Critcal load battery backup instead of generator

program.coordinator
program.coordinator Registered Users Posts: 13 ✭
in Grid Tie and Grid Interactive Systems #1
I am installing a new project for a client, Instead of using a generator for a power source it will be a 3 day atonomy battery bank. I will be using a Outback VFX3648 inverter/charger/transfer switch that's right it does it all. I will bring the critical loads from the main breaker to a 100Amp sub panel, to an AC disconnect to the Outback VFX3648 to the battery bank. Has anyone done a system like this before? The power here only goes out possibly once a year for no more than six hours, I was going to use a generator but the grants do not allow it. So the main idea is when the power goes out the Outback will transfer power to the battery bank and power the critical loads only without back feeding into the grid and harming utility workers, so it works like an off-grid system without an RE source. On the side we did install two 10kW bergey grid-tie to the property.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Critcal load battery backup instead of generator

    Oh my yes. Very popular application, that. :D

    It is very simple to do: feed from Main service panel goes to AC IN on the inverter, AC OUT feeds critical loads. The Outback will take care of everything else. You will need a MATE or MATE II to program the inverter's specs so that they match the power requirements.

    The most important thing to determine is how much those critical loads will be and thus how large a battery bank is required. 3 days of autonomy is fairly long for occasional outages of no more than six hours.

    Solar recharge could be added anytime later if needed/wanted.
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  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    #3
    Re: Critcal load battery backup instead of generator

    That was the genesis of my system, I don't intend to sit through another ice storm in the dark and cold! :)

    I did go ahead and get solar panels. I also use my system daily, lets me shave a few kWh per day off the electric bill - AND makes sure the system is ready to run! How often I've seen (and owned a few) UPS systems that sat unneeded for months, then the power goes out and *then* I find out the batteries lost capacity and can't handle my loads...

    I simply mounted a subpanel beside my original breaker panel and pulled the circuits I wanted over to it. Now have most of the house on backup. The Outback inverter switches so quickly between grid and battery that I usually can't tell. I know I've missed a few outages since setting it up, only knew the power went out when I looked at my logs and saw the inverter state change to "No AC"! :cool:
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #4
    Re: Critcal load battery backup instead of generator

    Another useful feature of a hybrid grid tied inverter system is making asyncronous phase transitions to and from a generator and grid tie. It is practically impossible to syncronize the phase/frequency/voltage of a small generator to the grid.

    The inverter idles locked to the grid, ready to pick up loads if grid goes down. If the grid stays out for a preset period of time (typically based on how much battery power you want to consume) it then auto-starts a generator. The inverter will gradually slew it phase/frequency/voltage to match the generator's then, when syncronized, releases loads to generator. When grid comes back on it reverses the process using the inverter as the transition go between generator and grid. Everything happens with uninterrupted power to loads.

    It also avoids starting up generator for very short periods of grid outage.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Critcal load battery backup instead of generator

    Actually RC in this instance it isn't a hybrid GT inverter but a standard off-grid inverter. It simply treats the grid as a generator. Never seen the slightest blip in power change-over with my VFX when the generator activates AC IN.
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  • program.coordinator
    program.coordinator Registered Users Posts: 13 ✭
    #6
    Re: Critcal load battery backup instead of generator

    I was going to install an AC disconnect after the critical load sub panel as well to have a secondary shut down. I was not going to use a mate because I was told I will not need one. The battery bank was planned at a 3 day autonomy but the batteries are at a 10 hour discharge rate so if a power failure did happen the battery bank will be discharged at max potential after approximately 30 hours

    Are you sure I need a mate to program, should I call Outback and verify?
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #7
    Re: Critcal load battery backup instead of generator
    program.coordinator wrote: »
    Are you sure I need a mate to program, should I call Outback and verify?

    You need a mate. Outback sells the mate separately from the inverter. Other manufacturers also sell their control hardware separately from their inverters.

