Wire size for wall charger

[Sage Brush]

All said and done this DIY saved me about $1000. The high bid I got was $1200 and the low was $780.

I kept it super basic and cut a small hole in the drywall below the panel in an area I knew the charger would cover up. 4/2 Romex took up every bit of the room provided by knockout in the bottom of the panel. 60 AMP Double Pole breaker on a 200 AMP service bus. All said and done I’m into this under $80 total. The cost of the wall charger was covered by my Energy Provider.

Total install time was 1 hour from flipping the main to emptying the dustpan after commissioning. I had to cut 1 hole into the drywall to route the Romex, use one 1/2” knockout at the bottom of the panel. A hole saw was helpful in making a clean hole for the back of the Wall Charger. Along with that the install required basic tools: a cordless drill, wire strippers, a pocket knife, and an insulated screwdriver.

I’m pulling a full 48 AMPs at 240v and am pretty happy with how it sits now.

 

[jcanoe]

In some places local code may have a minimum height requirement for switches, outlets and equipment installed in a garage or outdoors. In my location (Maryland) it is 48 inches minimum from the garage floor for electrical equipment installed inside a garage.

 

[iluvmacs]

It seems it would be a lot easier running through the basement joists and along the garage ceiling rather than using thhn via sch40 conduit.

Definitely way easier. Note that MC has the same ampacity ratings as NM-B (Romex) at 6 AWG — 55A. I don't know of any EVSEs that support a 55A setting (though they really should!!), so you will need to use a 50A setting and circuit breaker now. Most people would have just used NM-B instead of MC, to be honest (assuming it's allowed in your jurisdiction). Flex conduits are annoying in many other ways, with little benefit over NM-B. And you need a special cutting tool to cut it right. It's used way more in commercial electrical work since that's not normally a place for NM-B.

 

[iluvmacs]

4/2 Romex took up every bit of the room provided by knockout in the bottom of the panel. 60 AMP Double Pole breaker on a 200 AMP service bus. All said and done I’m into this under $80 total. The cost of the wall charger was covered by my Energy Provider.

Total install time was 1 hour from flipping the main to emptying the dustpan after commissioning. I had to cut 1 hole into the drywall to route the Romex, use one 1/2” knockout at the bottom of the panel.

Uhhhh did you put a NM-B clamp or bushing on that cable as it exited your panel?? I'm guessing from the suggestion that you used a 1/2" KO that you didn't, since 4/2 would surely need at least 3/4"... That's definitely a code requirement.

 

[MY-Y]

Uhhhh did you put a NM-B clamp or bushing on that cable as it exited your panel?? I'm guessing from the suggestion that you used a 1/2" KO that you didn't, since 4/2 would surely need at least 3/4"... That's definitely a code requirement.

I was going to say the same thing. Sounds like no clamp. You should re-pull the wire, use a bigger hole with the proper clamp. I suspect there is a 1" hole available in the bottom of your panel.

Since it looks like you are fairly new at this type of job, I suggest you use a torque wrench for the connections. Tesla gives the spec for their lugs in the manual.

 

[MY-Y]

Definitely way easier. Note that MC has the same ampacity ratings as NM-B (Romex) at 6 AWG — 55A....

I've never seen 60C MC. Why would 6 gauge MC be rated for 55 amps instead of the typical 75 amps at 90C? Even considering 75C equipment, 6 gauge MC is rated for 65 amps, not 55.

 

[Sage Brush]

Uhhhh did you put a NM-B clamp or bushing on that cable as it exited your panel?? I'm guessing from the suggestion that you used a 1/2" KO that you didn't, since 4/2 would surely need at least 3/4"... That's definitely a code requirement.

Yaffirm I had clamps on both the back of the wall charger and bottom knockout. They were the most time consuming part of the process!

 

[iluvmacs]

I've never seen 60C MC. Why would 6 gauge MC be rated for 55 amps instead of the typical 75 amps at 90C? Even considering 75C equipment, 6 gauge MC is rated for 65 amps, not 55.

