Picked up my black Model 3 LR AWD with Aero wheels on May 22. Installed High Power Wall Connector (HPWC) at home by myself in the following weekend and save $800.
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eprosenx
Active Member
Welcome to the forum!
I love DIY installs! Thanks for putting together the video.
A few comments:
That NM cable (Romex) should have come all the way into the back of the Wall connector with a strain relief clamp on that. You are not supposed to run through the wall without sheathing / conduit. Now clearly though the wire is not likely to be damaged in the wall in that setup...
NM cable is limited by code to the 60c rating and so it is only good for 55 amps which means at the 80% derate (required for EV's due to continuous load), you can't set the Wall Connector to the full 60a/48a setting. This is the only actually concerning thing I wanted to point out. I suspect in reality it would be ok (the 60c rating limit on NM cable is a hold over from in ceiling luminaries getting too hot - the actual romex you bought is probably 90c insulation rated). But this very much clearly is a code violation as-is. To resolve it you would need to downgrade to a 50a breaker and set the Wall Connector dial one notch down, OR upgrade to 4 AWG NM cable. (or do 6 awg THHN in conduit)
The white conductor is I think supposed to be "permanently" marked as a hot conductor (typically by wrapping the entire thing in black or red electrical tape).
But I like it! Thanks for sharing!
Thank you very much for your comments and concerns.
I have double checked my video and found that I did not have sheath inside the wall. My wall is an interior wall and should be safe. But I will correct it by adding a plastic tube, once I have a chance. Thank you very much for pointing that out.
I have done a lot of research and watched many videos on YouTube. I saw many people used conduit to run the wire. Later I was pretty sure that only exposure to exterior or active places, like garage, requires conduit. NM cable (Romex, Non-Metallic Sheathed) is good for indoor, especially basement. You can see in the video, there are lots of different Romex cables, 15A(white), 20A(yellow), 30A(orange), stapled on beams and walls in my basement. So I decided that NM cable is OK for my project. I think the only thing I did not do is to use the clamp inside the Wall Connector. I saw many people use clamps and even put silicon gel to protect it, but they are installing Wall Connector outside of garage/apartment. My garage wall is cool and dry, I don't have to deal with weather at all.
For cable spec, the Romex cable I used is NM-B which the insulation rating is 90C. Tesla recommendation is 60A circuit breaker, 6 AWG wire, Wall Connector setting is 48A. All YouTube video poster were using that configuration. Only difference is that all of them use 6/3 cable instead of 6/2 cable. I have found 6/2 cable (2 x 6 AWG + 10 AWG bare copper ground) does meet all requirements and save almost 1/3 of copper. 6/2 cable saves money and make installation easier as well.
SDRick
Active Member
The chart above references THHN wire in conduit. Romex (NM cable) has its own chart which utilizes the 60° rating even though the individual conductors are rated 90°. Best I have been able to discern is that for EV charging applications a 60 amp breaker requires 6 gauge THHN in conduit or 4 gauge Romex.
Has anyone found different?
Has anyone found different?
eprosenx
Active Member
Yeah, I don't know all the nuanced details of where NM wire is allowed to be run exposed by heart, but it is allowed to be run exposed in unfinished basements (which I think yours qualifies as) with certain restrictions. I am not sure if your installation is technically allowed as is or not (the part where it runs across the wall may require some form of protection technically).
You are correct that the NM-B cable is rated to 90c, but there is this specific code stipulation 334.80 (in 2017 NEC - NFPA 70) that says you are only allowed to calculate NM cable using its 60c rating. 6/2 absolutely makes sense over 6/3 though. The neutral wire is otherwise totally a waste for a Wall Connector.
It is a bummer that it sounds like there is a lot of bad information out there on YouTube. This is about as cut-and-dry of a code mistake as you get. I have posted below the term of the code that specifies you can only use the 60c rating:
The NFPA (who publishes the national electrical code) has recently capitulated and now allows free access to the code if you register. You can find it here:
NFPA 70®: National Electrical Code®
You can also read all about where exposed romex is OK and not ok in section 334.
