Charging from l14-30 generator outlet at the house (but NOT a generator)

Seattle · Mar 18, 2014

I had my house wired for a generator by a real electrician and it was inspected, so it should have been done properly. I realized the other day that I might be able to use this to charge my car at 220v and 30 amps but I don't have the right cables. Normally I just use 120v which has worked well enough. This is not about using my generator to charge my car, & I understand why that wouldn't be likely to work, I would need the kind of invertor generator that would produce perfect sinewave inverter. This is about connecting my external generator outlet to my car.

My house has a male l14-30 plug on the outside of the house in a waterproof box (the curved type 14-30), and I have a pretty heavy cable that I can use to connect that outlet to my generator (which also has a l14-30, my cable is female to male). In the event of a power failure, to use the generator, I have a switch on the electrical panel that I throw. The switch ensures that when generating power I am disconnected from the grid, so that when my generator is running, it won't send power back through the normal electrical system and shock a hypothetical lineman. Pretty standard stuff.

The Tesla adapter for 14-30 is not the curved variant 14-30 variant, so I think that won't work for me. What I think I need to connect this to my car is:

1. to set my tesla to only draw 30 amps on the 5-50 plug
2. get a female to female l14-30->5-50 adapter

I think this will work & is safe. Another way to accomplish this is:

1. get the tesla 14-30 adapter
2. get a double female l14-30 to 14-30 adapter.

The second way to do this might be better because I don't have to dial down the amps in the car.

Thoughts, advice?

Thanks,

Nick

Alysashley79 · Mar 18, 2014

If the 14-30 adapter doesn't work then I'm wondering if the 14-30 that you think you have is not a NEMA 14-30 but actually a TT30 possibly. I do find it a little odd that an electrician opted to use a 14-30 vs a 14-50 for a generator rough in. It would work but not for a very high wattage generator. Can you take a picture of the outlet?

@davewill it isn't live until you flip the breaker on the house which to the op is that something you would want to do to charge the car?

l would recommend just spending the $ and having a NeMA 14-50 installed.

Edited as I read the ops post incorrectly the first time.

davewill · Mar 18, 2014

I wouldn't expect that plug (it's not an outlet if it's male) to even be live unless you are actively feeding it from your generator. If it were live, the prongs on the plug would be a shock hazard...so I'd say, no, you can't use it.

FlasherZ · Mar 18, 2014

A couple of things - what you have is called an "inlet". By NEC code, it must be isolated from the mains by using either a transfer switch or an interlock. As a result, when the main breaker is active, this inlet may not be connected to the electrical system. The reason it's a male plug is that it's intended for feeding power to the house. It should never be used to provide power from the house (because having open, live pins is extremely dangerous).

It's a 14-30 because that's what typical portable generators use as an output, so you can use a standard 14-30 extension cord to connect the generator to the house, throw the interlocked breaker or transfer switch, and you're powered up.

- - - Updated - - -

Seattle said:
I think this will work & is safe. Another way to accomplish this is:

If you defeat the interlock, it will work. It is, however, NOT safe and you should never, ever do this. Having a male plug with live pins is called a "suicide cord" by most electricians and linemen for a reason.

Cosmacelf · Mar 18, 2014

Seattle - I'm not sure what you are trying to do here? Grab power from the L14-30 plug that is supposed to be plugged into the generator when the power fails? As FlasherZ said, that plug doesn't supply any electricity at all. It is supposed to receive electricity from the generator. So unless you rewired what the electrician set up, that L14-30 plug isn't connected to anything in the normal case.

When you throw the transfer switch, then the L14-30 is connected to the panel. But at that point, you've also disconnected the panel from the power grid, so you still have no power on the L14-30.

If you want to charge faster than your 120V connection, call your electrician and have him install a 240V outlet.

Rainbow · Mar 19, 2014

FlasherZ said:
A couple of things - what you have is called an "inlet". By NEC code, it must be isolated from the mains by using either a transfer switch or an interlock. As a result, when the main breaker is active, this inlet may not be connected to the electrical system. The reason it's a male plug is that it's intended for feeding power to the house. It should never be used to provide power from the house (because having open, live pins is extremely dangerous).

It's a 14-30 because that's what typical portable generators use as an output, so you can use a standard 14-30 extension cord to connect the generator to the house, throw the interlocked breaker or transfer switch, and you're powered up.

- - - Updated - - -

If you defeat the interlock, it will work. It is, however, NOT safe and you should never, ever do this. Having a male plug with live pins is called a "suicide cord" by most electricians and linemen for a reason.

Agreed. Not only is it unsafe but in most I think it is considered illegal, to have a hot male plug and to backfeed electrical power from a house to the utilities.

Seattle · Mar 19, 2014

What I was trying to accomplish was charge my car from a 220v outlet on the regular mains. I will test it but I'm almost positive it doesn't normally run power through this generator connection. What confused me was that I knew when using generator power in my house, I needed to turn the to switch to disconnect those circuits powered from the generator from the normal power system. But if that is really necessary, doesn't that imply that when I don't disconnect the generator circuits, there is a connection from the regular power? I guess the generator switch must do two things: (1) disconnect those circuits from regular power, and (2) connect the generator switch to those circuits. If it didn't do #2, then the gen outlet would be powered from main power and dangerous.

I was just hoping I had thought of a free way to get 220v. My garage is very far from the panel, so it was going to cost $1200 to run 80 amp 220 v there. But I could barely reach from the edge of the driveway to where the generator external power outlet box was.

FlasherZ · Mar 19, 2014

Seattle said:
What I was trying to accomplish was charge my car from a 220v outlet on the regular mains. I will test it but I'm almost positive it doesn't normally run power through this generator connection.

By code and law, it is not permitted to do this, so that generator power can't accidentally be back-fed to the grid while linemen are trying to work on it (it can kill them).

What confused me was that I knew when using generator power in my house, I needed to turn the to switch to disconnect those circuits powered from the generator from the normal power system. But if that is really necessary, doesn't that imply that when I don't disconnect the generator circuits, there is a connection from the regular power? I guess the generator switch must do two things: (1) disconnect those circuits from regular power, and (2) connect the generator switch to those circuits. If it didn't do #2, then the gen outlet would be powered from main power and dangerous.

Yes, you should have one of two solutions -- either a "breaker interlock" which is a mechanical protection that forces your generator breaker open (or "off") while your main grid breaker is closed (or "on") and vice-versa, or a "transfer switch" which (manually or automatically) selects between two power feeds - your grid and your generator. If you post photos of your panel and generator switch, I'll be able to help identify.

I was just hoping I had thought of a free way to get 220v. My garage is very far from the panel, so it was going to cost $1200 to run 80 amp 220 v there. But I could barely reach from the edge of the driveway to where the generator external power outlet box was.

Is your generator inlet near your panel? If so, you may be able to place another outlet there for less, and connect to it. You may also find that a 50A circuit is less expensive than the 100A circuit you had quoted.

Seattle · Mar 20, 2014

Thanks for the great idea to add an outlet near my generator inlet - that should well work for me and be cheap.

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Charging from l14-30 generator outlet at the house (but NOT a generator)

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