Model S - HPWC (High Power Wall Connector)

[FlasherZ]

It would be better than what I'm doing now. AWG 4/0 to the garage, anyone?

That stuff is not fun to work with.

Personally, I prefer individual cables in PVC for sizes that big.

Instead of one huge cable to my garage, I'm going the route of doing multiple branch circuits in multiple conduits. So from a dedicated service panel for car charging (which must be co-located with my other 2 service panels in the basement), I'm running one conduit for each HPWC to a big junction box in the garage each with #2 copper, and each #2 run goes to a disconnect above each garage bay. I also put a breaker in each disconnect for a NEMA 14-50 that takes advantage of the non-concurrent load rule as a backup. That avoids having to work with very large conductors. I can get 100A each out of #2, while 4/0 AL is limited to 180A and can't even support 2 HPWC's configured at full power.

 

[AWDtsla]

I can get 100A each out of #2, while 4/0 AL is limited to 180A and can't even support 2 HPWC's configured at full power.

But somehow 4/0 is rated for service entrance @200A?

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There is also prior art - Evercharge uses this model. There are a few other companies who have developed charging solutions for multi-family housing as well. I wouldn't be surprised if Tesla puts something like this out there in the next couple of years as more and more households become 2+ EV households.

I think it will need more than that by Model 3, just so pole transformers don't start blowing up. JB Straubel hinted at such things.

 

[scaesare]

It would be better than what I'm doing now. AWG 4/0 to the garage, anyone?

That's beautiful...

 

[FlasherZ]

But somehow 4/0 is rated for service entrance @200A?

Well, it can be interpreted one of two ways:

310.15(B)(7)(1) says that when a feeder or service entrance cable delivers the entire load for a single-family dwelling / individual dwelling unit, it can be rated at 83% of the load. So yes, it's good to 216A. This is because the code anticipates a lower usage on a highly aggregated main feeder, vs. something designed for a couple of loads. (Note that 2011 NEC had a table that specified AWG sizes based on amperage, and in 2014 they just refactored it to a static percentage.)

...or, if the calculated load required is only 180A, you can use 4/0 cable but protect it with the "next breaker size" up. The rating of the service is still 180A, it's just that it won't trip until the fault current exceeds the levels established by the 200A breaker. It's still illegal to violate that by adding circuits that would cause the art. 220 load calculation to exceed 180A.

The basic approach is you size a conductor for the load, then you size the breaker to protect the conductor. The conductor may never be rated less than the calculated load, but the OCPD (breaker) may be sized next-trade-size up from the conductor rating.

 

[andrewket]

I'm putting a panel in the garage with a 200A breaker on it fed by this cable. On it will be two HPWCs with 100A breakers, and a 14-50 for backup. Are you saying this violates code?

I have another 14-50 for the volt, but that's staying on the other panel which is served by a different feeder.

 

[FlasherZ]

I'm putting a panel in the garage with a 200A breaker on it fed by this cable. On it will be two HPWCs with 100A breakers, and a 14-50 for backup. Are you saying this violates code?

I have another 14-50 for the volt, but that's staying on the other panel which is served by a different feeder.

If you anticipate that both HPWC's may be used at the same time, then yes it does violate code.

Now, some electricians will "cheat", because they argue that as the current never exceeds 80A per HPWC, it's ok to skimp on the feeder. However, there's nothing in the code that gives that flexibility in the install. This is the same case where some electricians will argue that #2 NM cable is sufficient for a 100A HPWC install - they argue that the combination of the 25% overhead for continuous loads combined with the fact that the conductors in NM cable are really rated at 90 degrees, not the 60 degrees the code requires, means they can use a 95A-rated cable to serve a calculated load of 100A. Some inspectors may allow it to slide by, but the inspectors I've asked said they would fail it because nothing in the code gives them that flexibility. Your best bet is to contact your local permitting office and ask them if they will accept it.

There is a rule that permits a 75% demand factor for 4 appliances that are fastened in place, but you don't have 4 HPWC's here, so you can't rely upon that.

