ask the electrician
Electrician Training Electrical Certification wiring recessed light fixtures Electrical Wiring Electrical Troubleshooting and Electrical Repairs wire outdoor light fixture Home Electrical Wiring Diagrams
wiring home generator and transfer switch wiring a 220 volt range cord outlet Wiring for GFCI Outlets Wiring Outlets and a Switched Outlet Wiring and Installing Ceiling Fans and Remote Controls wire dimmer switch wiring diagrams for switches wiring a dryer cord and 220 outlet circuit breaker panel
Electrical Wire and Cable


Guest House Electrical Wiring

Question: I own a 1960s home with a 100 amp service panel. Behind the house is a detached guest house. There is a 40 amp 220 feed going from the main panel to a sub panel outside the guest house. They used number 8 wire in metal conduit through the attic going into the ground.


Electrical Video #1

Generator Automatic Transfer Switch
and Electric Circuit Sub Panel

Check out my YouTube Channel and Subscribe to my Videos
» AskTheElectrician «

NOTE: A List of All my Helpful Videos
Will Display at the End of This Video
So Keep Watching So I Can Help You Wire it Right!

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


Electric Service for a Guest House

Question:
I own a 1960s home with a 100 amp service panel.
Behind the house is a detached guest house.
There is a 40 amp 220 feed going from the main panel to a sub panel outside the guest house.
They used number 8 wire in metal conduit through the attic going into the ground.

At one time the guest house sub panel had a spa hooked up to it but is long since been removed.
It was a old 70s spa that used swimming pool pump and blower and sucked down a lot of power.
Only a lighting and outlet circuit is required for the guest house now as cooking and heating are all gas.

A 1.5 inch metal pipe runs down from the attic at a corner of my house into a access box and then goes underground to the guest house.
This side of the main house has two bedrooms, and they each require more power then the current circuits allow.
They both have small window ACs in them, one uses max of 5 amp and the other 10 amp which I have measured.

My Question:
Can I go into the 40 amp junction box with EMT, splice in 12 gauge wire to the 8 gauge = hot, neutral and green ground and then surface mount outside my wall coming in to my bedrooms with a single outlet 20 amp GFI in each bedroom to plug the two ACs into?

Can I safely do this just by splicing into the 40 amp 8 gauge wire or am I going to need to put another sub panel.

Thanks

Additional Comments: good resource

Electrical Question from Winterlight about Electrical Wiring

Received from Winterlight a Contractor in Santa Barbara, California

Dave’s Reply:
Thanks for your electrical question.

Guest House Electric Power

NO – Do Not Splice the Wiring as you have described – This would be very unsafe.

The right way would be to install a NEMA 3R sub-panel on the wall where the existing junction box is where circuit breakers could provide power to the bedroom air conditioner units or any load.
The correct wire type and size must be used along with circuit breaker protection.

This topic is discussed in several articles, here are a few links to help you:
Electrical Wire Table

Electrical Codes

The Following links will assist you with your electrical question:

For more information about Electrical Wiring
Electrical Wiring

This link is helpful as a Contractor
Electrical Code Articles

Make sure not to miss these Resources:
Home Electrical Wiring Resources

Be Careful and Be Safe – Never Work on Energized Circuits!

For Best Results Consult a Licensed Electrical Contractor.
Locate An Electrical Contractor in Your Area


The following may also be helpful for you:

Electrical Video #2

How to Wire a GFCI Outlet

without a Ground Wire

Check out my YouTube Channel and Subscribe to my Videos
» AskTheElectrician «

NOTE: A List of All my Helpful Videos
Will Display at the End of This Video
Keep Watching So I Can Help You Wire it Right!

Learn more about Home Electrical Wiring
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.
  electrical wiring  

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.

Electrical Tips to Help You Wire it Right

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.


More articles about Electrical, panel and Home Electrical Wiring:
« Previous Next »
Electrical Question from Pat about Circuit Wiring Electrical Question from George about Dryer Wiring