Main panel / Sub Panel (V2)

[PatrickGoodyear]

Larry, thank you for your reply. Your reply describes my initial thought. However, if I consider how a circuit breaker trips, the need for the fault current to return to the utility transformer, it seems like an EGC is needed back to the meter-main/transfomer neutral connection. NEC 250.32(B)(1) requires the EGC, and a re-grounded neutral is only allowed in installations prior to 2008 NEC.

 

[mikeames]

I think he is talking about 80% of the over-current protective device which is 56 amps

What he wrote

I could put an 80 amp on the Tesla charger which will draw 64 amps.

makes it sound as if increasing the breaker size will allow the charger to draw more current. As per the doc I linked to the largest charger pulls 48 amps.

 

[mikeames]

Larry, thank you for your reply. Your reply describes my initial thought. However, if I consider how a circuit breaker trips, the need for the fault current to return to the utility transformer, it seems like an EGC is needed back to the meter-main/transfomer neutral connection. NEC 250.32(B)(1) requires the EGC, and a re-grounded neutral is only allowed in installations prior to 2008 NEC.

This should be its own thread so not to hijack the OPs question, but I agree with Larry. Remove the service disconnect at the meter. Run the conductors as service conductors for 500 feet. Then make your neutral bond at the service disconnect which is your remote panel. No need for a separate 500 foot egc. Fault current will use the egc/neutral conductor which is the same conductor. The egc, neutral bond takes place at the service disconnect which is why it should be relocated to your panel and not the existing disconnect.

 

[wwhitney]

What he wrote makes it sound as if increasing the breaker size will allow the charger to draw more current. As per the doc I linked to the largest charger pulls 48 amps.

So, the fixed wall station is often called a charger, but it is really an EVSE. The charger, that turns DC into AC and charges the battery, is on the car.

The EVSE is just a slightly smart switch with a pilot signal that advertises to the charger how much current it is OK to draw, plus some simple safety features. So if you run a 70A circuit to the EVSE, and if the EVSE is rated for it, you configure the EVSE to advertise 56A; if instead you run an 80A circuit to it, you configure the EVSE to advertise 64A. The charger on the car will draw the lesser of its rating and what the connected EVSE is advertising.

There are EVSEs available that do handle currents at that 70A/80A level, and there are cars out there that have on-board chargers that can utilize that much current. I haven't kept up with what current Tesla offerings are in this regard.

Cheers, Wayne

 

[mikeames]

So, the fixed wall station is often called a charger, but it is really an EVSE. The charger, that turns DC into AC and charges the battery, is on the car.

The EVSE is just a slightly smart switch with a pilot signal that advertises to the charger how much current it is OK to draw, plus some simple safety features. So if you run a 70A circuit to the EVSE, and if the EVSE is rated for it, you configure the EVSE to advertise 56A; if instead you run an 80A circuit to it, you configure the EVSE to advertise 64A. The charger on the car will draw the lesser of its rating and what the connected EVSE is advertising.

There are EVSEs available that do handle currents at that 70A/80A level, and there are cars out there that have on-board chargers that can utilize that much current. I haven't kept up with what current Tesla offerings are in this regard.

Cheers, Wayne

That's good info and I suspected that thus why I looked up the Tesla manual. Perhaps the OP has one that's not Tesla, or a larger unit that's not on their site.

 

[PatrickGoodyear]

May apologies for hijacking the thread.

Thank you all for your patience and help.

Cheers!

 

[don_resqcapt19]

Before you change that 70A to an 80A, are you sure there is really #3 wire feeding that panel? The diameter looks the same as that 60A circuit to the Tesla charger. A worn 6 digit can look like a 3... It appears the wire is copper. #6 copper can do 65 amps using the higher 75C temp ratings. With NM cable, it would be limited to 55A. You can round up a 65A feeder to 70A if the calculated load is 65A on #6 wire. Also, #6 (and smaller) wires can't be recolored white -- has to be native white insulation like the Tesla circuit.

If you have #4 copper feeding the panel, it is good for 85A and changing the breaker to 80 is fine, and taping wires white is fine.

Only the upstream breaker counts here...the second panel breaker could be a 1000 amps and be code compliant, assuming the conductors are matched to the upstream breaker rating.

 

[jsieczko]

Where are you getting this 20% less idea? Generally the charger will draw what it wants. It does not know what size breaker its on. If you put it on a 1000A amp breaker it would draw the same as if it were on a 40 amp breaker. Unless Tesla chargers are programmable( ie: you tell it the breaker size and they auto adjust draw) I mention this because you used the numbers 70 and 56 which is 20% less and you used 80A and 64, also 20%. Generally circuits are sized where the breaker is 125% greater than the calculated load or the load is calculated to be 20% less than the breaker size. That does not mean the load will actually draw that. I know nothing about Tesla chargers, but based on their largest charger it only draws 48 amps. Increasing that breaker size is fine but it wont change the performance of the charger.

I did note that there is commission programming for circuit size, but he max is still 60/48 amps

page 7 manual for circuit sizing https://www.tesla.com/sites/default...ng/Gen3_WallConnector_Installation_Manual.pdf

The Tesla Wall Charger has a rotary switch where you tell it the size of the breaker. It then draws 80% percent of the size of the breaker. NEC calls for 80% breaker size for continuous loads. (It may take the car several hours to charge).

 

[jsieczko]

BTW: The confusion is the Gen 2 wall connector could deliver up to 80-amps to the vehicle and the Gen 3 is now limited to 48-amps. Cars with the dual-onboard charger option could charge at 19.2 kW (80-amps). However, Tesla no longer sells cars that can accept more than 48-amps, so they updated their wall connector accordingly.

 

[mikeames]

BTW: The confusion is the Gen 2 wall connector could deliver up to 80-amps to the vehicle and the Gen 3 is now limited to 48-amps. Cars with the dual-onboard charger option could charge at 19.2 kW (80-amps). However, Tesla no longer sells cars that can accept more than 48-amps, so they updated their wall connector accordingly.

Great info thanks!

I wonder why tesla limits the charge size now? Seems like the it would be a nice option to have a 100 amp charger in a garage at home.

 

[rnatalie]

Understand first that the thing you are installing on the wall isn't the charger. It's properly an EVSE. It provides essentially is a large GFCI and what it does (based on what you tell it with that switch) is what to tell the car (via a pair of wires in the plug) how much current is available. The actual charger is part of the car. The output of that plug on the cord is still 240V at 60HZ.

48A is all that any of the current TESLAs can suck out of this port. Some of the prior Model S and X could go as high as 80 via that interface.

The "supercharger" on the other hand is a different beast.