This article is about the multiwire branch circuit wiring technique in home electrics. It is not common. This panel might appear like that you would find at any home, but there is a key difference that a knowledgeable inspector should recognize and explain.
But first, let’s cover some basics to set the stage.
A conductor is the metal that carries electricity. That metal is copper or aluminum. A wire is a bare conductor or a conductor covered with a plastic insulator. So, whether we say conductor or wire, it is the same for practical purposes. Two or more wires covered in a sheathing or jacket is a cable as shown.
Home electrical systems are mostly single strand insulated copper wires in 2-, 3-, or 4-wire cables. For this topic, we focus on 3-wire cable.
3-wire cables are most often used in one of these ways:
So that leads us to the point of this article: non-typical use of 3-wire cable.
A multiwire branch circuit is a different way to use a 3-wire cable. The National Electric Code (NEC) defines it as a single electrical cable with two circuits that have a voltage between them and that share a common neutral. There are two takeaways from that definition:
Don’t panic if your home or prospective home has Multiwire Branch Circuits. If a smart Home Inspector like Chester County Home Inspections identified your electrical system as utilizing this technique, then any and all electrical work must be done by a certified electrician. If you are buying the home, you may wish to have a licensed electrician certify that the wiring is still proper.
A core principle at Chester County Home Inspections is that we educate our clients, whether verbally at the inspection, through our detailed reports, or through specialty articles like this. Schedule online now, or inquire online, or call or text (484) 212-1600.
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