System Grounding

rschoolf Registered Users Posts: 8
I am putting together a small off grid system.

This 12 volt system consists of 350 watt's of 44 volt panels, a MorningStar Tri-Star 45 amp MPPT controller, a MorningStar SureSine 300 watt inverter, and two 115 ah deep cycle batteries. My load consists of 130 watts maximum, and 78 W average over 16 hours per day usage.

Up till now, the grounding that I have been using consists of the neutral from the AC output of the inverter being connected to the grounding lug on the inverter, and from there going to earth ground. Also connected to ground is the grounding lug in the controller.

One thing I have noticed is that when I walk up to my controller, and start to poke meter buttons, more times than not an electrical static discharge from my finger into the meter will cause the computer in the meter to reset. Just about any time I walk up and touch the heatsink of the controller, it will arc out. It makes me think that I might have to rethink my grounding approach.

I am considering hooking up the negative terminals of the controller (which include solar negative and charging output negative), as well as battery negative to ground, as well (as mentioned above).

Does this sound correct: solar panel negative, controller output negative, controller grounding lug, battery negative, inverter grounding lug, and inverter AC output neutral all go to ground?

Thanks in advance for your comments.


  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
    Re: System Grounding

    I am going to recommend that you call Morning Star about this problem...

    Your local ground will not make any difference in how static discharge from your finger tip will affect the unit.

    This is a problem the manufacturer needs to look at. I hope that they have done static discharge testing on their units already (needed for CE mark for Europe, and just plain good sense to test for US/North American markets). Perhaps there is an assembly error (painted surface that should be bare for good grounding, etc.).

    Generally, from what I have seen, most "computers" that pass FCC testing do pretty well on Static Discharge Testing. Buttons and LCD displays are the weak point of any design and do need to be addressed by the manufacturer in their design and manufacturing.

    In my humble opinion, you are doing nothing wrong and this needs to be addressed by Morning Star.

    Your grounding scheme will (usually) have very little effect on the units behavior to ESD (electrostatic discharges). For many cold regions, winter heating drives down the humidity and causes massive static build up with people (winter jackets can create large static charges too).

    For now, all you can do is "ground yourself" on some nearby metal before using the buttons. If you work around electronics as a hobby, you can get an ESD wrist strap to prevent discharges.

    Let us know what they say.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset