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Convert one branch of grid tied system to off grid

I have a 3 branch Enphase Microinverter Grid tied system. It works great. One of the branches is only 4 panels. We are on well water so I would like to convert the small branch to a non-grid tied. The reason for that is so that in the event of a power failure, we would still be able to use the 4 panel backup system to get water. I assume that I would have to take off the 4 Enphase units, but what would I need to make my plan work? My well pump is a 220 volt line. Greatly appreciate your help.

Comments

robert1250a:

You are currently grid-tied; how often do you loose power, and for how long? What is your budget and how well does the current grid tied system meet your power demand?

Depending on your answer, here are your choices:

  1. Use a small gasoline generator for emergency pump power. Just unplug the pump and plug into the generator. Run the gen. when you need to fill your resevoir. Use less water until power comes back on.
  2. Set up a battery based UPS system at the well which charges at off-peak hours. This is just a backup battery for the pump with an inverter.
  3. Get rid of 4 Enphase inverters and build a mini off-grid system. You could take any off-grid package and size the batteries for 'N' days of autonomy.
  4. Get rid of the 4 Enphase and do a straight DC pump system - convert the well to DC direct or DC with battery back-up.
  5. Use the new Xantrex MPPT 80 600 XW to create an Off-grid / Enphase hybrid system. This is an experimental approach that may be able to allow the Enphase to run with grid power down by using a transfer switch.

All of these options could work and they're roughly organized by increasing cost and complexity.

Your requirement is similar to the system I am designing for my own use. I want to get water from my well which has the same type pump as yours when no comercial power is available. The differenced is I am starting with no material and no solar experience. However I have done the research and am finalizing my system and ordering components. I suspect I can answer most of your detailed questions. While I am short on solar expereince I am a retired electron circuit designer with equipment on most US comercial and military planes flying today. Given you have the panels, your material cost will range from $600 up to about $3000 depending on your system and detailed design choices. I will spend about $3000 for ability to run my pump, a small refrigerator, brief use of a microwave, and watch a few movies on TV per day. If not careful in my design choices the cost could easily rise to $7000 for the same benefits.
Here's an update to my previous post: Now you can just add a Midnite solar E-Panel to the system. You can connect up to 4kW of the enphase to the AC Coupled E Panel and they will run normally while the grid is up. If the grid fails, the battery inverter on the E-panel will start up and power your pump, plus keep the solar running.
Submitted
13 years 3 months ago
Asked by
Robert Andrews