GFI Breaker at Subpanel - Does it need a separate neutral to the main box


I'm real close! I disconnected the wire connecting the main to the subpanel (at the main). I then did a continuity test between ground and neutral and got a tone. So I went to the subpanel, disconnected the feeding wire from the subpanel bus bars and checked it - no tone. So, the wire connecting main to subpanel is good (phew - that was an expensive wire)

I found three circuits in the subpanel that were causing the continuity check to register. Two of them I cleared up - there was an outlet box that I rewired and it's now not an issue.

The last issue is the 240v double pole breaker in the subpanel. More on that in a minute.

I wired up the main panel with the 50A GFCI breaker, disconnected the 240v breaker in the subpanel (neutral and ground both disconnected too). I flip on the 50A GFCI doesn't trip! Who hoo! I go into the garage and flip on all the breakers (- the 240v which is hanging out of the box - and it doesn't trip anything either! Who hoo...

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See larger 60 amp Subpanel / with 240Volt and 120Volt
Use with both 240Volt and 120Volt breakers
1) 60-150 Amp breaker replaces any 240 breaker in main box near top of box

2) Two Hot wires connect to 60-150 Amp breaker in main breaker box. Either hot wire can connect to either hot busbar inside subpanel.

3) Neutral connects to Neutral busbar so subpanel can power 120 and 240 breakers.

4) Ground wire connects to Ground busbar. Ground busbar can be purchased separately.

If Subpanel located at another structure, for example garage several hundred feet away, might be cheaper to use ground rod located outside other structure. If structure is farther than 140', then wire gauge increases from #6 to #4. Consult local electrician for correct gauge.

See wire size chart
Electrical formulas

Main breaker wires are HOT when main breaker is OFF
Main breaker wires are HOT when main breaker is OFF unless meter is pulled
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Remove all sub panel covers or doors.


Measure about 5 feet (1.5 m) from the floor to mark the spot where you will mount the panel. This is a good height that is within comfortable reach of most adults.


Remove the lowest amp rated double pole circuit breaker or 2 low rated single pole circuit breakers from the main panel to make room for the new double pole circuit breaker that will supply the new sub panel.

The 2 circuits you removed will need to be re-fed from the new sub panel. If the sub panel is the same brand, you might be able to reinstall the original circuit breakers in it to re-feed those 2 circuits.

If you have breakers terminal screws that are serving more than one conductor, called double-lugging; consider moving circuits to the sub panel so that none are double-lugged - or combine the them with a short length of the same size wire (called a "pigtail") in a wirenut and use the pigtail to feed them.



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Why does a power sub panel have to have separate neutral and ground bars other than code satisfaction?

Also, does the sub panel need a ground wire connected back to the main panel in the same building?

Bonded ground/neutral

If you have the neutral and ground bonded at a subpanel, then you'll get neutral return current through the ground wire back to the main panel (since there are now multiple paths). Even worse, as @Tester101 points out, if the neutral ever has a fault, everything will continue to work but you'll have all the current on the ground, which also means that you can now be electrocuted by touching the panel chassis, for example.

The ground and neutral must be bonded only at one place (in the main panel) to avoid this.

Subpanel main breaker

A main breaker on a sub-panel is not necessary because this is in the same building (if you are in a different building then NEC 225.31, 225.32, 225.33 apply). That said, having a main...

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Hi Russ,

Thank you for your question regarding the separation of the ground bar from the neutral bar in an electrical sub-panel, it is our pleasure to help.

The difference between a ground wire and neutral wire is often misunderstood. The problem primarily comes from the inappropriately named “neutral” wire. There is nothing neutral about a neutral wire. It is a current-carrying conductor, just like a hot wire and has all the potential for danger and should be treated with the same respect.

Consider the schematic for a flash-light. Your typical flashlight consists of a battery, a switch, a few wires, possibly a fuse, and a light bulb. Let’s ignore the switch, as it doesn’t relate to the point we are trying to make. In a flash light without a switch, you would see a black wire running from the battery to the light bulb, and a white wire running back from the light bulb to the battery. The black wire would represent the “hot” wire, and the white wire would be...