Oops, my bad on this one. 75°C ratings should be fine as long as that's the insulation type for the wire used and all termination ratings (which it surely is).

(Ugh, I can't go edit my post now... )

 

[GP1200X]

Why not just attach the conduit to the bottom of the joist instead of drilling them all out?

I never really saw it done that way. Probably code acceptable since it is a metal jacket. I may look into that.

 

[GP1200X]

Oops, my bad on this one. 75°C ratings should be fine as long as that's the insulation type for the wire used and all termination ratings (which it surely is).

(Ugh, I can't go edit my post now... )

Shoot!......I missed these last two posts and only saw the original first one. I tried to stop the MC 6/2 shipment just in case but that was a waste of time. I then researched their site again (NNC) and it stated that the cable was THHN -75 amps at 90C so I figured it wouldn't it have the same home installation rating (65 amps) as THHN in conduit. I spent a few hours trying to verify that MC 6/2 was treated as NM and found nothing. Came back to ask why and then I read these two notes! At least I'm good to go now and have my pathway laid out. MC will make the install so much easier with fewer additional pieces needed.

 

[MY-Y]

Looks like you're in good shape. Don't forget the special tool to cut MC.

 

[GP1200X]

Looks like you're in good shape. Don't forget the special tool to cut MC.

I bought one for the MC 12/2 I was running but I realized it probably won't work with the MC 6/2 ...diameter too large at .8"

Don't have the MC 6/2 yet but only have to make one cut for the needed length. Can I cut the MC with an extra few feet on both ends, unravel it and then snip or dremel the metal off? Don't know what the MC 6/2 is like compared to the 12/2 I have.

Question: Someone mentioned attaching the MC to the underside of the joints in the basement. Mine is unfinished but insulated for the above floor living space. By code are there any restrictions as why I couldn't just attach it to the underside of the joints right up along the top of the wall and follow the inside edge of the wall? Bought two wiring books but haven't seen anything yet about this.

 

[iluvmacs]

I bought one for the MC 12/2 I was running but I realized it probably won't work with the MC 6/2 ...diameter too large at .8"

Don't have the MC 6/2 yet but only have to make one cut for the needed length. Can I cut the MC with an extra few feet on both ends, unravel it and then snip or dremel the metal off? Don't know what the MC 6/2 is like compared to the 12/2 I have.

Question: Someone mentioned attaching the MC to the underside of the joints in the basement. Mine is unfinished but insulated for the above floor living space. By code are there any restrictions as why I couldn't just attach it to the underside of the joints right up along the top of the wall and follow the inside edge of the wall? Bought two wiring books but haven't seen anything yet about this.

Yeah, you could pretty certainly do that to cut the MC. Just put on work gloves when you do this -- not just because of the sharp edges, but the metal tends to be really grimey/greasy and will get your hands really dirty.

Putting MC exposed on the bottom of joists (or outside edge of wall studs) depends on how your inspector interprets "subject to physical damage". Might be best to just ask them first.

 

[MN-MS100D]

Need to use a red hat at the connector to eliminate sharp edges from compromising the insulation.

 

[GP1200X]

Have the MC 6/2 wire from NNC cable.....75 feet at $3.05 a foot even with a promo code! It is .79" OD and JUST fit the HD cutting tool for $39.
I think their MC 6/3 is .855" OD and probably won't fit in the track. 1" drill bit perfect size for the few spots I had to go through.

 

[ChrisMPK]

Question: Someone mentioned attaching the MC to the underside of the joints in the basement. Mine is unfinished but insulated for the above floor living space. By code are there any restrictions as why I couldn't just attach it to the underside of the joints right up along the top of the wall and follow the inside edge of the wall? Bought two wiring books but haven't seen anything yet about this.

If using metal clad wire you can definitely just fasten this wire to the bottom of the joist. It will be a lot quicker and easier. If, however, you are planning on finishing your basement in the near future, you may want to drill the joist to make that project easier.

