CHOOSING HOUSE HOLD WIRING

Modern buildings have electrical wiring in all walls, and often in ceilings and floors as well. As electricity runs through the cables to be consumed elsewhere, an electromagnetic field [EMF] is generated. This field surrounds the cable in its entire length and becomes weaker with increasing distance to the cable. Electromagnetic fields are bothersome to some individuals and can be measured by a gaussmeter.

When wiring a new building, or upgrading an existing building, it may be prudent to choose a type of cable that emits less EMF, but which one to choose? To find out, a selection of cables and metal conduits were purchased. Only types that are widely available and in general use in the United States were chosen.

A Wiring Primer

In the electrical trade, the grounding wire is always present in a cable and is not counted as a conductor. A “2-conductor cable” thus has three wires inside – a black one for the phase, a white for the neutral, and a bare copper wire for the ground. In some cases, the ground wire is green instead of bare.

A 3-conductor cable has one additional wire, which is usually red. This type of cable is commonly used for bringing two-phase (230 volt) electricity to electrical stoves, clothes dryers and water heaters. It can also be used for lighting circuits with two switches, such as in each end of a hallway.

Test setup

A combination of cables and metal conduit were tested under identical conditions. To provide a test load, a 1380 watt space heater of brand Intertherm (now SoftHeat) was placed approximately 20 feet away. The metal conduits tested were sold in 10-foot sections, but we used six-foot samples due to transportation restrictions. The measurements were done at the middle of the conduit. In all tests, the ground wire in the cable was connected to the ground in the wall outlet, as it normally would be. The ROMEX 3-conductor cable tested was used without connecting the extra wire to anything. It was not tested whether connecting it to the ground would be helpful. Doing so would violate the National Electric Code, which is very specific about the color codes, and forbids running wires in parallel. To limit outside interference with the test, a specially shielded outlet was used, while the breakers were off to all the other outlets within twenty feet. The outlet used had regular wiring inside EMT metal conduit, which went all the way back to the breaker box.

The EMF levels were measured by a gaussmeter of the TriField brand, produced by Alpha Labs in Utah. The TriField meter was outfitted with the optional external Choosing Household Wiring 3 probe that makes it one hundred times more sensitive and able to pick up EMF down to 0.01 milligauss. The 120 volt AC power in the building did have some overlying static (“dirty power”) which could be picked up with an AM radio. This static was present whether any current was running or not. It appeared to come from the outside of the building and this was deemed not to be a problem for this comparison.

Results

The results from the gaussmeter readings are shown in Table 1. It is clear that the

3-conductor ROMEX wire (ROMEX 12/3) is vastly superior to the 2-conductor

(ROMEX 12/2). This is due to the fact that the individual wires inside the cable

happen to be twisted around each other. This effect is used in wires for computer

networks and long telephone cables, so it was not a surprise that it also worked

well here.

What was surprising was that the ROMEX 12/3 cable also is superior to the other

cable combinations tried, i.e. the flexible metal-clad cable (MC 21/2) and when

the ROMEX 12/2 was put in metal conduit and even when put in the heavy duty

IMC conduit.

When the ROMEX 12/3 cable was further shielded by EMT conduit, the radiation

level become so low that it only measured 0.4 milligauss directly on the surface of

the conduit.