The Fluke PV Ground Fault Locator GFL-1500 – A Clear Path Forward

By Will White, Fluke Senior Application Specialist, DER

If you've spent time troubleshooting PV arrays—especially larger, more complex systems—you know how frustrating and time-consuming it can be to chase down a ground fault. The Fluke GFL-1500 Solar Ground Fault Locator is a tool designed specifically to reduce that frustration. It's not a multi-purpose meter with a new feature bolted on—it's a dedicated system for one job: finding and pinpointing solar ground faults quickly, safely, and accurately.

As someone who's worked alongside field techs for years and helped develop tools tailored to their real-world challenges, I can confidently say the GFL-1500 brings something special to the table. It's not about replacing existing test methods—it's about speeding up what takes too long and improving precision where there's usually too much guesswork.

What Is the Fluke GFL-1500?

At its core, the GFL-1500 is a ground fault locator for PV systems, rated for up to 1500 V DC. It's designed to trace the actual fault path using a signal injection method. Once the signal is in the circuit, the technician uses either a signal tracing clamp or a receiver to follow the path to the point of failure.

The system is built around three components:

• GFL-1500 Transmitter – Injects the traceable signal into the PV circuit
• GFL-1500 Receiver – A handheld device that detects the signal, with audio and visual feedback to guide the user
• GFL-1500 Signal Tracing Clamp – Helps isolate the faulted branch without disconnections. Supports better signal detection in noisy or high-interference environments.

The transmitter and receiver are rated CAT III 1500 V and CAT IV 600 V and built to IEC 61010 standards—essential for working safely in today's utility-scale systems. The signal tracing clamp is rated for use on insulated conductors up to 1500 V.

What Does It Actually Do?

The GFL-1500 offers several diagnostic functions, each built to support different stages of troubleshooting. Here's a quick breakdown:

• Analyze Function: This is your starting point. It measures the open-circuit voltage between the positive and negative terminals, then from each terminal to ground. If a fault is present, it estimates the fault's resistance. It can also provide the approximate location of the fault if you enter the number of modules per string.
• Fault Function: After identifying the presence of a fault, Fault Function injects a traceable signal that can be followed to the exact location of the fault using the clamp or receiver. This allows technicians to follow the signal to the physical location of the fault—no need to isolate strings or pull conductors from a busbar unless necessary.
• Open Circuit Function: If the problem is an open conductor (rather than a ground fault), this function lets you trace where the break occurs, particularly useful on strings that are producing no current and aren't tripping GFDI.
• Mapping Function: Ideal for systems with poor or outdated documentation. This function helps trace healthy strings, confirm layouts, and identify where components tie in, without relying on site maps that may or may not match reality.

Where and When Would You Use It?

The GFL-1500 is designed for high-efficiency troubleshooting across all types of PV systems: residential, commercial or industrial rooftop, and utility-scale ground mount. It's especially valuable on large sites where faults can occur anywhere—from module-level wiring to homeruns through combiner boxes—and where time spent hunting is money lost.

Some specific use cases:

• When a fault isn't triggering GFDI protection but is still reducing production: The GFL-1500 can detect high-resistance faults that wouldn't trip an inverter, helping catch faults early before they escalate.
• When system documentation is incomplete or inaccurate: Mapping Function and fault tracing take the guesswork out of troubleshooting arrays that aren't clearly labeled or where the design doesn't match the physical layout.
• When techs need to move quickly and safely: The tool doesn't require frequent disconnection of conductors, which not only saves time but helps reduce wear on terminals and eliminates unnecessary exposure to energized equipment.

What Makes It Different?

Traditional methods like insulation resistance testing and voltage-to-ground measurements are valuable—but they require a lot of set up, training, and often some degree of trial and error. The GFL-1500 sidesteps much of that. By injecting a traceable signal directly into the PV circuit, the tool gives technicians a much faster way to locate faults, especially across large distances.

This is particularly useful in a field environment where multiple arrays and strings are involved, and where techs may be dealing with dozens or even hundreds of potential fault locations. Instead of taking systems offline for hours, you can isolate and confirm the issue with minimal disruption.

What Problem Does This Actually Solve?

In short: it saves time, reduces risk, and helps restore production faster.

The GFL-1500 isn't just about convenience, it addresses key pain points that have real operational and financial impact. Faster fault location means fewer truck rolls, less downtime, and fewer strings sitting idle waiting to be reconnected. For O&M teams working against performance guarantees and uptime KPIs, that's a major benefit.

It also helps keep experienced technicians focused on high-value work. With tools like this, less time is spent on brute-force troubleshooting and more on strategic repairs and system optimization.

Final Thoughts

The GFL-1500 isn't a silver bullet—and it's not meant to be. It's a sharp, targeted tool that fits neatly into a modern solar troubleshooting workflow. Whether you're confirming suspected faults, tracing wiring issues, or simply validating that what's on paper matches what's in the field, this tool accelerates every step of the process.

It reflects what's needed in today's O&M landscape: faster diagnostics, fewer assumptions, and safer work. If you're responsible for the uptime across large or complex systems, this is a tool worth having in your arsenal.

About the Author

Will White began working in solar in 2005 for a small integrator. After starting as an installer, he worked in sales, design, and project management, and he eventually became the Director of Operations. In 2016, he joined the curriculum team at Solar Energy International (SEI), where he focused on developing course content and teaching solar classes. In 2022, Will moved into a solar application specialist role at Fluke, where he supports their renewable energy testing equipment like IV-curve tracers, electrical meters, and thermal imaging cameras.

Will has experience in wind power, solar thermal, energy storage, and all scales of PV. He is passionate about implementing high-quality, code-compliant installation techniques. Will has been a NABCEP Certified PV Installation Professional since 2006 and was previously a NABCEP Certified Solar Heating Installer. He has a B.A. in business management from Columbia College Chicago and an MBA from the University of Nebraska-Lincoln. In his free time, he can be found working with his wife and daughter on their homestead in central Vermont, which features an off-grid straw-bale house.

Connect with Will on LinkedIn.