Kill-a-Watt surprises

You can get an idea just from the temperature of the device when it is on standby. Cold devices can be ignored. I've found the worst offender in all my AV equipment is the cable box.

The Parasound was always slightly warm, despite its size, so the power it pulled was not surprising. But a unit with a "compact" power supply might be warmer -- in that area -- than a unit that pulls more power, but whose supply uses a bigger transformer or is further from the cabinet's cover.

One measurement is worth many guesses. I have 3 kill-a-watt meters. Very handy.

If it's not all together true, then it must be all apart false.

Halloween was Saturday, so I'm not surprised that you're still seeing vampires.

Your electric meter measures watts, not VA. If you know the power factor, you can convert these VA measurements to watts and eventually to your cost of electricity. The kill-a-watt meter shows both VA and watts (as well as PF).

It's the ones that are left on 24x7x365 that will get you. Borrowed from one of my previous rants on the subject:

My DirecTV R15-500 DVR burns: Operating power: 22 watts or 42 VA Standby power: 21 watts or 40 VA That's only 8 cents per day or $29/year (at $0.15/kw-hr). Much better. However, the 0.5 power factor isn't very impressive but it's under 75w so it doesn't have to comply with EN61000-3-2.

Using the revised numbers, yields: 12.5 watts for the 120GB Seagate hard disk

3.5 watts for my single LNB Subtracting from the 22.0 watts total leaves: 6.0 watts for everything else including switcher efficiency. I don't think there's room for much improvement (except for power factor correction).

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

A device that pulls a lot of power won't just have a hot transformer. It'll have a number of VLSI chips all gettng rather warm heating the entire cabinet. The difference between a component pulling 5W and one pulling 60W isn't subtle.

Or use a strip with separate ON/OFF switches for each outlet.

No, its true. You just tend to erroneously dismiss things that you *think* you aren't using -- but really *are*!

I've taken to installing power switches in all of the devices that don't have them. They all *claim* to "sleep" but even sleeping they often are wasteful.

My current worst offender is the 100Mbps switch. Sure, I can turn it off -- as long as nothing will have to talk to anything else! :< (this will be problematic when I switch to VoIP phones; I guess I'll have to install a low power 10Mbps switch/hub just for those loads)

My understanding was that the watt-hour meter actually measure VA-hours. I asked the electric company once, and that said that was the case. But I wasn't speaking with an engineer.

I beg to differ. If it measured volt-amps, it would say volt-amps, not watts.

See:

"Demand is normally measured in watts..." and: "Modern electricity meters operate by continuously measuring the instantaneous voltage (volts) and current (amperes) and finding the product of these to give instantaneous electrical power (watts) which is then integrated against time to give energy used (joules, kilowatt-hours etc)."

"Note that residential meters only measure only real power (watts) and PF of your appliances do not affect your cost of electricity".

Note that some utilities charge extra for low power factor loads:

Marginally related but interesting drivel:

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Same here. I checked all my devices for standby power and found that the LCD TV (Pavo) drew a ridiculous 55VA in standby. The other devices weren't exactly power savers either.

I found that my Yamaha surround sound amp has only a few Watts standby power and also has a switched AC mains output socket, which unfortunately can only handle

100 or so VA.

I built a relay box controlled by the amp's switched mains output and controls a power board in which all the "bad" devices are plugged in. Now I can switch the whole "entertainment" corner (except PVR) on and off with the amp's remote control. Since the TV forgets its setup when switched off the universal remote has to go through a 1 minute setup procedure though. That'll deplete the batteries early .... :-(

Tony

Spin the disk down when it isn;t being used! I.e., the device knows when it needs to turn itself on to *record* a show. So, it can conceivably spin down the drive when it knows it does NOT need to record anything! (it can spin the drive up 6 seconds before air-time and thus ensure that nothing is "missed").

Likewise, it can see when you are *using* itself to play back video so it could safely spin down the drive at other times (and force you to incur that 3 or 4 second spin-up delay when you *do* grab the remote and start poking at it)

Done properly, even that 6W figure could turn into 1/2W as the entire device could sleep when not in use -- and just wake-up when the next "alarm time" is scheduled *or* when IR is sensed from the remote.

Sure, but I don't have any control over the DirecTV firmware. What I have is what I have to live with. My guess(tm) is that they spin the disk continuously to improve the operating life of the hard disk drive. I have servers that run 24x7x365 that never seem to eat a disk drive. I have one in the office that's been running continuously since about 1995. However, the same drives, will die after 3-5 years with start-stop operation.

