Scam Alerts

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Comments

  • RobertMfromLIRobertMfromLI Solar Expert Posts: 34
    Re: Scam Alerts
    XRinger wrote: »
    It must be a heat pump, because 624 watts is 2129.176 BTUh,
    2,662 BTUh is equal to 780.1552 watts. :p

    Interesting... it's rated .78KVa - I used an online converter to convert that to watts.
  • BB.BB. Super Moderators, Administrators Posts: 29,318 admin
    Re: Scam Alerts

    kVA is not kWatts... More or less. They are two different measurements for different uses.

    The "real" equation for power is:
    • Watts = Volts * Amps (DC)
    • Watts = Volts * Amps * Cosine of the angle between Volts and Amps (current)
    • Watts = Volts * Amps * Power Factor
    Power Factor can equal Cosine of the V/A angle for linear circuits (motors, inductors, capacitive circuits, etc.).

    Or Power Factor is a measured/mathematical term used to describe the V/A relationship for non-linear circuits (typically computer power supplies, lamp dimmers, battery chargers, etc.).

    Looking at the picture I posted earlier:

    attachment.php?attachmentid=1557&d=1294163849

    You see that the blue line (current) is not a sine wave at all...

    Why is this important--Volts*Amps (or amps directly) better describes the current carrying capacity of wiring, how generator windings/magnetics behave, waste heat from I^2*R heating, etc. can be modeled/defined/designed...

    Watts or Power is the amount of energy the system is using...

    So, it is very possible to have a circuit that pulls 1 amps at 120 VAC, but with a Power Factor of 0.6 (motor, CFL lamp, etc.) and you get:
    • 1 amp * 120 VAC = 120 VA (wiring design, generator/inverter maximum VA rating, etc.).
    • 1 amp * 120 VAC * 0.6 PF = 72 Watts (amount of heat/energy the load is taking, how much fuel the genset will use, how much energy an inverter will pull from the battery bank).
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Scam Alerts
    XRinger wrote: »
    It must be a heat pump, because 624 watts is 2129.176 BTUh,
    2,662 BTUh is equal to 780.1552 watts. :p

    taint quite right as a watt is about 3.4btu.
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Scam Alerts

    Blame Josh, not me!

    http://joshmadison.com/convert-for-windows/

    I use Convert.exe, because it can convert a lot of different 'factors'..

    An engineer at MIT told me it was pretty good, and I've been using it for many years.

    Cheers,
    Rich
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