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I have a 30 amp 240 volt circuit out side in my garage and I want to hook up two 10 amp 240 volt circuits. The equipment I am hooking up are battery chargers. Can I install fused down disconnects on the 30A circuit? I looked up the National Electrical Code and section 240.21 talks about a tap.

Am I violating the code?

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  • Where are you? UK?
    – longneck
    Nov 3, 2014 at 21:01
  • @longneck, that's doubtful since he is referencing the NEC.
    – Speedy Petey
    Nov 3, 2014 at 22:20
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    If you have two outlets on that 30A circuit, and other loads don't exceed 10A, you should be able to plug in both chargers without risk of blowing the 30A breaker.
    – keshlam
    Nov 6, 2014 at 21:30
  • @keshlam -- yes, but tap conductors feeding receptacles are a no-no, and those outlets need to be 30A to be used on a 30A circuit.
    – ThreePhaseEel
    Jan 27, 2015 at 0:49
  • As permanent wiring, sure. As a splitter box that plugs into the outlet -- assuming the outlet itself is rated for 20A -- this seems entirely reasonable, given proper wiring; it's just a heavy-duty power strip. Might even add a 20A breaker to that box
    – keshlam
    Jan 27, 2015 at 2:03

3 Answers 3

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First things first: ignore the tap conductor rules in the NEC! You can't use them for receptacles anyway: 240.21(A) refers you to 210.19, which sadly is a bit confusing-looking as it refers to receptacles in two different places, only one of which refers to a notion of 'tap conductor', which furthermore isn't in the NEC's definitions section! But, 210.19(A)(2):

Branch Circuits with More than One Receptacle. Conductors of branch circuits supplying more than one receptacle for cord-and- plug-connected portable loads shall have an ampacity of not less than the rating of the branch circuit.

states that conductors on a multiple receptacle outlet branch circuit must have the same ampacity as the rest of the branch circuit (or better, of course), and Exception 1 to 210.19(A)(4):

Exception No.1: Tap conductors shall have an ampacity sufficient for the load served. In addition, they shall have an ampacity of not less than 15 for circuits rated less than 40 amperes and not less than 20 for circuits rated at 40 or 50 amperes and only where these tap conductors supply any of the following loads:

(a) lndividual lamp holders or luminaires with taps extending not longer than 450 mm (18 in.) beyond any portion of the lampholder or luminaire.

(b) A luminaire having tap conductors as provided in 410.117.

(c) individual outlets, other than receptacle outlets, with taps not over 450 > mm (18 in.) long.

(d) Infrared lamp industrial heating appliances.

(e) Nonheating leads of deicing and snow-melting cables and mats.

explicitly excludes receptacle outlets.

This leaves you with two options here:

  1. Put a pair of 6-30 receptacles in the garage (yes, you must use 30A), and leave the circuit otherwise as-is, wiring the new receptacle(s) using 10/2. (Using 15A receptacles on a 30A circuit violates NEC 210.21(B)(3) and the associated table.)

  2. IF you have a 120/240VAC circuit running to the garage (2 hots, neutral, ground), you can fit a subpanel there and then use a pair of dual pole 15A breakers and 14/2 wire to run independent circuits to 6-15R outlets for each charger. If the existing 30A circuit was run using 10/2 though, you cannot do this -- single pole breakers aren't rated for 240VAC service!

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Technically, the NEC does not specify the limit to how many receptacles are allowed on a circuit. A little common sense is at the discretion of the installer. You have to take the total ampacity of the primary side of the chargers.

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  • @kris Use the edit link underneath your post if you want to modify it to address the question, or the delete link to remove it altogether.
    – Niall C. ♦
    May 27, 2015 at 19:46
  • Thx, I was looking for a delete button but couldn't find it. I'll modify it.
    – Kris
    May 27, 2015 at 20:00
  • Edited. Let me know what you think. And for whatever reasons I cannot find a delete button or a comment button. All I have is an answer button and edit button.
    – Kris
    May 27, 2015 at 20:44
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I recommend adding new circuits for the battery chargers.

Keep that 30 amp 240v intact. You can use it to hook a generator to your house in case of long term power outage.

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  • 2
    No, you cannot do that.
    – Ecnerwal
    May 27, 2015 at 13:55

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