Should I put in 50 amps or 30

[twinboat]

Originally Posted by Timon

Don't assume you can pull another wire. I've seen this attempted and in the end they had to pull all the wires back and repull the bundle. Pull all the wires now and make it easier on your self.

Now for those that think you can pull two #6 hot and a #8 neutral forget it. It's not up to code anywhere is the US. Neutrals and hots are REQUIRED to be the same guage although the ground can be smaller. In this case a #8 ground is good up through, I think, a #4 hot and neutral.

Not arguing but wondering why theu can sell appliance cords with a smaller neutral.

[Krazy Kajun]

Just went through this myself. I have a TT that is 30amps but I ran 4 #6 wires in a conduit. Why 4 #6 wires you ask, I'll explain. My conduit run was 115 ft long. 4 x 115 equals 460 ft. A 500 ft reel of #6 THHN wire was cheaper than trying to buy two different wire sizes (#6 for 2 hots and a neutral and#8 for ground) in the correct lengths. I installed an RV panel that has a 50, 30 and a 20 amp sockets and it has the breakers as well....this one. I also ran a water line and a cable TV coax cable while I had the trench open.

I just retired as an electrical engineer for a power company and I've dealt with power distribution all of my 38 years in the power utility business. As others have said NEC will allow you to downsize the ground, not the neutral. In a 220v world the neutral carries the inbalance of the two hot wires. For example, let's call the hot wires H1 and H2. If there is 100 amps on H1 and 120 amps on H2 the neutral will carry 20 amps. Even if you have 2 50 amp circuits hooked to the coach, which is what you actually have, the neutral will only carry the difference between the two hot wires due to the wiring at the utility transformers. If you look up on the pole where a transformer is installed you'll see 3 secondary bushings. The center bushing is the neutral and the two outside bushings are the hot legs....H1 and H2. It does not matter how you distribute the power at your house or RV pedestal, it still comes from the source at the transformer. If you take the lid off the transformer you'll see that there are actually 2 120v coils on the secondary side. One leg of each of the coils is actually hooked together to the center bushing on the transformer, the neutral bushing. The reason you get 240 volts across the two hot legs is because the 2 secondary coils are connected in series in the transformer tank. This same principal is used when you connect 2 6v batteries in series in your coach to get the 12 volts.

To the OP, by all means run the proper wiring for the 50a service and install something like what I did so that you'll have everything you need installed the first time. We have a saying..."buy once, cry once."

To the other person asking about running the service for additional load and feeding it from the RV pedestal....you can do this but know that if you are running a heavy use on the RV you are doing it at the expense of capacity that you might want to use for the other load. If you wouldn't be using much off the sub circuit then I'd just use the 20amp breaker in the panel like I used to feed the barn or garage or whatever you are going to use. You should install wire capable of carrying 20 amps (#12 in most cases, depends on the kind of wire that you'll use) so as not to limit your capacity. You'll also have some voltage drop to your garage or shop due to the additional distance in the wiring. If you are installing the wire in conduit to the garage then THHN would work well. If you are direct burying the wire then you'll want to use UF cable....looks like Romex but has thicker insulation and is meant for direct burial.

Hope this helps.

[twinboat]

Originally Posted by Old Scout

Don't look now but the RV 50 amp cord in your coach has two #6 hot legs and two #8 neutral/ground wires. " [smile]

I looked up 3, 50 amp RV power cords. One is a cord reel. All have 3, #6 awg conductors.

What brand is yours ?

#1; Power Cord: 50 AmpPower Cord Length: 36'Power Cord Type: SOW Super Flex #6 awg x 3 / #8 awg x 1Power Cord Plug: Molded 4 Prong with LED Power indicator & EZ-Out LeverPigtail Type: SOW Super Flex #6 awg x 3 / #8 awg x 1Pigtail Length: 3'

#2; Features include:
Rugged constructionDesigned for outdoor use
75 ft. length of heavy duty 6/3 8/1 STW cable
Easy pull handles for safe disconnectsLED light to show when the power is connected

# 3; 50 feet 50 amp rv extension cord, angle plug and female receptacle with pull handles, 125/250V, 6/3 + 8/1 AWG, STW, NEMA 14-50, made by NU-CORD.

[Timon]

Originally Posted by twinboat

Not arguing but wondering why theu can sell appliance cords with a smaller neutral.

I've never see that and I don't think UL would approve one like that.

Originally Posted by Dr4Film

Well then that makes my Florida licensed electrician kinda stupid if that is true.