My apologies for raining on your parade here! But the code is the code...
I did not TRUST "youtube videos". I did my own research. But the things are not all listed clearly. When I searched for what "-B" in NM-B strands for, all material I could find explains "-B" means rated 90C instead 60 without "-B". I would not argue with @eprosenx, but 334.80 never mention about NM-B type cable. That still puzzles me.
I have tune down my charge current from 48A to 40A. The ampacity should have no question anymore, while it is still much better than mobile connector's 32A max (240v) and 16A max (120v).
UL tests NM cables with and without -B suffix. Both are Listed within the scope of UL 719, and both are treated as NM cables as called out in the NEC. NM-B is a subset of NM cable.
NM cable is ampacity rated under the 60 degree C column, not the 90 degree C column, but the higher temp rating can be used to offset other deratings such as high ambient temperature, or grouped conductors. I hope his NM cable followed a path back to his panel in it's own holes through joists.
NM cable is ampacity rated under the 60 degree C column, not the 90 degree C column, but the higher temp rating can be used to offset other deratings such as high ambient temperature, or grouped conductors. I hope his NM cable followed a path back to his panel in it's own holes through joists.
The code has overhead built in, but there’s always inherent risk of conductor damage on install, and degradation over time with thermal cycling. The hotter the conductor gets the more this is exacerbated. Normally in residential service, you don’t see enough load for long enough to sustain high conductor temperatures aside from space heater use. And space heaters are a common cause of electrical fire. I’d imagine a great deal of the time the issue is the wiring or outlet and not the heater itself. But for applications like EV charging where you do intend to load the conductor considerably and subject it to significant thermal cycling, it’s sensible to both use the 60C rating and oversize from there. If the whole house has sketchy wiring and the EV charger is loading an old main panel near design limits, the justification to exceed code probably isn’t there. Most reputable electricians would tell you to rewire the whole house in that case, but more often people just find another electrician that does what they tell them to.
Electrical stuff tends to be about acceptable risk. If you can minimize the uncertainty and know the risks for failure are low, you can get away with loading the conductors more. For chassis wiring the ampacity for the same conductors is considerably higher. And for power transmission sensible limits are much lower. You’re probably fine using the 90C table, but I wouldn’t do it, and you’d have a tough time finding an inspector to not notice that. But then again, I’m running a #1 THHN homerun in EMT with the intent of it being loaded at 36A.
Electrical stuff tends to be about acceptable risk. If you can minimize the uncertainty and know the risks for failure are low, you can get away with loading the conductors more. For chassis wiring the ampacity for the same conductors is considerably higher. And for power transmission sensible limits are much lower. You’re probably fine using the 90C table, but I wouldn’t do it, and you’d have a tough time finding an inspector to not notice that. But then again, I’m running a #1 THHN homerun in EMT with the intent of it being loaded at 36A.
SDRick
Active Member
You couldn't find anything bigger to run for that 36A circuit?
eprosenx
Active Member
Yeah, I am sure you will be completely fine with 40a of charging! I have 48 and it is pretty overkill most of the time. ;-) Note that I think technically you should downgrade that breaker from 60a to 50a in addition to changing the setting on the Wall Connector. While the next-size-up breaker rule would allow for a 60 (since the wire is rated to 55a), I think for that to apply you may need to have a load that is over 50a but is 55a or less. (i.e. you should only use that rule exception if you need to get every last ounce out of that wire - though I would need to go re-read that code section to verify if it is allowed or not) From a practical standpoint though, I have seen vastly worse things done. That one raises an eyebrow for me, but I would not loose sleep over it (though I would do a 50a breaker just to make sure there was never any question).
I apologize, I feel like I am beating up on you a bit (I really do love DIY installs!). I noticed something else in the video that raised my eyebrow but before I mentioned something I needed to go look a couple of things up (which I have now done).
