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Kill-a-Watt surprises

Discussion in 'Electronic Repair' started by William Sommerwerck, Nov 2, 2009.

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  1. Its been pointed that you don't really need a watt or watt-hour meter to
    save money -- you just turn off things you're not using.

    This is not altogether true.

    My electric bill was ridiculous, so I started checking. I'd been too lazy to
    regularly turn off my A/V system's equipment, which includes a number of
    vampire devices.

    I was surprised to discover that the Parasound controller pulled 30VA, even
    when not turned on. And a Lexicon CP-3plus drew 20VA, simply in standby. As
    I rarely use it, I turned the standby switch to "off".

    Most of the vampire devices are items I don't use regularly. I'm going to
    move them to their own strip, so that they will always be off, except when
    actually being used.
  2. Most of the vampire devices are items I don't use regularly.
    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.
  3. UCLAN

    UCLAN Guest

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

    D Yuniskis Guest

    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)
  5. Your electric meter measures watts, not VA. If you know the power
    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.
  6. D Yuniskis

    D Yuniskis Guest

    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.
  7. N_Cook

    N_Cook Guest

  8. D Yuniskis

    D Yuniskis Guest

    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.
  9. D Yuniskis

    D Yuniskis Guest

    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.
  10. David

    David Guest

    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.

  11. My understanding was that the watt-hour meter actually measure VA-hours.
    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.
  12. Jeff Layman

    Jeff Layman Guest

    What is meant by "standby"? You may think you know (as I thought I did,
    too), but it isn't that simple. See here:

    It's not just Sony. I queried Panasonic about the regular clicking from my
    LCD TV, even when it was in "Standby" mode, and also the less-than-green
    readings I was getting from a power meter attached to it (15w in standby,
    and 30w when it clicked. I do not know what the power factor of the TV is,
    so do not know how these figures correlate with Panasonic's stated standby
    consumption of 0.3w, but they don't seem very different from those reported
    with the Sony). This was their reply:

    "In response, I would advise that first please ensure the SETUP menu option
    for “auto search in standby” is switched off. (this is in the “System
    Update” SETUP menu option.

    Turning off this option will also stop intermittent clicking from the TV
    that are caused as the internal PSU relays are turned on to allow the
    Freeview decoder to work for software updating.

    2.) Please note that the set takes approximately 2 minutes for all the PSU
    relays to click off and so the power will only read 0.5W after this time.

    3.) Ensure that the power meter used can read the power factor of the unit
    required to calculate AC power and is using this to calculate power.

    4.) Ensure the meter is capable of accurately reading 0.5W; many meters
    cannot go this low. Please refer to the meter’s specification."

    That reply was open and very helpful, but (a) "auto search in standby" is
    the default condition (b) there is no mention of this in the manual (c) I
    still do not know how often the TV goes into auto search mode, for how long,
    and what the actual power consumption is in this mode.

    I have now taken to switching off at the plug when the TV is not in use.
    Info on the DTG pages let me know when to leave the TV in standby/autosearch
    for an update.

    It makes me wonder just how accurate many other low consumption "standby"
    figures are.
  13. David Lesher

    David Lesher Guest

    It measures true watt-hours. A bad PF device will cost you only SLIGHTLY
    more in losses than if it had 1.0 PF. [Increased I, ergo more I^2R]

    You can look up "Electricity meter" in Wikipedia..
  14. Franc Zabkar

    Franc Zabkar Guest

    FWIW, Energy Australia responded to my query as follows:

    "Most residential classification customers are metered by a spinning
    disc meter, or a basic electronic meter which does not have enough
    'smarts' in the meter device to enable billing to be carried out at a
    KVA pricing.

    Currently small customers are billed on KWh pricing, and KVA Demand
    pricing usually relates to large commercial and industrial
    installations where poor power factor may impact upon the EA network,
    and there may be an economic billing benefit in the customer pricing
    to ensure that Power factor is closer to Unity."

    - Franc Zabkar
  15. Franc Zabkar

    Franc Zabkar Guest

    Calculate the VA consumed by the X2 EMI suppression capacitor across
    the mains terminals.

    For example, a 2.2uF cap across a 240VAC 50Hz supply consumes 39.8VA:

    - Franc Zabkar
  16. My understanding was that the watt-hour meter actually measure VA-hours.
    This is really confusing. Looking solely at the second paragraph, the
    implication is that industrial metering is at the VAh level, not Wh.

    I don't think this person really knows what he's talking about. The fact
    that his statements are redundant ("a basic electronic meter which does not
    have enough 'smarts' in the meter device") and jargony strongly suggests

    Nevertheless, thanks for asking. I think I'll call the Seattle utility
  17. Sylvia Else

    Sylvia Else Guest

    It may well be, and for the reason given, which seems valid.
    Perhaps a bit clumsy, but I think the word meter is being used in two
    different ways. The scribe probably wasn't employed for his writing talent.

  18. Guest

    I used to work for a submetering outfit and Kill-a-watt was cool.
    We tried real hard to find as cheap a doppler ultrasound flowmeter
    for water and fuel but the lowest we got was two grand.

    But my stud finder is ultrasound. THe only difference should be software.

    - = -
    Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
    ---{Nothing herein constitutes advice. Everything fully disclaimed.}---
    [Homeland Security means private firearms not lazy obstructive guards]
    [Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]
  19. D Yuniskis

    D Yuniskis Guest

    I think there are competing products with better specs (?)
    No doubt partly due to market? E.g., someone makes a gizmo
    used to check the integrity of (wooden) telephone poles:
    attach to pole, wack pole with hammer, "listen" to
    vibrations. Cool, eh? No doubt *very* expensive as
    there are few companies interested in "telephone poles"
    and, those that are, have deep pockets for this sort
    of PM!
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