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2-pole breaker to feed power to electrical sub-panel.

Updating Old House Wiring:

Adding A Sub-Panel - Part 2 - Changes At The Main Panel

A 50 Amp 240 Volt Circuit Breaker Is Installed

In This Article:

The 6-3G sub-feed cable is run into the main circuit breaker panel. The ground and neutral wires are connected to the ground bar. The two hot wires are connected to a 2-pole breaker.

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Skill Level:
3+ (Intermediate and Up)
Time Taken:
About 30 Minutes
, Editor
Project Date:
March 2006
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In The Basement:
Newer main circuit breaker panel in basement of century-old house.

This is the main breaker panel, in the basement of this old 1898 house.

This 200 Amp panel was installed two years ago during a major remodeling project. The brown material is just a 1/4" hardboard cover that is held in place by the panel's metal cover. The electrical inspector requested that we build a cover over the wires that come out of the panel.



The Main Panel:


I removed the metal cover and the home-made wiring shroud.

The coiled-up large black cable (red arrow) is the sub-feed that supplies power to the new sub-panel.

Main circuit breaker panel with cover removed and wire for future sub-panel nearby.


Large knock-out in top of main breaker panel to be used for sub-panel feed wire.

We left one large knock-out for the sub-feed cable.



But... when we ran these wires, we had placed the sub-feed (arrow 2) off to the side. This cable needs to enter the main panel at arrow 1, so we had to re-route the cable behind all those other cables.

Previously-run sub-feed cable needs to be re-routed to enter main panel.


3/4 inch cable clamp for large electrical wire entering main breaker panel.

We installed a 3/4 inch cable clamp (red arrow).

This clamp is just big enough for the 6-3G sub-feed cable.



There was just enough room on the top of the panel for this clamp. I doubt that a larger clamp would've fit.

Top view of 3/4 inch cable clamp used for large 6-3G electrical wire.


6-3G sub-feed cable run through cable clamp to enter the main breaker panel.

We fished the 6-3 cable (red arrow) through the new clamp.



Then we stripped away the cable jacket and paper filler, leaving 3 conductor wires sticking out (white, red, black) and the ground wire.

Sub-feed cable after outer jacket has been stripped, showing red, black, and white conductor wires, and ground wire.


Ground wire is connected to the neutral/ground bus in back of main breaker panel.

We routed the ground wire around the perimeter of the panel and made a 90-degree bend so it could be attached to the ground/neutral bus bar.



We connected the ground and the neutral wires to empty slots in the bus bar.

Note: It's ONLY at the MAIN panel where the ground and neutral (white) wires are connected to the same bus bar.

At the sub-panel, the neutral bus needs to be isolated (insulated) from the metal panel box.

Tightening screw in ground/neutral bus bar in main breaker box.


Sub-feed hot wires routed to an open slot in row of circuit breakers.

Then we ran the two hot wires around the left side of the panel, and made bends for the wires to turn and connect to the breaker.



We stripped about 1/2" of insulation from the ends.

Pair of hot wires for sub panel, showing stripped ends.


Sub-feed hot wires connected to 50 Amp 2-pole circuit breaker.

We connected the red and black hot wires to a 50 Amp 2-pole circuit breaker.

This is what many people call a "220-Volt" breaker. (Actually, the voltage is no longer 220 Volts... now it's 240 Volts.)

There is 240 Volts between the two hot wires, and 120 Volts between each hot wire and neutral.



We installed the breaker in the main panel:

The first step for this Cutler-Hammer breaker is to hook the breaker over the mounting flange.

At this point the metal contacts were not yet seated on the hot bus bars.

Cutler-Hammer 2-pole circuit breaker being installed in main panel, showing back end hooked on metal tab.


Cutler-Hammer 2-pole breaker just before being installed in circuit breaker panel.

Arrow 1 points to one of the connectors on the breaker.

Arrow 2 points to one of the hot bus bar tabs.

This connection is simply a press fit. The breaker connectors are spring-loaded and squeeze against the tab of the hot bus bar.



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We pushed the breaker firmly until it was seated against the hot bus bars, and the new breaker was physically aligned with the other breakers.



We removed two metal knock-outs from the cover panel.

After we double-checked all the connections, we re-installed the cover panel.

When the sub-feed cable had been connected to the sub-panel, we turned on the 50 Amp breaker.



Continue to Part 3 - Connecting The New Sub-Panel


Warnings And Cautions:

I strongly recommend anybody who plans on doing their own electrical work to do more research besides just reading these articles. I am not an electrician and I certainly do not know everything about wiring. I could be wrong. The electrical codes in your area may be different than in my area.

While minor electrical changes and repairs may not require a permit, larger projects usually do. Consult your local Building Department (look in the "local government" section of your phone book) before making your own major electrical changes. Local electrical inspectors usually are available during their early morning hours to answer your code questions, normally free of charge. If you've done your homework, you can speak intelligently and learn about lots of valuable rules and regulations.

Read HammerZone's disclaimer.


Recommended Reading:

I highly recommend the book Wiring a House (For Pros By Pros) by Rex Cauldwell, which is available on

More Info:
Tools Used:
  • Cordless Drill/Driver
  • Basic Hand Tools
  • Wire Cutters
  • Needle-Nose Pliers
  • Flat-Blade Screwdriver
Materials Used:
  • 2-pole Circuit Breaker, 50 Amp
  • 3/4" Cable Clamp
  • Cable Straps
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