What are you recommendations for system protection?

lightsky Registered Users Posts: 13 ✭✭
 Inverter, battery charge controllers, PVs etc, protection against damage.


  • MichaelK
    MichaelK Registered Users Posts: 234 ✭✭✭
    Every substantial system should have a power panel incorporated into it.  Here's an example of a Midnight solar panel made for Outback systems.

    Note that they are brand specific, and you can buy different panels designed for Schneider, Outback, Magnum, ect.

    These power panels can have either DC or AC (or both) breakers that all your wiring gets attached to.  So, the solar array, charge controller, and inverter all have breaker protection.  The company will provide wiring diagrams on how to assemble your system using their components.

    They typically have a central grounding connection that gets wired to a ground rod you pound in the earth, or an attachment to other approved below grounding points such as water pipes, concrete rebar, ect.

    The general rule of thumb is that all the "below ground" ground elements like pipes, rods, rebar, ect, can be connected together, and all the above ground elements like the controller, inverter, main sub panel, wall sockets, ect can be connected together, but the above-ground elements can be connected to the below-ground elements at one and only one place.  In my systems, that's at the power panel described above.  This is to prevent the whole-house grounding system from becoming an antenna that could attract lightning.

    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
    Good practices is a good place to start... Use drip loops in cables (you don't want water following a cable through a wall/box and bringing water into the electrical connection areas).

    Fuses and circuit breakers--Fuses and breakers do not "protect" your equipment from damage per say (a FET fails in nano or micro seconds--Breakers and fuses work in seconds to minutes to hours)--They are there to prevent short circuits (as can happen in AC inverters, or charge controllers, or even failed insulation on wiring) from causing a current overload, and the red hot wiring starting fires.

    Many times, it is easier in the long run to use circuit breakers instead of fuses... You do not need to keep spare fuses on hand (high current  and high voltage fuses are not cheap), plus breakers make for hand on/off switches (debugging, shutting system down for winter, etc.).

    If you are in a lightning prone area--The surge suppressors are pretty much required. Midnite makes a very nice range of MOV based surge suppressors for Solar panel and AC circuits.


    Nothing will usually survive a direct strike, but spressors can limit the damage from nearby strikes and help reduce the chance of lightning coming into your home.

    And there is grounding... Which is mostly useful for lightning control (get the lightning current to the earth as soon a possible.

    Other things to think about--Stuff does fail. Using a shed for batteries+inverters+charge controllers--And possible a second for genset+fuel... (limit losses to outbuildings instead of the home).

    And some battery chemistries can make a toxic waste site if there is a fire (some Li Ion chemistries) which may not even be able to clean up (may have to tear down the building/home).

    Following your local electric code (such as the NEC) for system and wiring design is always a good start. Even if your off grid system never needs an inspection--Building it "right" will make for a safer system (and help with insurance claims and payments if everything was done correctly--If you can even get insurance--Getting more difficult these days).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lightsky
    lightsky Registered Users Posts: 13 ✭✭
    I thought of equipment earthing as more of a user safety than a device safety.
    I hardly fully understand it's benefit apart from keeping equipment chassis on a zero potential and tripping few breakers if there's potential difference.
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,783 ✭✭✭✭✭✭
    Equipment earthing such as a solar array frame & panels to ground right below it is one of the key elements of protecting the downstream electronics.

    With modern BMS in battery systems, it is not a good idea to skip the 48V buss SPD. It can also protect to some extent electronics inside an inverter charger, its mppts, and any devices on the buss. Definitely anything coming in like HV PV needs it's own SPD.
    "we go where power lines don't" Sierra Nevada mountain area
    E-mail offgridsolar@sti.net