Limited Amps

[Dan Detweiler]

Question for everyone here. I have a HPWC on a 60 amp dedicated circuit. When I plug my Model 3 into it, it only pulls 36 amps and gives me about 30 miles of range per hour of charging. The car is capable of up to 48 amps, right? If so, why will it only pull 36? What am I missing? Is there a setting somewhere that is preventing it from charging over 36 amps?

Any help would be greatly appreciated.

Dan

 

[Petrlol]

I assume you have the rotary switch set to 9 as per the installation guide?

 

[GigaGrunt]

Read the manual for the HWPC. Inside the housing, there is a DIP switch that can be set for different amperage. Most likely your electrician didn’t change the setting. Just turn the breaker off before opening the cover.

 

[Kirby64]

Is your HPWC set up properly? Have you confirmed other cars (Like a Model S) can pull the full 48A off the HPWC? If not, it's probably a switch setting like others have mentioned. You need to make sure it's on the 60 amp setting.

Does the inside of the car only show "36A/36A" when charging? If it shows 36A/48A then it's another issue and the HPWC has it's settings correct and it's probably a voltage drop problem.

 

[ai4px]

Be careful pulling the cover off... cable inside is kinda short.

 

[Dan Detweiler]

I assume you have the rotary switch set to 9 as per the installation guide?

Had an electrician do it. Where is the rotary switch? Is that something I can adjust without calling him back in?

Dan

 

[Dan Detweiler]

Is your HPWC set up properly? Have you confirmed other cars (Like a Model S) can pull the full 48A off the HPWC? If not, it's probably a switch setting like others have mentioned. You need to make sure it's on the 60 amp setting.

Does the inside of the car only show "36A/36A" when charging? If it shows 36A/48A then it's another issue and the HPWC has it's settings correct and it's probably a voltage drop problem.

The car does say 36A/36A. What now?

Dan

 

[Petrlol]

Look at page 22 of the guide found here:
Installation Manuals - Wall Connector

Appears if you actually have a 60amp breaker, you should be on position 9. Which would mean turning the breaker off, opening the HPWC and making the change. 36/36 means you're probably on position 7.

 

[GWord]

The breaker size is not necessarily indicative of the proper HPWC amp selector position. If your electrician used NM-B (Romex) style cable, your HPWC dial will need to be set for 50A (position 8).

 

[Kirby64]

The car does say 36A/36A. What now?

Dan

Do you know how to turn off a breaker and use a screwdriver? If so, you just need to take apart the cover and adjust the switch so it's at the 60A setting. If it's already set to the 60A setting, then you have another problem that's either voltage droop or car related...

Here's the install guide for the HPWC: https://www.tesla.com/sites/default...nstallation_manual_80A_en_US.pdf?201612081439

I assume if an electrician did this, you have a properly sized breaker and wiring. They likely just set the switch wrong.

 

[TexasEV]

Memo to anyone having a Wall Connector installed— make sure your electrician has RTFM.

 

[GWord]

Do you know how to turn off a breaker and use a screwdriver? If so, you just need to take apart the cover and adjust the switch so it's at the 60A setting. If it's already set to the 60A setting, then you have another problem that's either voltage droop or car related...

Here's the install guide for the HPWC: https://www.tesla.com/sites/default...nstallation_manual_80A_en_US.pdf?201612081439

I assume if an electrician did this, you have a properly sized breaker and wiring. They likely just set the switch wrong.

This is not necessarily correct. 60A breaker is the proper rating for 6awg NM-B cable but that wiring type limits the branch design to a 55A draw (see NEC 240.4). Thus the proper switch setting on the HPWC is for 50A if you want to be code compliant. If the wiring method used is suitable for the full 60A, then you can set the HPWC to the 60A setting.

 

[Dan Detweiler]

Just confirmed with the electrician that it is indeed a 60 amp breaker with #6 wire. That shouldn't be a problem carrying the 48 amp max, right?

I'm thinking the charger was just default at 36 and he never thought to change it.