The jacket on the 6/2 is similar to the 12/2 you have. You can use tin snips to cut it, just use the red plastic sleeve to protect the conductors where they exit the metal (it should come with them).

 

[GP1200X]

The jacket on the 6/2 is similar to the 12/2 you have. You can use tin snips to cut it, just use the red plastic sleeve to protect the conductors where they exit the metal (it should come with them).

Had to buy those red hats for all my MC (pretty cheap for a bag of them). Both the 12/2 and the 6/2 did not include them - puchased 12/2 at HD and 6/2 at NNC. Maybe they're all cutting corners nowadays.

 

[GP1200X]

I have my Chargepoint mounted and cabled to the panel...57 foot run. The Chargepoint uses 2 hots and a ground and it states in the manual that for hardwiring the maximum THHN AWG size supported by the integrated thumb clamps is 6.

Here's the part that I do not understand. It shows with a 60 amp breaker the Chargepoint can be set for 48 amps. But then it also shows that with a 70 or 80 amp breaker the Chargepoint can be set to use up to 50 amps. The Chargepoint Home Flex is for a homeowners installation, so what are they implying by stating that 50 amps can be set with a 70 or 80 amp breaker using THHN AWG 6? Can I install a 70 amp breaker using the THHN #6 and set the Chargepoint to 50 amps since they seems to be what they are implying. Thanks,

 

[jcanoe]

The maximum amperage using THHN No. 6 wire (THHN wire being rated for 90C/194F), in this installation, would be determined by the temperature limit of the circuit breaker. A residential breaker will be rated for up to 60C (140F) or 75C (167F). Assuming the breaker is rated to 60C (140F) then a 55A limit would apply.

The Chargepoint EVSE can be set to a maximum of 50A. This is under the 55A limit and well within the 80% rule for EV charging for a 70A circuit. In this installation No. 6 THHN when used with a 70A (60C rated) breaker can support the Chargepoint EVSE set to operate at 50A.

 

[Rocky_H]

The maximum amperage using THHN No. 6 wire (THHN wire being rated for 90C/194F), in this installation, would be determined by the temperature limit of the circuit breaker. A residential breaker will be rated for up to 60C (140F) or 75C (167F). Assuming the breaker is rated to 60C (140F) then a 55A limit would apply.

I think all residential breakers are rated up to 75 degrees C. 6 gauge wire in conduit (THHN) is rated to 65A at 75 degrees C.

The Chargepoint EVSE can be set to a maximum of 50A. This is under the 55A limit and well within the 80% rule for EV charging for a 70A circuit. In this installation No. 6 THHN when used with a 70A (60C rated) breaker can support the Chargepoint EVSE set to operate at 50A.

Your numbers aren't being done correctly, but I think you're accidentally coming out to the right answer.

Here's the part that I do not understand. It shows with a 60 amp breaker the Chargepoint can be set for 48 amps. But then it also shows that with a 70 or 80 amp breaker the Chargepoint can be set to use up to 50 amps. The Chargepoint Home Flex is for a homeowners installation, so what are they implying by stating that 50 amps can be set with a 70 or 80 amp breaker using THHN AWG 6? Can I install a 70 amp breaker using the THHN #6 and set the Chargepoint to 50 amps since they seems to be what they are implying. Thanks,

So I think this is one of those odd examples where you do get to use the "round up rule" in NEC. The numbers look weird, but I think it's being followed correctly.

As I mentioned above, the limitation for 6 gauge THHN is 65A as the maximum rating limitation of the circuit. Continuous load can only be 80% of that, which is 52A. So that's where they get the 50A setting, which properly fits within it. But to have a 65A rated circuit, you generally can't find a breaker that is exactly 65A. So code allows a next sized up reasonably available breaker size, which would be 70 or 80. BUT THAT DOES NOT MAKE IT A 70 OR 80 AMP RATED CIRCUIT! It is still limited by the wire, so it's a 65A circuit.