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When counting receptacles or outlets for a branch circuit (where the limit is typically 10 or 12 outlets), does a typical duplex receptacle count as one or two? It seems that they each count as two, but I'm having trouble finding something that clarifies that (one post I saw said two on the same yoke count as one).

I'm wiring up an electronics lab space and I need lots of outlets. This is usually solved with long power strips containing 10 or more outlets. I wanted to put in three 2-gang boxes with duplex receptacles in each spot. That's 12 or 24 outlets, depending on the interpretation.

So, is this one or two receptacles/outlets?

enter image description here

Thanks!

  • There is no NEC limit on number of receptacles - some LAHJ may have such cockamaimie rules. Calculated load on the circuit rules - in a typical "electronics lab" you'd be hard pressed to overload a 20A circuit with 20 outlets on it, unless you really love vacuum tube equipment. OTOH, why not toss a couple of circuits at it and put white outlets on one and brown or black on the other so you can manually load-spread? – Ecnerwal Feb 13 '18 at 2:28
  • See: diy.stackexchange.com/a/63330/18078 – Ecnerwal Feb 13 '18 at 3:11
  • I get that there's no NEC limit, but there is the industrial/commercial limit, and I actually lied; this is in a commercial setting (I was using that guideline anyway). But that answer doesn't answer my question. My question is, is a duplex receptacle one or two outlets? See the image I added to the question. Thanks! – Rick Feb 13 '18 at 8:30
  • Oh, and the reason I can't add another circuit is because I've hit the limit for box fill through the conduit path that feeds this office. – Rick Feb 13 '18 at 8:33
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First of all let me point out that there is an NEC limit to the amount of receptacles you can put on a circuit (see Exhibit 220.4). Second I have attached the page in 220.14 in the NEC hand book that answers your question on how your receptacles are counted on a circuit(Exhibit 220.3). Feel free to read the entire page. enter image description here

I would suggest that since you are indicating you are installing quad's for a tech bench you actually use the calculation for "Fixed Mutlioutlet Assembly" NEC article 220.14 (H). I have attached that page also (see Exhibit 220.2). enter image description here

Keep in mind that the NEC is a minimum requirement and should be considered as such.

Good Luck

  • I think your post beat mine by 45 seconds. – Swanson Feb 13 '18 at 13:36
  • But this one fails to note that the limit in question only applies to commercial, not residential. – Ecnerwal Feb 13 '18 at 20:30
  • Thank you for this very thorough answer. I just bought the NEC Handbook ($191!) because of it. Thanks! – Rick Feb 14 '18 at 2:59
  • One point of clarification: I only have duplex receptacles available to me, and it's simplest to wire them in 2-, 3- or 4-gang boxes. (H) shows long strips with wide spacing between outlets. How do duplex receptacles figure into H? Is a "fixed multioutlet assembly" a product I need to buy specifically? – Rick Feb 14 '18 at 4:12
  • @Rick - Let's start with your question. First you are saying your are wiring up an electronics lab. That's telling me this is a commercial application. Even if this is in a residence a commercial application applies. Also you are saying you are doing this "instead" of using a power strip, so you are actually using the quad's you are installing in lue of a power srtip. So any good designer would use the 180VA per foot calculation to make sure you have adequate power for your work area. Hope this helps. – Retired Master Electrician Feb 14 '18 at 13:38
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There is a limit on the number of plugs for non-residential projects.
enter image description here NEC 220.14(I) Each yoke is counted at 180 VA. If there is one outlet, two outlets (most common) or 3 outlets it is still counted as 180 VA. If there are (4) or more outlets then it is counted as 90 VA per outlet.

What you are describing, a double gang box, with (2) duplex outlets will equal 360 VA. Having a total of (3) pairs of duplex outlets will be 360 * 3 = 1080 VA. Since each duplex is 180 VA it can also be counted as 180 * 6 = 1080 VA.

The long power strips that you are used to with 10 or 12 outlets is commonly called plugmold. In the NEC it is referred to as a fixed multioutlet assembly. Per NEC 220.14(H) the load depends on if the plugs get used simultaneously or not. Simultaneous use equals 180 VA per foot of length. Non-simultaneous use equals 180 VA per 5 foot length.

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Its two receptacles

A duplex receptacle is two receptacles, sharing the same device yoke -- you can also get a single receptacle on a yoke, which looks like this (product in image for illustration purposes only):

single NEMA 5-15 receptacle

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