Ac coupled question

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jesusmve
jesusmve Registered Users Posts: 1 ✭
in Grid Tie and Grid Interactive Systems #1
Hi everyone im new to the forum I have one question about ac coupled.
I have already a system with micro inverters and I want to do a ac coupled for backup power. In every explanation and diagram i see that every body talk about a sub panel for critical load. But what about if I dobt want critical load panel and I want all my house to be power when the grid goes out. Is complete necesary to do a backup of every breaker in my house or i just connect the battery inverter to the grid tie inverters and to the main panel of my house.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited October 2017 #2
    It's all a question of economics, normally critical loads are retained to match the limited capabilities of the backup system, thereby extending it's reserve capacity in case of emergency. If all loads are deemed critical, as in the whole house, then the backup system must be sized appropriately to cover outages for the anticipated length of time of outage, most backup systems are sized to provide minimal essential or critical loads, hence the critical load panel. Isolation from the grid will be essential, so a seperate main panel would be required where the main  grid feed and grid tie would be connected, the existing house panel would then become the critical load panel, all connection to the grid must be isolated via a transfer switch, otherwise you would feed the neighborhood, or possibly kill a line worker. There are many other considerations, like where excess power producd, if applicable, goes. Such a system would need to be engineered and approved, at least in most jurisdictions, not really a DIY proposition. This pdf from Outback has useful information.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited October 2017 #3
    A question, how are you proposing to use the grid tie inverters in the absence of the grid? Equipment wise.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 7,025 ✭✭✭✭✭✭
    #4
    An example to what mcgivor wrote. If you backed up the whole house, Assume the main panel is 200A
    The battery inverter  (an XW+)  internal transfer switch 60 amps would blow it's breaker if you exceeded the 60A.
    So, you can see an unknowing person could kill the power to the house not to mention kill the batteries.
    This is the main reason for a subpanel in suburbia :)
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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