Should I put in 50 amps or 30

[TonyMac]

If you're drawing 30 amps, it's safer to do so thru a 50a system.

[Gary RVRoamer]

I'll disagree a bit and ask that you do some further thinking. A future 50A coach doesn't "require' 50A to work, so its not an all or nothing proposition. And 50A does cost more to install (though not always a lot more), so there are some tradeoffs.

If you are mostly just storing the RV, you probably won't be using anywhere near the full 50A capability anyway. You can run one a/c unit, power the fridge, and handle other routine needs easily enough on 30A power. Probably about the only time you will need the full 50A at home is if you have guests staying in the RV during very hot or cold weather and need both a/c or heat pump units operational.

At our home I installed a 30A supply for the RV and have a second 30A outlet available for those rare occasions when we wanted to have more power to it. A twin-30A adapter for a 50A coach is easy enough to make or buy. The secondary 30A outlet "borrows" power from my workshop supply, so I can't use all my power tools if the RV is also using very much.

The other use for a second 30A outlet is for RV visitors. We have room for a second RV in the yard, and occasionally have visits from RVing friends who can plug t our second outlet without disrupting our own coach.

[Dr4Film]

Originally Posted by Dr4Film

Yes he did. I questioned it at the time and he stated that according to local code you can go down one gauge for the neutral and one more gauge for the ground.

Therefore 6 gauge for the load legs, 8 gauge for the neutral and 10 gauge for the ground.

I will bring this subject up to him once again when he returns to complete the balance of the work.

He may be thinking about how a 240 VAC appliance using the 50 amp outlet versus a RV which splits the 240 VAC into two 120 VAC legs which can be unbalanced.

I'll post back when I have that information.

My electrician is now here finishing up the work that he was hired to accomplish under the contract. Yesterday he ran conduit to another 50 amp RV box that I wanted on one concrete pillar under the RV Port where my coach is now parked.

I asked about using the lower 8 gauge neutral instead of 6 and his remark was that is what NEC national code allows. He is not worried the least bit about unbalanced loads. He has been doing this type of licensed work all around this area of Florida and in fact has his own 50 amp RV hookup at his residence for his large 5er.

He also stated and actually showed me that my main panel had one size smaller gauge copper neutral than the two larger load legs. Plus pointed out for other 240 VAC devices that are wired into the panel where the neutral is smaller than the load legs.

I am not about to argue with a licensed electrician so if anyone has any doubts then I suggest purchasing the NEC for electricians and read for yourself as that the bible that he is required to adhere to.

He did say that some local municipalities may have their own special restrictions or "rules" to go by but those are mostly people needing to express their "power" versus what is recommended by National Electrical Code.

Dr4Film ----- Richard

[CharlesinGA]

Originally Posted by Dr4Film

I asked about using the lower 8 gauge neutral instead of 6 and his remark was that is what NEC national code allows.

He also stated and actually showed me that my main panel had one size smaller gauge copper neutral than the two larger load legs. Plus pointed out for other 240 VAC devices that are wired into the panel where the neutral is smaller than the load legs.

I am not about to argue with a licensed electrician so if anyone has any doubts then I suggest purchasing the NEC for electricians and read for yourself as that the bible that he is required to adhere to.

Dr4Film ----- Richard

Without starting an argument or beating this dead horse any further..........

I realize that you are at the mercy of the electrician to do the "right thing" which still makes me wonder why he would have undersized the neutral.

For your RV use at home, it is doubtful that you could ever overload the undersized neutral, however looking forward, its alos quite possible that the circuit or the receptacle could be utilized for other purposes (weddings, gatherings, parties, etc in the future that no one anticipates now)

NEC 551 addresses the special requirements of RV's (internal wiring) and of RV park wiring also. With respect to park pedestal wiring, NEC 551.73 Calculated Load, (D) Feeder-Circuit Capacity. Recreational vehicle site feeder-circuit conductors shall have an ampacity not less than the loads supplied and shall be rated not less than 30 amperes. The neutral conductors shall have an ampacity not less than the ungrounded conductors.

What this is saying, is that in this installation, you are NOT allowed to undersize the neutral.

Neutrals in residential main panels (Service) (the conductors supplying the panel from the meter and disconnect) are allowed to be undersized as there is an anticipation of 240v loads and a reasonable balancing of the 120v loads.

The NEC also allows the undersizing of neutrals in certain Feeder circuits based on specific calculations of loads in the intended installation, but again, sends you off to article 551 for RV's

Its a gray area that the electrician probably should not have taken advantage of, given a myriad of potential future uses of the receptacle or the re-purposing of the circuit.

Footnote: I am NOT a licensed electrician, however, I am a licensed aircraft mechanic and am familiar with electrical circuit sizing. I also have completely wired, or rewired a couple of buildings, and have studied the NEC extensively. My most recent copy of the NEC is the 2011 edition, I do not have the 2014 nor 2017 editions (the NEC is revised on a 3 year cycle)

Charles

[TQ60]

Just because anyone has a license to do whatever they claim it does not mean they know what they are doing or always do things right.

Given the op configuration the neutral only carries non balance loads so it is likely going to be fine.

Asking the electrician how the code is applied is like asking the teenager if it okay to drive faster than the speed limit.

Only the county inspector in the op county can state how the code applies.

If the work is such that requires a permit then inspector will judge it if permit issued and if no permit then hope it works well.

Just because other work in box is a certian way does not make it to code.