Dan

 

[Kirby64]

This is not necessarily correct. 60A breaker is the proper rating for 6awg NM-B cable but that wiring type limits the branch design to a 55A draw (see NEC 240.4). Thus the proper switch setting on the HPWC is for 50A if you want to be code compliant. If the wiring method used is suitable for the full 60A, then you can set the HPWC to the 60A setting.

I assume if the electrician knows his codes he would use the proper sized wiring. If he used NM-B 6 gauge, per the chart it's technically supposed to be 55A only. If it's 75C rated wiring, then 6ga should handle 65A.

Are you suggesting that if the electrician was asked to install a 60A breaker for continuous 48A load that he'd undersize the wire? Not saying that isn't possible, but seems to me they'd know to use 75C rated 6ga to handle things fine.

@Dan Detweiler , check what type of wire the electrician used. If it's NM-B or UF-B (60C rated), that's not high enough gauge. If it's THW/THWN or any other 75C (or higher) rated wire, you should be fine.

 

[Vines]

Like was pointed out above, NM-B (Romex) is only good for 60 C connections. #6 = 55A maximum.
If its SER ( Like Romex but more heavy duty, also not in conduit) or individual wires ()THHN-THWN-THWN-2 ECT) in conduit then that wiring is rated at 75 C so #6 = 65A

 

[GWord]

I assume if the electrician knows his codes he would use the proper sized wiring. If he used NM-B 6 gauge, per the chart it's technically supposed to be 55A only. If it's 75C rated wiring, then 6ga should handle 65A.

Are you suggesting that if the electrician was asked to install a 60A breaker for continuous 48A load that he'd undersize the wire? Not saying that isn't possible, but seems to me they'd know to use 75C rated 6ga to handle things fine.

@Dan Detweiler , check what type of wire the electrician used. If it's NM-B or UF-B (60C rated), that's not high enough gauge. If it's THW/THWN or any other 75C (or higher) rated wire, you should be fine.

If a branch circuit ampacity results in a non standard breaker size (i.e. 55A), NEC 240.4 B allows one to uprate the breaker only to the next standard size if it is a single outlet branch. NM-B 6awg is still ok with a 60A breaker but the max ampacity of the circuit will still only be 55A.

 

[Birdman325]

similar problem and confirmed with the electrician that he didn’t RTFM so didn’t change / adjust any of the dip switches / dial inside the unit.

 

[GWord]

Just confirmed with the electrician that it is indeed a 60 amp breaker with #6 wire. That shouldn't be a problem carrying the 48 amp max, right?

I'm thinking the charger was just default at 36 and he never thought to change it.

Dan

You need to know what kind of #6. If Romex you will need to use position 8 (50A).

 

[eprosenx]

If a branch circuit ampacity results in a non standard breaker size (i.e. 55A), NEC 210.4 B allows one to uprate the breaker only to the next standard size if it is a single outlet branch. NM-B 6awg is still ok with a 60A breaker but the max ampacity of the circuit will still only be 55A.

And note that I find zero value in upsizing the breaker since the Wall Connector can't be set to 55a (it can only be set to 50a), so I would never upsize the breaker as there would be no practical value. Having the smallest breaker possible would seem to maximize safety.

(but also note that I have asked the Tesla Wall Connector team if in the future they could provide two rotary dials such that you could support 1a increment settings on the Wall Connector - that would allow you to actually get the full rated 55a - 44a after derate - out of your wiring - and that would require a 60a breaker)

 

[eprosenx]

If a branch circuit ampacity results in a non standard breaker size (i.e. 55A), NEC 210.4 B allows one to uprate the breaker only to the next standard size if it is a single outlet branch. NM-B 6awg is still ok with a 60A breaker but the max ampacity of the circuit will still only be 55A.

Apologies for being nit-picky, but just a note for folks that might find this in a future Google search: The code that @GWord speaks of is actually 240.4(B). He is indeed correct about everything else though! (but I personally would just use a 50a breaker since the Wall Connector can't make use of 55a due to its limited number of settings)