Well, it's not quite so simple. The box downloads firmware updates and program listings erratically. It also calls home on the phone line in the middle of the night for pay per view and quality control. I can also make record schedule entries via the internet. If the LNB is powered down, it takes about a minute for things to settle down and stabilize again. Power consumption can probably be drastically reduced using some manner of standby mode, but my box is VERY busy, which means the algorithm may be rather complex and the savings rather limited. If it costs me about $3/month to avoid complications and extend the life of the hard disk, I would probably pay the price.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

to

even

As

when

I bought a set-top box (UK Freeview) and thought to myself "hang on a bit the box is as warm with green LED on as on red standby" I measured consumed watts in both states and standby is 80 percent of the on state. I put in a hard on/off switch , data held in EEProm or whatever and no difference in function except programme info pages takes a couple of minutes to gather

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

Of course! My point was that *they* could still make significant savings in their dessign.

Spin the drives down and then try spinning them back up! :>

(i.e., the stress seems to be on the spin-up)

I think modern drives have really long MTBFs. What kills disks is the same thing that kills most electronic things: heat.

I haven't lost a disk in 30 years (touch wood). The drives in my primary machine have date stamps of 2002. They see a fair bit of power cycling (since the machine doesn't have a reset button, the only way to truly reset it is to cycle power and wait for all the drives to spin up again).

These aren't random events. There is software inside the box *deciding* when to do these things. So, it could go to sleep and still have told something to wake it up at its next scheduled activity.

Modern processors have very complex power management features

*in* the processor (SMI). If they aren't being exploited, it is because the box's manufacturer was just lazy (and had no incentive to do so!)

I've been moving all of my "software" (movies, music) onto large disks (several TB) so that I can serve this from a single machine. I let the drives power down when not in use. My biggest problem is the network switch that I rely on for distribution as it can't be powered down.

No -- with caveats.

The vast majority of KWHr meters (in the US) are old "motors". These are tuned electromechanical kludges that are absolutely amazing in that they work AT ALL! :> And, that they are so easily mass produced and have such long service lives!

The are typically calibrated at 10% load and 100% load. And, again, at 50% (lagging) power factor (e.g., 60 degrees).

I *think* that the nature of most loads is such that they can still claim their 1% accuracy despite all the perverse loads that have come into being since they were created (decades ago).

Many electronic KWHr meters are motors outfitted with mechanisms to "count revolutions". This allows the "new technology" to benefit from all fo the design tweeks that the meters have experienced in their history.

It is possible to convert a KWHr meter to a VARHOUR meter (an RC network in one of the coils, IIRC).

Some newer "solid state" meters can produce a variety of metrics (VAR, KW, ToU, Q, etc.) as they typically have access to more data than a regular "motor" would.

I've often wondered how far you can push an old "motor" in terms of distorting the load. E.g., how would a 120Hz

*impulse* load be registered? But, its just an intellectual exercise as coming up with a way to make *use* of power "extracted" in this form would be problematic.

"William Sommerwerck" wrote in message news:hcn3ak$4fj$ snipped-for-privacy@news.eternal-september.org...

I have just two comments on this:

1) If you are a residence, you are metered and billed by watts (re: real power) rather than volt*amps. Measure the watts to see the power consumption that actually is part of your billing. 2) If you live in an area that requires heating your house for a majority of a year, the power dissipated is added to the heating of your house during the heating season and reduces energy consumption from the furnace energy supplier. The power is not wasted in this situation. This fact is rarely considered by the media.

David

That's VARs, not VA-hours. For 'volt-ampere reactive'.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

I

If you can have watt-hours, you can have VA-hours. Both are units of energy.

Is VAR a unit of energy? No, it's a unit of (reactive) power. Energy and power are not the same.

I went from 400kwh a month to 200kwh but putting all vampire devices on power strips and shutting things off that are not needed. My oil burner alone takes 100kwh a month until I switched to pellets and wood boiler when it's real cold. I like free hot water.

Yes, of course. But a VA-hour is a meaningless unit unless you know the power factor--real power costs money and fuel, whereas (apart from transmission losses) reactive power just sloshes back and forth cycle by cycle. That's why multiplying it by any period of time longer than a cycle is meaningless.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net