Wiring for Outside to Inside Install (Romex, MC or THWN)

[blancmik]

Hoping to get some clarification on my specific use case. I'm a new M3RWD owner (5 weeks now) and I quickly installed a 14-50 outlet after I picked up the car. I thought I was doing good:

- Installed a 50A Circuit Breaker from the Panel feeding power to the house
- Used 6/3 Romex (from Home Depot) through Conduit to the soffit and then right down the wall to the 14-50 outlet

As I continue to read the threads, I believe I should not have used Romex since some of the wire it in PVC conduit, thinking I should replace with THWN, but not sure that's appropriate for use behind drywall? If this makes any difference, I have a wall charger on order to replace the outlet (should have just done the wall charger in the first place).

The wire run is 12 feet - up the wall from outside via PVC, through the soffit into the attic space, drilled the top plate and then back down the wall behind the drywall to the outlet.

PVC run for the EV charger is the far right side one. The left PVC run is for my pool panel.

Current 14-50 outlet.

 

[Cosmacelf]

Running NM-B (romex) in conduit is allowed by code. When replacing your 14-50 receptacle with a Wall Connector, just set the maximum charge rate to 40A when you do the initial Wall Connector set up and you’re good to go. Your charge rate will increase from the 32A you get from the Mobile Connector.

 

[ATPMSD]

just set the maximum charge rate to 40A

Actually you will set the wall connector to a 50A circuit and it will charge at a maximum of 40A.

 

[Cosmacelf]

And you are correct that THHN wires are not allowed to be run free behind drywall, they need to be in conduit. So if you wanted a 48A charge rate, you’d have to run continuous conduit in your attic and behind your drywall, then you’d be able to pull 6 gauge THHN wire and get 48A charge rate. Not worth it IMHO.

You can‘t use 6/2 MC cable to replace the outside conduit since MC cable isn’t weather proof. You could run continuous conduit to an attic junction box and then transition to MC cable for the run down the drywall.

OR the way I would have done this from the start is to enter the panel from the back, drill a hole there and run MC cable through the wall straight into your garage without having to go up and over.

 

[blancmik]

Awesome, thank you both for the quick reply! I may look at going straight through the panel when I install the wall connector.

 

[ATPMSD]

If you decide to run new wire, check the wire’s rated capacity. If it is 60A or greater you can run the wall connector at 60A and it will charge at 48A. Note that #6 Romex is rated at 55A and is not acceptable for use in a 60A circuit.

Good luck on your project!

 

[Big Dog]

And you are correct that THHN wires are not allowed to be run free behind drywall, they need to be in conduit. So if you wanted a 48A charge rate, you’d have to run continuous conduit in your attic and behind your drywall, then you’d be able to pull 6 gauge THHN wire and get 48A charge rate. Not worth it IMHO.

You can‘t use 6/2 MC cable to replace the outside conduit since MC cable isn’t weather proof. You could run continuous conduit to an attic junction box and then transition to MC cable for the run down the drywall.

OR the way I would have done this from the start is to enter the panel from the back, drill a hole there and run MC cable through the wall straight into your garage without having to go up and over.

Not an electrician, but as I hate the look of unnecessary conduit, my first reaction was, 'why not drill straight thru the garage wall from the panel?' Not only for the cosmetics but it's a much shorter run. At least that is what I woudl have asked an electrician since I'm not that much of a DIY'er.

 

[Eric33432]

Nice job. I would not change anything, but install the Tesla Wall Connector if you feel the urge. Keep in mind, the M3 RWD maximum charge rate is 32 amps.

If you already installed a GFCI breaker (which most locations now require), you will need to replace it with a regular 50 amp breaker for the TWC.

If you did not install a GFCI, you should do so, or install the TWC.

It is a Wall Connector. The charger electronics is in the car.

You can now buy them at Best Buy, at least in SE FL where I live.

 

[brkaus]

Running NM-B (romex) in conduit is allowed by code. When replacing your 14-50 receptacle with a Wall Connector, just set the maximum charge rate to 40A when you do the initial Wall Connector set up and you’re good to go. Your charge rate will increase from the 32A you get from the Mobile Connector.

While NM-B is allowed in conduit, outdoor conduit is considered a wet location. NM-B is not allowed in a wet location.

 

[Cosmacelf]

While NM-B is allowed in conduit, outdoor conduit is considered a wet location. NM-B is not allowed in a wet location.

Outdoor conduit (metal, pvc) is the weather protection and you are allowed to run Nm-b in an outdoor conduit assuming it is installed correctly.

 

[brkaus]

Outdoor conduit (metal, pvc) is the weather protection and you are allowed to run Nm-b in an outdoor conduit assuming it is installed correctly.

NEC 300.9? Or are there more exceptions? (This is what I was told by the electrician that installed our pool sub-panel)

Just now searching I did find this -

Exception: The raceway shall not be considered a wet location if:

(1) The section of raceway routed in a wet location above grade does not exceed 1.8 m (6 ft) in length;
(2) Any fittings or conduit bodies are watertight and listed for use in wet locations; and
(3) All termination points of the raceway are only open in any of the following:

1. A dry location;
2. Equipment suitable for outdoor use; or
3. Equipment listed for use in a wet location

 

[blancmik]

Thanks, based on that description, I think that further confirms that I'm okay with the conduit and NM-B.

With that said, I really liked the idea of just running out of the back of the panel directly through the wall as Cosmacelf suggested and I did confirm that there is even a knockout available on the back of the power box. Just need to convince the wife that I need the wall connector... she seems to like the idea of not having the conduit on the side of the house. Decisions decisions

​

 

[brkaus]

Thanks, based on that description, I think that further confirms that I'm okay with the conduit and NM-B.

With that said, I really liked the idea of just running out of the back of the panel directly through the wall as Cosmacelf suggested and I did confirm that there is even a knockout available on the back of the power box. Just need to convince the wife that I need the wall connector... she seems to like the idea of not having the conduit on the side of the house. Decisions decisions

​

It's really up to the inspector. Most of these type of installs requires a permit.

 

[Eric33432]

You did a really good job with your installation.

If you did not already install a GGCI breaker, you should consider changing it to such if you want it to be a perfect job, or install the Tesla Wall Connector, which I like but is not necessary and will not charge the M3RWD any faster since it is limited to 32 amps.

Hope you are enjoying the M3RWD! My daughter has one and loves it! My Model X came with a Mobile Connector (back before they stopped providing them) which I gave to her and it is plugged into a NEMA 6-50 in the garage with no issues.

 

[davewill]

Thanks, based on that description, I think that further confirms that I'm okay with the conduit and NM-B.

With that said, I really liked the idea of just running out of the back of the panel directly through the wall as Cosmacelf suggested and I did confirm that there is even a knockout available on the back of the power box. Just need to convince the wife that I need the wall connector... she seems to like the idea of not having the conduit on the side of the house. Decisions decisions

​

If you do decide to do the Wall Connector, why remove the 14-50? Keep it as a backup just in case the wall connector ever fails.

 

[Eric33432]

If you do decide to do the Wall Connector, why remove the 14-50? Keep it as a backup just in case the wall connector ever fails.

But wire them to separate circuits!