    The reason is simple: the outbacks are designed to be stackable. If you were stacking four inverters you would only need one mate. If the mate were built into the inverter you would be buying four mates with your four inverters.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: Critcal load battery backup instead of generator

    You can not reprogram a VFX without a MATE, and you will want to reprogram it as the factory defaults rarely suit the application.
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  • program.coordinator
    program.coordinator Registered Users Posts: 13 ✭
    #9
    Re: Critcal load battery backup instead of generator

    Thank you for the information I was told by another party that the factory settings would be adequate in this senerior, but I am going to order one and use it to make sure everything is running smoothly
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  • program.coordinator
    program.coordinator Registered Users Posts: 13 ✭
    #10
    Re: Critcal load battery backup instead of generator

    Cariboocoot,

    I'm fresh out of college and this is my first install, just making sure I do not miss anything. I will have a 48V 600Amp-hour battery bank with 1/0 AWG conductor wiring to Outback VFX3648 Inverter. A 200 Amp main panel will feed Six critical loads to a 100 Amp Sub panel. The 200 Amp main panel will feed the A/C Hot IN to the inverter and the A/C Hot out will go to 60 Amp A/C non-fused disconnect then feed to the sub-panel to power the critical loads.

    I will be using a MATE to program the inverter
    I will be using 6 AWG for the A/C Hot IN and A/C Hot Out

    Q: for the inverter what about the Chassis ground and A/C Neutral IN and A/C Neutral out

    The ground near the battery terminals will be attached to the negative cable where would be the best place for me to ground this.

    I appreciate all the knowledge unfortunately my college did not teach me very well of course. I am trying to do research but not much detail like I need. Anything helps and is knowledge gained.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #11
    Re: Critcal load battery backup instead of generator
    program.coordinator wrote: »
    I will have a 48V 600Amp-hour battery bank with 1/0 AWG conductor wiring to Outback VFX3648 Inverter.
    I would use heavier wire even if the cables are only 4 or 5 ft long. They are not longer than that, are they?
    program.coordinator wrote: »
    I'm fresh out of college and this is my first install, just making sure I do not miss anything.
    My advice is to buy a prewired outback inverter on a prewired Midnite Epanel. It is unlikely that anyone, on their first install, can match the quality of these professionally wired panels.

    Just screw it to the wall, hook up the batteries, ground rod, AC in and out, (and solar if desired). Comes with all circuit breakers, shunt, lightning arresters, bypass switch, etc.

    Here is a link: http://www.solar-electric.com/ouinsy.html Even though you have grid, you are looking for one of their off-grid systems. (off-grid, in this context, just means that you are not selling power to the grid)

    All the systems on that NAWS link have solar charge controllers included, but I know that Midnite builds to order and will be happy to wire up a box to your specifications. Talk to NAWS or Midnite.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • program.coordinator
    program.coordinator Registered Users Posts: 13 ✭
    #12
    Re: Critcal load battery backup instead of generator

    I put the system together, hopefully its in no violation of the NEC code. The main length of my battery cables are 13ft the rest are less than 24" 1/0 if I increased the size of my wiring my conduit would also have to increase because of cleanerance reasons. For this acquired use 1/0 should hold just fine. I sent my A/C in from the main panel with a hot/neutral/ground, and my A/C out is going to an A/C disconnect then to a sub panel hot/neutral/ground, then I have my ground for D/C going outside to a grounding rod. I have the inspector coming out this week to verify everything is in operational condition. I deffinetly will consider one of these Epanel next time though that is a lot less wiring and purchases of componets.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #13
    Re: Critcal load battery backup instead of generator

    13' is a "long way" to send "low voltage/high current" DC power...

    What is your conductor awg, peak expected DC current (charging/discharging) and battery bank voltage?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • program.coordinator
    program.coordinator Registered Users Posts: 13 ✭
    #14
    Re: Critcal load battery backup instead of generator

    This system is considered back-up only used only if power fails and that is possible once or twice a year, I moved the inverter closer to the battery bank so now its only 8' which is still long considering its a 48V system @ 600 Amp-hours, but I talked with one of my engineers and he said that 1/0 guage will be good.
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