And I thought lower wattage meant lower current draw. Not!

ILFE
ILFE Solar Expert Posts: 364 ✭✭
in Solar Beginners Corner #1
Okay, here is the skinny.

I installed a 300 watts solar array at our farm in a rural province in Cambodia.

I decided, due to the savings in cost of going with an inverter, not to mention the loss of converting from DC to AC, that this was the best choice for now. After we move there full time, and have AC requirements, that will probably change.

So, I brought some 7 watts fluorescent bulbs to replace the original 15 watts fluorescent bulbs I had originally installed. According to the ProStar-30 meter, the "load amps" were 1.5, running two 15 watts bulbs. I replaced both with the two 7 watts bulbs. The draw went from 1.5 to 2.3. So, I swapped the 15 watts bulbs back in place. Back to 1.5 amperes.

Can anyone help me understand why this would be, please?
Paul
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Comments

  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #2
    Re: And I thought lower wattage meant lower current draw. Not!

    IS that 15 Watt a measured amount or is it the 'rating' of the 'bulb;? likewise with the 7 watt...

    I have some leds rated at 4 watts that only use 2 watts, in use....most happy with the 'actual' consumption...
     
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: And I thought lower wattage meant lower current draw. Not!

    You are probably looking at the power factor problem. Many of the new compact fluorescent lights have a lousy PF due to ballast design. As a result you can have a "13 Watt" rated CFL that actually pulls 26 "real" Watts.
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  • ILFE
    ILFE Solar Expert Posts: 364 ✭✭
    #4
    Re: And I thought lower wattage meant lower current draw. Not!

    Sorry about that. These are the ratings listed on the bulbs.

    So, I guess I will be buying more 15 watts bulbs. I just ass-u-med that lower wattage would automatically be lower draw. I'm glad I learned it now, though. I won't make such assumptions in the future.
    Paul
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  • ILFE
    ILFE Solar Expert Posts: 364 ✭✭
    #5
    Re: And I thought lower wattage meant lower current draw. Not!
    westbranch wrote: »
    I have some leds rated at 4 watts that only use 2 watts, in use....most happy with the 'actual' consumption...

    Oh, I meant to ask, are those 12vdc LEDs? I am looking for some LED's for 12vdc here. But, I have yet to find them.
    Paul
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  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #6
    Re: And I thought lower wattage meant lower current draw. Not!
    ILFE wrote: »
    Oh, I meant to ask, are those 12vdc LEDs? I am looking for some LED's for 12vdc here. But, I have yet to find them.

    Try ebay. I get them from Hong Kong and China, great prices, free shipping and so far, high quality.
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #7
    Re: And I thought lower wattage meant lower current draw. Not!

    12v CFL, particularly low wattage bulbs, are very dependent on inverter within the CFL. A 12v CFL has a high voltage inverter operating at high frequency producing a couple of hundred volts to the bulb.

    A poor quality (cheap) CFL can have very poor efficiency inverter.

    Another factor that confuses the rating is fluorescent bulbs put out 10% to 15% more light when excited at higher frequency (40 KHz) so some manufactures drop the drive level down to yield the equivalent light output of a fluorescent light operating at 50 to 60 Hz. A 15 watt bulb may only be run at 12 to 14 watts of power.

    Aging of fluorescent bulb and how the inverter driver reacts to aging is another factor. CFL yielding shorter then expected life span are usually due to poor inverter driver that does not handle the changing startup and run conditions well as bulb ages.
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  • ILFE
    ILFE Solar Expert Posts: 364 ✭✭
    #8
    Re: And I thought lower wattage meant lower current draw. Not!

    Well, I am under the impression then, that it would not matter if the bulbs are 12vdc OR 220vac? The inverter inside is going to be efficient, or not, regardless of the input voltage?
    Paul
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