Skip to Content

Installing a new Subpanel – Part 1


Installing a New Subpanel is a multi-part series article, broken into Part 1, Part 2, Part 3, Part 4 and Part 5.



The focus of this project was to install a sub panel in the basement in a residential setting. As I take on additional electrical projects, I will include such scenarios as installing a sub panel for the external shed, pool, etc. I learned quite a bit by first borrowing, then purchasing few books (listed in this site via Amazon). I strongly recommend that you do the same to expand your knowledge about electricity.

In addition, this subpanel installation occurred in a New Jersey town where the National Electric Code (NEC) 2010 was in use. Although most US states follow NEC 2010 codes today, some towns may be lax or more strict. I consulted extensively with my township’s electrical inspector do get the job done in a safe, correct manner so I would suggest you do the same.


So what exactly is a sub panel? Simply put, it is an electric distribution center much like the main electric panel. Subpanel’s electricity is fed directly from this main panel, connected via special cable. Many times, a subpanel is necessary when there are no more “slots” or breaker spaces left in the main panel or you need to create an electrical load center to save money on installing electrical wires.

Project Background

I have a 2 story house built in the 1960’s with access to full basement. I had recently upgraded my main electrical service to a 200 amp panel to allow me to add a subpanel in the basement, directly below my kitchen. The reason for this location was that I planned on completely remodeling my kitchen so I needed to bring up the kitchen electric code up to 2010 NEC standards.

As part of a multi phased project, I first decided to remodel my adjoining mudroom so that I would have the perfect opportunity to rip down existing sheetrock to route and install my new electric feeder cable from the main panel (located in the garage) down to the basement.

I could have ran a bunch of 15- and 20 amp wires from the main panel directly to the kitchen area but I decided against it because:

  • Kitchen remodel did not start yet so I would have a bunch of wires hanging in the basement;
  • I would not have enough space to route 10+ wires through the shared-wall without risking nail puncture later
  • It would have been cost prohibitive to run 10+ wires with each wire being approximately 75 feet in length


Although this project did not look as complicated, there were lots of small but important parts. So as usual, I carefully laid out my project objectives:

  • Determine the location of subpanel
  • Calculate electrical “load” requirement
  • Determine subpanel size
  • Determine service entrance feeder cable size

Determining the subpanel location

allthumbsdiy-images-electrical-subpanel-a14-layout-flIdeally, it should be located where you can easily run a feeder cable from the main panel without too many turns.

What I did first was to draw a simple stick diagram to visualize the location of the main panel, how the wiring will be pulled, and where the subpanel ultimately will be located.

TIP: Purchase some cheap rope (mine was 120 feet for $30) to gauge the actual distance to your new subpanel location. I “estimated” my distance without it first and ended up purchasing $200 worth of feeder cable that ended up being 20 feet too short (ouch!) Whatever you use to measure, make sure to increase the total length about 15% to anticipate unforeseen turns or obstacles.


  • NEXT >> Installing a new Subpanel – Part 2




    Wednesday 8th of February 2017

    I have a utility shed on an RV lot and am trying to wire it with a 30 amp 3 wire service. The shed was wired direct and plugged into a 30 receptacle with it's own breaker. I am still plugged into the 30 amp receptacle. I installed a main lug in the shed and there is not any current coming through the breakers. I connected the black wire to the center main lug, the white wire to a bus bar and the green wire to separate bus bar. There is not a jumper between the neutral and ground. Current is in the main bus bar but does not come out the breakers. I tested the breakers and whey work correctly. I connected the neutral wire to the ground and then to the main bus bar and the results was the same. Is there a way to connect 30 amp 3 wires to a main lug? If so, how? Thank you.


    Thursday 9th of February 2017

    Hi Gary-

    Sorry but this project is way out of my league. You may want to pose your question at this forum ( )

    I am not an electrician but I don't think you should EVER try to connect directly to a main lug.

    Good luck and please stay safe!

    Installing a New Subpanel – Part 5

    Monday 16th of July 2012

    [...] Installing a new Subpanel – Part 1 [...]

    Installing a New Subpanel – Part 4

    Monday 16th of July 2012

    [...] Installing a new Subpanel – Part 1 [...]

    Installing a New Subpanel – Part 2

    Monday 16th of July 2012

    [...] Installing a new Subpanel – Part 1 [...]

    Installing a New Subpanel – Part 3

    Sunday 15th of July 2012

    [...] Installing a new Subpanel – Part 1 [...]