[villagetinker]

I was helping a neighbor, when I accidentally found 2 independent power feeds to a single double wide box. One circuit from each of 2 circuit breakers! My neighbor thanked me for pointing this out as he was only turning off one breaker.

Now here is the interesting point, as far as I know the building codes and electrical codes state ONE CIRCUIT PER BOX, and this is what I was always told. When I looked carefully at the wiring this all appears to be ORIGINAL (2013 vintage) wiring as all of the wiring had the same paint overspray.

IMHO, this is a dangerous situation, so in case the codes have changed, check ALL of the wiring when working in any box. I have a handy non contact tester that I bought at Lowes and this is what tipped me off to the second circuit.

[metoo21]

I also thought that there was supposed to be only 1 circuit per box. I always check one set of wires in the box and have never thought about checking multiple should they be there. Thanks for the heads up.

[Altavia]

Seen this before, so you have to assume the possibility.

Can Multiple Circuits Share A Junction Box? (Find It Now!) – PortablePowerGuides

But if you want a single box to accommodate multiple circuits, the size is your only limitation. You can use as many circuits as you want if the box is large enough to hold them.


FYI - They do it here in the disconnect box for the air-conditioner where you have 220 v for the AC plus a separate 120 v circuit/outlet on a GFI.

One off my favorite electrical tools.

Klein Tools NCVT-2 Voltage Tester, Non-Contact Dual Range Voltage Tester Pen for Standard and Low Voltage, with 3 m Drop Protection https://a.co/d/bMEvJ9n

[Blueblaze]

While the codes may have changed a lot since the '70's when I was a journeyman electrician, I seriously doubt that there is any rule in the national code about having more than one circuit in a box. In fact, in my day it was very common to run a 14/3 romex to a recep box on the far side of a house and split off two 15 amps circuits from there. Dishwashers and disposal circuits were almost always done that way -- 12/3 to the switch, and one leg would feed the dishwasher and the other the disposal.

Here in the Villages, I can almost guarantee that the switch leg from the switched receps in your living room is on a different circuit from the ceiling fan in the same 3-gang box. I know that my own house is wired that way.

But you bring up a very important point that a lot of amateur "electricians" may not be aware of. If those two circuits are on opposite legs of the 220 service, you could be playing around with lethal levels of power without knowing it.

I can tell you from experience, you haven't seen fireworks until you've seen a 220 volt dead-short in your face (I had a blind spot and picked copper specks out of my face for a month when a screwdriver slipped as I was working on a hot breaker box). And while you have to try pretty hard to electrocute yourself with 110 volts, 220 will typically kill you instantly.

I almost got to experience that one myself, too. I was working on an air conditioner on the roof of an apartment building, and I specifically warned the woman in the house to not touch the breakers while I was working on her A/C. I bet you can guess where this is going. I was standing in a puddle on a flat roof, pulling the wires through the conduit when this moron decided to start flipping breakers after she overloaded her garbage disposal. I had the grounded conduit in one hand and all three conductors in the other hand at the moment she threw the switch. Fortunately, most of the power blew up in my hand from the dead short of the three conductors. It tripped the breaker (and I was a 20-year-old kid), or I would never have survived. It still felt like someone had hit me with a sledgehammer in the chest. It knocked me right off my feet, and blistered both hands and the bottom of my feet inside my rubber-sole boots.

Every electrician I've ever known could tell you stories like this. If you don't know what you're doing I would advise you to leave the shocking stories to the professionals!

[Maker]

The proper way to use a non-contact voltage detector is important. When doing a test, first verify it does detect power on a live circuit. Them immediately check the box/wiring you are testing, and if it fails to detect power then immediately verify it still does detect power on a live circuit.
Better detectors are sensitive enough that they will detect the static generated by rubbing it across a shirt. That's a quick way to see if the device is working.

[villagetinker]

After doing some additional research, it APPEARS that 2 supply circuits in a single or multiple ganged box is legal (who knew!!). So apparently, I have been wrong for the last 40 or 50 years. Please as noted above check and double check that ALL power is off if you are doing any DIY electrical work.

As for getting shocked: I have personally experienced 34,000 volts hand to hand, threw me 30 feet, fortunately it was a current limited source (about 30 ma). I have also gotten across 125 VDC with a jumper, as noted above copper sprayed all over including my glasses. The jumper vaporized, the 30 amp fuse never blew and I had burn marks on both thumbs, it is a long story. And I have personally seen the results of faults a 4000 to 230,000 volts from work experience, these were all very impressive.

Based on my personal experience, I am very careful around electricity.

[Altavia]

Appreciate the reminder!

My surprise was the GFI outlets hidden in the AC disconnect ;-)