Troubleshooting Common Electrical Sub-panel Problems

An electrical sub-panel is a smaller version of an electrical panel that is useful for feeding current to a section of a building or house away from the main panel. An electrical sub-panel requires a number of circuits. Just like any electric component of your home, your electrical sub-panel can experience a number of problems that you may be able to troubleshoot and fix yourself. You may read about several common problems below.

An Unbalanced Load

Most of the time, your code will ask for a four-wire feed when you install an electrical sub-panel because that is the only way for you to achieve a balanced load. With a three-wire feed, you get an unbalanced load that will cause problems along the way. You can always correct the problem by installing the appropriate feed.

An Improperly Installed Neutral Wire

For this problem, there will be a difference between your ground wire and your ground rod, although everything should be fine as long as your system is grounded properly. You should then check the voltage between your systems’s EGC and that of the neutral wire. The number that registers is the voltage drop from the point of measurement and the main bonding jumper. If you find a voltage drop, you will have to check how your sub-panel’s wires were installed, especially the neutral wire. A voltage drop on the neutral will mean that the neutral wires were not installed properly.

A Fault Current

Electricity runs in circuits, and the current will always look for a way back to its starting point. The current will go through all open paths. That fact is the main reason you have to install an EGC in the ground bar of your electrical sub-panel. The EGC will be in charge of carrying that fault current.

If something in the system goes awry, like if a hot conductor touches the metal casing or any piece of the equipment in the system, the fault current will be redirected to the equipment. This redirection will electrocute anyone who touches the equipment. This electrical shock is strong enough to kill people. In such a case, your circuit breaker trips, but it may not always do so if you do not have an EGC installed.

The EGC will always redirect the current back to the ground bar and from there to the bonding jumper and then the neutral bar. This will increase the current enough for the circuit breaker to trip. A tripped circuit breaker will prevent any kind of shock from happening because it will cut any current from entering the circuits that it controls.