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Steve G.
Steve G., Electrical Engineer
Category: Electrical
Satisfied Customers: 17898
Experience:  Spent 20 years as an Electrical Engineer, designing electrical plans and specifications.
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I have a very, very similar question as to the one I read regarding

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I have a very, very similar question as to the one I read regarding the temporary use of 120 to power my breaker box in order to check circuits. To clarify, it is a garage. The garage is 200' from the house so "big" power will be run later. Bought a 100 amp panel from Home Depot, it came with 5 20AMP breakers plus its "main" 100AMP breaker. I have not run a grounding rod nearby yet. Can I use an extension cord with 120 to check my circuits? I figured I could run a plug end on the 12 3 romex jumper to the box somehow. I too have the typical vertical neutral bars on the sides of the breakers. So, what is the wiring process?

Hello there and welcome to Just Answer. My name is XXXXX XXXXX I will be assisting you today. I am an engineer with over 30 years of electrical and electronic training, repair and installation experience. I will try and answer your question accurately and precisely so that we can get you on your way.

Now..I'm not completely sure I understand what you are trying to do here.

Do you want to temporarily power up the new panel with an extension cord to see if your branch circuits are working?

Please let me know so that we can continue.

Regards

Steve

Customer: replied 3 years ago.

Yes I am trying to test each circuit in the panel. I don't mind hooking the temp jumper to each breaker if need be.

Ok, a lot of stuff here to cover.

First, on your sub panel, you can't land the neutrals and the grounds on the same bar. There are two bars in that panel and they are likely tied together with a grounding screw or green jumper. You need to put ALL the ground wires on one bar and ALL the neutrals on the other and then remove the jumper/screw.

Once you have done that, you can power up the panel in any way you want so long as it is temporary. Understand that your extension cord is going to be woefully inadequate and I do not think it is a good idea at all. In addition, if you are plugging it into a 120V source, you will only be able to power up one half of the panel since the panel is likely 120/240 like the one in your home. I suppose you could hook up your extension cord to a double pole 20A breaker in your house panel and run that across and land it on the main incoming terminals to the sub panel. That would power up the whole board but you are only going to have the capacity of a single 240V 20A circuit and you will be missing your neutral anyway unless you have a three conductor extension cord plus ground.

I want you to be clear that I am not recommending you do this. I'm simply stating that technically it will work.

I'll be here if you need further help with this issue. Please let me know.

Regards

Steve

Customer: replied 3 years ago.

I am very close to understanding your answer. I realize the inadequacy of my 120v cord for sure! I am only trying to "test" the circuits. Seeing how I have already wired the vertical neutral bars with both white and bare wires I need to separate them into one side with white and one side with bare wires right?

Yes. Absolutely. That is the biggest issue here. The ONLY place in your distribution system where the neutrals and ground wires can be tied together is at the service entrance i.e. your main panel.

If you tie them together downstream of that service entrance you are going to have major issues including issues of safety.

So, bare grounds on one bar, neutrals on the other and then separate the two bars by removing the jumper or screw.

I'll be here if you need further help with this issue. Please let me know.

Regards

Steve

Customer: replied 3 years ago.

Darn! Looks like I have some splicing in to do! So, for the final product on this "downstream" garage panel, I need to have them separated, got it. so whether it is the temp test mode or the final product i need them separated?

Yes.

Best Regards

Steve

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