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Future-proof NEMA 14-50 install

Discussion in 'Model 3: Battery & Charging' started by cleveland97, Aug 23, 2018.

  1. cleveland97

    cleveland97 Member

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    Sorry for starting yet ANOTHER NEMA 14-50 thread, but I've been reading this wonderful forum for days and still have a couple questions...

    Background - waiting on delivery of my Model 3 AWD and trying to get my charging situation squared away. I have an attached garage and my electrical service is fine. I've decided to install a NEMA 14-50 for now. I had an electrician come take a look and we agreed that I would run a 6-3 romex from the garage into the basement, with the garage portion being inside conduit, and he would then come back and do the panel work and install a surface-mounted 14-50 outlet to make sure everything looks good.

    Since then, though, I'm second-guessing the plan - I would like to "future-proof" things so I can easily switch to a Wall Connector if I decide later.. From everything I've read 6-3 romex won't safely support much more than 40 amp charging (especially since at least part of it will be in conduit) because it gets de-rated for being romex and again for being in conduit.

    So I've priced out 4-3 romex instead... it's only ~$50 more than 6-3. Seems like a no brainer if it would work. In the short-term I could use the UMC on the 14-50 to charge at 32 amps, but someday down the road I could swap the 50 amp breaker for a 60 amp and replace the 14-50 with a Wall Connector and charge at say 48 amps.

    Here is the question:
    Would it be ok for me to run 4-3 romex instead of the 6-3 romex, and still have the electrician put a 50 amp breaker on it and a 14-50 outlet on the other end? Will the #4 wire fit into a standard 50 amp breaker? will it fit into the connectors on the back of a standard 14-50 outlet? I don't want to do this and have him show up and tell me I've screwed up.

    btw - I'd prefer to stick with the romex so I don't have to run conduit the entire way - current plan would only have conduit in the garage but not on the basement portion of the run.

    Thanks in advance for your advice!
     
  2. brkaus

    brkaus Active Member

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    Yes, you want to run 4-3 romex for future 60A breaker. You may (must) use a 50A breaker as long as there is a 14-50 outlet on the circuit.

    The only thing I'm not sure about your plan - is running partially in conduit. I don't think you can put the romex in conduit. You did mention derating, which is probably possible but I do not know the rules for it.

    Edit to add - I just checked the labeling on my spare 14-50 and it does say it will accept #4 wire.
     
  3. cleveland97

    cleveland97 Member

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    Thanks a ton, brkaus, for checking the breaker! Didn't know where to confirm that.

    In terms of romex in a conduit I've read LOTS of conflicting things on that over the last few days. But my electrician said it was the right thing to do to protect it in the garage. I'd really prefer to avoid THHN because I think that would require me to run conduit all the way to the panel?
     
  4. Cosmacelf

    Cosmacelf Well-Known Member

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    I think what is normally done in these situations is to run romex to a junction box where you connect the conduit to. Then you run THHN wire in the conduit, and romex in the exposed basement, and wire nut the runs together in the junction box.

    Honestly, I would go ahead and just install the Wall Connector now. It is a more robust charging set up.

    But yes, you can still install a 50A breaker if you use heavier gauge wire. I think the 4 gauge should still fit in the receptacle and breaker lugs.
     
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  5. brkaus

    brkaus Active Member

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    Romex can be run in conduit short distances for protection. I was never able to find the complete rulesrules. I wanted to use it as a stub up from my outside breaker box into the attic. Ended up with a totally different approach as I finally decided on adding a meter for my EV.

    The only other thing I can suggest is if you can "hide" some slack in the wires, so you could later pull more out of the outlet and connect to the WC, you will avoid a future splice. Depends on how you are planning on installing the outlet.
     
  6. cleveland97

    cleveland97 Member

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    Thanks for the thoughts on the junction box idea... worth considering for sure.

