is going to trip the breaker in the main box. I did actually used both boxes for a short time while we had two coaches. Ran the coaches and one AC in each with no problems. Again, the total load never approached 50A. I only used the 4 wires (no bare copper) since I did not have a 110V receptacle in my setup.

TOM

Re: 50 AMP RV Connection Box

Reply #5 – July 04, 2021, 12:24:10 pm

Quote from: OldManSax – July 04, 2021, 12:14:00 pm

I bought direct bury cable, no need to run it in conduit. Running 4ga in conduit is a major PITB, don't ask how I know

I would certainly look into that option. Compare prices both ways. I don't know why the electrician ran the underground wires how he did. Our ground is VERY rocky. Better protection from rocks for the wire?

Re: 50 AMP RV Connection Box

Reply #6 – July 04, 2021, 01:19:37 pm

Quote from: Chuck & Jeannie – July 04, 2021, 12:24:10 pm

I would certainly look into that option. Compare prices both ways. I don't know why the electrician ran the underground wires how he did. Our ground is VERY rocky. Better protection from rocks for the wire?

Also easier to pull additional or replacement service wires if needed.

Re: 50 AMP RV Connection Box

Reply #7 – July 04, 2021, 03:05:07 pm

Where we are the wire size to the second box is based on the total length from the first box to the second as long as only one or the other outlets can be used at a time. From your panel to the first box that length determines the wire size for that run. The first box is like a sub panel, you get sufficient power there with appropriately sized cables for a 50 amp load. From there moving the power available from the first box (sub panel) to the next box safely requires wire size based on that distance. In this case only one or the other of the outlets cans safely be used. A circuit breaker or non fused AC disconnect for each outlet at the first box would let you lock out the first box when the second is in use. A circuit breaker or a non-fused AC disconnect should also be at the second box.

Since it is possible to use both at the same time, you could see an argument made that you need to wire and provide circuit protection for 100 amps to the first box and have a 50 amp breaker for that outlet and a 50 amp breaker and appropriately sized wire for the 100 ft run to the second box.

If you do line Craneman suggest and use a 100 ft 50 amp extension cord then you eliminate the possibility of both outlets being used at the same time. There is only one.

It might just be cheaper to run 150ft of appropriately sized wire to the second box on its own circuit breaker. Less extra bits. Can you use aluminum cable? We cannot here for an inside sub panel but could for an outside post, it is cheaper but you have to carefully torque connections and then recheck them after a year and the periodically. Aluminum compresses and deforms more easily than copper and connections become loose.

Conduit is good, it may not beed to be buried as deep as underground feed cable. Size is important, big enough to deal with heat generated from the wires, maybe the next size up to make it easier to pull the wires. Use cable pulling lube.

220 volt 50 amp 100 ft is 2ga wire, 150 ft is 1 ga wire with 1% voltage loss.

Alum 1/3 ser cable is under $3/ft.
Copper /3 ser cable is more than $13/ft.

I have 2 50 amp RV connections on the side of my shop, each wired independently with separate circuit breakers.

Re: 50 AMP RV Connection Box

Reply #8 – July 04, 2021, 03:15:13 pm

Aluminum wire can be a less expensive option (if permitted in local codes) but if the insulation ever gets nicked and the wire is exposed to water it can corrode. I just had that problem here at our Colorado lot. When I got here I had 120Vac on 1 leg and 40Vac on the other leg. This is at my service panel. Called the electric company and thankfully they were in the neighborhood. I was able to wire a 30 amp receptacle on the good leg. They came out the next day and found a hole had been dug next to the meter panel. Yep, whoever dug the hole nicked the insulation with a shovel. The electric guy made a splice and gave me the bad piece. The aluminum wire had turned to powder!
Of course if it's in a conduit you should be ok.

Re: 50 AMP RV Connection Box

Reply #9 – July 04, 2021, 03:35:20 pm

Chuck,
I can only see one 50A breaker. There should be two 50A breakers. One for each leg. They may be there, I just can't see the second one.
50A RV service is actually 100A service. Two 50A legs out of phase with each other. These to out of phase leges can provide 240 volt power if needed.

