Need advice on my setup while awaiting HPWC

I'm not an electrician (FlasherZ will be along soon...) but the HPWC only needs 3 wires (2 hots and a ground) while a 14-50 needs 4 (2 hots, 1 neutral, and a ground) even though the Tesla UMC doesn't use the neutral, code would require you to have it to install the 14-50. Now if you were to install the 14-50 outlet yourself you could leave the neutral off, label it "Tesla UMC only" or something and then swap it for the HPC when it arrives. It wouldn't be code but it's a temporary install and it's your house...

Alternatively you could do a 6-50 which is only 3 wires but I don't know if Tesla is making a 6-50 adapter for the UMC yet (it's planned but many of the adapters are still at various stages of design, completion, and UL certification).

strider said:

Alternatively you could do a 6-50 which is only 3 wires but I don't know if Tesla is making a 6-50 adapter for the UMC yet (it's planned but many of the adapters are still at various stages of design, completion, and UL certification).

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Tesla DS supplied me with a 6-50 (as well as standard 110V, 14-50 and J1772) adapter because I too am back ordered on the HPWC. I had my electrician install the 6-50 socket because, as mentioned by strider, it uses only 3 wire, same as the HPWC. Electrician also downgraded my breaker from 100A to 50A (will return to 100A when the HPWC ships and is installed).

btw I am charging at 10kW (40A/237V) as we speak with the 6-50 adapter!

Car will automatically charge at 40A with the 6-50 adapter. The switch from 100A t0 50A is to meet code so the circuit matches the receptacle.

dcopperfield said:

Thanks. Do you guys know if you have to lower the amperage (from 80 in my case down to 50) to use the plug or will the charger automatically do that.
Pilotsteve, from your comments it looks like your electrician did it anyway so maybe it has to be done...

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Electric code requires that the breaker not exceed the rating on the plug. So, yes, code requires that you swap out the 100A breaker with a 50A breaker when you have the NEMA 6-50 plug installed temporarily.

I know pictures can distort sizes; however it looks to my eyes the wire is #8 or # 6 gauge. Can you confirm the wire size?

dcopperfield said:

would the gauge be written on the wire itself??'

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Looks like "romex" was used, it should be on the outside of the romex sheathing. You may have some left over from the install. I only ask because of the 80 amp breaker. The 80 amp breaker is another question unto itself; what was the reason that was chosen rather than 100. i.e. panel capacity, wire size, price, or???. Just curious.

> would the gauge be written on the wire itself??' [dcopperfield]

Probably, or just measure the diameter & look up the gauge. 6ga and 8ga are different enough to tell apart easily.

The 14-50 (with proper breaker) will likely satisfy 98% of your needs. Find a good home for the HPWC off in some EVSE vacuum which you will likely discover soon.
You can show them the unit in the box which should impress them. Somewhere east of you: Idaho or Wyoming.

You will need #3 wire for the HPWC. That does not look like #3!

http://www.cerrowire.com/ampacity-charts

@ Lloyd, from the OP's initial post and pictures (the 80 amp CB and what appears to be size #6 wire) I wasn't sure if the HPWC was going to be used in a down-rated setting which can be internally set. From your chart, #6 wire looks to be undersized even for a 80 amp CB. Hope the OP can clarify for us.

Tommy said:

@ Lloyd, from the OP's initial post and pictures (the 80 amp CB and what appears to be size #6 wire) I wasn't sure if the HPWC was going to be used in a down-rated setting which can be internally set. From your chart, #6 wire looks to be undersized even for a 80 amp CB. Hope the OP can clarify for us.

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80 amp will require #4 wire if using THHN or THWN wire, and on the HPWC this will result in a 64A charge current (80% of rated load). If you want the full 80A charging, it will require #3 wire and 100A circuit breaker.

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Tommy said:

Looks like "romex" was used, it should be on the outside of the romex sheathing. You may have some left over from the install. I only ask because of the 80 amp breaker. The 80 amp breaker is another question unto itself; what was the reason that was chosen rather than 100. i.e. panel capacity, wire size, price, or???. Just curious.

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If that's 6/3g Romex, an 80A breaker shouldn't be installed -- it's only good for 75A at 90C rating. It may be 4-4-4-8 cable. You'd need to look at the outer sheath and give me the markings -- cable type and AWG. Alternatively, see if there are markings on the inner wires themselves.

dcopperfield said:

See attached picure of the wire with a ruler for reference. Thoughts? Will this work with the HPWC?

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dcopperfield said:

I had my builder set this box up specifically to accommodate the HPWC .....

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Check with your builder on the size he/she installed. If it's #6, the breaker will need to be changed to 50 amp and the HPWC internal settings changed to max 40 amp charge. If it's #4 wire, the 80 amp breaker is fine provided the HPWC is internally changed to max 64 amp charge; thou a temporary 50 amp breaker will need to be in use for your temporary outlet until the HPWC arrives. If it's #3 wire than the HPWC can be utilized to its full potential. Same caveat about installing 50 amp breaker until HPWC arrives.

P.S. If the builder is long gone, a trip to Home Depot to visually see and/or purchase the wire size in question will answer which wire size it is. Look at the cross section of the wire ends to compare.

dcopperfield said:

See attached picure of the wire with a ruler for reference. Thoughts? Will this work with the HPWC?
View attachment 12227

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The thickness of the insulation can vary, but will be pretty close. I took a spare piece of #2 and #6 THHN/THWN and measured with the outer jacket. The #2 comes in at about 1 cm and the #6 comes in at about 5 mm. It's likely you're sized for the 80A appropriately. Question is whether that's a #4, #3, or #2 wire -- and only the markings on the jacket will tell you such.

If you can give me a measurement of the diameter of the wire itself -- not including jacketing -- that will help much better.

dcopperfield said:

Looked again and no markings on the jacket... Here is a cross section view with measurements. If you guys dont know what size it is form the pictures, i might just take your advice and run down to home depot and compare...
View attachment 12243View attachment 12244

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It's too hard to see without you holding the tape flat against the widest portion of the wire so we get the diameter. With that said, from what you show it appears to be #2 or #3 which would work for the full power of the HPWC. You'll want to swap that 80A breaker with a 100A breaker for the full load. In the meantime, you'll need to use a 50A breaker with a 14-50.