We shall see when he shows up again to finish the electrical work that he was hired to do.

Dr4Film ----- Richard

Let me make one correction to my statement. You may be allowed to have an oversized neutral that will carry the load of both hots if they were in phase.

Originally Posted by Old Scout

Don't look now but the RV 50 amp cord in your coach has two #6 hot legs and two #8 neutral/ground wires. Appreciate the issue...

I'd love to see who makes that cable with a UL sticker on it. I've gone through UL testing and I'm sure they would never approve it.

[twinboat]

Here is a 50 amp power cord with 2, 6 gauge and 2, 8 gauge conductors.


4-Wire 50A Range Power Cord - 4' LengthBy*EZ-Flo*(61245)
SpecificationsTop
Rated at 50 Amps - 125/250 VoltsClosed eyelet terminals(2) 6AWG wires and (2) 8AWG wireLength: 4'UL listed
Part NumbersMCM Part #:140-1339EZ-Flo*Part #:61245Package Specifications & DimensionsWeight:2.125 lbs.Hazardous:NoRoHS Comp:NoWarranty:90 days
Need to Return?Length:12 in.Width:9.5 in.Height:2.5 in.Shipping Information.

I have read where some RVers have used cords like this. They install portable surge guards in their electric compartments, without cutting the ends off.

Yes, they are out there.

[Dr4Film]

Originally Posted by Dr4Film

Well then that makes my Florida licensed electrician kinda stupid if that is true.

We shall see when he shows up again to finish the electrical work that he was hired to do.

Dr4Film ----- Richard

Originally Posted by Timon

Let me make one correction to my statement. You may be allowed to have an oversized neutral that will carry the load of both hots if they were in phase.

Now I am totally confused!

Oversized neutral versus undersized neutral.

I know enough about electricity to be dangerous to myself at times but I do know about phasing. 240 VAC - 2 Legs - in the same phase is not true 240 VAC.

That's why I have a Power/Pedestal Tester that will alert me to a "Fake 50 Amp Pedestal" which are not common but they are out there. It usually happens when older RV Parks cheat when re-wiring an older section from 30 amp to 50 amp.

Dr4Film ----- Richard

[wa8yxm]

A comment on codes and dropping a wire size for the neutral

In a now (at least officially, have not checked yet) closed forum I used to moderate in.. back when it was top dog on the internet for forums of its type (not named here) we had a saying "Your millage may vary"

Your code may vary (from state to state and evfen from city to city within a state)

Many codes are written with houses in mind, and in a hours you have only a few 240 volt devices

Air Conditoiners (may not even use the nutral wire not present)
Range (Uses it but.. Well there is a clock/timer and a light, total perhaps 50 watts or 1/2 amp max. that's it for the neutral)
Dryer (likewise clock timer and optional light) The main motor on a dryer may also be 120 volt (1/2 hp or less, 5 amps tops)

But on an RV circuit.. Well in THEORY you can dra the full 50 amps on one leg.. in practice, you never will

Fact: My Generator fuses (breaker actually) both legs 30 amps.. I do from time to time trip a breaker but more from vibration than overload.. Only time I overloaded I was feeding power to other services (I can daisy to another RV if there is a power fail)

[70ChevelleSS]

Originally Posted by twinboat

Not arguing but wondering why theu can sell appliance cords with a smaller neutral.

The codes relate to the wiring up to and including the outlet. After the outlet is not covered by the electrical codes. You most likely have many small gadgets that have 16g or even 18g cords that plug into 15 amp outlets feed by 14g wire.

[Hit_the_Rhod]

Originally Posted by Timon

Don't assume you can pull another wire. I've seen this attempted and in the end they had to pull all the wires back and repull the bundle. Pull all the wires now and make it easier on your self.

Now for those that think you can pull two #6 hot and a #8 neutral forget it. It's not up to code anywhere is the US. Neutrals and hots are REQUIRED to be the same guage although the ground can be smaller. In this case a #8 ground is good up through, I think, a #4 hot and neutral.

I'm not going to argue with you, I'll let you argue with the COUNTY ELECTRICAL INSPECTOR on that point . . . .

Make sure he understands that you are doing an RV hookup, 50 amp, two legs of 50 amp, 120 volts each, NOT a clothes dryer hookup . . .

