Aluminum Wiring in Home and Home Charging

quantumslip said:

This is still a ways off for me, but given my future plans (in 2-3 years I hope to be a Model 3 owner) this may become an issue for me.

A lot of homes in the area I would like to go to are remodeled homes from the '60s-'70s, which means that some of them may still be stuck with aluminum wiring if it wasn't replaced yet. Assuming the home wiring wasn't upgraded to all-copper in renovations, I'm wondering is it safe to add on a NEMA 14-50 outlet in such a house? HPWC? What other considerations were taken to install such an outlet in such an environment? Did you decide to bite the bullet and replace all the wiring to copper?

Apologies in advance as this isn't a model-s question per se, but there doesn't seem another place for me to put this.

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When adding on a new outlet you are likely to also be installing a new wire run from that outlet back to the panel, this means that the run in question wouldn't have any aluminium on it and therefore none of the downsides.

Aluminium by itself isn't a problem if handled properly, but it tends to expand and contract more due to temperature changes, so the connections are more finicky, and it's also a problem any time you connect aluminium to a terminal not designed to accept it (common problem when people replace an old outlet with a new one, old outlet was rated for aluminium, but the new ones never are)

My house was built in 1973, and was built all aluminium, subsequent renovations (before I purchased the house) resulted in a mix of copper and aluminium. During renovations that I have done since owning the house I have replaced many aluminium runs with copper when the walls have been open anyway, but I still have a mix. I have however made sure that anywhere that has aluminium wire connected to a new fixture or outlet, it is properly pigtailed to copper using the appropriate marrettes with the appropriate anti-oxidizing gel in them. The same for anywhere that has copper and aluminium joined. My 14-50 for the car is however run all on copper (and interestingly enough, the original stove and dryer outlets (or at least I assume they're from when the house was built) were copper, not aluminium.)

quantumslip said:

This is still a ways off for me, but given my future plans (in 2-3 years I hope to be a Model 3 owner) this may become an issue for me.

A lot of homes in the area I would like to go to are remodeled homes from the '60s-'70s, which means that some of them may still be stuck with aluminum wiring if it wasn't replaced yet. Assuming the home wiring wasn't upgraded to all-copper in renovations, I'm wondering is it safe to add on a NEMA 14-50 outlet in such a house? HPWC? What other considerations were taken to install such an outlet in such an environment? Did you decide to bite the bullet and replace all the wiring to copper?

Apologies in advance as this isn't a model-s question per se, but there doesn't seem another place for me to put this.

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You will probably have to run a new circuit for you HPWC. It will have nothing to do with the other wiring in your house. The HPWC does require copper only, but you may need a disconnect (code varies by jurisdiction), and you may run aluminum to another box or switch first, as long as the breaker is rated for both copper and aluminum (Most of them are).

Of note: the aluminum used in cable now is a different alloy from the product used in the 70's. The alloy is much more mechanically and electrically "forgiving". Saying that, you must still use devices that are rated for use with aluminum wire. I'd also recommend using anti-oxidant paste for all connections. Aluminum is lighter, and much less expensive that copper, even though the sizing will be larger than copper.

RE your existing wiring: to fix this, either pigtail copper to existing devices - using anti-oxidant paste and CU/AL wire nuts, or change out existing devices to CU/AL rated switches and plugs

(Confession: I used to work for Alcan Cable)

DMC-Orangeville said:

(Confession: I used to work for Alcan Cable)

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Do you really want to admit that in public....

Just an FYI...Most houses are fed by Aluminum wiring anyways...just ask the utility. Much cheaper than copper.


You would be running a new line anyways so at least that part would be copper.

RAM_Eh said:

Just an FYI...Most houses are fed by Aluminum wiring anyways...just ask the utility. Much cheaper than copper.


You would be running a new line anyways so at least that part would be copper.

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Yes. Aluminum from power company to your main panel, and CU from there to circuits in your house.