So I was wondering why (or even how!) you bought Murray breakers instead of Siemens ones. Siemens bought Murray forever ago... My suspicions as to why are I think confirmed though. Back in the 1965 NEC they came up with this concept that there should not be more than 42 total poles in a breaker panel (which I think includes the mains, so practically it was 40 breaker positions). Since then (up until recently) all the manufacturers had to come up with a way to keep folks from installing more than 40 breaker poles (even with tandems). Most did this via a "keying" system that did not let you put a tandem breaker into a position on the bus unless that bus stab was notched. So there are a lot of panels out there that are 20 bus stabs, all of which are notched (all can be tandems for a total of 40). Then some panels have 30 bus stabs, 10 of which are notched. Others have 40 bus stabs and NONE of them are notched.
I am guessing your panel falls into this last category. I suspect you are not technically allowed to use ANY tandems in your panel.
Now panels prior to 1965 did not have these notches at all, but they were allowed to use tandems, and so they kept making breakers that were "non CTL" - so non "circuit total limiting". But they are only *supposed* to be used in those ancient panels. But a lot of folks use them in modern panels anyway of course...
Fast forward to today, and 2008 NEC did away with the limit on the number of breaker poles, HOWEVER, all the manufacturers had to come out with new product to allow more than 42 poles and have it re-certified. This has taken a very long time since code is not adopted that quickly everywhere (and they did not want to limit where they could sell their panels), and a lot of this stuff has not otherwise been updated in YEARS. So it is only fairly recently that new panels have been widely available with more than 42 breaker poles allowed.
It is also very important to note that the panels sold in between 1965 and 2008 all must be used in accordance to their testing/ratings, and so you still are not allowed to exceed the 42 poles even though that requirement no longer exists in more modern code.
So unless you have a panel newer than 2008 that is clearly marked and allowed to have more than 42 breaker poles, all the tandems in your panel are not allowed.
I am guessing that technically those Murray breakers are not allowed in the Siemens panel (even if they were CTL style breakers) as they are not listed as compatible with your panel.
From a practical standpoint, I highly doubt you will ever have an issue (I see the wrong breakers even from other manufacturers used all over the place), but I can only advise you on what I understand of the code. ;-)
P.S. How come you used a 60a Murray breaker and not a Siemens one? You did not need a tandem for that one, so I would have assumed the Siemens for your panel would have been a lot cheaper?
Just answer your PS question first.
I went to Lowes and Home Depot, they both sell Murray only. All sales clerk said they are all compatible. I hope they don't have significant quality difference.Good suggestion on 50A breaker. Just about $12 and very easy to change it. The worst danger is running current slightly under 100% of the the breaker ampacity. The will not trip the breaker but generate enough heat to burn it.
I choose to use tandem breakers to make room for HPWC due to that is a quick solution. I am sure I am very safe for now. Most of the circuits in my house have very light load and most of the NEMA connectors are hooked with cell phone chargers, laptop power supplies and etc. . Of course, inspector may argue that potentially all lines might run full 15A and it will be a problem. Just like when I applied for a home loan and the lender complaint that I have too many credit cards. Even I had proved that all cards have zero balance but he argues that what if I charge all of them in full.
For that concern, I have purchased a clamp multi-meter and plan to survey all lines in the panel to make sure all lines are balanced. I might be able to combine some light load lines and remove some tandem breakers.
eprosenx
Active Member
Just answer your PS question first.
Good suggestion on 50A breaker. Just about $12 and very easy to change it. The worst danger is running current slightly under 100% of the the breaker ampacity. The will not trip the breaker but generate enough heat to burn it.
I choose to use tandem breakers to make room for HPWC due to that is a quick solution. I am sure I am very safe for now. Most of the circuits in my house have very light load and most of the NEMA connectors are hooked with cell phone chargers, laptop power supplies and etc. . Of course, inspector may argue that potentially all lines might run full 15A and it will be a problem. Just like when I applied for a home loan and the lender complaint that I have too many credit cards. Even I had proved that all cards have zero balance but he argues that what if I charge all of them in full.
Very weird that Home Depot did not have Siemens. I buy Siemens breakers around here all the time from Home Depot.
