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How to wire RV connection

RV connection
A. 14-50R 240 vac / 50 amp
B. TR-30R 120 vac / 30 amp
C. 6-20R 120 vac / 20 amp
ALL NEMA TT-30R (Travel Trailer) are 120 vac

Do not confuse NEMA 10-30R or 14-30R; people have tried to "adapt" their RV 30 amp power cord to plug in a dryer receptical. Mucho damage.

Perhaps a special section for RV power considerations.

NEMA 14-50R Trailers / Motor Homes are 240 vac / 50 amp

NEMA 6-20 "T-Slot" is 120 vac / 20 amp

TT-30R is NEVER configured as 240 vac

Nearly ALL RV Sites have a peristalsis with all 3 services

Nearly ALL RV Sites have a pedestal providing all 3 RV power sources - 240 vac / 50 amp and 120 vac / 20 & 30 amp.

Resource:
Trailer 120 volt connection
50 amp connection
Read about 240 volt outlets

50 amp/ 3-prong/ RV


For RV,  the 50 amp is 240 volt and 30 amp outlet is 120 volt, not 240 volt, and wires are typically Black-white Hot-Neutral... with silver screw for  Neutral ... see illustration below

50 amp/ 3-prong/ RV



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Hey Gene,

The first diagram I mentioned was of course the one labeled "30 amp/3-prong/RV outlet".  It's the last receptacle wiring diagram before the section on "Locking plugs/ twist lock".  As I mentioned before, RV 30 amp service is strictly 110V,* and the receptacle is wired hot-neutral-ground.

The second diagram is three diagrams above that and is labeled "30 amp/3-prong/dryer".  You show that as a hot-hot-ground configuration.  Technically the NEMA 10-30 is a no-ground circuit.*  Immediately to the left of that receptacle diagram, you show a picture of the 10-30R with the following caption:

30 Amp
Profile NEMA 14-30
NEMA 10-30R

Actually the 14-30(R) is the 4 wire receptacle shown in the diagram immediately below this (labeled "30 amp/4-prong/dryer").  The wiring diagram for that receptacle is shown correctly (with both neutral and ground), but the caption underneath the picture of the outlet on the immediate left says "Neutral is NOT required for 240 volt circuit".  This is not correct as the neutral is used between the the hot legs when the loads aren't balanced.  The only real difference between this service and the one shown directly below it ("50 amp/4-prong/RV") is the current carrying capacity. 


* Some background source material:

NEMA 10 devices are a deprecated type that had been popular in the United States for use with electric clothes dryers and kitchen ranges. They are classified as 125/250 V non-grounding (hot-hot-neutral), yet they are usually used in a manner that effectively grounds the appliance, though not in a manner consistent with most modern practice. This was before the requirement of a separate safety ground was a incorporated in the National Electrical Code. As commonly used, 10-30 and 10-50 plugs have the frame of the appliance grounded through the neutral blade. This was a legal grounding method under the National Electrical Code for electric ranges and clothes dryers from the 1947 to the 1996 edition. Since North American dryers and ranges have certain parts (timers, lights, fans, etc.) that run on 120 V, this means that the wire used for grounding is also carrying current. Although this is contrary to modern grounding practice, such installations remain common in older homes the United States.

NEMA 14 devices are four-wire grounding devices (hot-hot-neutral-ground) available in ratings from 15 to 60 A. Of the straight-blade NEMA 14 devices, only the 14-30 and 14-50 are common. The 14-30 is used for electric clothes dryers and the 14-50 for electric cooking ranges. Both are used for home charging of electric vehicles. The voltage rating is 250 V. They are essentially the replacements for the NEMA 10 connectors above with the addition of a separate grounding connection.

All NEMA 14 devices offer two hots, a neutral and a ground, allowing for both 120 and 240 V (or 120 and 208 V if the supply system is three-phase rather than split-phase). The 14-30 has a rating of 30 A and an L-shaped neutral blade. The 14-50 has a rating of 50 A and a straight neutral blade sized so that it does not fit in the slot of a 14-30.

NEMA 14-50 devices are frequently found in RV parks, since they are used for shore power connections of larger recreational vehicles. Also, it was formerly common to connect mobile homes to utility power via a 14-50 device.

NEMA 14-30 and 14-50 receptacles


NEMA TT-30 plug and receptacle. (The center hole on the receptacle is not a contact.)
NEMA TT-30 (TT stands for Travel Trailer) is a 125 V, 30 A recreational vehicle standard (hot-neutral-ground), also known as RV 30. It is frequently (and sometimes disastrously) confused with a NEMA 10-30. The RV receptacle is common in nearly all RV parks in the United States and Canada, and all but the largest RVs manufactured since the 1970s use this plug. The hot and neutral blades are angled at 45 from vertical and 90 to each other, similar to NEMA 10 devices. The plug is slightly smaller than a NEMA 10 but larger than ordinary 5-15 plugs. The ground pin, however, is round, like those on straight-blade NEMA grounding devices. Referring to the diagram, the orientation is the same as the NEMA 5 plug and socket, with the receptacle neutral on the lower right. The appearance of this plug makes many people assume it is for 240 V, but this is a 120 V device.

Hope this helps :-)
Hey Gene,

A light bulb went off in my head at 2:00 this morning, and I realized what (I think) you meant by the language that "Neutral is not required for 240 Volt circuit" next to the picture of the NEMA 14-30 receptacle.  I was of course approaching this from the standpoint that the 240v circuit is made up of two 120v legs.  If you have no 120v loads and are using nothing but a 240v load, then the neutral conductor will indeed carry no current.  So, it's "not required" in the sense that with a pure 240v load the circuit will work without a neutral.  In most circumstances though I'm pretty sure it would still be a code violation to wire a 14-30R without the neutral conductor.  If you want to run a 3 wire circuit, then you would use the 10-30R shown directly above the 14-30.
LOL about the 2am light bulb idea !!
Sounds like me... jumping out of bed and writing down something so I don't forget

Here's an illustration that might clarify 120-240 volt wiring a bit..
http://waterheatertimer.org/images/Inside-Main-Breaker-Box-12.jpg

I havn't had time to digest your emails ... however the 120 volt Neutral does not carry voltAGE
The function of the neutral is to complete the circuit back to generator ... it 'balances the equation' so to speak, stablizes the grid against surge events, assists circuit breakers, and connect all ground wires into one giant array across the grid. No small task.
http://waterheatertimer.org/240-volt-generator.html
Just a word of caution about your page showing how to wire 240 volt outlets.  You have a diagram showing a "30 amp/3-prong/RV outlet" wired as a 240 volt circuit.  Thirty amp RV service is strictly 120 volts only.  Because of the shape of the outlet & plug, the TT-30R & TT-30P are often confused with the old NEMA 10-30, but if you wire a TT-30R for 240 volts and plug an RV into it, you will smoke everything in the RV in seconds.

And I'm not trying to nit-pick, but on the diagram you show for the NEMA 10-30, you have the neutral labeled as "ground".  

Just thought I'd pass that along.....

Thanks for your page.

I feel your Website is in error. Under your 30 amp / 3-prong / RV
http://waterheatertimer.org/How-to-wire-240-volt-outlets.html
 
The 30 amp 3-prong RV service is 110 vac and not 240 vac
 
It is a TT-30R receptacle which is 110 vac only. Your configuration will fry a Travel Trailer. A lot of RV’ers try to hook up to a house dryer receptacle and fry RV their electrical system.
 
I have bookmarked and fine your site very informative.
 
Regards,
 
David Little

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