vampires and power usage

[Zephyr]

Hey folks,

I'm curious about power consumption of things like the power supply for my dell laptop its and AC/DC adaptor, and when the unit is charging my laptop it gets quite warm. from that I infer that its using a fair amount of power.

now, if I leave it plugged into the wall, but remove the laptop, it does not heat up, but. there is a little light on it that indicates it is receiving power. aside from that little light, is it using any significant amount of power? The label on the unit says the input is 1.5a

same question goes for my cell phone chargers 0.2a

I understand that some of these things do use power constantly, but... how much?

I found this link but it doesn't get into the Nitti gritty I was looking for

Dave

[HeyBub]

Buy a "Kill-A-Watt" (see eBay) and test it for yourself.

[ransley]

If you add up everything you might save 15$ if you have an old tv, dvd, microwave etc, Get kill a watt meter and do your own audit

[jmagerl]

Heres a link to "kill-a-watt". It was very useful to slay my vampires

[cornytheclown]

It gets hot when it is hooked up to the laptop because the laptop puts a load on the charger. No load...there is not a lot of heat.

Any device with a transformer directly connected to the mains will draw a very minute amount of power...it is called the magnetizing load of the transformer.....if there is a rectifier and regulator after the xfrmr...which there most likely is ...I dont see it drawing any power unless there is a load passing thru it.

of course your indicator light will draw a small amount of power.....

[mm]

Good question. Not only the ones with wall warts, those black "adaptor" boxes that plug into the wall with a cord coming out of them, but many radios etc. with the transformers inside, have no switch in the primary of the power transformer, and they are ON all the time.

For electronic reasons I don't well understand, when there is no current in the secondary of a transformer, there is higher impedance in the primary of the transformer, so less current flows even through the primary. The heat one can feel, that you feel, the waste heat would be iiac the same percentage of energy used, as when the device is running and there is current through the secondary.

From your touch, it sounds like the current is a lot lower, but otoh, it's on all the time if the thing is plugged in, even for things that are only used an hour a year.

Does anyone know what the percentage is, or how much these things use when off?

xposted to sci.electronics.repair

[m kinsler]

Well, there's been a lot of discussion on this. Essentially, when there's no load on the phone charger or other appliance, it's like having an inductance across the power line of your house. There will be some very small current flow, but only because it's not a perfect inductance. All of the energy used in these wall transformers when they're just idling is dissipated in the form of heat in their black plastic case, so you can get an idea of how much power they're using by just feeling them. It's not really very much. Note that you'll have a tough time measuring the power drain with a multimeter, because both current and voltage will show rather high readings. But since they're almost 1/4 cycle out of phase, there's almost no power being dissipated, and only a good power meter will take this into account. (This problem is the basis for a lot of free energy claims, you'll be happy to note.)

In general, wall transformers aren't a big deal.

M Kinsler

[James Sweet]

You can pick up a gadget called a Kill A Watt and other similar devices for under 30 bucks. It's a pretty impressive power analyzer, the wonders of modern technology. Pick up one of those and you can find out how much power anything in the house draws, as well as the power factor, cumulative consumption, etc. I have one and love it.

[N Cook]

Is vampire some in-joke conflation of V(olt) + amp that I'm out of the inductive loop with (sorry Mr Churchill)

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

[HeyBub]

Not really. I'm gonna share a tip that may save your life!

This business about about a wooden stake through the heart of a vampire is pure Hollywood bullshit! If you read Bram Stoker's book, you'll find that the tool to use is a BOWIE KNIFE, not some pissant tent-peg!

I'm in Texas. We have a LOT of Bowie knives here and almost no vampire problem.

[m kinsler]

on

I believe that it has to do with the idea that a vampire is something of a parasite, living as he or she does on the blood or electric current of the host. It's one of those imprecise terms up with which we all must put.

M Kinsler

okay, _you_ try to match wits with Winston Spencer C.

[N Cook]

on

So is Vampire = Wall Wart another term to add to my USA/UK (2 nations divided by a common language) file ?

anyone, reading this, is aware of any other tool/technical terms in US or UK, my real email address is spelt out on the URL below

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

[Mike Paff]

From my understanding of the term, a vampire device is any one that continues to draw power even when in the 'off' state. This would include devices powered by a 'wall-wart', devices with a built-in clock, devices that are powered on/off by a remote control (the circuit that receives from the remote needs power all the time), etc.