Regardless though, I am pretty sure from what I have heard that they are literally identical from what folks have been able to compare. They use the same plastic molds anyway...
On the Tandem breaker thing (total number of breaker poles allowed) I actually have no idea what folks thought they were trying to solve with that rule.
Load calculations have nothing to do with total number of circuits (well other than small appliance circuits) so who cares how many breakers you have? To your point, encouraging folks to consolidate down to less breakers just to meet that stupid rule does *not* make things safer!
On the NM cable only being allowed at 60c- From the reading I have done, this was done because they were having an issue with wires melting in light fixtures that were in ceilings with thermal insulation in them with really hot attics above them. Rather than make some rule specific to these kinds of fixtures they force derated ALL NM cable regardless of application. This clearly impacts EV charging installs like this even though you would never have an EV install in thermal insulation. So I would not stress too much about your install.
Note that had you bought SE wire (which is virtually identical to NM cable) it would have retained the 75c insulation rating.
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SDRick
Active Member
Can you elaborate on the SE wire or provide a link? Thanks.
eprosenx
Active Member
Yeah, so SE wire is more typically intended for "Service Entrance" applications (like from the meter can to the main panel), but it is also allowed for branch circuits in many (most?) situations. Code has gone back and forth on it, but I believe in 2017 NEC you can use it at the 75c insulation rating. The issue I have found is that getting it in the exact right form factor has been hard. Most of it is aluminum wire (but they absolutely make it in copper too). Nearly all service entrances are done with aluminum and most sub-panel feeders (which is the other really common application) are also aluminum. The Tesla Wall Connector does NOT accept aluminum wire. So wire intended for sub-panel feeders has four wires, hot, hot, neutral, and ground. The Wall Connector only needs hot, hot, ground. Then there are a couple styles of SE cable. One has the neutral/ground concentrically wrapped around the hot conductors. I think this is intended for protection, but it makes terminating the wire a pain in the butt. They do make "round" versions of the cable (I think labeled SER - R for reinforcement tape vs. the concentric ground).
So basically I am looking for this: Southwire 500 ft. 6-6-8 Gray Stranded CU SEU Cable-13081505 - The Home Depot But I need it in SER so I don't have to deal with the pain of the ground wire being all separate strands.
From what I can tell, nobody makes SE wire in the exact forms I am looking for off the shelf.
I have tried contacting Southwire in the past (a major manufacturer) to suggest they make a form of wire specifically for EV charging. Specifically, something with two 6 AWG wires plus an appropriately sized (round) ground wire, and a cable with two 3 AWG wires plug an appropriate side ground. Those two variants would be GREAT for 60a Wall Connectors and 100a Wall Connectors respectively. Having it be SE wire vs. NM wire would deal with the stupid 60c issue. ;-)
Here is what Southwire makes today: (but their explanations of SEU vs SER are really bad...)
https://www.mysouthwire.com/medias/...duct-specifications/he6/h1f/8854083436574.pdf
The descriptions of SEU vs SER are a lot better in the aluminum version of the product specs:
https://www.mysouthwire.com/medias/...duct-specifications/haa/h6c/8854083371038.pdf
This site has a decent explanation:
SER & SEU Cable
eprosenx
Active Member
I am struggling with this as I am planning on building a house soon. Part of me is tempted to just run conduit and pull in THHN as needed. :-( But if you are not doing the work yourself then that is super expensive. Optimally I want to be able to support a 100a circuit (which means 1” conduit) and I also want to have the ability to do “sharing” of the circuit which means some kind of signal tie wire (which could change in wire style from brand of EVSE to EVSE). I then also want to be able to have separate 50a circuits to each side of the garage OR one single 100a circuit shared. So this makes the conduit design complex.
Most folks are probably just running NM cable (Romex) at 6 gauge copper and limiting themselves to the 40a charge rate (which is what a 6-50 or 14-50 is limited to anyway). To be honest, this is sufficient for nearly everyone’s home charging needs and 6awg NM cable is probably really easy to come by since it can be used for ovens (not sure what most electricians are running these days - some may still run aluminum since it is way cheaper).
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