PV system running a UPS

adas
adas Solar Expert Posts: 136 ✭✭✭✭✭
in Advanced Solar Electric Technical Forum #1
Aloha, I cannot get my PV system (from inverter) to run a UPS to my computers. I have been running without a UPS and just fried a computer (after running OK for 1 year). Ground is OK voltage is 124vac. Will a Triplite not like a ModSine wave inverter?
thanks
Frank
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #2
    Re: PV system running a UPS

    Not sure why you would want a UPS to run from an inverter, since a UPS is basically just another inverter.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: PV system running a UPS

    UPS systems do not like modified sine wave. I know this from experience. The input voltage 'appears' low and badly distorted, which will repeatedly trigger the UPS. Eventually the UPS battery will be killed because it isn't getting properly re-charged.
    A pure sign wave inverter doesn't cause this problem, but why bother? As Windsun said: a UPS is just another inverter. I ditched mine (which I used to keep the comp running with my old jerry-rigged system) once I got the FX. No problems.
    There's no reason why a MSW inverter would fry a computer either, unless there's something wrong with it. Comps have very good power supplies in them, capable of 'cleaning up' the even worst AC input.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: PV system running a UPS

    Also, many of the better (?) UPS's require both a safety ground and a grounded neutral... If you float the neutral (as many MSW inverters require)--because it causes a fault path if the battery is ground reference too)--then the UPS may never turn on.

    I also had, years ago, a computer power supply blow when they were working on our cubical wiring--I wondered if it was because the neutral got grounded--or probably lifted from the neutral reference bar--and may have gotten cooked by ~240 across the hot/neutral (can happen when the neutral to center tap connection fails/opens on a 120/240 VAC circuit--another reason not to put a fuse/breaker anywhere on a neutral leg).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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