May 2012 Electrical Apparatus

May 2012 Electrical Apparatus

This is a summary of the Electrical Apparatus May 2012 featured technical article,  by Richard L. Nailen, P.E.     

Owners of residential properties are naturally interested in reducing their payments for electrical energy. For decades, they have been exposed to advertisements for energy-saving devices for attachment to their electrical system–mysterious “black boxes”–that promise reductions of as much as 34 percent in utility bills.

When such claims do offer any details of how such a device works, these are the functions usually cited, singly or in combination:

1. Improved power factor
2. Voltage “stabilization”
3. Harmonic reduction

What’s meant by voltage stabilization is seldom explained. It is sometimes said to be “phase balancing”–relevant only for commercial or industrial properties supplied from three-phase sources, but meaningless for single-phase residential distribution. It may mean voltage reduction, which can decrease energy usage by lightly loaded motors. However, residential appliance motors are so small, and operate so few hours annually (and then only when fully loaded), that the energy reduction is seldom significant.

A higher power factor will reduce the reactive current supplied by the utility. The most persistent misunderstanding fostered by the makers of these devices is that less current from the utility means less power supplied. Unfamiliar with the behavior of alternating-current circuits, the average homeowner is easily taken in by claims that “less electricity” means a lower energy charge.

Harmonics may be present on residential circuits when computers or similar electronics are in use. They have little influence on the system, however. Also, they cannot be readily quantified and may be highly variable over time.

What these devices actually do is often explained in terms that appear reasonable but make little sense, such as the assertion that electrons can be made to flow more easily, with fewer energy-wasting “collisions.” Savings reported by users are seldom supported by sufficient technical detail to verify their validity. That, plus the unsound electrical theory contained in some of the claims, should make prospective users quite skeptical.

To mitigate these hazards, various circuit options have been recommended. Of particular importance is the location of the overload contacts within the circuit. Also, use of dual start or stop switches can prevent several undesirable consequences of accidental circuit grounds.

To order a back issue with the full article, “Energy savers: claims vs. reality” call 312-321-9440 or visit our online webstore.

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