The way you determine this is pretty simple...

First, start by calculating your load. If you expect to be using both HPWC's and want the 14-50 to be backup (meaning, non-concurrent), then you'll require 160A of continuous load.

215.2(A)(1) says that you calculate the load per 220 parts III/IV/V.

220.40 says "the calculated load of a feeder or service shall not be less than the sum of the loads on the branch circuits supplied., as determined by part II of this article, after any applicable demand factors permitted". There are no demand factors that apply to 2 HPWC's in this case, and we'll take advantage of the 220.60 non-concurrent loads rule for the 14-50.

So, back to 215.2(A)(1)(a)... "where a feeder supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum feeder conductor size shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load". 160 x 1.25 = 200A, so the minimum feeder conductor size shall not be rated at less than 200A.

310.15(B)(16) is the table that shows maximum allowable ampacities of conductors. The 4/0 conductors you use are going to be rated at 90 degrees, but you almost always use 75 degC columns because it's extremely rare that you find residential equipment rated for 90 degC termination. Therefore, the conductors are good to 180A. Because your calculated load is 200A, you can't use this cable for these loads. Red flag #1...

Now, there's also another twist in here: You're using a cable assembly. When you use NM or SER, there are special rules. If that SER cable runs in a space with thermal insulation, 338.10(B)(4)(a) states that "where installed in thermal insulation the ampacity shall be in accordance with the 60 degC conductor temperature rating", which is 150A. As many garage walls and attics are insulated, this tends to be the case in many installations. (As a side note, NM or "Romex" must *always* take the 60 degree C column in its rating, per 334.80). Red flag #2...

I would recommend contacting your inspector and asking if they would permit that. Be sure you tell them you're offering an 80A *continuous* load when you ask the question. I've seen a lot of inspectors fail to consider the EV load as continuous.

Personally, I would run PVC and consider either AL 250 mcm / CU 3/0, or run parallel conduits with parallel conductors, since above 1/0 you can parallel them per 310.10(H).

 

[andrewket]

Also of interest, I'm planning on placing my second HPWC on the wall, almost to the ceiling. This way I can spool excess cable up high before the cable drops down between the two garage doors. Placing the HPWC at a "normal" level would be problematic as the excess cable would likely interfere with the operation of the garage doors. There just isn't enough space.

My electrician found code that says the coupler can't be placed more than 4ft above grade. He is interpreting this to mean the handle, or the part that plugs into the car. That seems a bit redundant to me, because if the handle == coupler, where else are you going to put it other than in easy reach, I.e. no more than 4 ft?

 

[andrewket]

If you anticipate that both HPWC's may be used at the same time, then yes it does violate code.

Now, some electricians will "cheat", because they argue that as the current never exceeds 80A per HPWC, it's ok to skimp on the feeder. However, there's nothing in the code that gives that flexibility in the install. This is the same case where some electricians will argue that #2 NM cable is sufficient for a 100A HPWC install - they argue that the combination of the 25% overhead for continuous loads combined with the fact that the conductors in NM cable are really rated at 90 degrees, not the 60 degrees the code requires, means they can use a 95A-rated cable to serve a calculated load of 100A. Some inspectors may allow it to slide by, but the inspectors I've asked said they would fail it. Your best bet is to contact your local permitting office and ask them if they will accept it.

There is a rule that permits a 75% demand factor for 4 appliances that are fastened in place, but you don't have 4 HPWC's here, so you can't rely upon that.

The way you determine this is pretty simple...

First, start by calculating your load. If you expect to be using both HPWC's and want the 14-50 to be backup (meaning, non-concurrent), then you'll require 160A of continuous load.

215.2(A)(1) says that you calculate the load per 220 parts III/IV/V.

220.40 says "the calculated load of a feeder or service shall not be less than the sum of the loads on the branch circuits supplied., as determined by part II of this article, after any applicable demand factors permitted". There are no demand factors that apply to 2 HPWC's in this case, and we'll take advantage of the 220.60 non-concurrent loads rule for the 14-50.