    To your other point - Another factor on going with the NEMA 14-50 first is that we might only be in this house for a few more years and, if I do go with the wall charger later, I'd have the option of putting things back to 14-50 for the next owner (and take the WC with me).
     
  7. brkaus

    brkaus Active Member

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    It's always easier to shorten wire...
     
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  8. NickFie

    NickFie Member

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    Makes sense to me. As long as the breaker rating is at or below the outlet's rating, and the wire is at or above the outlet's rating, you should be OK.

    Two stories.

    1. Did a similar approach with a friend. We installed a 14-30 outlet so I could charge the S100D during my visit. He supplied the 30-Amp breaker. I provided 6-3 romex with ground, the 14-30 outlet and a 14-50 outlet. If he wants to up-rate the setup, he can swap the breaker and the outlet. The box and the cable stay.

    2. Visited a cousin with a 14-50 outlet in the garage. Foolishly, didn't check the nearby subpanel to see whether it had a 50-Amp breaker. Starting charging at 40 Amps, power cut out in about 5 minutes. The 50-Amp outlet was supported by a 30-Amp breaker - easy to spot after it tripped. Restarted at 24 Amps and by morning had 100 Amps for non-stop drive home.
     
  9. Cosmacelf

    Cosmacelf Well-Known Member

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    Yeah, I’ve been burned a few times by random 14-50s connected to smaller breakers. What I do now when I don’t know which breaker protects it, is start charging at 40A, and then feel the various double pole breakers and see if any of them get warm or hot. It’s crude, but works usually.
     
  10. cleveland97

    cleveland97 Member

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    I was thinking about this overnight.... I MIGHT be able to run the 4-3 romex up the garage wall, into the garage attic, across the attic and back down the other wall as an alternative to running the conduit in the garage. That would add about 15' of run and that would be inside insulated walls where I couldn't really fasten it to anything (without cutting a bunch of holes in the drywall) - it would just be loose in there.

    If I could do that do you folks think that would be better than running romex in conduit or introducing a splice to switch from romex to THHN in the middle?
     
  11. Runt8

    Runt8 Active Member

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    I don’t think it matters from a technical or safety point of view, but I always like to hide the wires if possible just for a clean look.
     
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  12. Lasttoy

    Lasttoy Member

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    My electrician said the breaker size depends on house service.
    200 amp service, 100 amp breaker
    100 amp service, 50 amp breaker
    Then you get the 4.3.
    I installed a 14.50. 50 amp breaker. Charges my S from empty to full over night. Easy.
    Not sure what max amps a 3 will pull? My S senses what I am plugging into. I have dual chargers. I plugged into a charger at the Hilton in Daytona. It was wired wrong, it smoked. The TRYP hotel here has 220v, 100 amp. My car senses it and charges at 80 amps.
    Good luck.
     
  13. LonestarV

    LonestarV Member

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    48 from a HPWC
     
  14. Chak

    Chak Member

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    #14 Chak, Aug 24, 2018
    Last edited: Aug 24, 2018
    Can you please clarify, "As long as the breaker rating is at or below the outlet's rating" and "The 50-Amp outlet was supported by a 30-Amp breaker"? Both are contradicting? In the second statement your breaker rating (30 amp) is below outlet's rating (50 amp), correct?

    I am about to start 14-50 install in my garage and just wanted to make sure I got this right. 14-50 outlet, 6-3 romex, with 50 amp breaker.
     
  15. eprosenx

    eprosenx Member

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    Romex is not de-rated when run in conduit. It is NM style cable which typically has an insulation rating all the way to 90c, but the NEC rules say you have to treat it as if it was only 60c rated, so it is already significantly derated (the reason for this is they assume you are running it in thermal insulation in attics and such).

    Yes, if you ran 4 awg romex you could actually install a 70 amp breaker later and set the HPWC to that. Over 60 won't help with a Model 3, but it could later help with an S, X, Roadster, Y, etc...