Re: 50 AMP RV Connection Box

Reply #10 – July 04, 2021, 03:58:19 pm

It is a TOTAL of 4 wires for 50 amp: Two hots, L1 and L2, One neutral and One ground.

Re: 50 AMP RV Connection Box

Reply #11 – July 04, 2021, 04:21:59 pm

RV Safety | No~Shock~Zone

Re: 50 AMP RV Connection Box

Reply #12 – July 04, 2021, 04:35:59 pm

Quote from: John Duld – July 04, 2021, 03:35:20 pm

Chuck,
I can only see one 50A breaker. There should be two 50A breakers. One for each leg.

John,

Are you talking about in the house main circuit breaker panel (second set of photos)? I'm not sure what is going on there. The electrician said he needed two slots when he installed that 50A breaker. He had to use those two tandem 20A breakers (below the 50A) to free up the two slots for the 50A. It looks just like the "two-pole" breaker in the link below. Is that a possibility?

https://www.homedepot.com/p/Square-D-QO-50-Amp-2-Pole-Circuit-Breaker-QO250CP/100067584

Re: 50 AMP RV Connection Box

Reply #13 – July 04, 2021, 05:26:18 pm

Chuck,
I see what you are talking about. That looks good.
As long as each leg has it's own 50A breaker.
If you take a meter and measure at the RV plug each leg to ground you should see 120V and measure leg to leg if you see 240V your good.

Re: 50 AMP RV Connection Box

Reply #14 – July 04, 2021, 05:55:15 pm

Quote from: John Duld – July 04, 2021, 03:35:20 pm

Chuck,
I can only see one 50A breaker. There should be two 50A breakers. One for each leg. They may be there, I just can't see the second one.
50A RV service is actually 100A service. Two 50A legs out of phase with each other. These to out of phase leges can provide 240 volt power if needed.

Good catch and question! - that house breaker definitely looks "different".

Re: 50 AMP RV Connection Box

Reply #15 – July 04, 2021, 06:03:07 pm

"Difference in Double Pole Breakers With Two Switches & One Switch | eHow" https://www.ehow.com/info_7796307_difference-two-switches-one-switch.html

Re: 50 AMP RV Connection Box

Reply #16 – July 04, 2021, 06:08:14 pm

Quote from: prfleming – July 04, 2021, 06:03:07 pm

"Difference in Double Pole Breakers With Two Switches & One Switch

Thanx for the explanation! So, I have a two-pole breaker with one switch in our garage (main panel) and a two-pole breaker with two switches (tied together) at the outside RV power box. Kool.

Re: 50 AMP RV Connection Box

Reply #17 – July 04, 2021, 06:25:37 pm

The Square D 2pole 50 amp breaker only has one trip handle, takes up 2 adjacent spaces, so phases are 180 deg out for 240 volt 50 amp circuit. Simultaneous trip of both legs if one exceeds 50 amps. Looks normal to me Chuck. You only need a 4 wire circuit, only one grounding wire needed, green or a bare copper wire, not both. The bare copper wire in the box in your photo could be a bonding jumper from the circuit grounding conductor to the box grounding screw.

Total voltage drop should be calculated from the main panel in your house to the Rv outlet whether it is in your first J-box or to your new to be second Rv outlet. try not to ecxced 5% from your main panel to the Outlet.

Re: 50 AMP RV Connection Box

Reply #18 – July 04, 2021, 07:00:13 pm

The Paigewire calculator switches from 6 ga to 4 ga at approx 170 feet, for 3% voltage drop. I'm thinking your run to the existing box + the 100 feet to your new box is approx that or less?

3% voltage drop (3.6 volts each leg) would occur at 50 amps (12000 watts). I don't think you would ever use 12000 watts - both A/Cs running together is about 4000 watts. I think 6 ga copper should be fine.

