Jobsite Safety 101: The History Of Ground Fault Protection

July 31, 2015 at 2:46 pm  •  Posted in Company Profiles, Safety  •  0 Comments

Back in the ‘70s, there were roughly 700 electrocutions from ground faults every year.

Electrical Safety Of Yesteryear

In the ‘70s, what passed for electrical safety (and fashion) was questionable. At that time, accidental electrocutions in the U.S. exceeded 1,100 per year. Since then, we’ve ditched the bell-bottoms and tightened up on electrical safety in a big way.

Since the introduction of ground fault protection, electrocutions have decreased considerably. Clearly, we’ve evolved. But there’s still work to be done. To make every building safe, from schools to jobsites, UL continues to tweak the standards of UL 943 to bring this number to zero.

Ground Faults (The Basics)

Just 25 years after the GFCI was introduced, the number of accidental electrocutions in the U.S. dropped in half.

Ground fault protection isn’t sorcery—it’s science. (But you already knew that.) If you’re a rookie who’s learning the ropes, or a seasoned contractor looking for a refresher, here’s how ground fault protection works:

Our friend here, let’s call him Bob, is standing in a pool of coffee he spilled all over himself. (Nice one, Clumsy Bob.)


In this situation, there’s 6 amps going out and 5.9 amps coming in. The load’s off balance, so Bob becomes the default ground. (That’s not good.) That 0.1 amps of leakage will course right through his body. Without a GFCI, Bob’s in a real pickle.

Basically, the GFCI monitors the load and what’s coming back on the neutral, and trips in the 4-6 milliamp range. If the load balance is off, the GFCI cuts power from the circuit (saving Bob).

Portable Ground Faults

The GFCI was first required in 1968 for lighting in pools. Later, code required GFCIs in other areas of the house.

A portable ground fault is a different animal than a GFCI receptacle. If an employee needs to use a power tool, for example, a portable allows them to bring ground fault protection with them wherever they’re working—from the plant floor to the jobsite.

Forget cobbling together your own makeshift portable GFCI protection. It’s not only a terrible idea, but it won’t fly with OSHA either. (Just don’t do it.) A portable ground fault must have the added safety of an open neutral relay. So if a ground fault happens, or the cord gets run over by a backhoe (and cut in the process), you’re still protected. Save your DIY skills for building a deck this summer.

The Safety Revolution

In the desire to make jobsites safer, Hubbell launched the first portable circuit guard in the early ‘70s.


Just for fun, we dug up an “old school” ad for Hubbell’s first portable circuit guard: the GFP-115.

Before the ‘70s, the technology for ground fault protection didn’t exist. So Hubbell stepped up and brought it to the market, happily sharing the technology with competitors. Out of this collaboration, the ground fault receptacle was born.

Today’s Portable Circuit Guards

Hubbell’s Circuit Guard® solutions, available in hard-wired and portable options, deliver the powerful ground fault protection we rely on today.

Hubbell’s portable Circuit Guard products:

  • Feature a 30 amp rating (can be wired with 15, 20, or 30 amp plugs and connectors)
  • Are available in 120 or 240 volt configurations for single-phase applications
  • Come in manual or automatic reset
  • Include open neutral protection
  • Boast Class A GFCI protection at a 4-6 milliamp trip level
  • Come with LED indicators to show ground fault and power interruption
  • Feature a UL Enclosure Type 4X rating
  • Come with a heavy-duty cord (10/3 AWG SJEOOW for the 50-foot portable, and an 8/3 AWG SEOW for the 100-foot portable)

Learn more about Hubbell’s Circuit Guard products.

Over To You

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Todd Reed, National Market ManagerAbout The Author
Todd Reed, National Market Manager

As National Market Manager at Graybar, Todd’s goal is to find the best products and solutions to help contractors work more efficiently, stay safe on the job, and win more productive and profitable business.   




Sources & Credits

Mike Holt Enterprises
InterNACHI: GFCIs Code Changes History Chart
Underwriters Laboratories: Some History of Residential Wiring Practices in the U.S

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