Is my garage safe with a 30amp breaker and some odd wiring

Question

I recently bought a house and have found several things wrong and I'm trying to prioritize which to fix first. I have some very limited electrical knowledge but not enough to know if this needs to be fixed immediately or can wait. I live in Texas. I'll try to use correct terminology but no gaurantees

I went into my attic to see about adding a recepticle in my (attached) garage. I find the junction box and see that the romex is just running straight from the direction of the main breaker box over insulation and whatever else is up there no staples. This is very thick 10gauge romex.

Inside the junction box it is wire nutted to three other cables one 10gauge, and two 14gauge cables. The 10gauge is then ran to a ceiling cicle box which holds the recepticle my garage door opener is plugged into, then continues on to be spliced (using only wire nuts and electrical tape). One (14gauge) leads to a switch and the other (10 maybe 12gauge different color romex) to an outside light controlled by the switch.

Back to first junction box. The two 14 gauge romex cables are ran to 15amp recepticals on two different walls (I was wanting a recepticle on the third wall). One of these recepticles has a single red very thickly insulated regency wire ran from it to a switch and continue on to the overhead light fixture. A single white common wire (same type very thick insulated wire) is ran to the fixture from the other receptical for some reason, and no ground wire.

At the main breaker box I find the 10 gauge cable is attached to a 30amp breaker and is just ran out of a hole punched out of the bottom of the box, ran up the side of box, and into the soffit.

I need to know if there are any immediate hazards I should fix this weekend. Then what is going to need to be switched out to get to/near code. I know the electrical taped splice needs to be boxed, but the 30amp breaker i haven't a clue if it's a hazard or if its fine since only 15amp recepticals are attached. The 30amp breaker is not ground or ark fault.

Answer 1

Good diagnostic post! You have a number of safety issues, chief of which is all those receptacles and 12/14awg wiring should not be fed by a 30A circuit breaker. How fast you decide to fix them is up to you, but you're right that it is a fire hazard.

For example, a 14awg NM-B cable can carry 15A without exceeding a 60C design temperature (someone will surly correct me if I'm remembering the values wrong.) The requirements for installing this type of cable (no conduit needed, okay to be in contact with insulation, etc.) are specified with that 15A in mind. When you exceed it by using a 30A breaker, some person could plug two big space heaters into a receptacle, cause the 14awg cable to overheat, and it could start a fire, all without tripping the circuit breaker.

My suggestion is to start by replacing the 30A breaker. If you change it to 15A the wiring you have currently (aside from the improper splices) is basically safe. If you change to a 20A breaker you will need to upgrade the 14awg wire to 12awg.

Book recommendation

By the way, you may want a book to help you get started. As @ThreePhase explains, there are plenty of other things you want to do to make all this safe and up to code; and it's hard to cover them all in Q&A form. I like the Black & Decker Complete Guide to Wiring, which is available at home improvement stores and many libraries. It's heavily-illustrated and aimed right at DIY homeowners.

Answer 2

That breaker needs to be 15A, for starters

Since there's 14AWG wire in the circuits, you'll have to replace that 30A breaker with a 15A breaker to give this situation any hope of being safe. This would be the first thing I'd do, even, before fixing any other issues with the circuit. The good news is that for most panels, a 15A breaker is readily available at the home store, although you will need to match up the labels on the breaker to the labeling on the inside front of your breaker box. If you are having trouble matching the labeling up, the labeling on your box is missing, or your breaker box has breakers that have single tabs on the back instead of pairs of "jaws", post back and we can help you here.

Working our way along the circuit...

The easiest way to approach this once you have the breaker swapped is to work your way along the circuit from start to finish, fixing issues as you go. We start by replacing the existing outdoor run of 10-2 NM with 10-2 or 12-2 UF, depending on if you think the garage will need more power in the future or not. This is because running NM outside isn't allowed by the NEC as ordinary NM cable isn't rated to be shone or rained on, and will wick water up its paper separator, leading to failures indoors even. You'll also need to use a cable clamp (one of the plastic button clamps will do) where the UF run exits the bottom of the breaker box to keep the cable's jacket from being damaged by the hole as well as to provide strain relief for the cable as it enters the box.

Moving on, you'll then need to box up the open splices, as you indicate; single gang plastic old work boxes installed into the garage ceiling will work just fine for this job, although you'll want to redo the splices with fresh wire nuts of the appropriate size. Make sure to write down which wires are connected to which before undoing the splices, though!

Finally, we get to the red and white wires standing alone, which violate several sections of the NEC. You'll want to rip them out and replace the red wire with a proper NM-B cable, as wires by themselves need to be in a conduit or other sort of raceway to be used legally under the NEC. At the switch box, the black wire in the new cable goes to the screw on the switch that the red wire went to, while the white wire in the new cable goes to the spare neutral screw on the receptacle, and the bare wire in the new cable gets connected to any and all existing bare wires in the box. Don't forget to make sure the cable is clamped when running out of the box!

As you run the cable, you'll also need to make sure it's at least 1.25" back from the edge of the stud so it doesn't get nailed into by accident, and secured with a staple or clip every 4.5' as well as within 12" of the boxes at each end. You'll also need to enlarge the hole in the top plate the old wire ran thru so that it will fit the new cable, of course.

Finally, when you reach the light box and run the cable into it (use a new cable clamp if needed), you can wire the black wire to the hot terminal or wire on the fixture, the white wire to the neutral terminal or wire on the fixture, and the bare wire to any green or bare wires from the fixture if present, as well as to a pigtail to a grounding screw into the back of the box if the box is made from metal. Last but not least, the holes that the old white wire went through will need to be plugged with knockout plugs, replacing any cable clamps that once held the white wire in.

If you want more power to the garage...

If you want to upgrade the garage power arrangement at this point, my bet would be to run a fatter /3 cable up to a subpanel in the garage since the existing 10/2 NM run isn't salvageable anyway, then run replacement 14/2 NM off a 15A breaker from the subpanel to the existing complex. You'll need to make sure that the bond screw is pulled, a ground bar is fitted, and neutrals and grounds are separated in the subpanel if you do this, of course.