[Timon]

First the neutral only carries the difference between the 120V legs. Thus it if you pulled 20A on L1 and 50A on L2 the neutral would carry 30A but if L1 leg went to 0 then The neutral jumps to 50A. It's a extreme jump but if the neutral was undersized you'd be overloaded. Would this happen with an RV? Likely not.

[Dr4Film]

Originally Posted by CharlesinGA

For your RV use at home, it is doubtful that you could ever overload the undersized neutral, however looking forward, its also quite possible that the circuit or the receptacle could be utilized for other purposes (weddings, gatherings, parties, etc in the future that no one anticipates now)

NEC 551 addresses the special requirements of RV's (internal wiring) and of RV park wiring also. With respect to park pedestal wiring, NEC 551.73 Calculated Load, (D) Feeder-Circuit Capacity. Recreational vehicle site feeder-circuit conductors shall have an ampacity not less than the loads supplied and shall be rated not less than 30 amperes. The neutral conductors shall have an ampacity not less than the ungrounded conductors.

What this is saying, is that in this installation, you are NOT allowed to under size the neutral.

Neutrals in residential main panels (Service) (the conductors supplying the panel from the meter and disconnect) are allowed to be undersized as there is an anticipation of 240v loads and a reasonable balancing of the 120v loads.

The NEC also allows the under-sizing of neutrals in certain Feeder circuits based on specific calculations of loads in the intended installation, but again, sends you off to article 551 for RV's

Its a gray area that the electrician probably should not have taken advantage of, given a myriad of potential future uses of the receptacle or the re-purposing of the circuit.

Footnote: I am NOT a licensed electrician, however, I am a licensed aircraft mechanic and am familiar with electrical circuit sizing. I also have completely wired, or rewired a couple of buildings, and have studied the NEC extensively. My most recent copy of the NEC is the 2011 edition, I do not have the 2014 nor 2017 editions (the NEC is revised on a 3 year cycle)

I also have the NEC 2011 Edition as it is the only one that is currently free to download on the Internet.

It is HIGHLY unlikely that the 4-pole 240 VAC 50 amp outlet would be used for any other purpose except for possibly a electric range or dryer which would be a rather strange place to plug one into unless you are just "testing" the appliance.

Plus I did skim through most of chapter 551 on RV Park installations. I have posted a few sections that pertain to a 50 amp RV coach.

The first one pertains to wiring INSIDE the RV.

551.42 Branch Circuits Required.

Each recreational vehicle containing an ac electrical system shall contain one of the circuit arrangements in 551.42(A) through (D).

(D) More Than Five Circuits Without a Listed Energy Management System. A 50-ampere, 120/208–240-volt power-supply assembly and a minimum 50-ampere rated distribution panel board shall be used where six or more circuits are employed. The load distribution shall ensure a reasonable current balance between phases.

The following paragraph below is listed in the code book just prior to the 551.73 paragraph that you had quoted above in your post. The first part pertains to 30 amp or less outlets whereas the part highlighted in red pertains to 50 amp outlets.

551.72 Distribution System.

Receptacles rated at 50 amperes shall be supplied from a branch circuit of the voltage class and rating of the receptacle. Other recreational vehicle sites with 125-volt, 20- and 30-ampere receptacles shall be permitted to be derived from any grounded distribution system that supplies 120-volt single-phase power. The neutral conductors shall not be reduced in size below the size of the ungrounded conductors for the site distribution. The neutral conductors shall be permitted to be reduced in size below the minimum required size of the ungrounded conductors for 240-volt, line-to-line, permanently connected loads only.

Not trying to defend what the electrician did in my case. Only attempting to point out information in the code.

Bottom-line, for the purpose for which these 50 amp hookups were installed and will be used the chances of having a significant unbalanced load is zero.

Dr4Film ----- Richard

[Spaceball]

Originally Posted by Dr4Film

...

Bottom-line, for the purpose for which these 50 amp hookups were installed and will be used the chances of having a significant unbalanced load is zero.

Dr4Film ----- Richard

Even if you did have an unbalanced load, the neutral may not get overloaded to where it's dangerous.... however voltage drop is a very real situation in an unbalanced load with less than optimal wire sizing. The first time you fire up an AC in the summer you will see the imbalance if only one unit is running. The unloaded leg will drop in voltage, if it drops far enough and if you have protection built in, your transfer switch could cut the power in that situation. Just speaking from experience.

I ran into a somewhat similar situation where a garage had an 80 foot run to it on only #8 wire, and the knuckleheads put a 100 amp box in the garage /facepalm. They probably thought at the time hey this garage will ever only see a light bulb and maybe a battery charger no big deal lets save a buck on the wire. But fast forward 40 years and several change of ownerships and here I have a 100 amp box that the feed wiring is only good for about 30, which I did not know about until I loaded up one leg with about 45 amps and the voltage dropped to 105 on the other side. Had to bury a new wire feed to the garage. I used #2 on all 3 wires, zero issues now but wouldn't have been if the original builders had not wanted to skimp a buck on wire.

If it were me I'd tell the guy to run the same size neutral as the hots and pay the extra 50 bucks for the wire to end all arguments, but I'm very bullheaded that way.

[olustee bus]

Thanks for all the information and I actually understood lots of it.

I have decided to use this Connecticut Electric CESMPSC75GRHR as suggested by l1v3fr33ord1. It would save a lot of time on installation and wiring.