Inverter temperature ratings ?

sunbunny
sunbunny Solar Expert Posts: 59 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
Some of the inverters I've read about, the specs say the operating range is only above 0C/32F. Others say they work to -20C. What's the deal ?
It goes to -30F here sometimes and -20F quite often. Is the temp. rating for real or a "CYA" spec ?

Thanks
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Inverter temperature ratings ?

    Differences in how well sealed the components are against moisture condensation and/or variations in component values affecting performance. Most electronic components can take much lower temperature ratings.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: Inverter temperature ratings ?

    Probably a lot depends on the Electrolytic capacitors selected and the design ripple current.

    Regarding cold, the electrolyte in the capacitors can freeze around -10C. And cold capacitors have much higher dissipation vs warm/hot capacitors (very cold inverter may not operate correctly because of poor capacitor performance--May have problems with local "hot spots"??? due to poor dissipation).

    On the hot side, you may have capacitors rated to 105C with 1,000 hour life--So, if you want an inverter to last longer than 1 year (~8,000 hours), you better run it significantly cooler (doubling of life for every 10C drop in operating temperature).

    Otherwise, a significant failure mode for electronics is temperature cycling... The more cycles and the deeper the cycles, the shorter the life.

    I used to test disk drives in the early 1980's... I could get the "bad drives" to fail in a couple weeks with ~2-4 temperature cycles per day by just running between their Min/Max limits. The "good drives" would go for months and still function reliably.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • sunbunny
    sunbunny Solar Expert Posts: 59 ✭✭✭✭
    #4
    Re: Inverter temperature ratings ?

    I don't have a plan to keep the inverter warm.
    Can anyone recomend one that performs well in cold temperatures or has at least survived being below freezing for 6 months ?

    I've been looking at 1000-2000 watt ones by Samlex and Exceltech. As much as I desire an Outback or Magnum, my battery situation may change and so my voltage may change and so I'd rather have a less expensive inverter to start with.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Re: Inverter temperature ratings ?

    Will you be operating the inverter or just storing it (unpowered) when freezing?

    The Exeltech are rated to -25C (supposed to be popular/rugged brand from government use).

    http://www.solar-electric.com/exsiwain.html

    You can try and call them and ask for details about your install.

    My suggestion--If you have a "frozen" inverter, either heat the room to -10C or warmer, and/or run at 10% or so of rated power to get warmed up a bit before hitting them with full power if below -25C.

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