    I believe most 50a breakers will take up to 4awg wire and the same with 14-50 receptacles, though you might want a bigger junction box to deal with the stiff wire slack. The wire gauges allowed are printed on the breakers/receptacles. Typically they are able to take larger wire to accommodate aluminum, but since you would be using copper you can just use an overly large ampacity wire.

    You might need a larger conduit in the garage to run it in.

    Romex is allowed in conduit. It is actually required for some short sections for physical protection as you mention. I don't even know of any code section that says you can't run it in conduit long distances, but that would just be silly. THHN is way easier to deal with.

    Yes, Romex in conduit without a doubt is fine. Again, you are already forced to derate it to the 60c rating where it otherwise would be able to use the 90c rating. The 60c derating apparently was due to wire overheating in ceilings with thermal insulation with hot attics above them and going into light fixtures that were themselves very hot.

    I am a huge fan of the Wall Connector. I love mine. If you are planning to do one I might just go that route day one... But planning to remove it and replace with a 14-50 is not a bad idea for when you move. That way you can still advertise EV charging, but not have to leave the $500 unit.

    I am *not* a fan of needing to wire nut things together wherever possible. More points of failure is bad. I think the max size wire nuts I have seen are for 6 AWG. Then you need to be using split bolts or terminal blocks or something to do the connections.

    Yes! While normally not a good practice, storing a few extra feet of wire somewhere in the basement in a service loop might be a good idea for this install in the event you need to adjust the height later for an outlet vs. a wall connector.

    So the above statement is correct. The receptacle must be of equal or greater ampacity than the breaker. Basically it is to keep stuff from melting. A 50a rated receptacle on a 30a breaker is fine since the breaker will blow before the receptacle melts. The other way around is no bueno.

    While it is probably poor practice to put a 50a receptacle on anything less than a 40a breaker (50a is always preferred, but there are many valid installs out there for ranges and such on 40a circuits since there is no NEMA 40a receptacle), it is allowed by my reading of the NEC when it is the ONLY receptacle on the circuit (which is a requirement for EV outlets anyway).

    For your install: 14-50 receptacle, 6-3 romex, and 50a breaker is all perfect. You can't go wrong with that. Just as long as you are not running the romex in exposed locations. Good luck!
     
    • Informative x 5
  16. NickFie

    NickFie Member

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    Not sure why the 50a receptacle and 30a breaker combination was chosen. Though my story about the 30a breaker tripping illustrates that such a configuration would be low risk but high frustration.

    The 30a breaker doesn't trip when the attached high-capacity air compressor with giant air tank operates. Suspect there's substantial surge when compressor starts, then lower current draw. Air compressor may have come with a 14-50 plug since the power cord was about 6 or 7 feet. Reasonably confident it's the only outlet on that circuit, though I didn't open the panel.

    Maybe that's the difference between and engineer and a psychologist. When visiting, the engineer looks at plumbing and wiring. The psychologist looks at the magazines, books and decor.
     
  17. cleveland97

    cleveland97 Member

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    Is there a code-friendly way to run THHN outside of conduit? I'm wondering if I could just use THHN the whole way, exposed in the basement and in conduit in the garage. Thus avoiding a) the need to run conduit in the basement, b) the concern about cramming romex through conduit AND c) a splice in the middle.
     
  18. Chak

    Chak Member

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    Awesome, thanks a lot eprosenx.
     
  19. eprosenx

    eprosenx Member

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    No. You could run MC cable though. I think that would even let you run higher ampacity on the same gauge wire. It is not as pretty as EMT in the garage but I think it meets all the criteria.
     
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  20. Atoms

    Atoms Member

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    Romex cannot be run in a conduit. There is too much thermal insulation and the wire will get hotter and may exceed its rating. If there is a fire, don’t expect the insurance company to cover. Romex is to be used INSIDE walls without conduit. I used AWG4 XHHN-2 inside 1” EMT. You can also use flexible conduit if that is easier. Make sure you have a permit for the work before you start.
     
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