HPWC SER vs Romex Wire?

[Reddy Kilowatt]

2-3 romex is what you want to run $6.14 a foot was my price at local supply house it is a 4 conductor cable. they don't offer 2-2 Romex. Copper only, do not use Aluminum.

I stuck with the 6/3 NM Romex (4 wires) for a 42A charge. it was only $1.74/ft which is a lot cheaper. I thought I might get a 100 series at some point but that is so far away I'll deal with it then. I also thought I would need a second unit but will add it later when i really do need it, and will pull a second cable. which is still cheaper than the big cable. The 2-3 gives you future flexibility to use an outlet which is a 4 wire requirement.

I see the cut sheet you have for the SER shows a un-insulated ground, most of the cables I see only has a braided ground that you have to twist in to a stranded conductor. it looks like hell and I don't think you could get that under the ground lug in the HPWC, and could break it trying. You would be foolish to try it. It's not worth the cost difference. ( I might be thinking of USE cable)

 

[Reddy Kilowatt]

You can use #2 SER Aluminum then connect a disconnect switch (100A) from the circuit breaker. Next, from the disconnect switch, use #4 COpper to HPWC. It meets the NEC spec.

How do I know? An electrician gave me a quote with that job. I did it myself.

It says right in the charger book "DO NOT USE ALUMINUM"

 

[voip-ninja]

It says right in the charger book "DO NOT USE ALUMINUM"

The charger book can say whatever it wants, there's no reason that aluminum can't be used unless they are talking about connecting aluminum wire directly to copper terminals on HPWC and having an oxidation issue happen.

Does Tesla require owners to change out their existing aluminum SER that runs to an existing sub-panel and replace it with copper, even if the final run to the Tesla charger is done with ROMEX?

I rather doubt it.

My electrician, when commenting about using aluminum SER vs copper for the main entrance run for a new 125 amp service sub panel asked me how much I liked wasting money, since for a 50 foot run the efficiency difference between copper and aluminum are negligible.

 

[mongo]

It says right in the charger book "DO NOT USE ALUMINUM"

They said it correctly:

Next, from the disconnect switch, use #4 COpper to HPWC.

 

[mongo]

The charger book can say whatever it wants, there's no reason that aluminum can't be used.

Does Tesla require owners to change out their existing aluminum SER that runs to an existing sub-panel and replace it with copper, even if the final run to the Tesla charger is done with ROMEX?

I rather doubt it.

My electrician, when commenting about using aluminum SER vs copper for the main entrance run for a new 125 amp service sub panel asked me how much I liked wasting money, since for a 50 foot run the efficiency difference between copper and aluminum are negligible.

I believe @Reddy Kilowatt misread @cmaster 's part aluminum, part copper installation suggestion.

Yeah, if the HPWC instructions say to only use copper at the HPWC, then only copper is allowable at the HPWC. It has no bearing on the rest of the run.

 

[Reddy Kilowatt]

I believe @Reddy Kilowatt misread @cmaster 's part aluminum, part copper installation suggestion.

Yeah, if the HPWC instructions say to only use copper at the HPWC, then only copper is allowable at the HPWC. It has no bearing on the rest of the run.

Yes I misread the part to the disconnect. just the HPWC requires copper for UL listing.

 

[Craig-Tx]

Yeah, all this discussion has some good ideas.
One option depending on your scenario / situation is to run a much cheaper Aluminum SER feed to a sub panel in the garage. Perhaps even a 120A feed. (No idea on cost of 120 vs 100)
If the panel is very close, you could simply run a very short 60 amp circuit to the HPWC (all you currently need for the Model 3), with the idea that you could easily bump it to 100 in the future if you ever need. Or go ahead and do it at 100 now.
You could then even pull any new 120 V plugs off of the sub panel if you need any (Seriously who has a garage that has enough plugs? I'm sure you could use more.)
This also allows future growth if you wanted to feed a second HPWC in the future.

The additional benefit is that you now have a disconnect in the vicinity of the HPWC (which may be required for that size of circuit)

 

[cmaster]

I also was thinking of just running Copper from panel to HPWC, needed about 100 feet. It was more expensive than just using 85 ft #2 Aluminum and the remainder will be Copper #4.

Costs a total of about 400$. I picked up a 100 Amp Disconnect Switch from ebay for 50 dollars as oppose to 150$ from Home Depot.

It's amazing how much people charge for labor nowadays.

