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Thread: Maximun allowable voltage variation?

  1. #1
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    Maximun allowable voltage variation?

    First post/ not an electrician. What is a normal/reasonable voltage fluctuation in a small retail facility? The main panel reads 208Y/120 3P 4W, 250 amps max.

    Thanks

  2. #2
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    I am not sure what is normal but I believe each utility may have their own standard of acceptability. What are the readings you are getting? And what is going on that has you concerned about this issue?

  3. #3
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    Most new equipment is designed for +/-10% on nominal Voltage, but most older equipment is NOT. Switching supplies usually take anything from 90-264VAC.

    I'm not aware of what the power company will promise, but they do their best. In some foreign countries, the power is marginal.

    If you are transforming, you can tweak your tap settings to get closer to desired.

    Matt

  4. #4
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    Quote Originally Posted by megloff11x
    If you are transforming, you can tweak your tap settings to get closer to desired.
    Matt
    OP is looking to point fingers, as not in electrical trade, he won't be tweeking anything, but someone... May not own anything to measure voltage with??? (If he does - he shouldn't be) Or maybe the POS salesmen told him it was 'electrical'... Or maybe lost neutral... Either way would not be able to recongize the difference.

    Quote Originally Posted by bdub
    First post/ not an electrician. What is a normal/reasonable voltage fluctuation in a small retail facility?
    Are lights dimming? GETTING BRIGHTER?!?!?!? Coincide with other things going on or off? Could be serious - could be nothing to worry about... We would not be able to diagnose any problem over the internet - sorry forum is Electricial Trade only! But reading between the lines - maybe you want to call one in your area.
    Last edited by e57; 07-11-07 at 03:00 AM.
    Electric heretic
    It's always gonna be in the last place you look....

  5. #5
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    You need to get ANSI C84.1(1) but it will cost you, it can be purchased at NEMA.

    This is from a POCO Web site, it appears to be at least some of the ANSI standard.

    You would need to talk to your POCO to see if they follow this standard.

    Voltage Range
    The American National Standard ANSI C84.1(1) establishes nominal voltage ratings and tolerances for 60-hertz (alternating current, AC) electric power systems above 100 volts and through 230, 000 volts.

    Voltage operating ranges are recommended for two voltage categories:

    1) the service voltage, typically the point of connection between utility and customer; and

    2) the utilization voltage, typically the termination point to equipment. The utilization voltage range takes into account a voltage drop within the end user’s distribution circuits.

    ANSI C84.1 expects equipment to operate at service voltages between 95% to 105% with a utilization voltage range of 87% to 106% (120V to 600V)

    Refer to ANSI C84.1 for additional operating voltage ranges).

  6. #6
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    Quote Originally Posted by bdub
    First post/ not an electrician. What is a normal/reasonable voltage fluctuation in a small retail facility? The main panel reads 208Y/120 3P 4W, 250 amps max.

    Thanks
    Check this location for the CBEMA Curve . http://www.dorrough.com/What_s_New/P...ema_curve.html

  7. #7
    Quote Originally Posted by iwire

    ANSI C84.1 expects equipment to operate at service voltages between 95% to 105% with a utilization voltage range of 87% to 106% (120V to 600V)
    Wow, 120V power down to 104V. I'd expect a lot of noticeably bad behavior at 104. I had a panel here running at 105V (originally fed with 240D, 1P transformer to 240/120, they converted to 208Y120 and swung the transformer over, 240V primary transformer was running from 208V and only supplying 105V, DOH!), all the fluorescents running from it had difficulty starting on the low voltage.

    Vern

  8. #8
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    I have seen bdub's profile and says that he is involved in electrical facilities.

    you have to ask your utility for the allowed voltage variations. here in the philippines, it is plus/minus 1 percent of the nominal voltage. which is 230V, 460V and 34.5 kV

  9. #9
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    Quote Originally Posted by robbietan
    I have seen bdub's profile and says that he is involved in electrical facilities.

    you have to ask your utility for the allowed voltage variations. here in the philippines, it is plus/minus 1 percent of the nominal voltage. which is 230V, 460V and 34.5 kV
    You have to check first ERC guidelines. Maybe you are pointing a -/+ 10% of the nominal voltage. Nominal voltage in the phil for low voltage side is 220 not yet 230. But this was on further debate on the PBR, that eletric utility must based on a 230V Nominal.
    :smile:

  10. #10
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    Quote Originally Posted by AM_0228
    You have to check first ERC guidelines. Maybe you are pointing a -/+ 10% of the nominal voltage. Nominal voltage in the phil for low voltage side is 220 not yet 230. But this was on further debate on the PBR, that eletric utility must based on a 230V Nominal.
    :smile:

    sorry about that. I meant to write 10%, not 1%. my bad

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