So they would include most microwave ovens (the clock), TVs, VCRs, DVD players/recorders, DVRs, personal computers, etc.

[M Q]

Power Vampires are a significant problem. While each one is (usually) not significant, altogether they can add up to quite a bit. I have found that they can add up to several hundred watts. "Kill-a-watt" can be quite useful if you can guess where they all are and they are plug-in devices. As you can see, not all plug in the wall. Here are some idle power consumptions that I have measured:

Doorbell transformer 8 watts cordless phones 4-9 watts DirecTV receiver (off) 34 watts TV (off) 17 Garage door opener 2.5 Fax machine 10 Gas furnace 20 Newer gas furnace 27 Central AC outdoor unit 20-40 watts (two different units)

Other devices to consider: Any device with a remote control (stereo, DVD player, X-10, etc.) Any portable device with a rechargeable battery: (cordless phones, toothbrush, vacuum, drill, etc.; cell phones) Timers of any sort (irrigation, lights, etc.) UPS for your computer. DSL modem motion activated lights

200 watts c> Hey folks,

[Pat]

And as you know, it was someone from Texas who killed Dracula.

I suppose that Texas did the world a service killing Dracula, but you guys also gave us TWO Bushes. Given my choice, I'd rather have Dracula. The only thing he sucked try was blood.

Of course, I can't talk. I'm from NY. We have Hillary Clinton, Rudy Guianni, AND Mike Bloomburg running for President ... and you thought people hated New York BEFORE this ....

[mm]

These are the sort of things that bother me.

I don't understand this one. Have AC's changed, or do all brands have this, and what is outside that is using current when the AC isn't running? Are we talking about 12 months a year?

[HeyBub]

We also gave the country Eisenhower and Lyndon Johnson. I admit, it's a mixed bag. Fortunately, there's JEB Bush for eight years then that good-looking Hispanic nephew. By then, the dynasty will be firmly established. It's then but a small step to a monarchy.

Nah, Clinton is everyman's ex-wife. She's a goner. Bloomburg is the quintessential nanny-state leader. Guilianni isn't so bad. "A conservative is a liberal New Yorker who realizes he hasn't been mugged in several weeks now and attributes it to Guilianni."

I remember talking to one of my customers in Manhattan on 9/12. I told him: "We're ALL New Yorkers today!" He was touched.

[James Sweet]

It's a term used mostly by the solar/wind guys running houses off-grid. It refers to any device which draws power even in the off state, regardless of the sort of power supply.

[M Q]

... Yes, we are talking 12 months a year unless you turn off the breakers.

One of the ACs was a 4 Ton Carrier unit. The power was consumed by a 40 watt "crankcase heater". These are more common in larger (4, 5, or more ton) AC condensers (outdoor units), those that are a longer distance from the indoor unit, those that use R-410a, and in heat pumps. Sometimes they are thermostatically controlled. This one was not.

The other is a 3 Ton Trane 2-stage condenser. The 20 watts appeared to be consumed by a variable speed fan controller. This one is totally inexcusable, as an added relay would pay for itself in less than 1/2 a year.

These are the sort of things that California's Vampire Slayer bill (which appears to have not become law) that the OP referred to might embarrass manufacturers into cleaning up.

Note: some of the power consumption figures that I mentioned were apparent power (measured in "Volt-Amps" -- the vector sum of real power and reactive power) because it was easier to measure, and some were in real power (measured in Watts). Kill-A-Watt measures both. Residential power meters generally measure real power. The cost to the utility is somewhere in between.

[Dave Martindale]

It's pretty bogus to add up VA power numbers as if they were watts, then calculate how much you would pay per year. If your meter measures real power (and as you say, it probably does), then the cost depends on the real power consumed.

For things with resistive heaters, real and apparent power are about the same and it doesn't matter. But for something like half of the loads you listed, the power is probably almost all magnetising current in a transformer, with a very low power factor. For these loads, the real power is a fraction of the apparent power, and using apparent power will produce a large error.

Dave