 

[SureValla]

Have you looked at flexible metal conduit? I used it for a hot tub run (inside section). You can pre-install the THHN, then rout the whole thing. 1 in. Flexible Reduced Wall Aluminum Conduit, 50ft or 500ft

Interesting, can I use this and still use the rear entry method on the HPWC? I'm guessing just needs a similar connector to that used at the panel in the back of the HPWC right?

 

[Reddy Kilowatt]

To add one more twist to the equation about these 100 amp HPWC's. The NEC article 625-42 requires a disconnecting means to any charger over 60A. so there is another item you will be required to add for a legal installation. Yet more cost. So this reinforces comments above for just run a sub panel up to your garage and the breaker will act as that disconnecting means. You will notice on a lot of the destination HPWC's there is a disconnect right next to it when it is wired for over 60 amps. ( OR the sub panel).

I didn't read the whole thread if anyone had mentioned this or not.

 

[mongo]

Interesting, can I use this and still use the rear entry method on the HPWC? I'm guessing just needs a similar connector to that used at the panel in the back of the HPWC right?

Yah, you can get a right angle flex to threaded nut terminator (possibly with a short conduit nipple for wall thickness). Like others are saying, this run would need to go to a disconnect switch if you run 60+ Amps. The subpanel idea is a good one, I'm using one the same for an indoor swim spa install that needs local disconnects.

 

[Trebor Srevlis]

I am not sure of just using two conductors. Just because the Tesla charger only needs two doesn't mean some future charger won't need three, right? Do people agree it seems like a bad idea to just run the minimum? I am still reeling from trying to put in WiFi thermostats when the original home builder only used two wires to hook up the original thermostats.

So THHN is always used within conduit, right? Even if inside walls? Because if no conduit, then someone would use NM-B?

And either SER cable or NM-B 2-3 can be used interchangeably, depending on cost?

What about MC cable - aluminum armor? I guess that is no different than buying THHN and flexible conduit? Except it is thinner as it is already installed.

3/3 MC Cable w/ Ground, Stranded Copper Conductors
2/3 MC Cable w/ Ground, Stranded Copper Conductors

If I want a 100 amp breaker people are saying I can't use 3 AWG for a 100 foot run due to the 60C limit? But I need confirmation on one thing..... The Tesla wall unit would be set to 78 amps. Does the 60C limit get calculated from the 78 amps actual max draw, or from the 100 amp breaker?

Not sure if I want the local cutoff to be just a cutoff, or a 100 amp panel. The panel will both cost more, and need four wires. Not sure what else I would ever hook up to a panel in my garage. Maybe if I wanted to weld or something?

 

[qdeathstar]

It says right in the charger book "DO NOT USE ALUMINUM"

At the point of connection, because the connector is not rated for aluminum. But a disconnect will be rated for aluminum so if you switch from aluminum to copper there you meet code.

Also, nothing wrong with using 2awg aluminum ser.

 

[Trebor Srevlis]

This thread was useful because it gave me the idea of putting a sub-panel in the garage rather than just directly wire a Wall Connector.

Here are the notes I made after reading this thread:

Install small 12 circuit flush-mount sub-panel in garage. Must have 75C rating for panel and breakers and 90C for wire.

100 amp:

THHN 3 AWG 90C $5.15 with 1” conduit.
SER 3-3-3-5 90C $5.38

NM-B (Romex style) 2 AWG (90C) (3+1) $6.74 (although it is rated at a conductor temperature of 90°C dry, its ampacity is limited to 60°C according to the NEC 2008 and NEC 2011. So 95 amps)

60 amp:

THHN 6 AWG $2.70 90C with ¾ conduit. Or maybe use 1” conduit to allow future updates.

SER 6-6-6-6 90C $3.79

NM-B (Romex style) 6 AWG 90C (3+1) $2.15 (although it is rated at a conductor temperature of 90°C dry, its ampacity is limited to 60°C according to the NEC 2008 and NEC 2011. So 55 amps)

 

[Rocky_H]

I am not sure of just using two conductors. Just because the Tesla charger only needs two doesn't mean some future charger won't need three, right?

Actually that is a known fact, because of the nature of what EVSEs do. The reason for using three conductors on other kinds of outlets is for appliances like dryers and stoves that are getting enough electronics in them that they need that dual voltage capability. They want to use the 120V supply to run timers and small motors and lights, but they also need the 240V higher power for a large heating element.

For electric car charging, its main function is just to pass through high power. It's a slightly fancy switch. And so they are all built to just the two wires of a 240V connection and that's it. There is not much purpose to requiring the neutral for a 120V system also. There is a little bit of DC electronics on a circuit board inside it, but they can cover that with a small transformer to step it down to 5V DC or whatever the board needs.