Re: 50 AMP RV Connection Box

Reply #19 – July 04, 2021, 08:45:01 pm

Also (I am not a licensed electrician) I believe a detached sub panel needs a ground rod. Don't see one in your pics, but, some codes may allow a metal fence post to provide the ground. Any electricians please chime in...

Re: 50 AMP RV Connection Box

Reply #20 – July 04, 2021, 09:24:10 pm

Old codes you could use a Ground rod in place of the forth wire. Now need forth wire for Ground. New code also says must be gfi protected for the plug

Re: 50 AMP RV Connection Box

Reply #21 – July 04, 2021, 10:51:12 pm

Quote from: turbojack – July 04, 2021, 09:24:10 pm

Old codes you could use a Ground rod in place of the forth wire. Now need forth wire for Ground. New code also says must be gfi protected for the plug

I really must say that GFI ground fault circuit interruption breakers really are genuinely safer. If you short out a regular breaker it makes a big powerful arc flash. A GFI kinda goes click and pops with minimal arc flash. Yes they do cost more but in life you generally get what you pay for. Priceless in my opinion. Also can be installed in old houses without a ground wire and function well. But you must supply a ground to ops check the circuit to verify function. 👍👍
Scott

Re: 50 AMP RV Connection Box

Reply #22 – July 05, 2021, 12:59:52 am

QO250GFI GFCI CIRCUIT BREAKER 120/240V 50A. Is $165 at Amazon. Ouch!

3% voltage loss should be a maximum, less is better. My main panel that feeds the sub panel in the garage that feeds the barn and the panel in the barn are all "bonded" to a common copper rod in the ground. Even my roof top sat dish and all of my solar equipment is grounded to the same point I was told by the electrical inspector that multiple ground points for each service cannot be used.

I am not an electrician either but wired half of my house, my shop, and the barn. All with state permits and state electrical inspector signing off on all of it. The rules and codes change. Whatever you do follow the local code and do it in the safest way possible.

Re: 50 AMP RV Connection Box

Reply #23 – July 05, 2021, 01:28:55 am

I will start by saying that I am not an electrician, but I have done extensive commercial and residential electrical work. I would not use aluminum wire — if I could not afford copper wire, I would not do the project. Also, if you consider direct burial, understand that it requires much deeper burial than rigid metal conduit (I would have to look up the exact burial depths). You mentioned that you are in Texas in an area with rocky soil. I did a similar project before I sold my home in Central Texas, and after attempting to dig deep enough for direct burial, I gave up and used rigid conduit. The ground was simply too hard for me to dig to the depth required by code (and even if you are in a rural area where codes are not enforced, you should always follow the national code standard). Finally, to supply the full 50A service that the RV is rated at, you would need #4 copper at 150', which is what I would guess you are looking at when combining the original and the new run. You may not need to have the full 50A if you are just parking it, but be sure to look at exactly what current draw you will have at the location and plan accordingly. Again, I am not an electrician, so all of this is just my opinion based on experience.

Dave & Kathy Bennett
2004 U270

Re: 50 AMP RV Connection Box

Reply #24 – July 05, 2021, 01:43:30 am

Lots of dated information regarding Aluminum vs copper conductors.

Aluminum is NEC code approved, and lots of UL listed Aluminum wire is available for this type use, including TCER-JP THHN composite cable.

In my business, Aluminum outsells the copper equivalent 2:1 in feet sold per month.

Our 3x3 Cu and 3x1 AU are both rated @ 100 amps at 75C.

Of note, all the terminals (on breakers, lugs, receptacles) need to be dual rated for CU and AU, which today is almost always the case.

A white paper that discusses AU vs CU in conductors can be found at the link below.

http://www.eaton.com/content/dam/eaton/products/medium-voltage-power-distribution-control-systems/vacclad-w-pages/aluminum-other-conductor-ap083003en.pdf

Feel free to PM me with any questions that you may have regarding your project

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