What is a Parallel Circuit

 How can I troubleshoot a problem with a Multi-Wire Branch Circuit? The Difference Between Series and Parallel Electrical Circuit Wiring.

How To Hook Up a Generator to the House Panel Using a Circuit Breaker Interlock Kit For Backup Power

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Electric Circuit Problem
Electrical Question: How can I troubleshoot a problem with a Multi-Wire Branch Circuit?

I have a legacy, incorrectly wired 15A MWBC (0V between black and red) with one loop feeding a whole house fan and the other feeding a 1/2 bath, desk outlet and light, and two ceiling fans. I am leaving the breaker for the house fan off until I can correct the wiring in the panel and purchase a tie bar to connect the breaker switches.
Originally, the 3-wire Romex was split into the separate circuits inside a double wide outlet box with only one outlet in it. It was a jumble of wires, so I moved the split to a separate junction box.
I added two “convenience” outlets to the BR loop, the first being a GFCI that cuts power to the whole circuit.
I have tested all the outlets, and they read 121V. I have one set of switched wires waiting for a light for over the sink, and a ceiling fixture box with a temporary drop light socket.
The light socket reads 121V, but all light bulbs screwed into it burn out immediately.
They never did with the previous fixture. So, I am at a loss to figure out what could be the source of the problem.
Any help would be appreciated.

This electrical question came from: Frank, a Homeowner from New England, USA.

Thanks for your electrical question Frank.

How to Troubleshoot an Electric Circuit Problem

Application: Wiring a Light Fixture.
Skill Level: Beginner to Intermediate. This electrical project is best performed by a Licensed Electrician.
Tools Required: Basic Electricians Pouch Hand Tools and a Voltage Tester.
Estimated Time: Depends on personal level experience, ability to work with tools.
Precaution: Identify the circuit, turn it OFF andÂ  Tag it with a Note before working with the wiring.
Notice: Installing additional electrical wiring should be done according to local and national electrical codes with a permit and be inspected.

Frank, one possibility is that it sounds like you have wired the lighting circuit in series and not parallel.

An Example of Series Circuit and Parallel Circuit

Using a light circuit as an example:

• Series Circuit Wiring is where the load of the entire light circuit is being passed through each light bulb, which would essentially make the light bulb work just like a resistor, which would resist the full circuit power from being available to all of the light bulbs.
• Parallel Circuit Wiring is where the circuit is tapped into for each light or electrical device, and the circuit will not fail if one of the electrical devices is removed or disconnected.

Double check the electrical circuit wiring configuration and your connections.

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Home electrical wiring includes 110 volt outlets and 220 volt outlets and receptacles which are common place in every home. See how wiring electrical outlets for the home are done.

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House Wiring Circuits and Circuit Breakers
This article looks at common 120 volt and 240 volt house wiring circuits and the circuit breakers that are installed identifying the types and amperage sizes used in most homes.

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Electric Circuit Listing
The size of the home electrical service panel is designed by calculating the square footage of the home and factoring in the code requirements for the electrical circuits that are required.

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A guide to home electrical circuit breakers and how they work to protect your electrical wiring. When properly installed, your home electrical wiring is protected by a circuit protection device.

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This article looks at common 120 volt and 240 volt house wiring circuits and the circuit breakers that are installed identifying the types and amperage sizes used in most homes.

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with my online Video Course:
Basic Home Electrical Wiring by Example

Dave's Guide to Home Electrical Wiring:

» You Can Avoid Costly Mistakes! «

Here's How to Do It:
Wire It Right with the help of my Illustrated Wiring Book

Great for any Home Wiring Project.

Complete Guide to Home Electrical Wiring

Perfect for Homeowners, Students,
Handyman, Handy Women, and Electricians
Includes:
Wiring GFCI Outlets
Wiring Home Electric Circuits
120 Volt and 240 Volt Outlet Circuits
Wiring Light Switches
Wiring 3-Wire and 4-Wire Electric Range
Wiring 3-Wire and 4-Wire Dryer Cord and Dryer Outlet
How to Troubleshoot and Repair Electrical Wiring
Wiring Methods for Upgrading Electrical Wiring
NEC Codes for Home Electrical Wiring
....and much more.

Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all Electric Wiring Projects.

The Safest Way to Test Electrical Devices and Identify Electric Wires!

The Non-Contact Electrical Tester
This is a testing tool that I have had in my personal electrical tool pouch for years, and is the first test tool I grab to help identify electrical wiring. It is a Non-contact tester that I use to easily Detect Voltage in Cables, Cords, Circuit Breakers, Lighting Fixtures, Switches, Outlets and Wires. Simply insert the end of the tester into an outlet, lamp socket, or hold the end of the tester against the wire you wish to test. Very handy and easy to use.

The Quickest Way to Check for Faulty Electrical Wiring!

The Plug-In Outlet Tester
This is the first tool I grab to troubleshoot a problem with outlet circuit wiring. This popular tester is also used by most inspectors to test for power and check the polarity of circuit wiring.
It detects probable improper wiring conditions in standard 110-125 VAC outlets Provides 6 probable wiring conditions that are quick and easy to read for ultimate efficiency Lights indicate if wiring is correct and indicator light chart is included Tests standard 3-wire outlets UL Listed Light indicates if wiring is incorrect Very handy and easy to use.

Strip Off Wire Insulation without Nicking and Damaging the Electric Wire!

The Wire Stripper and Wire Cutter
My absolute favorite wire stripping tool that I have had in my personal electrical tool pouch for years, and this is the tool I use to safely strip electrical wires.
This handy tool has multiple uses:
The wire gauges are shown on the side of the tool so you know which slot to use for stripping insulation.
The end of the tool can be used to grip and bend wire which is handy for attaching wire onto the screw terminals of switches and outlets..

The wire stripper will work on both solid and stranded wire. This tool is Very Handy and Easy to Use.

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