[Old Scout]

Setting aside the appliance cord example, seems like I have seen cable multi-wire cable at HD/Lowes with smaller neutral and ground--probably wrong. Regardless, my challenge is to cost out using a single 500ft spool of #6 for three or four 50-amp runs in the barn, vs trying to down size at least the ground wire to reduce overall cost. Savings on spooled wire vs buying it by the ft. is significant enough to allow using #6 for all 4 wires. Just need to estimate how much short or overage wire I'll have from a 500 ft spool.

[TQ60]

Yes there are regulations regarding conduit fill.

It relates to the ability to transfer heat from the wire.

Heat on wire?

Every wire has a resistance as do superconductors and energy flowing through a resistance generates heat.
E=I/R then P (power in watts) = I X E finally heat in BTU is P X 3.42

So more wires in a conduit reduces their capacity so a 20 amp wire in a stuffed conduit is debated to say 15.

Further...Some wires for shorter distances can have a larger capacity as in the example above but please pay careful attention to the SHORT length.

Google amp rating of wire and you will find a great many charts that can confuse folks.

We once was a power engineer for telco switch rooms and requiring voltage drop less than 0.25 volt with dc means heavy wire and one learns about wire capacity.

A number 12 wire is common specified as a 20 amp wire but some charts show 25 and others show 30 but depending on length and application it may only be good for 5.

The wire can carry more current than the nominal specification when I is used in an application that allows that.

In a 4 foot cut length there may be a specification that allows the ultimate listing of the CUT 4 FOOT LENGTH.

The ultimate listing is only for that specific part.

We used 5 amps for the number 12 wire as we had an instance where that was the required wire size to meet the design...number 14 did not meet spec.

As stated multiple times...The local building department is the "law enforcement agency" responsible for the application of regulation set by the NEC.

Many folks cut corners to save time and money and this one may save a few bucks in wire cost but damn little but the smaller wire is easier to pull so the person is being lazy.

Me...If I was doing work for someone I would insist on being to code as to not have it haunt me and if I was selling materials then larger wire is more profit.

If I was doing this work and amp rating of wire was 50 (do not have chart handy) and was installing an rv panel with multiple circuits I would up the wire size to compensate for losses over distance and to allow for sub circuits at a later time as you may want to add something later.

This thread is regarding a parking spot so short cable run should be fine but those running cable to barn should consider both distance and additional loads from other tools and toys.

[Mr_D]

Originally Posted by Hit_the_Rhod

I'm not going to argue with you, I'll let you argue with the COUNTY ELECTRICAL INSPECTOR on that point . . . .

Make sure he understands that you are doing an RV hookup, 50 amp, two legs of 50 amp, 120 volts each, NOT a clothes dryer hookup . . .

And in some cases, mine is one, the RV is 50 amp and dryer is 220-240 volt so...

[Old Scout]

Suggest the following internet link to a variety of electrical computation tables: "electrician2.com"

[Krazy Kajun]

Originally Posted by Old Scout

Setting aside the appliance cord example, seems like I have seen cable multi-wire cable at HD/Lowes with smaller neutral and ground--probably wrong. Regardless, my challenge is to cost out using a single 500ft spool of #6 for three or four 50-amp runs in the barn, vs trying to down size at least the ground wire to reduce overall cost. Savings on spooled wire vs buying it by the ft. is significant enough to allow using #6 for all 4 wires. Just need to estimate how much short or overage wire I'll have from a 500 ft spool.

So, the question is....how long will the conduit run be from your breaker box to the RV pedestal where you will have the RV plug installed? Don't forget to add in footage for the depth of the conduit trench (at least 24 inches) and also be sure to allow for some extra length to provide for wire to do the make up of the connections at both ends....I'd allow 10 ft on each end, you probably won't need that much but its better to be safe...you can't add wire after its in the conduit but is sure is easy to cut off. If the total length of the conduit run is 105 ft or less then a 500 ft spool of #6 THHN wire would work fine.

What you are considering is exactly what I did...see my post above. I bought a 500 ft spool of #6 THHN and cut them into equal 125ft pieces and then put them together so that the ends were all the same length and then taped them together at 10 ft intervals. I used a fish tape and pulled all of them in the same conduit from my breaker box to the RV panel that I installed on a post beside the pad I had poured to park my camper at my house. While the trench was open I also dropped in a water line and a CATV coax run as well so I'd have all the comforts of home in my camper should I need them. The main cost was to open the trench, adding the water line and coax cable was a small incremental cost.

Be sure to let us know what you did, it's always interesting to hear about this type discussion and then see what the OP actually ended up doing.