So, back to 215.2(A)(1)(a)... "where a feeder supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum feeder conductor size shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load". 160 x 1.25 = 200A, so the minimum feeder conductor size shall not be rated at less than 200A.

310.15(B)(16) is the table that shows maximum allowable ampacities of conductors. The 4/0 conductors you use are going to be rated at 90 degrees, but you almost always use 75 degC columns because it's extremely rare that you find residential equipment rated for 90 degC termination. Therefore, the conductors are good to 180A. Because your calculated load is 200A, you can't use this cable for these loads. Red flag #1...

Now, there's also another twist in here: You're using a cable assembly. When you use NM or SER, there are special rules. If that SER cable runs in a space with thermal insulation, 338.10(B)(4)(a) states that "where installed in thermal insulation the ampacity shall be in accordance with the 60 degC conductor temperature rating", which is 150A. As many garage walls and attics are insulated, this tends to be the case in many installations. Red flag #2...

I would recommend contacting your inspector and asking if they would permit that. Be sure you tell them you're offering an 80A *continuous* load when you ask the question. I've seen a lot of inspectors fail to consider the EV load as continuous.

Personally, I would run PVC and either 250 mcm conductors (AL) or 3/0 (CU) individually.

Both HPWCs will be used at the same time and often at their highest amperage. Conduit isn't really an option. You should see what these guys are doing to get the single cable through some of these walls.

Sigh.

 

[FlasherZ]

Both HPWCs will be used at the same time and often at their highest amperage. Conduit isn't really an option. You should see what these guys are doing to get the single cable through some of these walls.

Sigh.

Truth is that from a safety standpoint, they're not installing anything that's really, really dangerous and you'll find plenty of engineers that say you'll be just fine. From a legal standpoint, however, you obviously have to be concerned. As long as the inspector is good with it and green-tags it, you should be fine.

(Note that I've made a couple of edits since you quoted my text... nothing earth-shattering, mostly just clarifications.)

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Also of interest, I'm planning on placing my second HPWC on the wall, almost to the ceiling. This way I scan spool exceed cable up high before the cable drops down between the two garage doors. Placing the HPWC at a "normal" level would be problematic as the excess cable would likely interfere with the operation of the garage doors. There just isn't enough space.

I'm doing that, too. As long as your lockable disconnect is "accessible", generally means handle in highest position is no taller than just over 6', you're good.

My electrician found code that says the coupler can't be placed more than 4ft above grade. He is interpreting this to mean the handle, or the part that plugs into the car. That seems a bit redundant to me, because if the handle == coupler, where else are you going to put it other than in easy reach, I.e. no more than 4 ft?

Yes, that's a leftover from the first generation of code that anticipates big, bulky, fixed outdoor EVSE's that look like gas pumps. The coupler is indeed the part that plugs into the car.

In NEC 2014, 625.50 says that the coupler shall never be stored below 18" indoor or 24" outdoor. NEC 2011 had 625.29(B) which said the coupler shall not be stored or located below 18" or above 4'. In NEC 2014, they took out the maximum height.

 

[andrewket]

Great. Btw, I also made some spelling corrections that didn't make it into your quote.

 

[FlasherZ]

Great. Btw, I also made some spelling corrections that didn't make it into your quote.

I didn't even notice them, I read it the way you had intended I guess.

 

[Fezzik]

Andrew. are you using Al for both runs of both your cars?

 

[andrewket]

Andrew. are you using Al for both runs of both your cars?

Yes.

 

[FlasherZ]

Yes.

I'm going to assume you're using AL to the panel in the garage, then CU over to the HPWC. IIRC, the HPWC contacts aren't rated for #1, required to deliver 100A via AL (I believe the instruction manual says this, but I'd have to go through it to verify).

 

[andrewket]

I'm going to assume you're using AL to the panel in the garage, then CU over to the HPWC. IIRC, the HPWC contacts aren't rated for #1, required to deliver 100A via AL (I believe the instruction manual says this, but I'd have to go through it to verify).