This old house talks about aluminium wiring, starts at 10:32

One thing you DO have to think about is the size of the electric service to the house. These days 200a is pretty standard and 400a not unheard of. Back in the '60s and '70s 100a was more the norm. You might find yourself having to upgrade the electric service and panel in some of those houses to accommodate 80a charging especially if the house has AC as well.

Just make sure you have an electrician that knows what he is doing. That's the important part. Aluminum wiring in your case, as others have said, makes no difference. I decided to add a subpanel in my garage when I got my S. Aluminum is cheaper than copper, so the run between my main panel and the garage is all aluminum. From the subpanel to the S outlet is (about) 2 feet of copper since it's right next to the panel.

The problem with aluminum and copper is when you mix metals; over time, they'll corrode. So if someone working on your house doesn't know what they're doing and splices in a piece of copper to a piece of aluminum and doesn't take the proper precautions/safeguards, that's where you'll have issues.

PatD said:

The problem with aluminum and copper is when you mix metals; over time, they'll corrode. So if someone working on your house doesn't know what they're doing and splices in a piece of copper to a piece of aluminum and doesn't take the proper precautions/safeguards, that's where you'll have issues.

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This is one of many considerations in using Aluminum cable. Copper and aluminum may be joined, but you must use the correct wire nuts, and anti-oxidant paste (in most jurisdictions). The biggest "must" is to insure that any devices connected to the aluminum cable are rated for use for both copper and aluminum. All devices are marked as thus.

PatD said:

Just make sure you have an electrician that knows what he is doing. That's the important part. Aluminum wiring in your case, as others have said, makes no difference. I decided to add a subpanel in my garage when I got my S. Aluminum is cheaper than copper, so the run between my main panel and the garage is all aluminum. From the subpanel to the S outlet is (about) 2 feet of copper since it's right next to the panel.

The problem with aluminum and copper is when you mix metals; over time, they'll corrode. So if someone working on your house doesn't know what they're doing and splices in a piece of copper to a piece of aluminum and doesn't take the proper precautions/safeguards, that's where you'll have issues.

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While it is true that mixing metals will cause galvanic corrosion, today's story is a bit different. Today's aluminum alloys are designed to have the same rough mechanical characteristics, and termination devices typically contain alloys that are more compatible. Look for CO/ALR marked devices - these can accept copper or aluminum wiring.

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DMC-Orangeville said:

This is one of many considerations in using Aluminum cable. Copper and aluminum may be joined, but you must use the correct wire nuts, and anti-oxidant paste (in most jurisdictions). The biggest "must" is to insure that any devices connected to the aluminum cable are rated for use for both copper and aluminum. All devices are marked as thus.

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It's not true that you must use anti-oxidant paste in most jurisdictions. In the US, anti-oxidant is required only if the instructions call for it. Many electricians have a habit of applying it anyway, but the letter of the law comes down to whether or not installation instructions for your cable and/or terminating devices require it for aluminum termination. Most devices today are CO/ALR rated and don't have that requirement, even when connecting to the older alloys of the 1960's and 1970's. Today's newer 9000-series alloys are mechanically similar to copper.

Use NoALox on all the Aluminum connections to delay corrosion.

FlasherZ said:

Most devices today are CO/ALR rated.

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Most modern devices I've found are copper only, and not rated for use with aluminium, when I've replaced switches and outlets in my house I've had to pigtail to copper as none of the new switches or outlets can accept aluminium, and in fact all state specifically not to use them with aluminium.

The older stuff in my house (from 1973) is all rated for both.

FlasherZ said:

It's not true that you must use anti-oxidant paste in most jurisdictions. In the US, anti-oxidant is required only if the instructions call for it. Many electricians have a habit of applying it anyway, but the letter of the law comes down to whether or not installation instructions for your cable and/or terminating devices require it for aluminum termination.

