What is ground fault protection and do you really need it? A ground fault is an abnormal condition in which current is traveling along the ground wire, which is normally a non-current carrying conductor. This means that something in the Solar Array is shorting out, causing the current to flow into the ground wire. If the condition is left to remain, the point where the short is happening will eventually fail causing a fire. This can be seen in two recent devastating fires caused by Solar Array Ground faults. (Bakersfield, CA and Delanco, New Jersey)
Now is where the question arises, doesn't a circuit breaker of fuse remove the ground fault? In a ground fault, a circuit breaker of fuse may not open clearing the ground fault. The reason behind this is that in order for a circuit breaker or fuse to trip, the current flowing through that device must be higher than the devices rating. For example, a 20 ampere circuit breaker needs over 20 amperes to trip. In a ground fault there may not be enough current flow to trip the breaker.
The problem with ground faults is that not all of the current is flowing into the ground wire. There is always a certain amount of resistance that happens in a ground fault that reduces the amount of possible current. This means that even though there is a fault, it is not high enough to trip the circuit breaker of fuse that is normally in the system. Therefore, ground fault protection is added to the circuit. In general, a ground fault protective device is set to trip as low as 1 ampere.
A ground fault protection device will disconnect any loads on the Solar Array. By disconnecting the loads, there is no longer a flow of current stopping the short circuit from persisting. Now the Solar Array is brought to a safer condition until the short can be removed from the system.
Now for the million dollar question, do you need one? If you are planning on putting solar panels on your dwelling, the answer is yes. A ground fault protective device will help prevent your house from catching fire due to a ground fault. Remember, ground faults generally do not trip your normal circuit breakers or fuses. On the other hand, if your solar panels are going to be ground mounted, this isn’t a requirement, but still a good idea.
Having a ground fault protection device installed in your Solar Array is like having insurance.