This is not a vampire load

Phantom Loads and How To Prevent Them

In an earlier post, I mentioned how I save electricity by reducing the phantom loads (also called vampire loads) in my house. Someone almost immediately messaged me asking what that meant. Since it’s an interesting question to answer, I decided to to make it my next topic. Plus, I’ll talk about how to reduce your electricity bill as a bonus.





Rectifier filter assembly
An AC source is connected via a wall outlet to the assembly. The first stage of the assembly steps the voltage up or down as needed for the circuit. The alternating sine wave is then sent through a diode bridge that converts it to a pulsing DC signal. After that, a filter circuit converts the signal into a rippling DC signal. Further filtering and regulation will produce a smooth DC output.

Let’s consider your standard power converter. You know, the big black thing that you plug into the wall. I decided to demonstrate this using a quick design I threw together in PSpice, the CAD program used by electrical engineers. If you look at the left hand side of the screen, you’ll see a typical rectifier assembly. All of that except for the 120VAC source exists inside the black box. In real life, a more complex filter system is used to get a better output. However, that’s another lecture.

If you look at the circuit shown, you’ll see that even though there’s no load connected on the right hand side, there are still several paths for current flow. Granted, it will be minimal; however, that will still act as a *GASP* PHANTOM LOAD on the system. Even though the coffee maker, computer, or whatever is turned off, it’s still drawing power. That is the horrible truth behind vampire loads. Cue the spooky music.

How do you protect against these types of things raising your energy bill? Well, there are two ways. You can either evaluate the power draw as insignificant with a tool such as this.  It’s a pretty neat little device that acts as a wattmeter in-line with whatever is plugged in. It will give you the actual power use of any device that you connect. It’ll also give you the estimated yearly cost if you don’t want to calculate it yourself. You might be surprised by how much keeping your cellphone charger plugged in is costing you per year.

If you decide that the cost of phantom loads is too high, the best thing you can do is unplug them. It’s that easy. Well, I guess it’s less easy if there are a lot of them that you use regularly. A reader suggested I check out Belkin’s line of products for this and I found two interesting devices. The first one is basically a switch to turn off your outlet. They’re about $7 apiece so I can’t say I’d personally use them without doing some serious math on if I’d recoup my costs. However, the next item might be on my Christmas list. This thing seems pretty cool. It seems to detect large current transients indicating the main device on the strip has been turned off and kills power to everything else on the strip. Ideally you’d connect your TV/computer peripherals to it and when your TV/computer is off, the support gear has its power cut. DEFINITELY do not use this on a projector if it’s not the control device. Projectors have a cooldown cycle where the internal fan runs for a while to cool off the main light. Whenever I worked as a training rep, I was always having to fuss at people for unplugging the projector cart before the cooldown cycle had finished. Probably cost us ten thousand dollars in early equipment replacement.

Anyway, hope this answered your question!

Photo credit: Screenshot from “Internet Archive” of the movie Dracula (1931) /Foter.com / Public domain

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