0

Ok I have a 60 amp breaker at my main box outside of house with 4 gauge wire 2 hots and a common. Im trying to add a 70 amp load center that has 2 spots for breakers that I want to run a 30 amp breaker and a 15 amp breaker out of. the 30 amp will be run to a RV plug. The 20 amp breaker will be run to a reg outside plug.will this be able to work are do I have to use all the power that is being feed in to box. Cause I hooked it up and the reg outlet worked until. I plugged the RV up then when I flipped the breakers on and off in the RV. It turned the reg outlet off. And never had any power in the RV. What was strange is the 60 amp breaker at main did not flip are the 2 breakers I installed did not flip. What did I do wrong

Scott
  • 3
  • 2

1 Answers1

2

It's called "neutral" not "common" and it's not common at all, it's the normal return current path. You also need a separate ground wire.

On top of the ground wire you also need a ground rod.

Having run 3-wire cable is a bit of a problem. You will be forced to use 2 of the wires for neutral and ground, leaving 1 for hot, and that means only 120V and not 240V. But that is fine, your loads are 120V. And 4 gauge wire is plenty for the 50 amps.

Since the wire is quite large (4 gauge) you can tape the wires green for ground and white for neutral, if they aren't already.

You need to take the 1 remaining hot wire and split it so it feeds both lugs on the panel. That is a hard thing to do, unfortunately. This would've been easier if you hadn't been so cheap on the panel. I would take the panel back and get an 8-space panel. Then you can attach your hot wire to 1 bus bar, and place the breakers on the same bus bar. This will be cheaper than any option I can think of for splitting a #4 wire.

Pro tip, there are plenty of places to save money (like aluminum wire is 1/3 the cost of copper) but scrimping on the panel spaces is not a good choice.

Harper - Reinstate Monica
  • 295,284
  • 26
  • 275
  • 720
  • So I need a ground from main box and then just 1 ground rod at the sub box? The 3 wire was already run to a old garage that fell down. It was 2 black wires that connect to the 60 amp breaker then a black and yellow that was hooked on to the netural bar. I went with the small box cause all I needed was the 2 plugs outside. Im thinking i should have just skipped the regular plug and just ran a 30 amp out of main box straight to the plug and it would have worked. I just cant see what I did wrong except the grounds. But still im wondering why not 1 of the breakers flipped – Scott May 07 '22 at 21:47
  • @Scott because breakers aren't everything detectors, only overload detectors. If you're salvaging the old wire that's fine, but you must make a former hot into a neutral so you have separate neutral and ground wires. You're right you need 2 ground rods unless the 1 rod passes a test that costs *a lot* more than a second ground rod. However ground rods do not replace the ground wire, you need both. – Harper - Reinstate Monica May 07 '22 at 21:52
  • I just thought if something was wrong a breaker would flip. Im going to run the ground rod and try that. Just cant seem to figure it out. What is bad I called a electrician out and all he said was it needed a ground from the main box to the sub. And did not even try to fix it. But it was a Friday afternoon when he came so – Scott May 07 '22 at 21:59
  • 1
    Yes, the electrician did not want to change you from a 240V to 120V feeder, which is dumb because a 120V feeder is all you need. It would have been a 20 minute job... if you had a 4-space or larger panel, anyway. – Harper - Reinstate Monica May 07 '22 at 22:03