Inverters in parallel?

bluewickedburner
bluewickedburner Solar Expert Posts: 78 ✭✭✭✭
in Solar Beginners Corner #1
Through some misfortune I have two 2000 MSW inverter/chargers. I am pretty sure that the inverter is an even match for current uses of AC and so far have yet to do more than surge when something like the microwave starts up.

Is it possible or advisable to run two inverters or am I better off just dumping both and buying a new higher capacity inverter? As we're switching all our appliances to propane our use of AC will be greatly reduced. Lighting, computers and so on are all running off the 12 volt system.

My question comes from wondering if short surges shorten the life of the inverter since I run the microwave for about a minute and a half every day and it's possible to go above 17 amps which I'm assuming is in the surge capacity of the inverter. The hood fan and lights for the micro are AC so I'm changing them to 12 volt.

The inverters are the same. My other thought was to wire it in but leave it turned off as a spare just in case the primary stopped working and aside from an electrical problem elsewhere I could then just switch on the replacement without having to remove and rewire.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,601 admin
    #2
    Re: Inverters in parallel?

    You might choose to use two inverters... Keep the MSW ones for powering big "dumb" loads that have worked well for you so far... And get a smaller 300 watt (plus or minus) TSW inverter to run the cell chargers, laptop computer, small electronics, wall wart transformers, etc.

    The MorningStar 300 watt (600 watt 10 minute surge) TSW 12 volt inverter is a great little unit--and includes "search mode" (inverter turns on once a second to look for new >6 watt loads to save standby power; also has a low voltage On/Off input).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • bluewickedburner
    bluewickedburner Solar Expert Posts: 78 ✭✭✭✭
    #3
    Re: Inverters in parallel?

    That BB, is the ticket. Ah the wonder of multiplied intelligence. That makes much better sense. The low voltage feature will come in handy. So far my inverter has only done this once when I failed to check the batteries in the morning but never since.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,601 admin
    #4
    Re: Inverters in parallel?

    By the way--I think I was not clear enough on the low voltage On/Off... That is a separate pair of wires that you can send to a remote power on/off switch (just use a plain 12 VDC rated on/off switch).

    Instead of needing a large DC switch that can turn on/off 150+ amps of current.

    The switch can be installed in a convenient location (kitchen, near your desk, etc.) to allow you to turn on the inverter only when you need it (saving on standby losses).

    Almost all inverters have a low voltage turn off function to reduce the chance of electrical damage to the inverter or its AC loads (typically, the low voltage cutoff is not there to "save the battery bank").

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • bluewickedburner
    bluewickedburner Solar Expert Posts: 78 ✭✭✭✭
    #5
    Re: Inverters in parallel?

    Thanks BB because that makes things even better. I have done some surveys over the weekend and discovered that my largest draws are electronics and the electric refer. This is for a motorhome.

    If I only completely disconnect electronics during the hours after hitting the sack and turning the refer to propane I can eliminate 2/3 of my electric use as it comes from and reported by the grid (pedestal-PG&E). That puts me at around 120 kwh per month without any other economics on my side. I can reduce my use even further as soon as I replace the 37" LCD with the 40" LED LCD. The difference is amazing. The solar will float my batteries as someone kindly suggested and I'll turn off my charger. If the sun ever comes out again I'll try turning off the pedestal power and using solar incrementally to keep battery use and the ability of the solar to keep the charge up matched.

    Anyway, having the other inverter seems like a real good idea and I have a nice panel area in the middle of the motor home that makes accessing the on-off really handy.

    I'm starting my install of the solar system this weekend if the weather in the Bay Area holds up. Hopefully it will be all up by the end of the following week as I am taking it very slow. I'm going to hunt down someone local to check my work before I make things permanent.
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