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Model Y Wall Charger

Hi everyone,

Have 2 questions about wall Charger installation, hopefully someone can shed some light. We have recently built a house and we had asked the builder to run a 240v connection in the garage where the Tesla would be parked.

They installed a 4 prong dryer plug, and the other day I went to install the wall Charger and to my surprise the plug in the wall has 4 wires, black, red, white “neutral” and ground. The Tesla wall Charger only requires 3. So I’m a little confused as to which wire I will NOT be using. The white “neutral” maybe?

second question is, Tesla Wall Charger says only to use copper wires and the line that the builder ran in the garage is aluminum. Anybody knows what are the possible issues that the aluminum wire may cause?

Sorry for the long post, but I cant’t seem to find the answers anywhere.

Thanks in advance.
 

Sophias_dad

Active Member
Supporting Member
Jul 29, 2018
1,882
2,091
Massachusetts
You'd cap the white(Neutral). No offense but if you don't know that, you might not want to be installing your own HPWC, particularly when aluminum is involved.

The terminals in the HPWC are only rated for copper use, so you can't connect the aluminum to them. There are pigtails or connection-blocks that will safely convert the aluminum to a short length of copper(which would then connect to the HPWC). You absolutely must check the gauge of the aluminum wire that was installed and make sure you don't exceed its ratings for CONTINUOUS use. If its #8, you can take 32 amps from it continuously, #6 gets you 40, and #4 gets you >48(capped at 48 since the HPWC won't take more). Get pigtails/connectors rated for the aluminum gauge you have.

I am not an electrician by trade, but I understand that aluminum expands and contracts more than copper and tends to work itself loose as a result. Its also softer than copper, so if you just tighten the lug more it doesn't really get tighter, it instead deforms the aluminum. I have never used the pigtails I describe, but I imagine the aluminum-lug side is a captive rounded cavity that compresses the conductor on all sides, rather than a screw that just flattens the conductor. This is also very important for stranded connections because a screw terminal will tend to splay the strands rather than hold them together. I believe its also common practice to use a goo that protects the aluminum from corrosion, but I'm not real sure of that.

Here's just one of many examples of such a connector... https://smile.amazon.com/Morris-Products-Insulated-Splice-Connector/dp/B00UKG81GO?th=1
 
Last edited:
You'd cap the white(Neutral). No offense but if you don't know that, you might not want to be installing your own HPWC, particularly when aluminum is involved.

The terminals in the HPWC are only rated for copper use, so you can't connect the aluminum to them. There are pigtails or connection-blocks that will safely convert the aluminum to a short length of copper(which would then connect to the HPWC). You absolutely must check the gauge of the aluminum wire that was installed and make sure you don't exceed its ratings for CONTINUOUS use. If its #8, you can take 32 amps from it continuously, #6 gets you 40, and #4 gets you >48(capped at 48 since the HPWC won't take more). Get pigtails/connectors rated for the aluminum gauge you have.

I am not an electrician by trade, but I understand that aluminum expands and contracts more than copper and tends to work itself loose as a result. Its also softer than copper, so if you just tighten the lug more it doesn't really get tighter, it instead deforms the aluminum. I have never used the pigtails I describe, but I imagine the aluminum-lug side is a captive rounded cavity that compresses the conductor on all sides, rather than a screw that just flattens the conductor. This is also very important for stranded connections because a screw terminal will tend to splay the strands rather than hold them together. I believe its also common practice to use a goo that protects the aluminum from corrosion, but I'm not real sure of that.

Here's just one of many examples of such a connector... https://smile.amazon.com/Morris-Products-Insulated-Splice-Connector/dp/B00UKG81GO?th=1
Aluminum wiring in contact with air develops a high resistance patina that causes heat and ultimately fire. Pig tailing correctly will create an airtight connection between copper and aluminum.


Scary stuff, at least to a non-electrician like me!
 
You'd cap the white(Neutral). No offense but if you don't know that, you might not want to be installing your own HPWC, particularly when aluminum is involved.

The terminals in the HPWC are only rated for copper use, so you can't connect the aluminum to them. There are pigtails or connection-blocks that will safely convert the aluminum to a short length of copper(which would then connect to the HPWC). You absolutely must check the gauge of the aluminum wire that was installed and make sure you don't exceed its ratings for CONTINUOUS use. If its #8, you can take 32 amps from it continuously, #6 gets you 40, and #4 gets you >48(capped at 48 since the HPWC won't take more). Get pigtails/connectors rated for the aluminum gauge you have.

