50amp Tesla Service

[howie29]

The previous owner of my home had a Tesla, and installed what I assume is a 50amp outlet (can receive a 4 prong plug, says 50amp on it) for charging.  If I dogbone down from 50amp to 30amp off this receptacle, can I charge my 30 amp RV on this outlet or is the voltage something different than regular 50amp service at an RV park?

Thank you.

[57becky]

The only way to tell is with a voltmeter.  If this is exactly like an RV 50 amp outlet, the round hole in the outlet is the ground, and the flat terminal across from the ground terminal is the neutral.  The other two terminals are the hotlegs, and probably measure 240 volts across the two hots, and 120 volts from either hot terminal to the neutral or the ground, either one will give you the 120 volt measurement.  If all this checks out, a dogbone with male 50 amp 4 terminal plug on one end and a female 30 amp outlet on the other will enable you to power your RV.  Just be aware that you will not have a 30 amp breaker in your home electric panel to trip if you have a fault in your cable or RV, but the 30 amp breaker in your RV will still trip if you exceed 30 amps.

[mptjelgin]

It appears that Tesla recommends use of a NEMA 14-50 outlet, which is in fact exactly what our 50 amp RV's use. So as long as it was wired correctly, you should be fine as far as plugging in a dogbone. 

I agree with 57Becky above about testing the outlet, and being aware that you've got a 50 amp breaker from your home. 

[oldjohnt]

 If the Tesla Receptacle is wired and configured for 120/240 Volt Single Phase with Two Hots, Neutral, and an Equipment Ground ?????????????????  (I'm NOT there, use a volt meter to confirm that, so simple and easy to do)     SURE    it an be configured and utilized as the energy source for a 30 Amp 120 Volt RV which requires ONLY ONE Hot 120 VAC Leg. The 30 Amp RV requires 120 VAC with Three wires, One Hot, One Neutral, One Equipment Ground so you should be good to go. Even if the Tesla receptacle ONLY had 120 VAC and could only supply 30 amps, it could still be configured and utilized to power a 30 amp 120 Volt RV.

 NOTE AND CAUTION unless you provide the correct overcurrent protection for your only 30 amp rated RV power cord, there's a hazard (even if low) and you would be in violation of the NEC (If there's a 50 Amp breaker you CAN NOT use 30 amp rated wire in the circuit WELL DUH that's a no brainer for competent trained professional electricians). Reason being, if the Tesla circuit uses a 50 amp breaker that requites 50 amp wiring,   BUT  your RV cord is only rated for 30 amps. If you notice a 50 Amp RV uses a 50 Amp cord while a 30 Amp RV uses a 30 Amp cord that plugs into a power pedestal with 30 or 50 amp breakers !!!! WELL DUH.   Its cheap easy and simple to install a 30 amp fuse or circuit breaker to correctly supply your 30 amp rated RV power cord.  Of course you could just go back to your panel where there's a 50 amp breaker feeding that Tesla Receptacle and replace it with a 30 amp breaker NOW THATS SO SIMPLE CHEAP AND EASY to do and then you reduce the hazard and are in compliance with the NEC WHY NOT DO IT as it may prevent a fire or save a life !!!!!!!!!!!!!!!!!!!!!!!!!  

 FYI for the non sparkies here: SURE the 30 amp breaker in the RV panel will trip if loads DOWNSTREAM AND AFTER IT draw excess current, but the 30 amp rated wire FROM the Tesla receptacle TO the RV needs overcurrent protection of 30 Amps NOTTTTTTT 50 Amps  WELL DUH. In an RV its the power cord that's most vulnerable where it may lay in water or on sharp rocks or be run over by a bike or golf cart or you barefoot grandchild may step on it YIKES  30 Amp rated wire needs 30 Amp protection NOT almost double that !!!!  There's no place in the code or safe practice procedures where its okay to use 30 amp rated wire ran from the main panel to a sub panel with a 30 amp main breaker BUT USE A 50 AMP BRANCH CIRCUIT BREAKER IN THE MAIN PANEL !!!!!!!!!!!!!!!!!  Very very bad lol But okay if 50 amp rated wire is used...…..

 Still its Your RV, Your money, Your risk none of ours so do as you please.

 John T   Long retired Power Distribution Engineer and rusty on the NEC so no warranty but believe this remains true

[Kirk W]

7 hours ago, howie29 said:

 If I dogbone down from 50amp to 30amp off this receptacle, can I charge my 30 amp RV on this outlet or is the voltage something different than regular 50amp service at an RV park?

If your outlet is properly wired the answer is yes, but the only way to be sure is to check it yourself or get your own electrician. The odds are in your favor but unless it was checked you can't know for sure, just as with any outlet in a house that is new to you. If the house was inspected by a professional when you bought it, then you should be fine. 

[Darryl&Rita]

JohnT, if you're looking for "High Leg" power systems, look no further than the rail line. Most towns built along a railway line, have 3 phase power strung along Railway Avenue, to supply the grain elevator equipment. Watch out for the Red Leg.

[howie29]

Would a progressive industries 30amp EMS be sufficient protection and if I check with voltmeter what should I get 120v on each hot when probes are in a hot and a ground?

[Kirk W]

6 minutes ago, howie29 said:

Would a progressive industries 3amp EMS be sufficient protection and if I check with voltmeter what should I get 120v on each hot when probes are in a hot and a ground?

 

To your first question, yes the 30A EMS would be fine when using a dogbone from a 50A outlet and it will protect you from overvoltage or improper wiring. 