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In Canada it's a code rule to use anti-oxidant past (NoAlox as an example). I was told (when I worked at Alcan) that many States asked for the use of the paste as well - because it is a good practice. I will defer to you, as you are the NEC code expert (not being snarky)

FlasherZ said:

Most devices today are CO/ALR rated and don't have that requirement, even when connecting to the older alloys of the 1960's and 1970's. Today's newer 9000-series alloys are mechanically similar to copper.

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Some devices are still CU only. Please check prior to using. ...and as a point of reference, the 8000 series alloys are sometimes more malleable than copper.:wink:

DMC-Orangeville said:

In Canada it's a code rule to use anti-oxidant past (NoAlox as an example). I was told (when I worked at Alcan) that many States asked for the use of the paste as well - because it is a good practice. I will defer to you, as you are the NEC code expert (not being snarky)

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Someone did tell me once that Canada required an anti-corrosion agent, I'll defer to anyone who has a copy of the book - hard enough to remember all the crap in the US NEC much less the CEC too.

From an NEC viewpoint, if the manufacturer's instructions for a particular termination require it, then NEC requires it in the "manufacturer's explicit instructions" rule (110.3). There is no expressly-written element in the NEC requiring the application of anti-oxidant.

And perhaps I was a bit over-generous when I said "most devices"... almost everything I buy nowadays is rated CO/ALR, I imagine there are a bunch of bulk "builder grade" receptacles and switches where copper is guaranteed to be used, and CU-only is reflected. This is probably true for smaller circuits, but I can't think of a single device I have for #6 or greater that isn't CO/ALR.

FlasherZ said:

Someone did tell me once that Canada required an anti-corrosion agent, I'll defer to anyone who has a copy of the book - hard enough to remember all the crap in the US NEC much less the CEC too.

From an NEC viewpoint, if the manufacturer's instructions for a particular termination require it, then NEC requires it in the "manufacturer's explicit instructions" rule (110.3). There is no expressly-written element in the NEC requiring the application of anti-oxidant.

And perhaps I was a bit over-generous when I said "most devices"... almost everything I buy nowadays is rated CO/ALR, I imagine there are a bunch of bulk "builder grade" receptacles and switches where copper is guaranteed to be used, and CU-only is reflected. This is probably true for smaller circuits, but I can't think of a single device I have for #6 or greater that isn't CO/ALR.

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HPWC is copper only?

Lloyd said:

HPWC is copper only?

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Correct. Tesla's instructions say copper-only, at least in the revision of manual I have here. I meant wiring devices (receptacles, breakers, etc.)

FlasherZ said:

Correct. Tesla's instructions say copper-only, at least in the revision of manual I have here. I meant wiring devices (receptacles, breakers, etc.)

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breakers are the only modern device I've found with Al ratings, I suspected it to be because you aren't allowed to splice in a breaker panel, and they want to be compatible with wiring in older houses. Everything else I've looked at recently has explicitly stated for copper wire only.

green1 said:

breakers are the only modern device I've found with Al ratings, I suspected it to be because you aren't allowed to splice in a breaker panel, and they want to be compatible with wiring in older houses. Everything else I've looked at recently has explicitly stated for copper wire only.

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As FlasherZ said: " I imagine there are a bunch of bulk "builder grade" receptacles and switches where copper is guaranteed to be used, and CU-only is reflected. This is probably true for smaller circuits, but I can't think of a single device I have for #6 or greater that isn't CO/ALR." If you go into circuit size devices (10AWG and smaller, 15-20 amp) at Home Depot, Canadian Tire, Home Hardware, etc you will find mostly copper only requirement. As we no longer use circuit size aluminum cable for residential construction*, most builder grade devices aren't built for it. There are dual rated devices, but they are expensive, and have a poor selection.

* Not always true for dryer and stove circuits

In high rise residential, commercial and industrial use, #8 and larger aluminum cables have widespread use. As such, almost all switches, lugs etc 30 amp and above, are dual rated.

I have posted above to clarify circuit size cable use. FlasherZ is dealing with powering the HPWC and other higher power devices.....