Science Report Deems Stetzer Filters Useless

Report on Evaluation of Stetzer Filters 

 — by:  Greg Gajda, Art Thansandote Ph.D., Eric Lemay, D. Lecuyer, W Gorman and James McNamee, Ph.D.

Consumer and Clinical Radiation Protection Bureau Health Canada — May 11, 2006

Here are some excerpts from this report followed by a link to download a pdf file of its entirety:

Background.  Recent media attention has focused on the practice of installing electrical filters (called Stetzer filters) on the 120 V, 60 Hz electricity supply in the home. The filters are purported to clean so-called “dirty electricity” and are said to incur health benefits such as lowering blood sugar, relieving or reducing symptoms of multiple sclerosis and treating attention deficit hyperactivity disorder (ADHD) in school children [Havas and Stetzer, 2004].

Purpose: The purpose of this investigation was to see the effects on the line voltage of the 60 Hz supply and load currents carried by the supply when a Stetzer filter is plugged-in, alone and in conjunction with household appliances. For appliances, we selected an incandescent light bulb, a fluorescent light and a home computer and CRT monitor.

Stetzer Filter Alone: Effect on line voltage and load current:   Measurements were performed to see what effect a Stetzer filter has on the line voltage and to observe the current passing through the filter (load current). This sequence of measurements was performed in the Electromagnetics laboratory of the Clinical and Consumer Radiation Protection Bureau.

The purpose of this report was to assess the impact of Stetzer Filters on the electricity supply in the home, in particular to look at its claims to reduce the “dirty electricity” in the line voltage within the specified range of 4kHz to 100kHz. It is important to note that these filters do not claim to reduce magnetic fields at any given frequency.

We conclude the following:

1)  The Stetzer filter draws 0.9 amperes of reactive current on its own therefore increasing the amount of current supplied to the home, increasing the burden on the electricity supply and increasing ambient magnetic field levels in the house. The amount of increase may be large or small depending on the number of filters installed.

2)  The Stetzer filter does not clean up line voltage harmonics. Nor does it help to restore the current of a non-linear load back to a sinusoidal shape. The Stetzer filter current is highly distorted containing harmonic content up to 10 kHz. (Stetzer current harmonics are accentuated versions of the line voltage harmonics.) Since Stetzer filter currents add vectorily to the other load currents in the home, their distortion products (harmonics) are carried on the electricity supply and add to the level of “dirty electricity” in the house.

3)  The Stetzer filter is probably effective in attenuating high frequency (4kHz to 100 kHz) noise on the AC power lines although these components are small to begin with. No assessment can be made concerning its effectiveness in suppressing transient disturbances since these phenomena are random, infrequent events for which we are unable to test.

The impact of installing one Stetzer filter on an outlet has no financial effect on the homeowner since capacitive or inductive (reactive) loads are out of phase with the line voltage and do not consume energy. Consumers only pay for resistive load currents that are in phase with the line voltage. However, the electricity provider must generate the additional current and carry it on the network. An example of this impact would be as follows. In a community of 100,000 homes, if 25,000 homeowners decided to equip their homes with 20 filters per household (20 x 0.9amperes), this would add a constant demand on the network of 450,000 amperes reactive. In some situations, this could lead to the requirements of additional transmission facilities (towers) and would translate to higher magnetic field exposure in proximity to the towers.