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My parallel off-grid installation


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Hi All

I am a Noob with this and only found this forum recently (should have searched better) . The post is a bit long for which I apologize.

I am in the planning phase of my solar installation with a parallel non grid tied system at this point. 

Hardware:

  • 12 panels of about 300W each
  • 3 kW inverter/MMPT (Victron EasySolar II) - already ordered
  • Batteries PylonUS3000 - already ordered (might add second one in future)

I am still considering how to  do the wiring and this is where I can use so advise from the community.

General background on off grid installation:

  • I am planning to move some of my loads to only run during the day from solar
  • Swimming pool pump only run if the sun is shining - makes sense
  • Run one air con during the day if enough power is available
  • Power the internet permanently - to keep the rest of the house happy
  • (I already have a solar hot water system)
  • One or two separate plugs for general use
  • Connect some lights permanently to the off-grid system to make use to the available capacity and for backup (to conform to the wiring code, wire to be separate from grid supply)
  • Over time I might move more loads over to the battery to get maximum returns on my investment ;)
  • (I am comfortable with Raspberry pi and programming so the logic for the scheduling I hope to automate)
  • I did read the "My Solar 12V home" post
  • Some people suggest to rather have a DC system  (will still have an inverter for 220V loads during the day but will be switched off ) e.g.. https://www.scientificamerican.com/article/edisons-revenge-will-direct-current-make-a-comeback-in-us/ This make sense because it is more efficient to directly run low voltage loads from DC, e.g. LED lights, internet  router,  chargers, laptops, etc. The inverter also draws power permanently even if it has light load or no load. (Background: depending on the inverter it can draw significant power from your battery. typically 20W ->  20*16 = 320Wh  - Easysolar II is more efficient and draws 11W -> 11*16hours = 176Wh which is about 176Wh/(3.5Wh*0.90) = 5.6% of the battery's capacity  with 90% discharge which is still significant. Over a year this is  64kWh)
  • I know there are practical problems with a DC system, but as a backup I think you can side step most of these
  • I do understand that I need separate trunking for the DC and a desperate DB

What I do not know:

  1. So if I want to go DC, are there  standard plugs or can I use any plugs I like like barrel connectors?
  2. If I want to automatically switch my AC or DC loads individually, can I add these in the DB board and what relays/switches and controllers do I use to do this legally? Can I use a Sonoff for example?  (I want to run the logic on the Raspberry Pi the control signals can be either logic control signals, WiFi or RS485)

Thanks

 

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