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According to the answer from Can I wire my infrared heating panels to my existing circuits?, it is not allowed to have general purpose receptacles on circuits that have >50% fixed load.

Does this also apply to dedicated receptacles that only feed one device? If yes, anything specific to consider?

Background: I’d like to add power supply for a wall-mounted tablet. A frequent recommendation is to use a receptacle with USB that is UL listed. The dedicated receptacle would be installed in the attic (circuit breaker is GFCI+CACFI) and only a small USB charger would be permanently installed in that receptacle. (The 5V wires are then routed down from the attic a few feet)

If this really doesn’t work, which options are there to get 5VDC in a hardwired way?

It would be very ironic if that doesn’t work because I can neither hardwire it, nor use a receptacle at the same time.

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    What would cause someone else next week/month/year from unplugging the charger and plugging in a space heater?
    – crip659
    Commented Dec 16, 2023 at 21:45
  • 1) Because it’s an attic 2) because I’m the only one accessing the attic. But joke aside, that’s the reason for my question. A dishwasher for example is a dedicated receptacle. I’m asking if my example can count as dedicated receptacle and/or what can be done to make it one (for example, a single receptacle etc.)
    – divB
    Commented Dec 16, 2023 at 22:05
  • Lastly, if that really doesn’t work, what options do I have to hardwire something that gives me 5VDC?
    – divB
    Commented Dec 16, 2023 at 22:06
  • Does it have to be on that circuit? They do seem to like putting USB charging ports into almost everything these days, even receptacles. Code is written a lot of times for the next person(idiot) that lives in that house. You can't say what the next person will plug in to that receptacle.
    – crip659
    Commented Dec 16, 2023 at 22:28
  • 1
    How much space for a chunky box do you have at that location? Commented Dec 16, 2023 at 22:43

1 Answer 1

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The problem is you're considering "receptacle + USB". But you only actually want to use the USB, and the problem is the receptacle part. Hopefully no space heaters, but who knows - maybe the next owner will use the receptacle to power a huge light display on the roof.

The solution is easy: USB only. For example, the Leviton USB4P-002-00W:

4 port USB

No general purpose 120V receptacle, so the only issue is how much possible power requirement this adds to the circuit. Not clear from the Leviton page. But 4.2A x 5V = 21W. It will be a little more due to conversion losses, but even if it is double, that's 42W, and at 120V that's ~ 1/3 A. If your existing hardwired loads leave at least 1A of headroom (also accounting for 80% continuous derates) then you should be fine.

You do need to check the requirements for your tablet or other device. USB current varies from the minimum 0.5A on up to 3A or possibly more. The 4.2A on a device such as this one includes all 4 ports - I am pretty sure you can't get that much current on an individual port. In particular, USB C can handle up to 3A at 5V, and even more with higher voltage. So check the specs to make sure that you get enough power. And also use a good quality cable - all cables are not created equal.

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    This sounds like it! Great!
    – divB
    Commented Dec 17, 2023 at 2:00

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