208Volt Okay For 240Volt RV?

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Ravenvalor

Ravenvalor

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Piedmont region of NC
Hello,

I have a commercial customer who wants me to connect a 120/208-volt, 50-amp circuit to his 120/240-volt, 50-amp RV which he has purchased but has not received it yet. I spoke with the seller and he says the documentation specifies a 120/240-volt circuit where each 120-volt leg does not exceed 120-volts. All of the loads in the RV are 120-volt.
Can anyone think of a scenario where 120/208-volt could be a problem?
Thank you for the help.
 
At one time the NEC required RV park distribution systems to be 240/120 but 208/120 is now allowable which would lead one to believe the RVs are adaptable to 208v supply.
 
Nothing on an RV requires 240V. The only reason for a 50A RV outlet is because they have 2 air conditioners. But each A/C only requires 120V. A 30A with all the receptacles and lights, plus 1 A/C probably wouldn't handle another A/C so a 50A is required. The 240V part is because of both distributing the load off the feeder panel and a SP 50A is not a commonly stocked breaker.
So the 208V is fine for an RV since the line to neutral is 120V.
 
Just curious--is this connection going to involve a receptacle? And if it did, would NEMA 14-50 be appropriate, or is it reserved for 120/240V, and you'd need something else for 120/208V?

Cheers, Wayne
 
Ravenvalor said:
Hello,

I have a commercial customer who wants me to connect a 120/208-volt, 50-amp circuit to his 120/240-volt, 50-amp RV which he has purchased but has not received it yet. I spoke with the seller and he says the documentation specifies a 120/240-volt circuit where each 120-volt leg does not exceed 120-volts. All of the loads in the RV are 120-volt.
Can anyone think of a scenario where 120/208-volt could be a problem?
Thank you for the help.
Click to expand...
With all loads at 120V, the only issue I'm aware of with 120/208V is that the neutral conductor feeding the RV panel must be fully sized (i.e., the same size as the phase conductors). But I'm assuming that would be the case.
 
augie47 said:
At one time the NEC required RV park distribution systems to be 240/120 but 208/120 is now allowable which would lead one to believe the RVs are adaptable to 208v supply.
Click to expand...
Also, 551.46(D) says that for 4-wire supplies an RV shall have a safety label which says:
THIS CONNECTION IS FOR 208Y / 120-VOLT or 120 / 240-VOLT AC, 3-POLE, 4-WIRE, 60 HZ, ____AMPERE SUPPLY.

In addition, 551.40 (A) says that "Electrical equipment connected line-to-line shall have a voltage rating of 208-230 volts."
 
Last edited:
synchro said:
Also, 551.46(D) says that for 4-wire supplies an RV shall have a safety label which says:
THIS CONNECTION IS FOR 208Y / 120-VOLT or 120 / 240-VOLT AC, 3-POLE, 4-WIRE, 60 HZ, ____AMPERE SUPPLY.

In addition, 551.40 (A) says that "Electrical equipment connected line-to-line shall have a voltage rating of 208-230 volts."
Click to expand...
I doubt that any RV would be using a 3 phase connection...
 
synchro said:
Also, 551.46(D) says that for 4-wire supplies an RV shall have a safety label which says:
THIS CONNECTION IS FOR 208Y / 120-VOLT or 120 / 240-VOLT AC, 3-POLE, 4-WIRE, 60 HZ, ____AMPERE SUPPLY.
Click to expand...
Jraef said:
I doubt that any RV would be using a 3 phase connection...
Click to expand...
I'm thinking that their wording in this label is probably targeted at what the typical RV user might understand, and not what an electrician or engineer would consider as a 3-pole, 4-wire supply. It seems to be common to refer to single phase 125/250V plugs and receptacles as 3-pole, 4-wire. For example, the 14-50R from Hubbell:
...

Straight Blade Devices, Receptacles, RTP, Industrial Grade, 3-Pole 4-Wire Grounding, 50A 125/250V, 14-50R, Black, Single Pack. | HBL9450A | Hubbell Wiring Device-Kellems

Designed for plug-in EV charging applications, Hubbell’s 14-50R receptacle is a premium and dependable solution to exceed the requirements of electric vehicl...
www.hubbell.com www.hubbell.com

The only other label in 551.46(D) is for 110 - 125V AC, and so they must be intending the label that I mentioned for single phase applications.
 
Its fine, done all the time. 14-50R is the standard receptacle to install. Some RVs have a detachable cord with a 50 amp twistlock, some have an attached cord, either way they both have a 14-50 plug. As others have stated, 50 amp RVs don't have any line-line loads. We power dozens of RVs with 50 amp 4 wire connections all the time off towable generators with 120/208Y distribution.
 
Neutral becomes a current carrying conductor- should not be an issue.

If any 240 volt heating existed, they would output 75% of their rated power. Typically this isn't noticed by the common user.
 
zbang said:
Most RVs use a CS connector for this, not a NEMA.
Click to expand...

Not saying that’s wrong, but I’ve never seen a 50A CS cord on an RV, nor have I ever been to an RV park with CS receptacles. I’m not an avid camper, but my parents are, and I’ve traveled with them some, and have even borrowed their 5th wheel to take my family in. I’ve only ever seen a 14-50 at all of the RV parks I’ve been to. If my dad had ever been to a park with a CS receptacle my phone would’ve been blowing up. The man calls me when he can’t get HIS tv in the RV to operate.


Sent from my iPhone using Tapatalk
 
In the perhaps unlikely situation that the RV has electric heat or cooking instead of just propane, and it uses a line to line connection, it will deliver heat slower with a 208V connection than with a 240V connection.
 
GoldDigger said:
In the perhaps unlikely situation that the RV has electric heat or cooking instead of just propane, and it uses a line to line connection, it will deliver heat slower with a 208V connection than with a 240V connection.
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It would be very unlikely since the OP said 50A and the reason for 50A is for two A/C units.
 
brantmacga said:
Not saying that’s wrong, but I’ve never seen a 50A CS cord on an RV, nor have I ever been to an RV park with CS receptacles. I’m not an avid camper, but my parents are, and I’ve traveled with them some, and have even borrowed their 5th wheel to take my family in. I’ve only ever seen a 14-50 at all of the RV parks I’ve been to. If my dad had ever been to a park with a CS receptacle my phone would’ve been blowing up. The man calls me when he can’t get HIS tv in the RV to operate.


Sent from my iPhone using Tapatalk
Click to expand...

Alot of RVs will have a 50 amp locking inlet on the side of the RV and a 14-50P to 50 amp locking cord.
 
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