Using a voltmeter you should get 120V from each of the slots on the sides to the top U shaped opening that is ground and the same from either one to the bottom pin that is your neutral. If you measure from one side slot to the other you should see 240V. All of those are +/- 10%.

 

[howie29]

awesome thank you all as usual great info for the uniformed like myself.

 

[oldjohnt]

2 hours ago, howie29 said:

Would a progressive industries 30amp EMS be sufficient protection and if I check with voltmeter what should I get 120v on each hot when probes are in a hot and a ground

 Howie, good question, FWIW I agree with the above, here's my take:  NOTE FYI Hot and Ground are NOT the same (another complex topic) although either will still yield the voltages in question. 

 YES a 30 Amp EMS will suffice for a 30 amp RV not a problem.

 Given a proper wired 120 240 Volt Three Pole 4 Wire Grounding Outlet, If you stick one lead/probe of a volt meter on EITHER the Ground OR the Neutral terminals, you would then on the other lead/probe read 120 VAC from EITHER hot leg orrrrrrrrr if you measured L1 to L2 you would read 240. Of course a 30 Amp RV is 120 ONLY, so its 120 VAC from the Hot to EITHER Neutral or Ground. Piece of cake right ?? 

 Youre getting there, best wishes.

John T

[oldjohnt]

3 hours ago, Darryl&Rita said:

JohnT, if you're looking for "High Leg" power systems, look no further than the rail line. Most towns built along a railway line, have 3 phase power strung along Railway Avenue, to supply the grain elevator equipment. Watch out for the Red Leg.

 While they were used for good reason in certain applications (I designed several myself), if an amateur electrician or a lay person was messing with them things could go south in a hurry lol. You should have heard the electricians when I designed the first corner grounded Delta in our facility LOL.

Best wishes, John T

[Switchflicker]

On 9/27/2018 at 10:58 AM, oldjohnt said:

 Howie, good question, FWIW I agree with the above, here's my take:  NOTE FYI Hot and Ground are NOT the same (another complex topic) although either will still yield the voltages in question. 

 

 Youre getting there, best wishes.

John T

John T, On the first line I have a question. Should that not read NOTE FYI NEUTRAL and ground are NOT...??

Thanks for your excellent posts both here and on the YT forum.

Stan

[Lou Schneider]

On 9/26/2018 at 9:45 PM, howie29 said:

The previous owner of my home had a Tesla, and installed what I assume is a 50amp outlet (can receive a 4 prong plug, says 50amp on it) for charging.  If I dogbone down from 50amp to 30amp off this receptacle, can I charge my 30 amp RV on this outlet or is the voltage something different than regular 50amp service at an RV park?

Thank you.

In theory, the outlet should be the same as a 50 amp park outlet and you can use a 50 to 30 amp adapter to feed your RV.

But there is one very slight possibility to check.

The Tesla charger is a 240 volt load, so it sends little or no current back through the neutral wire.  Your 30 amp RV is the opposite, all of the current you use (up to 30 amps) will return via the neutral.

If the outlet is wired properly, no problem.  The neutral can handle up to 50 amps, just like the hot leads.

But if the installer went cheap and wasn't caught, he may have installed a smaller gauge neutral wire, since it's not expected to handle any significant amount of power.  This is a code violation but has been known to happen.

Unfortunately, a voltmeter test won't flag an undersized neutral as it doesn't draw any power from the circuit.  The only way to verify the neutral wire is the correct size is to open up the outlet and take a look.

On 9/27/2018 at 5:39 AM, Kirk Wood said:

If the house was inspected by a professional when you bought it, then you should be fine. 

I wouldn't expect a home inspector to go beyond verifying the outlet's voltages are correct, unless something else grabs his attention he won't open the outlet to check the wire sizes.

Like I said, this is a slight possibility but it's better to be safe than sorry.

[oldjohnt]

On ‎10‎/‎4‎/‎2018 at 9:09 PM, Switchflicker said:

John T, On the first line I have a question. Should that not read NOTE FYI NEUTRAL and ground are NOT...??

Thanks for your excellent posts both here and on the YT forum.

Stan

THANKS STAN !!!!!!!!!!!!!! My bad, my fingers get ahead of my OLD brain when I'm in a hurry grrrrrrrrrrrrrr see why I usually say NO WARRANTY LOL.

 

On ‎10‎/‎4‎/‎2018 at 10:00 PM, Lou Schneider said:

But if the installer went cheap and wasn't caught, he may have installed a smaller gauge neutral wire, since it's not expected to handle any significant amount of power.  This is a code violation but has been known to happen.

  Lou, INDEED code violations have been "known to happen"  Over many years practicing in the power distribution industry I couldn't count how many times I saw such, so often, however, they were NOT wired by a trained professional electrician....maybe the park owner or his non electrical trained hired hand ???

 

On ‎10‎/‎4‎/‎2018 at 10:00 PM, Lou Schneider said:

If the outlet is wired properly, no problem.  The neutral can handle up to 50 amps, just like the hot leads.

 I agree, the Neutral conductor from the panel to the outlet in question would (likely unless there's an exception ???) be rated for 50 amps. Of course, in the event one used a 30 amp RV power cord, its only rated for 30 amps and obviously requires 30 amp overload protection instead of 50  WELL DUH    (Electricians and NEC 101 lol).

 Better safe then sorry     DITTO THAT  Were sure on the same page there  !!!!

 As always, its been nice sparky chatting with you Lou, best wishes...……….

  John T

 

[NoDirectionHome]

I'm not sure but your Tesla charger may not work.  There is a handshake between the car and charger before a municipal charger turns on as there are two different types.  This may be incorporated into the home charger even if specific to that vehicle.