Do people agree it seems like a bad idea to just run the minimum?

That concern would really just be about the thickness of the wires for how much current they can carry. Most of cost of these kinds of installations is mainly about just putting the wire into place, so using a little bit thicker wire than you need might be a good consideration because the cost change would be small, and having to redo it later would be really expensive.

 

[Trebor Srevlis]

So glad I read this thread as it allowed me to ask the right questions.

Master electrician just came to talk about a 90 or 100 amp sub panel in my garage. He said he wanted to use individual wires (THHN) through 1.25” conduit from my garage to outside my utility room, then use a box to change over to “Romex” for the rest of the run to my panel (only about 30 feet that is on an unfinished ceiling and easy to access). He said he would use 4 gauge Romex for that portion. I replied that 2 AWG was needed. He said 4 was fine for 90 amps. I replied that it is fine as per the 5% drop limit, but although it is rated for a conductor temperature of 90°C dry, its ampacity is limited to 60°C according to the NEC 2008 and NEC 2011 - so 4 is only allowed for up to 70 amps, and 2 would be good for 95 amps, so a 90 amp breaker even if 2 AWG was used. Not sure he is used to these questions from homeowners, but I only learned this stuff last night.

I then asked why change over from THHN to NM-B when it would need a box to change over, suffer from the loss of an additional connection, and on top of that, NM-B costs more than THHN – even if you factor in conduit costs. He was not sure. I am glad I read up on this stuff.

 

[Reddy Kilowatt]

This thread was useful because it gave me the idea of putting a sub-panel in the garage rather than just directly wire a Wall Connector.

Here are the notes I made after reading this thread:

Install small 12 circuit flush-mount sub-panel in garage. Must have 75C rating for panel and breakers and 90C for wire.


Trebor we had a Mid Atlantic member who has a detached garage, got rejected by the AHJ for running more than one circuit into his DETACHED garage by the inspector. I don't know what code article was sited but might be good Idea for 100A sub panel. I ran a 60 Amp circuit for my HPWC charger and now I might be adding a second unit for a second Tesla. Wish I ran the 100A Sub panel at this point.


I know I can network two HPWC's together but would be reduced power.

Set your wire to 75C for the wire because the landing lugs will be restricted to 75C. Inspector will get you for that one. I never use 90C charts for wire.

 

[Reddy Kilowatt]

So glad I read this thread as it allowed me to ask the right questions.

Master electrician just came to talk about a 90 or 100 amp sub panel in my garage. He said he wanted to use individual wires (THHN) through 1.25” conduit from my garage to outside my utility room, then use a box to change over to “Romex” for the rest of the run to my panel (only about 30 feet that is on an unfinished ceiling and easy to access). He said he would use 4 gauge Romex for that portion. I replied that 2 AWG was needed. He said 4 was fine for 90 amps. I replied that it is fine as per the 5% drop limit, but although it is rated for a conductor temperature of 90°C dry, its ampacity is limited to 60°C according to the NEC 2008 and NEC 2011 - so 4 is only allowed for up to 70 amps, and 2 would be good for 95 amps, so a 90 amp breaker even if 2 AWG was used. Not sure he is used to these questions from homeowners, but I only learned this stuff last night.

I then asked why change over from THHN to NM-B when it would need a box to change over, suffer from the loss of an additional connection, and on top of that, NM-B costs more than THHN – even if you factor in conduit costs. He was not sure. I am glad I read up on this stuff.

Actually #4 is allowed to be fused at 90A for THHN. I have not used Romex in forever but it is also now THHN and should also be allowed in the 75C column. TW romex, I don't think is offered anymore in the 60C column. I would agree to run the #2 though so you have 100A no 90A.

How long was the romex run? mine was 85 feet so I didn't use pipe.

 

[Trebor Srevlis]

Question: If I just wanted to connect my main panel to a sub-panel, should I not use this?

https://www.lowes.com/pd/Southwire-2-2-2-4-Aluminum-Ser-Service-Entrance-Cable-By-the-Foot/4294349

I assume it is allowed underground in PVC conduit? Or not?

And the 75C column for aluminum is 90 amps, so I would have to use a 90 amp breaker. But Lowes claims it is 100 amp rated, so I wonder if electricians just use 100 amp breakers with it anyway?

 

[Trebor Srevlis]

In no way did I mean to use 90C charts for wire. I just said to purchase 90C wire.