Electrical Wiring in the Home/Sub-Panel wiring

Advertisement


Question
Hello Robert,
I am wiring in a 2nd breaker box which will be located in a smaller building located about 180ft away from my home, it will only have 4 lights and two receptacles. I am coming from my main breaker service box.
My 1st question: Can I use a 20amp double pole breaker to feed the sub panel, giving me 110 volts on each new Circuit?
2nd Question: Can I use #10 Guage wire, 4 wire in all two live one ground and a nuetral? Keep in mind its 180 feet away. I will be using two 15amp breaker on the sub panel to supply the lights and receptacle. Any advice would be appreciated.

Thank You!

Answer
Robert Wilber
Licensed Philadelphia Electrician
Philadelphia License # 3516 - 16765
*
LIFE SAFETY WARNING! [disclaimer]
Electricity is dangerous!
You can be injured or killed!
Improper installations can cause fire, injury and death!
Are you qualified to do this work?
*
National Electrical Code definition, NFPA 70 2008 Article 100: Qualified Person. "One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved."
*
Electricity is fire in a box!
*
Always check with the local “Authority Having Jurisdiction” for an official interpretation before making installation decisions.
*
In Philadelphia, it is unlawful for anyone except an individual licensed by the City of Philadelphia to install electrical equipment and wiring.
Homeowners are not allowed to install wiring.
The owner of any property wherein any such installation is discovered shall be issued a violation by the Department of Licenses and Inspections.
The limited exceptions include replacing devices and fixtures at existing outlets.
Contact the Department of Licenses and Inspections for more information.
*
You are more likely to be killed by 120 volts than any other voltage [120 volts creates the PERFECT fatal current through the human body's electrical resistance!]
TURN THE POWER OFF WHEN WORKING!
*
LIFE SAFETY WARNING! [disclaimer]
This information is provided for the use of parties as they see fit!
I am not responsible for the application of this information by any party, including those lacking sufficient skill or knowledge to perform these steps safely and any hazard created is the SOLE responsibility of the user.
*
Voltage Drop = KIL/CSA  where K is resistivity factor of conductor material [solid copper K is 11], I is current and L is round trip circuit length, while CSA is cross sectional area of conductor in circular mils [10 is 10,380 while 8 is 16,510 and 6 is 26,240].
A 15 amp load at 180 feet [360 round trip] would have an unacceptable voltage drop on 10 gauge wire [5.7 volts] at 120 volts and starting a motor with a running load of 15 amps might give a locked rotor amperage of 60 amps, which could drop the voltage at startup to under 100 volts. Unless the equipment you are planning to use won't be bothered by low voltages I would consider using 8 gauge wire or even 6 gauge.

It also depends on the voltage supplied by your utility. Some people get 115 volts. Some get as high as 135 volts.
About Electrical Wiring in the Home
This site answers questions related to home electrical wiring, home wiring, general electrical help,and other electrical questions related to aleternating current (AC). You can find help on the National Electical Code, home electrical issues, wiring electrical outlets, installing lighting, electrical grounding, and general electrical help for do-it-yourself projects not require an electrician. If you do not see your home electrical wiring question answered in this area then please ask your electrical wiring question here

Electrical Wiring in the Home

All Answers


Answers by Expert:


Ask Experts

Volunteer


Robert Wilber

Expertise

Licensed Philadelphia electrician serving Delaware, Chester, Montgomery and Philadelphia County in Pennsylvania. I install and repair residential, commercial and industrial wiring and lighting. Troubleshooting and repair of problems that stump other people is my favorite. I am willing to help people figure out why things don`t work. I understand motor controls, transformers and machine wiring. I do not teach basics to novices or do free design work.

Experience

Experience in the area I have 44 years experience in residential, commercial and industrial electrical construction and repair, 480 volts and below. This is not to be confused with one week repeated two thousand times.

Education/Credentials
44 years experience in residential, commercial and industrial electrical construction and repair

©2016 About.com. All rights reserved.