Subpanel Question

[TravisT]

Trying to plan out some electrical requirements and looking for some feedback. Currently have a 100A subpanel in the 3 car attached garage fed by a 200A main panel. Currently running 2-20A circuits for outlets and a 30 or 40A circuit for a mini-split (have to check, don’t recall). I just bought a Tesla, and need to install the L2 charger. It accepts multiple circuit sizes, but maxes out at 60A.

1. For a 60A circuit run about 50ft from the subpanel, can I run 6 awg thhn in 3/4” conduit, or do I need to bump up to 4 awg? If so, I’ll have to also step to 1” conduit (EMT) I believe.

2. I really had my eyes on one of the EMax compressors (40A circuit) and still need to wire my 220V TIG/plasma circuit. I know I can oversubscribed the subpanel, but I’m not sure by how much given the load types. Do I need to compromise somewhere?

 

[wyliesdiesels]

If it pulls 60a, then you would need wire rated for 125% of 60a, so 75a rated wire, thus #4 cu THWN.

 

[TravisT]

Thanks for the reply. Maybe I’m reading the documents wrong (see attached). Technically, I think it pulls 48A, but calls for a 60A breaker in the manual along with 6 awg wire, but says to upsize where required. Does the 125% rule still apply?

 

[AntonLargiader]

That's illegible.

 

[TravisT]

Sorry about that. Try this one.

 

[AntonLargiader]

It looks like they are building the 125% into their installation instructions. If installing for max output, just follow them. I think the "Upsize conductors if necessary" part is about derating for other reasons such as conduit fill.

 

[sberry]

If cable too.

 

[TravisT]

That makes sense, and why I wanted to check to get some opinions.

What about voltage drop? Is that a concern with a ~50ft run?

Also, any comments on question #2?

 

[sberry]

Do you need to weld and compress air at the same time? Same for charging. Not only that the breaker isnt the actual draw.

 

[justsam]

Current Tesla vehicles have a maximum charge rate of 48 Amps, so your 60 Amp circuit is correct, unless there is a chance of a second EV, in which case Tesla Wall Connectors are set up for power sharing, and could make use of the power. Remember the actual charger is in the vehicle, and the vehicle determines rate of charge. There is a reason Tesla calls their EVSE (Electric Vehicle Supply Equipment), a Wall Connector as there is no "charger" in it.

In regard to panel capacity it is all about concurrent use. Most people charge vehicles in "off hours" to make use of time of day billing. You will not use Tig and plasma together, you will use plasma and compressor, and you could have HVAC running. I do not see it likely that you would exceed the 100 Amp breaker for your sub panel, or at least it would be rare.

 

[wyliesdiesels]

Thanks for the reply. Maybe I’m reading the documents wrong (see attached). Technically, I think it pulls 48A, but calls for a 60A breaker in the manual along with 6 awg wire, but says to upsize where required. Does the 125% rule still apply?

ok so continuous load is 48a, then you apply 125%, which gives you 60a.

youre good to go with #6 THWN in conduit.

 

[TravisT]

That all makes sense, I guess I was getting hung up on whether the wire had to be 125% of the over current device (60A breaker) or of the actual demand from the device (48A). I would assume if this circuit wasn’t hard-wired to the wall connector, it may be different.

I checked my mini split circuit - it’s 30A. I feel better about not over subscribing the subpanel now, but there is a chance the compressor could kick on while the hvac is on and the car charging. I’ll just have to manage that a little better than I would with a bigger panel.

 

[sberry]

Your split may not use 30A and how many hp is the comp? Many 5 are now actually 22 run and would almost bet the AC is well under 20. A comp has such a short cycle also. I think you may be able to set the car for 30A service too.

 

[theoldwizard1]

I really had my eyes on one of the EMax compressors (40A circuit) and still need to wire my 220V TIG/plasma circuit.

Do you need to weld and compress air at the same time?

Plasma requires air at the same time.

 

[TravisT]

I believe you’re correct about setting the EV charger to a lower current draw via the wall connector.

