Some things are absolute. For instance, when it comes to any circuit running between the main panel in a building and a receptacle, no one wants excessive voltage drop and all the troubles that it could lead to without warning.

Inexplicable power problems can cause anything from repeated temporary annoyance to devastating computer or other electronic equipment malfunctions or, even worse, fires.

Many inspectors and contractors, aiming to find trouble before it evidences itself to end-users, rely on receptacle testers, which can verify proper wiring and test ground fault circuit interrupters (GFCIs). But, those receptacle testers typically reveal nothing about the integrity of the wire. (The lack of wire integrity carries many hidden hazards.)

Circuit analyzers, however, not only can verify wiring and test GFCIs, but can also offer much more thorough and comprehensive testing, including checking the integrity of the wiring all the way back to the panel. There was a time when using a circuit analyzer meant disrupting a workday to conduct the tests or performing the tests on off-hours.

Thanks to some new technology, however, there is now a new generation of plug-in circuit testers that enable electrical contractors and inspectors to easily conduct preventive troubleshooting tests on a circuit under a full load—without interruption to any equipment on the circuit, including computers.

There are a variety of sophisticated, easy-to-operate handheld circuit analyzers on the market that measure voltage drop under a full 15-amp load, when potential hazards are at their highest levels. These analyzers also offer a bounty of other information to those looking to identify electrical hazards in circuits before any, or much, damage is done, without interfering with end-user activity. These testers sport LED indicators rather than moving needles and, therefore, stand up better in the field to hard-knock or even gentle drop conditions.

Historically, most faults in electrical system branch circuits are not picked up until a specific situation—a blown fuse, a tripped circuit breaker, smoke—alerts the end-user of need for prompt or immediate attention. Yet, all too often, correctable situations are missed before damage is done because they can go undiagnosed until the symptoms appear, despite periodic receptacle testing or use of a neon tester, which can give false readings.

The latest plug-in circuit analyzers can verify proper wiring and GFCI operation; identify and locate loose wire connections, bad splices/receptacles, high-resistance grounds; and test line voltage and voltage drop under full load, without affecting equipment or stressing the wire beyond its 15-amp capacity. No single tool offers every capability, so check specifications before you buy.

While it is the inspector’s or contractor’s responsibility to determine how much voltage drop is “excessive,” (voltage drop of more than 5 percent or 6 volts in a circuit is, according to recommendations of the National Electrical Code (NEC) for achieving optimum efficiency, considered outside safety guidelines). High voltage drop can indicate a number of potentially dangerous problems, in-cluding undersized wire for the load or length of the run, or high-resistance connections caused by poor splices and loose or corroded connetions. High voltage drops can also result from high-resistance connections caused by inadequate connection in quick-connect “push-in” type receptacles and from faulty switches and receptacles.

It is critical to discern high voltage drop before any dramatic effects are felt, because high voltage drop can not only waste energy and result in poor power efficiency, but it can also cause inefficient or erratic operation of equipment on the circuit or even damage to the equipment.

Even worse, heating at high-resistance connections could result in fire at high- ampere loads.

Logical analysis often helps in diagnosis. For example, by using a circuit analyzer and testing receptacles in sequence, you can identify the first receptacle where there is significant increase in voltage drop. If, upon continuing the testing, the other receptacles turn out to have acceptable voltage drop, then the inspector or contractor can conclude that the problem is localized at the single guilty receptacle and work from there. If, however, the voltage drop is unacceptable at succeeding receptacles, then the problem is within the hot or neutral conductors. And should all the branch receptacles have unacceptable voltage drop, then most likely the problem is in the panel or in the circuit between the panel and the first receptacle.

It is possible to use some circuit analyzers to test the ground all the way back to the panel by pulsing onto the ground conductor to take a true impedance measurement of the system.

These new analyzers also offer another significant safety feature. Use of a ground continuity adapter allows the operator to test the grounding of a panel or of a piece of equipment by clipping an alligator lead from the adapter to the equipment chassis or side of a panel. Once the analyzer is plugged into a receptacle, the adapter will verify that the equipment has been grounded. This ability to verify that equipment has been grounded can help avoid shock or electrocution by users of equipment.

Depending upon the model and the selection of accessories incorporated into the testing process, other capabilities from these tools of many talents could include the ability to identify false grounds, dedicated circuits, and isolated grounds, and the ability to measure ground impedance, ground-to-neutral voltage, load on the circuit, and GFCI trip time.

Indeed, you can get basic circuit analyzers primarily dedicated to indicating line voltage and voltage drop and identifying and locating loose wire connections, bad splices and receptacles, and high-resistance and false grounds; or you can get more comprehensive circuit analyzers that handle not only line voltage and voltage drop but also ground impedance, event recording, true RMS, harmonics, power factor, load on branch, dedicated circuits, and isolated and false grounds. In commercial and industrial environments, however, large non-linear loads can cause harmonics, which distort the waveform and could affect the validity of the reading given by average responding meters.

The FELDMANS provide Web content for companies and write for magazines, trade associations, building product manufacturers, and other companies on a broad range of topics. They can be reached at or (914) 238-6272.