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I'm running 6 gauge cable for a NEMA 14-50 outlet for a Level 2 EV charger. I'm hoping to drop it down into a wall into a remodel box. Normally I'd drill a 3/4" hole on center of the 2x4 top plate but we have have a 4x8" old cedar beam running the length of the house (30'+, house was originally built in 1921 ). This beam is continuous and acts as a header for two doors and as a top plate for walls for the rest.

Should I treat this beast as a header and avoid drilling or is it really just an insanely thick top plate I can drill through? (Also is there a name for this kind of beam?)

Thanks!

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    I can't answer the actual question. One of the people who knows the answer will. But possibly important: what is the 14-50 going to be used for? If the answer is oven, I'd recommend hardwiring. If the answer is plug-in welder or other tools, fine. If the answer is plug-in RV, fine. If the answer is Electric Vehicle Charging then STOP and we can help. A 14-50 will work for EV charging but is usually not the best choice. Sep 5, 2023 at 3:49
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    It is for a level 2 EV charger. Our city has a guide on installing each level type and it recommends an industrial 14-50. I'd be interested in your thoughts.
    – mike
    Sep 5, 2023 at 18:48
  • Note that this "industrial" 14-50 may require a copper cable. You could use an aluminum cable and pigtail copper on the ends with the proper Polaris connectors, but this would take up more room in the box. Sep 6, 2023 at 1:53
  • Thanks! I have an all copper cable.
    – mike
    Sep 6, 2023 at 14:56

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I wouldn't have any concerns about such a hole over common wall studs. As you've implied there's no need for a header there, assuming stud intervals of 24" or less. You'd want to avoid doing so over an opening, but even then it would probably be fine--most modern headers have a gap in between two members anyway.

I'd just call it a continuous beam. I've installed similar over series of windows and doors in lakeside porches, for example, to ensure lateral stability.

I'd bet that the beam is fir, not cedar. I don't recall ever seeing cedar used in a structural capacity, and the pinkish color of fir can be deceiving. A clever nose can tell for sure.

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isherwood's answer covers the stated question of "can I drill this hole". But there is a very important issue: What do you do with the wires at the end?

I highly recommend NOT installing a 14-50 receptacle. Far better, in almost all situations where you intend to use a receptacle exclusively for EV charging (as opposed to, for example, sharing it with an occasional RV hookup) is to:

  • Figure out how much power is available using a Load Calculation.
  • Consider a lower charge rate, which could save you some money on the wire as well, particularly if your load calculation doesn't give you 50A of room.
  • Hardwire directly into EVSE (e.g., Tesla wall charger) rather than plug/receptacle, using the appropriately sized wire.

Take a look at the Technology Connections video to see a bit more information about charging speed. The bottom line is that 30A, or often even just 20A, is sufficient for most people, most of the time. If the EVSE is more than a few feet from your panel, that will save you quite a bit on wire.

But the bigger issue is the Load Calculation. A load calculation takes the size of your house, certain required circuits (kitchen, bathroom, laundry, etc.), fixed appliances (oven/cooktop, water heater, HVAC, etc.) and comes up with a number that represents the total expected load for your house. You compare that to your utility service to see how much you can spare. If your service is 100A and your current (pun intended) usage is 70A then you can, just barely, add 30A for EV charging. If your service is 200A and your current usage is 120A then 50A is no problem at all. If your service is 100A and your current usage is 90A then it is time for a heavy up. And if your service is 200A and your usage is 190A then (a) replace tankless water heating with a tank, (b) replace resistance electric heat with a heat pump, or (c) look into various load sharing/balancing options so that the EV only runs when there is power available.

The only part of the city guidance that makes sense is "industrial 14-50" - that is, if you are installing a receptacle for EV charging, make sure it is a really good one. There are many reports of problems with some of the less expensive (but UL or ETL listed) 14-50 receptacles when used for EV charging, likely because the run time is a lot longer than typical use for welding or other tools.

Another big advantage of hardwired EVSE is GFCI. EVSE, by design, handles GFCI. But the latest NEC requires GFCI for just about anything in a garage or outdoors, so a 14-50 now needs an expensive GFCI breaker. Not all jurisdictions have adopted NEC 2020 yet, and many have made exceptions to this rule, but it is a definite issue to consider.

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  • Didn't you have a writeup (or several) to which you could link, rather than writing up a misaligned answer here?
    – isherwood
    Sep 5, 2023 at 19:06
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    Sorry about the @ issue. And there should be a canonical post for exactly this purpose... Sep 5, 2023 at 19:10
  • Thanks for all your info! I was actually wrong about the city recommending the 14-50. We are looking at the 14-50 outlets because of flexibility. We think we will buy an EV from a differen to Maker in 5 to 10 years and want to be able to charge from the same outlet. I'm check the load! Thanks
    – mike
    Sep 5, 2023 at 19:20
  • Our city does require a GFCI but I've heard some inspectors won't accept the EVSE as meeting that requirement. I have already purchased the pricey gfci 50 amp breaker. It's really not that pricey considering the one bid we got for this was $3k and all my parts have totalled $300.
    – mike
    Sep 5, 2023 at 19:26
  • In the grand scheme of things (compared to the cost of the EV itself!) it isn't much. But the extra cost (beyond a regular breaker) for GFCI is $100 - $200 (depending on brand, and you have no choice on the brand - it has to match your panel), plus the cost of good quality 14-50 receptacle. So it is isn't a huge deal but it is still money that could be spent better elsewhere if it isn't actually needed. Key is that EVSE includes GFCI. Sep 5, 2023 at 19:36

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