You’re also correct that the mini-split likely pulls less than 30A. I would imagine a full current charge to the car and the compressor starting are likely the biggest demands. I think I’ll be good with all I have, and the compressor is a future add, so not even in the equation yet.

 

[Noltz]

My electrician approved 6ga THHN for my 17M run for a Tesla/Other L2 charger. I don't own an EV yet so I installed a 14-50 plug and a 50A breaker for now. That was into 1" PVC conduit, 6-6-6-6.

I think Travis is right and between your Tesla and your AC you'll be close to 80%, but not over, with enough space for your intermittent loads in the garage. But you won't be charging your Tesla while running your AC with your compressor & plasma going. I think that's just simple load management (like not running 2 space heaters on the same 120 circuit). When you're going to play with the plasma cutter, park the Tesla outside.

 

[sberry]

I have loaded up 100 a lot a couple times, never tripped the main but didnt have a single continuous load of 50 on it. I serviced a bar, tavern, it was astornomical how much was running on 200, they had 5 50A fryers, and the whole rest of the place, probably 30 run air on top of it, coolers, 3 micro, coffee, lights, gobs of s6tuff.

 

[75gmck25]

You might want to check prices for 2-2-2-4 AL Mobile Home Feeder or 2-2-2-4 AL SER vs. 6 AWG copper., since MHF and SER is available from so many sources and its relatively cheap. MHF is usually dual rated so it can be run indoors in conduit and also buried outdoors. SER is indoor only and does not require conduit inside. It would require bigger conduit for 2-2-2-4, but you would have no doubts about it handling the current.

Bruce

 

[TravisT]

I’ll probably stick with the copper route in EMT. Costs a little more, but my run isn’t too long.

One other question - I think I should only need 3x 6 AWG lines since the wall connector only requires L1/L2/G from what I can tell. Can anyone confirm? I can pull a 4th in 3/4” EMT and still be within fill specs I believe, but if the 4th line (N) isn’t necessary, I can cut a little bit of cost there.

 

[wyliesdiesels]

You might want to check prices for 2-2-2-4 AL Mobile Home Feeder or 2-2-2-4 AL SER vs. 6 AWG copper., since MHF and SER is available from so many sources and its relatively cheap. MHF is usually dual rated so it can be run indoors in conduit and also buried outdoors. SER is indoor only and does not require conduit inside. It would require bigger conduit for 2-2-2-4, but you would have no doubts about it handling the current.

Bruce

SER is permitted for both indoor and outdoor use but can ONLY be used above ground outdoors...

 

[dcg9381]

Note, 6ga is tight in 3/4 if you're pulling 4 wires. If you're pulling just 3, I get it. Make sure it's rated for 60A at appropriate length. If you want us to look at charger spec, post a link.

I'll be very surprised if your mini-split is doing 30 or 40A unless it's multi-head and cooling multiple rooms. My 24k units pull under 15A.. Probably more like 10A.

Doesn't the L2 charger allow you to set charge rate?

Even with everything you've got going on, I think that you'll be fine on 100A. You're concerned about over-subscribing the panel - you can post make/model, but I haven't seen one recently that wouldn't bus 100A.

 

[TravisT]

The charger specs/manual was attached in post #5:

https://www.garagejournal.com/forum/showpost.php?p=8802803&postcount=5

I haven't put an ammeter on it, but the mini-split called for a 30A breaker. That could have very well been with overhead included. I'm not sure exactly what it pulls, but would also agree it is probably much less than 30A. The mini-split is a 24K BTU and cools either a one-car garage or a 3 car garage, depending on if the door between them is open.

I believe there are a couple of options for charge rates - you can set the circuit size on the charger (from what I understand) as well as the charge rate in the car. I don't have either yet, so I'm not 100%

 

[dcg9381]

The manual referenced doesn't clarify it for me (for certain).. What generation charger is it?

 

[TravisT]

My mistake, that was just one page of the manual.

Here's the link to the full manual:

https://www.tesla.com/sites/default/files/support/charging/Gen3_WallConnector_Installation_Manual.pdf

It is a gen 3 wall connector...