I'll double check; you may be right. It's a much shorter distance. However, for the first HPWC, I believe it's higher gauge AL to a small junction box next to the HPWC and then it steps down to CU for the last foot.

 

[Fezzik]

Wow. Just finished a 4 day project. I had contacted a few electricians and one quote was for 9000 dollars. I was shocked. They wanted to drill to the outside of the house and then back into the house. I showed them a spot I thought would get access into the garage from the basement. They both said no. My previous house I had service wire in Al for as a temp until I got to the new house.
I have 2 200amp service. I ran nearly 80 feet to the first box and 175 feet to the second box. Oddly enough, I was able to get everything I needed from Home Depot.
Ran 2 sets of
1" conduit
100Amp breaker at the main, 100 amp breaker at the box, and 100 amp breaker going to charger.
2x #2 wire
1x #3 Wire
1x #6 bare copper wire for ground. I know I could use the conduit but I ran it anyway.
I ran two sets to the garage for the future electric car!
The box I have the HPWC connected to has 100 amp breaker for the HPWC, 50amp for the UMC incase the HPWC fails, and 30 amp for an air compressor. I have it written on the box there that only one breaker may be on at a time.

My dad helped me out and ran it, but GOD its tough to run those wires in 1" conduit. I found the trick is to keep the wires in the same position when running the conduit pieces through. I'll try to take some pics.

 

[Andyw2100]

I was charging earlier this evening at 80 Amps--something I almost never do--and received a "charging interrupted" notification on my phone. I went out to the garage to see what the situation was and found the HPWC with no lights on it whatsoever. I went down to my panel, and the circuit breaker was not flipped. I tried turning it off and back on, tried flipping the switch at the main box above the HPWC, but nothing had any effect.

I'm thinking it is more likely that somehow the HPWC stopped getting power than that the HPWC just went completely bad, and is showing no lights whatsoever.

With the power turned off at my main panel, I took the following two pictures of the fuses inside the box right above the HPWC--one in the off position, and one in the on position. Is there any way to tell from the pictures if anything is wrong with those fuses?

Thanks.

Switched Off

Switched On (Circuit Breaker Still Off)

 

[jerry33]

I was charging earlier this evening at 80 Amps--something I almost never do--and received a "charging interrupted" notification on my phone. I went out to the garage to see what the situation was and found the HPWC with no lights on it whatsoever. I went down to my panel, and the circuit breaker was not flipped. I tried turning it off and back on, tried flipping the switch at the main box above the HPWC, but nothing had any effect.

I'm thinking it is more likely that somehow the HPWC stopped getting power than that the HPWC just went completely bad, and is showing no lights whatsoever.

With the power turned off at my main panel, I took the following two pictures of the fuses inside the box right above the HPWC--one in the off position, and one in the on position. Is there any way to tell from the pictures if anything is wrong with those fuses?

There are fuses inside the HPWC. I'd check those.

 

[pgiralt]

I was charging earlier this evening at 80 Amps--something I almost never do--and received a "charging interrupted" notification on my phone. I went out to the garage to see what the situation was and found the HPWC with no lights on it whatsoever. I went down to my panel, and the circuit breaker was not flipped. I tried turning it off and back on, tried flipping the switch at the main box above the HPWC, but nothing had any effect.

I'm thinking it is more likely that somehow the HPWC stopped getting power than that the HPWC just went completely bad, and is showing no lights whatsoever.

With the power turned off at my main panel, I took the following two pictures of the fuses inside the box right above the HPWC--one in the off position, and one in the on position. Is there any way to tell from the pictures if anything is wrong with those fuses?

Thanks.

Do you have a multimeter to check if there is power coming in or not? Hard to know where the problem is without one. Could be a bad breaker, blown fuse, or bad HPWC. Would be easy to pinpoint where the problem is with a meter.

 

[Lloyd]

No, you will need to pull the fuses with the power off, and Ohm through them.