I am not an electrician by trade, but I understand that aluminum expands and contracts more than copper and tends to work itself loose as a result. Its also softer than copper, so if you just tighten the lug more it doesn't really get tighter, it instead deforms the aluminum. I have never used the pigtails I describe, but I imagine the aluminum-lug side is a captive rounded cavity that compresses the conductor on all sides, rather than a screw that just flattens the conductor. This is also very important for stranded connections because a screw terminal will tend to splay the strands rather than hold them together. I believe its also common practice to use a goo that protects the aluminum from corrosion, but I'm not real sure of that.

Here's just one of many examples of such a connector... https://smile.amazon.com/Morris-Products-Insulated-Splice-Connector/dp/B00UKG81GO?th=1

Thanks for the detailed information buddy. That clarifies everything. And you are right. I shouldn’t be touching that, this is way beyond my hand man capabilities ahaha. I’ll definitely hire an electrician to do the job. Thanks again!!!
 
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Aluminum wiring in contact with air develops a high resistance patina that causes heat and ultimately fire. Pig tailing correctly will create an airtight connection between copper and aluminum.


Scary stuff, at least to a non-electrician like me!

Aha, for sure! Thanks for the info.
 

OxBrew

MYLR - Prototype Design/Dev 1996-Pres
Sep 23, 2021
252
413
Spokane WA
For sure get a good electrician to do the installation/conversion. Aluminum must be cleaned properly, and coated with the special paste literally within seconds so the layer of oxidation does not form.

It may take years to catch on fire, but it will, if done wrong. If done right, it will outlast your grandchildren. Almost all service drops to houses are aluminum, no issues.

I was a general contractor in a former life, dealt with this all the time. I have some stories to tell about keeping electricians honest and repairing panels that caught on fire due to lack of proper installation, 8 years prior. Be careful.
 
For sure get a good electrician to do the installation/conversion. Aluminum must be cleaned properly, and coated with the special paste literally within seconds so the layer of oxidation does not form.

It may take years to catch on fire, but it will, if done wrong. If done right, it will outlast your grandchildren. Almost all service drops to houses are aluminum, no issues.

I was a general contractor in a former life, dealt with this all the time. I have some stories to tell about keeping electricians honest and repairing panels that caught on fire due to lack of proper installation, 8 years prior. Be careful.
Great info. Thanks!!!
 

EVer Hopeful

Member
Jul 7, 2021
819
649
Texas
I think one of the reasons Aluminum wire "catches fire" is that it's less malleable than copper, so if an outlet is to be replaced you should really snip off the existing bare wire and strip a new half inch. If you don't do this, you'll probably keep bending it and it'll soon fracture from fatigue, whereas copper you can bend all day. Having said that it's probably code to do the same with copper, but I bet most people don't

The second reason is that it appears to me at least that Al wire is slightly thicker than Cu wire, so when you strip it, it's easy to nick the surface, which just propagates into a break at some point. Any break causes arcing which causes fire

The other reason is, as mentioned earlier the different coefficients of expansion for Al and Cu. When Al wire is joined to Cu, or to a Cu only terminal, the constant heating and cooling can open up the joint, causing arcing etc etc
 

OxBrew

MYLR - Prototype Design/Dev 1996-Pres
Sep 23, 2021
252
413
Spokane WA
I think one of the reasons Aluminum wire "catches fire" is that it's less malleable than copper, so if an outlet is to be replaced you should really snip off the existing bare wire and strip a new half inch. If you don't do this, you'll probably keep bending it and it'll soon fracture from fatigue, whereas copper you can bend all day. Having said that it's probably code to do the same with copper, but I bet most people don't

The second reason is that it appears to me at least that Al wire is slightly thicker than Cu wire, so when you strip it, it's easy to nick the surface, which just propagates into a break at some point. Any break causes arcing which causes fire

The other reason is, as mentioned earlier the different coefficients of expansion for Al and Cu. When Al wire is joined to Cu, or to a Cu only terminal, the constant heating and cooling can open up the joint, causing arcing etc etc
Those are for sure contributing factors, and start a lot of the fires, but the scary one that will always fail eventually is lack of proper prep of the joints. Aluminum forms an oxide layer in air in a matter of seconds. Once formed, the layer continues to grow over months and years, increasing resistance to dangerous levels, eventually getting so hot it starts a fire. Without careful cleaning and immediate application of the right goop, the joint will always fail.

Copper oxide does not behave the same, so is safe.
 

MrJeep997

Member
Nov 1, 2021
80
74
PA
This is a good thread to have on record. I'll just add this.
A good friend is a "certified Tesla charger installer" and he is not an electrician. IOW if a knowledgeable electrician has run the line, then a certified Tesla wall installer can take it from there but it's all about having an electrician who knows what they are doing to run the line from the panel.
 

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