Arc Faults

Last modified on March 9, 2020

Arc faults are potentially dangerous wiring problems.
An arc fault is a tiny electrical arc jumping across a gap. This can happen if a wire is seriously damaged or a PV connector is failing or in any number of other parts of solar wiring.
Arc faults can cause fires.

DC vs AC Arc Faults
Arc faults can happen in DC circuits and in AC circuits. DC arc faults, however, are much more dangerous than AC arc faults because they can persist. AC arc faults tend to self-extinguish.

Most solar installations are required to have arc fault detectors in the DC circuits. When a DC arc fault is detected the system must shut down. A manual reset is required to ensure that a person is aware of the fault.

False Arc Faults
Sometimes the arc fault detector system makes a mistake and indicates an arc fault when none is present. A single arc fault should be documented and discussed with a qualified service provider, but may not warrant action as it may be a false detection. If that arc fault is repeated, however, and even if it comes much later, it could very well be a real arc fault.

Sometimes arc fault detectors fail. A failing detector may raise arc fault alarms. One cannot know if an arc fault alarm is a real arc fault or a failing detector, and so the fault must be investigated.

Real Arc Faults
A real arc fault must be addressed. A single arc fault could be real and may warrant a preliminary investigation. A repeating arc fault must be investigated.

Finding Arc Faults
Finding an arc fault is an important job. All wiring must be visually inspected. All connections must be visually and mechanically inspected. Any suspect connections must be replaced. This may require the removal of a solar array from its mounting. Real arc faults can also occur right inside inverters and other devices.

An arc fault investigation from a single arc fault will generally encompass an inspection of all accessible wiring and connections including the inverter (or charge controller), combiners, and all readily accessible wiring and connections. If the arc fault persists then a comprehensive inspection including array removal and inspection must be done.

Generation Solar is your source for arc fault investigation expertise. Please contact us if you are experiencing arc faults.