Phantom Loads Richard Perez Just because the switch says "OFF" doesn't mean a device is off. Many modern appliances are never really OFF. They contain clocks, memories, remote controls, microprocessors, and instant ON features that consume electricity when plugged in. That's 24 hours a day, 7 days a weekÉ While these Phantom Loads are often small, they add up if several are constantly on line. Some Phantom Loads are easy to spot- things like clocks and and timers have displays. Other Phantom Loads are truly hidden- the device seems OFF when switched OFF, but it really isn't. Obvious Phantom Loads Consider a clock. Many appliances contain a clock or timer. The electronic clock/timer and its display consume very little (Å0.5 Watts). However, there is a power supply in the appliance that converts120 vac into low voltage DC for the clock/timer. This power supply is very inefficient at low power, consuming many times the power actually needed. This consumption is about 40 to 75 Watt-hours daily- enough to run a lightbulb for TWO hours. Most of this consumption goes to do a job better accomplished by low voltage DC directly from the batteries. At night, when hardly any power is used, the inverter may stay on just to supply small Phantom Loads. This operation is very inefficient. One, these jobs are better done via DC. And two, it's forcing the inverter to operate for extended periods in its least efficient mode. Sneaky Phantom Loads Some Phantom Loads appear to be truly OFF when switched off. There are no lights or indicators showing power consumption, but the device is still using electricity. Offenders in this category include, stereos, VCRs, computers, calculators, computer printers, satellite TV systems, and any device powered by a "wall cube". Wall cubes are power supplies in plastic boxes that plug into 120 vac outlets. Let's visit a few of these Phantoms where they lurk. The Primary is Alive! Many 120 vac appliances contain power supplies. These convert 120 vac, either inverter or grid produced, into low voltage DC for the appliance's electronics. On some appliances the ON & OFF switch is placed on the secondary (low voltage side) of the supply's transformer. The primary is not switched and is always connected to the 120 vac source. See the diagram below. INSERTDIAGRAM The inverter or commercial power grid sees the primary of the transformer as a constant load. Power consumption on these devices may run between 50 to over 200 Watt-hours daily. Filters and Line Conditioners Many 120 vac business appliances like computers, printers, typewriters, FAX machines, and copy machines use filters on their power input. These filters serve a useful purpose- protecting the device from overvoltage, surges, noise and other electric trash that may wander onto the grid supplied electrical lines. Unfortunately, most of these filters are wired in ahead of the power switch, and are on line all the time. They consume power from the inverter- about 8 to 40 Watt-hours daily. Wall Cubes These small black boxes are really Phantom Loads. Wall cubes are actually small power supplies. Consider the case of a telephone answering machine powered by a wall cube. The wall cube is plugged into an electrical outlet and feeds the answering machine via a low voltage power cord. The ON/OFF switch is located on the answering machine itself. Even if the answering machine is turned OFF, the wall cube still consumes electricity. This is electrically the same as having a power switch on the transformer's secondary- the primary is alive all the time. A wall cube uses 20 to 50% of its rated power even when its device is switched off. How to detect Phantom Loads We find Phantom Loads by watching for signs of current flow where there should be none. If you are a technician with a meter, then break into the appliance's power circuit and measure consumption when switched OFF. This involves working with live 120 vac wiring and is dangerous if you don't know what you are doing. 120 vac will shock you whether it's produced by the grid or your inverter. What follows is a very simple circuit for detecting phantom loads. It can be assembled from hardware and Radio Shack parts for under $6. It can be wired before it is connected to 120 vac power, and is as safe to use as a wall socket. The schematic is below: INSERTSCHEMATIC Everything is assembled into a plastic wall box used in 120 vac homes. The two Light Emitting Diodes (LEDs) can be in any color. Use very small gauge lamp cord (Å18 gauge) wired to a male plug. Use the Phantom Load Detector as follows: ¥ Turn the appliance to be tested OFF. ¥ Unplug the appliance from the 120 vac power source. ¥ Plug the appliance into the Phantom Load Detector. ¥ Plug the Phantom Load Detector into the 120 vac power source. If you are using an inverter as a 120 vac source, then make sure that the inverter is "booted" and operating, not in standby mode. If the appliance is a phantom load and consuming power, then the LEDs will light. The more power the appliance is consuming, then the brighter the LEDs. This device is for testing power consumption in appliances when they are switched OFF. While the Phantom Load Detector will survive switching the appliance ON, the appliance will probably not operate. The entire circuit is current limited by the 10k½ resistor. With the 10k½ resistor, we were able to detect Phantom Loads as small as 0.3 watts. If the 10k½ resistor is replaced with a 3k½ resistor, then the detector becomes more sensitive (0.1 watts), but the LEDs will not survive operation into an appliance that is turned ON during testing. The Phantom Load Detector is very easy to build with only three electronic components. One detector should cover a neighborhood. Either a 120 vac appliance is a phantom load or it isn't. Once we have determined this we don't need to test it anymore, and the detector can circulate for others to use. Dealing with Phantom Loads Unplug the appliance! This works for sure because it is disconnected from its power source. However, constantly plugging and unplugging is a pain and wears out the hardware quickly. Just about every hardware or discount store sells extension cords with multiple female plugs that are SWITCHED on the plug strip. They sell for $5 to $10. When the plug strip is switched OFF, all the appliances plugged into the strip are disconnected from the 120 vac power source. We use these plug strips for all phantom loads. Here on Agate Flat, we have three SL Waber (Model EP7S, costing $7.99 at the local discount house), seven outlet, plug strips with neon indicator lights. The neon indicator glows when the plug strip is turned ON and supplying power to all the phantom loads connected to it. We have two Mac computers, an ImageWriter printer, an HP DeskWriter printer, a wall cube powering a modem, and a hard drive plugged into these strips. I don't mind feeding these appliances when they are actually operating, but I don't want them flattening our batteries when they are supposed to be OFF. INSERT PHOTO Selecting Appliances that are NOT Phantom Loads Any appliance with a built-in clock or timer is a constant and obvious phantom load. If you want a clock, then buy a clock, not a microwave or VCR. Avoid appliances with electronic memories unless these memories are kept alive by small batteries within the device. As a last resort, take a Phantom Load Detector to the store when you buy your appliance and check it out. In many cases all appliances of a particular type are phantom loads. VCRs, for example, all contain clocks and timers that are alive even if their displays are not lit. All appliances using wall cubes are phantom loads. Every piece of electronic office equipment is a micro phantom load because of its filtration. Here the switched plug strip comes to our rescue. The Bounty on Phantom Loads If you live on the commercial grid, you're paying an average of 7.75¢ per kilowatt-hour for electricity. A small phantom load of 4 watts costs you about $2.70 yearly. If you make your own electricity, then the savings situation is even better. Site produced power costs much more, about 90.¢ per kilowatt-hour. The 4 watt phantom load costs home power producers about $31. per year. The plug strip pays for itself in less than 3 months. And we get to use our power elsewhere. The bottom line here tells only part of the story. Sure we can save some money by disconnecting inoperative appliances that still consume power. We can also save resources for use elsewhere. Regardless of the electrical power source, phantom loads waste energy because they don't do anything in return for their consumption. While in the individual sense, these phantom loads are small; in the collective sense, we're wasting enormous amounts of electricity.