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Electrical Wiring in the Home/Separating an overloaded circuit

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Question
Our house was built in 1960, and the panel was upgraded to 150A service in 1971, which is problay when central AC was added.  Old wiring is gray (Bufrmax?) 12-2G NM.  One of the circuits includes plugs and lights for several rooms, incl. bathroom and family room.  Laser printer is causing flickering of lights, which prompted my looking into this.  I can see from the basement where the wires go up to each room.  I would like to make this into 3 circuits: with family room and bathroom on the new circuits.  Will the NEC allow me to run a new circuit(s) from the panel to a new junction box(es) in the basement (using same 12 gauge NM to match) where I tie into the existing runs where they go up into the individual rooms, or does ALL the wiring in the walls need to be replaced?  If I don't need to replace wiring in walls, I think I can do this myself (with permit and inspection, of course) at a reasonable cost for wire in basement, new CAFI breakers, and a couple of junction boxes.  (Bathroom plugs are already GFCI.). Thanks for your advice!

Answer
Robert Wilber
Licensed Philadelphia Electrician
Philadelphia License # 3516 - 16765
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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?
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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."
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Electricity is fire in a box!
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Always check with the local “Authority Having Jurisdiction” for an official interpretation before making installation decisions.
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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.
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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!
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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.
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That being said, it is absolutely allowable to split a circuit and re-feed a portion with properly sized and protected conductors on additional circuits. It might be a bit trickier than you think to separate sections out, as what you think goes up may come down in both places. It is not required to replace all the existing wiring.

It occurs to me that flickering lights can be a symptom of several conditions and a laser printer usually doesn't present a load that would cause that in a "healthy" wiring system. At 40-plus years I would consider that the "new" service may have issues. A failing service neutral connection can cause flickering lights when an applied load causes imbalances revealed by the defect.

Are the flickering lights and the printer on the same circuit or the same leg of the service? If not, I would examine the neutral throughout its path.
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Electrical Wiring in the Home

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Robert Wilber

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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.

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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.

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

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