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Tapping into Wall Mounted Connector to get 240 V, 25 amps or so.

dmurphy

Woof.
Dec 7, 2018
3,541
4,729
New Jersey - Morris County
No, that's not how that works. They would need the transformer to get 120V.

Exactly. The RV is trying to provide all of its 120V loads using a hot and the neutral to complete the circuit. The J1772 supplying this whole situation through that adapter is only the two hot lines that are 240V apart from each other (or 208V), and there is no neutral provided there. And I would be horrified to think if whoever made that adapter tried to use a hot to ground as a legitimate current path for the circuits. That would be dangerous.

Yikes! I apologize - I didn't look at the J1772 spec so didn't realize the neutral doesn't go through to the car. You're absolutely right, that's terrifyingly dangerous.

That said, a typical RV 50a setup is much like a residential circuit panel; two split-phase hots, a neutral and ground. Why would they need a transformer to step down to 120V? They use residential-grade circuit breakers - taps into either of the split phases. You're right though, there's no neutral with the J1772 adapter!

Smaller RVs of course use the TT-30 connector which is 120V/30a. Single hot phase, plus a neutral and ground.
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,270
7,322
Boise, ID
Yikes! I apologize - I didn't look at the J1772 spec so didn't realize the neutral doesn't go through to the car. You're absolutely right, that's terrifyingly dangerous.
I think you're still misunderstanding what this situation was, like you think it originates from a 14-50 outlet, before going through adapters and conversions, with your comments about "go through". There is no "through" because there is no neutral anywhere in this. This is about someone parking next to an actual J1772 charging station and trying to make that J1772 EV charging handle convert to something their RV can use. So all it has for voltage is the two power pins in that handle, which would be 240V or 208V. Someone made a really hokey fake 14-50 receptacle with it. I couldn't guess what someone did with the supposed neutral pin, since there's nothing that could connect to it--it's probably just disconnected.

I see now why EVSEAdapters only makes a 6-50 version of this, because that is semi-legitimate, providing only the appropriate Hot1, Hot2, and ground that that type of outlet would already have and not worry about a dangerous disconnected neutral.

That said, a typical RV 50a setup is much like a residential circuit panel; two split-phase hots, a neutral and ground. Why would they need a transformer to step down to 120V? They use residential-grade circuit breakers - taps into either of the split phases. You're right though, there's no neutral with the J1772 adapter!

Because all loads in an RV are made to use 120V, and this J1772 charging station that is the source for all this just doesn't offer that.
 

dmurphy

Woof.
Dec 7, 2018
3,541
4,729
New Jersey - Morris County
I think you're still misunderstanding what this situation was, like you think it originates from a 14-50 outlet, before going through adapters and conversions, with your comments about "go through". There is no "through" because there is no neutral anywhere in this. This is about someone parking next to an actual J1772 charging station and trying to make that J1772 EV charging handle convert to something their RV can use. So all it has for voltage is the two power pins in that handle, which would be 240V or 208V. Someone made a really hokey fake 14-50 receptacle with it. I couldn't guess what someone did with the supposed neutral pin, since there's nothing that could connect to it--it's probably just disconnected.

I see now why EVSEAdapters only makes a 6-50 version of this, because that is semi-legitimate, providing only the appropriate Hot1, Hot2, and ground that that type of outlet would already have and not worry about a dangerous disconnected neutral.



Because all loads in an RV are made to use 120V, and this J1772 charging station that is the source for all this just doesn't offer that.


Yes, we’re approaching from different angles. I’m coming from the “RV hooked up to normal power” angle ... but yes, with a J1772, there’s no neutral to be found. That’s what I glossed over initially! Duh. You’re right of course.

Scary enough, EVSE *does* make a J-772 to 14-50 adapter. J1772 to NEMA 14-50 Adapter – EVSE Adapters
https://www.evseadapters.com/products/j1772-to-14-50-adapter/
I’m guessing neutral is a dead pin and not tied to ground since that would be a failure of epic proportions.

The only thing I could see this adapter being useful for is to run a resistive heater of some sort. Otherwise .....?
 

davewill

Active Member
Feb 5, 2014
1,825
1,975
San Diego, CA, US
...
Scary enough, EVSE *does* make a J-772 to 14-50 adapter. J1772 to NEMA 14-50 Adapter – EVSE Adapters
I’m guessing neutral is a dead pin and not tied to ground since that would be a failure of epic proportions.

The only thing I could see this adapter being useful for is to run a resistive heater of some sort. Otherwise .....?
The most likely use for either adapter would be a welder or shop tool that uses 240v. You COULD run anything that is natively DC and has a 120/240v power supply, but most things like that can be run off a normal wall plug.
 

PhysicsGuy

Member
Apr 16, 2020
98
89
California
I am thinking there is a convenient spot right below the WMC where an electrician could connect a nema 14-50 box or tag. I don't think there would be a problem...
 

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