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Why do you need to hardwire a Tesla Wall Connector?

I noticed that if you're using a 14-50 plug version of the HPWC you get 40A, but if you hardwire, you get 48A.

I thought the 14-50 plug is 50AMP. So if you have 60A at the breaker, the appropriate gauge wiring, and a 14-50 plug, why doesnt it charge at 50A?

Looking at the ChargePoint Home Flex charger, it is the same. If you want 48A, you have to switch from plug to hardwire.
What if you used a plug, but just set the settings to say it is hardwired? Would there be an issue.

Thanks for the education!
 

Webeevdrivers

Active Member
Jan 2, 2017
2,492
4,762
Canada
I noticed that if you're using a 14-50 plug version of the HPWC you get 40A, but if you hardwire, you get 48A.

I thought the 14-50 plug is 50AMP. So if you have 60A at the breaker, the appropriate gauge wiring, and a 14-50 plug, why doesnt it charge at 50A?

Looking at the ChargePoint Home Flex charger, it is the same. If you want 48A, you have to switch from plug to hardwire.
What if you used a plug, but just set the settings to say it is hardwired? Would there be an issue.

Thanks for the education!

The plug is rated for 80 percent of 50 amps at constant duty. You would be over taxing the receptacle and plug. As it stands even at 40 amps constant these plugs get warm.
 
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Reactions: ImpetuousRacer
Currently I have a Gen 2 HPWC with 100A breaker/rated wiring hardwired and set to output up to 80A.

I have another 100A breaker/rated wiring that is off.

I'm looking to install a Charepoint Home Flex charger (for a Hybrid RR), The 14-50 plug-in version shows basically I can do a max of 50A breaker/rated wiring to a 14-50 plug and I can get 40A charging. Or I can hardwire and do an 80A breaker and get 50A charging.

I was trying to see if I could just plug in to a 14-50 receptacle with higher amperage so I didnt need to hardwire. The answer is clear, I can not. I need to make sure I have a max breaker of 50A on a 14-50 receptacle and the most I'll get is 40A. For the Tesla, I can simply plug the charge cable into 14-50A for 40A charging without a wall charger even needed.

Thanks for the clarification on everything!
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,297
8,989
Boise, ID
I was trying to see if I could just plug in to a 14-50 receptacle with higher amperage so I didnt need to hardwire. The answer is clear, I can not.
It was alluded to a bit but maybe not explained fully. This is a requirement of the National Electric Code in North America. They spec circuits and wire sizes to only use the full capacity of a circuit if it is for short term loads or things that cycle on and off. So heating elements in ovens and clothes dryers cycle on and off, so they are near the 50 or 30A capacity of their circuits/outlets.

But for long term "continuous" loads, that will be drawing for many hours, the circuit has to have a rated capacity of 125% of what that steady current draw is. Or turned around, you can only draw 80% of the circuit rating.

For the Tesla, I can simply plug the charge cable into 14-50A for 40A charging without a wall charger even needed.
Something to be aware of with this. The original 1st generation mobile charge cable did have the capability of using 40A. But if you are getting a newer car that was made in the last couple of years, it will have the 2nd generation mobile charge cable, which is a little cheaper and was built a little smaller and can only supply 32A maximum.
 
It was alluded to a bit but maybe not explained fully. This is a requirement of the National Electric Code in North America. They spec circuits and wire sizes to only use the full capacity of a circuit if it is for short term loads or things that cycle on and off. So heating elements in ovens and clothes dryers cycle on and off, so they are near the 50 or 30A capacity of their circuits/outlets.

But for long term "continuous" loads, that will be drawing for many hours, the circuit has to have a rated capacity of 125% of what that steady current draw is. Or turned around, you can only draw 80% of the circuit rating.

Great technical details. Thanks for this.

Something to be aware of with this. The original 1st generation mobile charge cable did have the capability of using 40A. But if you are getting a newer car that was made in the last couple of years, it will have the 2nd generation mobile charge cable, which is a little cheaper and was built a little smaller and can only supply 32A maximum.

I have the 1st Gen charge cable and get 40A. New cable from 40A - 32A. New Wall charger 80A - 48A. Really dont want you fast charging at home for some reason.
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,297
8,989
Boise, ID
I have the 1st Gen charge cable and get 40A. New cable from 40A - 32A. New Wall charger 80A - 48A. Really dont want you fast charging at home for some reason.
None of it is anything close to fast charging as far as the batteries are concerned. It's quibbling about 10-20kW when the batteries can take about 100kW. Any kind of home charging is basically slow.

I do see the reasons for the changes, and I agree with the mobile connector changes but not the wall connector changes.
Regarding the mobile connector:
There has been a long time exception in electric code where you are allowed to put a 50A outlet type onto a 40A rated circuit/wire/breaker. A lot of ovens are installed that way. There just isn't a 40A outlet type, and if a 40A rated appliance is going to be plugged into it, they allow that specific kind of mismatch. So it is not entirely uncommon to find these kinds of outlets in some places at houses people may visit. So someone plugs their charge cable into it, thinking it's a 50A circuit when it's really a 40A circuit with thinner wire, and......hopefully the breaker pops before Bad Things happen. So I get Tesla wanting a bit of CYA so they aren't blamed for meltdowns and fires from people accidentally discovering these weirdly wired outlets.

That's thing 1. The other part of it you can kind of see in the products they do still offer. The "Corded Mobile Connector" is literally a 1st generation UMC, except the plug is permanently attached, so it doesn't have that changeable connector with the pin and sleeve mechanism you can slide on and off. Those kinds of sliding connectors are a more resistive weaker connection than something permanently wired on, and running 40A continuously through that is kind of iffy. They did have some troubles with those connections melting a bit on people's 1st gen UMCs. I've been running mine for 6 years with the current set for about 31-32A just to keep it cooler and not have that problem. So I think the smaller 2nd gen UMC is just less current and heat with those changeable adapters, so less likely to have problems. So I do stand by the UMC changes.

The wall connector stuff, though, is directly related to chopping off the onboard charger capabilities, and I do hate that change. The hardwired connections can handle those higher currents, so it's not really for safety issues. They are just cost cutting something they think most people don't need, but not offering it as an option is really irritating to the people who do need it. So yes, they are basically just dumbing things down and causing some people some difficulties.
 

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