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Hello Everyone,

As part of my pool remodel, I am automating the pool with a Jandy Aqualink RS6 PS. The Aqualink will be located in a Jandy Power Center sub-panel (6614). The pool automation will control two pumps, pool lights, landscape lighting, and possible two outlets. There are two ways I can GFCI the devices attached to the Power Center.

1. Put a 50A dual pole 240V GFCI breaker in the main panel, and then run power to the Power Center. That means that everything in the subpanel will be GFCI. This is the least expensive way. However, troubleshooting ground fault will be more difficult.

2. Put a 50A dual pole 240V non-GFCI breaker in the main panel. Then in the sub panel, use GFCI breakers for the equipment. This more expensive than the first option. But since each breaker is it's on GFCI, trouble shooting problems may be easier.

Based on those two options, which one would be a better option?


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HOME SitemapInfo and Troubleshooting

There are often special looking electrical receptacles in bathrooms or kitchens that have "Test" and "Reset" buttons -- often black and red -- on them. Video. These are ground-fault circuit interrupters -- GFCIs or GFIs. Their purpose is to protect people from electrocution. They do not prevent shock altogether, only deadly shock. And they do not prevent overloads on the circuit. That is the job of a circuit breaker at the main panel. See my GFCI article. (What is the little light on some GFIs?)

Why Can't I Reset? Is GFCI Bad or Is There a Ground-Fault?
GFI Outlet Diagram -- Hooking Up
Is an Unknown GFCI the Cause of an Outage?
Finding a Tripped GFCI Receptacle
Confusing Terms: GFCI, GFI, Load, etc.

Bad GFCI or a Ground-Fault? -- Troubleshooting

Is a GFI tripping for a ground-fault? If you are pretty sure you need to troubleshoot a ground-fault itself, you may want to go to

Tripped GFI -- Why?


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Route in the subpanel feeder cable, and remove any neutral bonding jumpers to ensure that ground and neutral are only connected at the main panel. Join the branch circuit wires, and install the new breakers.

To finish the job, fasten the door to the subpanel, and turn the main panel's sub-feed breaker on. Turn on the main panel's main breaker and the subpanel's main breaker. Double-check that the circuits are working, and update the labels on both panels.

Before starting the job, shut off the main power breaker, and check with the city to see if you need a permit to undertake the job. Remember that the subpanel needs to be easily accessible, so it should be installed in an area of clear space. The National Electric Code contains specific guidelines for the space that is required around a subpanel.

Learn more about...
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Hi all - I have an outdoor subpanel with switches for my well pump and for the receptacles and light fixture in the well pump house. As you can tell from the pics it is old (1950s), and also, it does not have an off switch either at the subpanel, or connected to my main panel inside my house. The power company will have to come out to power it off in order to replace the breaker switches.

One of the switches has gone bad, ie, I turned it off and when I flip it back to the on position that circuit does not come back on. In the picture, it is the two switches on the right. The two on the left, which control the well pump, fortunately still work. But i figured I might want to replace those as well, as they all feel "soft" when flipped.

Based on the pictures, I was hoping someone might be able to tell me what I need to get as far switches - ie, brand, type, etc. I obviously can't take them out until the power company comes out, and I wanted to have the new switches ready...

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Churning with voltage and resembling an explosion at the wire factory, the breaker panel exudes mystique. But it's just a big switch, filled with other smaller switches, which lead to the switches that any home owner can fearlessly flip. Doing so conjures a current of electrons that runs along copper wires, energizing our appliances, lights and modern lives. Breaker-panel literacy isn't only for voltage veterans who recite the National Electrical Code. Even if all you wonder is whether your humble hot tub dreams are electrically attainable, or why the toaster oven kills the kitchen lights—the panel has a thing or two to tell you.

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J. Muckle


Current flows from the panel toward the load along the hot wires and returns along the neutral. Each hot wire's copper tip ultimately connects to its control switch at the circuit breaker, and each neutral connects to a common terminal called a bus...

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