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I was trying to locate the circuit breaker for an outlet in my garage and found a truly baffling setup. Two breakers control the same outlet (both plugs). After some head scratching, I opened the breaker box and found (see pic) breaker 4 (20 amp) wired to the outlet as expected but breaker 34 (30 amp) wired to breaker 4. Why would this be done? It was obviously intentional and possibly setup for a freezer. Is this safe and in anyway an accepted practice?

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Thanks everyone for the help! I know enough to keep from getting electrocuted and this just didn't meet the logic test. I'll be checking the wiring and hopefully this is the only work they attempted.

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    Do both the breakers stay set? By my math those breakers should be on opposite legs, which should create a 240V wire warmer.
    – Tester101
    Commented Apr 3, 2015 at 1:47
  • @Tester101 If that were the case, there'd be an open circuit between the two legs and both breakers would pop. I think his numbers must be wrong.
    – BlueRaja - Danny Pflughoeft
    Commented Apr 3, 2015 at 5:37
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    @BlueRaja-DannyPflughoeft That's what I said. But it would be a closed circuit (or short). Well... At least it would be closed for a millisecond, until one of the breakers tripped or the wire burnt up.
    – Tester101
    Commented Apr 3, 2015 at 10:00
  • Are they in parallel, or are they in sequence? Because that makes a difference, no? So Main -> B4 -> [Outlet, B34] or Main -> [B4, B34] -> Outlet?
    – Jan Fabry
    Commented Apr 3, 2015 at 14:02
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    If it is a 3 phase panel (and with at least 17 rows, it might be - it's a big panel either way) then it's on the same phase. Personally I'd like it if my garage had a 3 phase panel, wouldn't you?
    – Adam Davis
    Commented Apr 3, 2015 at 19:14

4 Answers 4

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As @Ecnerwall says, definitely not safe / legal / advisable.

My guess is that the guy kept tripping breaker #4 (maybe too many power tools in the garage?) and decided to share the load with another breaker by adding the extra wire. Approximately half of the current will flow through each breaker, effectively creating a 40 amp breaker.

EDIT: in fact it's possible / likely that the wires on that circuit were regularly carrying more than 20 amps. Wherever possible you should inspect the wiring, including all outlets on that circuit, to see if there are any signs of melted insulation or other damage. If you find any indication of heat damage I think it would be prudent to rip out the entire circuit and rewire it, since there may be damaged insulation in the walls just waiting to catch fire.

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  • It's possible that they guy did not want a 40 Amp breaker, but a 30 Amp breaker, i.e. intended the 20 Amp breaker to be left switched off. Perhaps the 20 Amp breakers was used originally, and the wire was too short to reach the bottom breaker, so he 'extended' it, intending breaker 4 never to be switched on. Obviously still not safe / legal / advisable, but very slightly less silly than breakers in parallel.
    – abligh
    Commented Apr 4, 2015 at 9:27
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    @abligh -- you can wirenut in most panels these days, so there's no reason at all for such ugly hackery.
    – ThreePhaseEel
    Commented Apr 6, 2015 at 3:28
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Alright, now that you found the blatant 240.8 violation:

240.8 Fuses or Circuit Breakers in Parallel. Fuses and circuit breakers shall be permitted to be connected in parallel where they are factory assembled in parallel and listed as a unit. Individual fuses, circuit breakers, or combinations thereof shall not otherwise be connected in parallel.

I'd grab a copy of the 2014 NEC, call up any electrician friends you have, and invite them over for a Code-violation Easter-egg hunt. I think it'll be a blast :D

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    I can hardly imagine situations where even a factory should be allowed to do that.
    – Russell McMahon
    Commented Apr 3, 2015 at 18:46
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    @RussellMcMahon, I don't know what the use-case would be, but if there is one, you can bet that the factory-assembled unit would be labelled for that use-case. Labelling means a lot to regulators.
    – Solomon Slow
    Commented Apr 3, 2015 at 21:37
  • @jameslarge I agree. I'm not questioning the power of regulatory approval :-). Just, as an EE, the idea of cascading cutouts is "interesting". Say breaker1 is the most weak-kneed and trips at say 2 x I_rated. If both are equally sharing the load then breaker2 is seeing 2 x Irated and wondering whether to trip when current jumps to 4 x Irated and its mind is made up. Operation would be very much faster than the time for the 1st trip. In many cases 4 x rated current is no great problem - which is where the designers benison is a very good idea.
    – Russell McMahon
    Commented Apr 3, 2015 at 23:47
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    If only I had an electrician friend... Where would you find one of these that accepts payment in beer?
    – John Miele
    Commented Apr 4, 2015 at 0:36
  • @RussellMcMahon You can't readily buy (much less bend) wire listed for much over 450A, so you are forced into using multiple wires and fusing each individually. Our panel is built to do this with 2 fuse sites per leg. "Never happen in residential" you might say, but a friend already has two 200A main panels (one for his heat pump) and wants to add two 180A on-demand water heaters.
    – Harper - Reinstate Monica
    Commented Aug 4, 2016 at 18:37
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Uh, NO!!! That was a hamfisted moronic code violating idiot wiring job done by a guy who said "hold my beer and watch this!"

Rip it out and look around for other work this guy may have done while three sheets to the wind.

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    ...and to think I expected I'd be explaining MWBCs before I read what actually had been done here...
    – Ecnerwal
    Commented Apr 3, 2015 at 1:10
  • I had the same thought.
    – Brad Gilbert
    Commented Apr 3, 2015 at 3:16
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    Someone had a lot of guts to open up the breaker panel and pull a stunt like this. I agree, a careful inspection of the house's wiring is in order.
    – Hank
    Commented Apr 3, 2015 at 3:25
  • It actually looked professional! I had to do a double take, black wire, clean install, bent to look like it belonged.
    – John Miele
    Commented Apr 4, 2015 at 0:35
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Two breakers on the same circuit that are not clipped or otherwise mechanically forced to trip at the same time... doesn't seem like a good idea.

Best case: Someone upgraded the wires/fixtures on the circuit to handle the extra load but didn't want to reconfigure the panel.

Worse case: Someone got tired of resetting the breaker and/or unplugging his garage grow op or garage full of beer fridges and decided to burn his house down instead.

Good catch on you. Make some smores before you fix it. Mmm, basement panel smores.

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