I'm looking to install a hardwired EVSE, but currently I have the necessary wiring going into a NEMA 14-50 outlet.
Can I splice the wiring going into the outlet and run new wire to the EVSE? The EVSE would go above the outlet in the picture. Advice on what's needed would be appreciated.
It's pretty straightforward.
Remove the wires from the old receptacle. Your two hots are brown and yellow, and it doesn't matter which is which. Usually that is color coded red/black or black/black, but brown/yellow is absolutely fine.
The cover plate on that junction box is what you call a mud ring, meant to be behind drywall. You don't need that, so you can get a blank cover plate for that box, they make domed covr plates if you want that.
The old receptacle and mud ring go into storage. A NEMA 14 is a nice modern safe receptacle, no reason to throw it out.
You run either a whip or EMT conduit from the charger to the junction box through one of the knockouts.
Then you splice the wires inside the junction box. You may not need neutral; if not, just put a wire nut cap on it and tape it so it stays.
Use the size of wire specified in the installation instructions, or larger.
Change the circuit breaker to the size specified in the installation instructions. If the instructions do not say, then look at the wires you used to connect, particularly if the wire whip came with the charger. Otherwise breaker size is determined from the smallest conductor size (do not consider grounds or wiring that is entirely inside the charger proper):
It depends on what version, if any, of the National Electrical Code is being enforced in your area.
The 2017 version of the National Electrical Code prohibits any other outlet but the EVSE. So you couldn't add it as a hardwired device unless you eliminate the receptacle.
2017 NEC 625.40 Electric Vehicle Branch Circuit. Each outlet installed for the purpose of charging electric vehicles shall be supplied by an individual branch circuit. Each circuit shall have no other outlets.
The 2014 would still allow it IF your wire size and breaker was large enough to handle 100 percent of the other load plus 125 percent of the EVSE. Probably not likely in your situation but possible.
2014 NEC 625.40 Overcurrent Protection. ..... Where noncontinuous loads are supplied from the same feeder or branch circuit, the overcurrent device shall have a rating of not less than the sum of the noncontinuous loads plus 125 percent of the continuous loads.
The 2014 version of the NEC would allow you to use that existing receptacle to plug in your EVSE.
The 2017 will not allow it unless it is portable equipment not fastened in place.
If you are under the 2014 Code consider attaching a plug to the EVSE and just plugging it in. Then swap it when you need to use the other equipment.
If you are under the 2017 Code, you need to run another circuit if the equipment is to be fastened in place or the receptacle can't be a 3 pole 4 wire like you have there.
So, it all depends on who will be inspecting it and which Code you are using.
Good luck and stay safe.
Why are your wires Yellow and Brown?
BOY (Brown Orange Yellow) color coding is supposed to indicate a three phase 480V power system, where each hot B,O,Y each measure 277V to Neutral and 480V Hot to Hot.
If there is any chance that outlet is a 480V outlet, you need to verify that before proceeding. If you installed this on your own and it indeed is a 240V outlet, please use correct color coding. Residential split phase 240V service is Black/Red/Blue Blue if you have 3 phase power coming in (common in apartment buildings/condos)
