What Tools Do You Need When Troubleshooting Ground Faults?

Ground faults are one of the more frustrating issues a solar technician can run into in the field. They can range from hard faults with a clear voltage signature to resistive or intermittent faults where voltage won’t show up on a standard multimeter at all. Knowing where to start and which tool to reach for first makes the difference between a fast diagnosis and a long day chasing a ghost.

In this clip, Alex Jahp of Solar Tech Collective walks through the foundational tools you’ll need for ground fault troubleshooting and how each applies to different fault scenarios.

Want to go further? Alex, Rebekah Hren, and Brian Mehalic’s full course – Solar PV Ground-fault Troubleshooting: Theory, Tools, and Field Application – covers the complete process from theory to hands-on field techniques.

Transcript below. 

Let’s start talking about how we identify, locate, and repair ground faults with an introduction to ground fault troubleshooting. A good place to start is by discussing the primary tools that we’ll use.

Regardless of the type of ground fault that we are troubleshooting, we’ll need to have a digital multimeter or an insulation resistance tester that can perform all of the functions of a multimeter on hand. We’ll use it for things like checking GFDI fuse continuity, measuring voltage to ground to identify hard faults. If there’s anything that’s good about having a hard fault that has voltage to ground, it’s that that value can be used to identify the specific fault location in a circuit. If there’s anything that’s good about having a hard fault with voltage to ground, it’s that the value can be used to identify the specific location of a fault in a PV circuit.

We’ll talk about exactly how you do this a little bit later. The key to this test is that the circuit must be energized by the PV array. Otherwise, even if there’s a fault, we’re not gonna see any voltage. We also want to have a current clamp on hand so that we can take current measurements on grounding conductors and PV circuit conductors.

We’ll need to have an insulation resistance tester to measure resistance between conductors and resistance to ground. We’ll use an insulation resistance tester whenever we’re troubleshooting resistive or intermittent faults or when we’re testing conductors that are disconnected from a PV power source. Low IRT results can be used to identify faults, like resistive or intermittent faults, that don’t present a voltage that a digital multimeter can measure. In fact, we actually need to verify that there is no voltage present between our two test points before running an insulation resistance test, as doing so on an energized circuit can be hazardous.

Because of this, most insulation resistance testers are gonna check to see if there is voltage present above a certain threshold, and if there is, they’re not gonna allow you to perform the test.