Surge protectors and the correct procedure for shutting down solar system

rp3703

So Midnite sells those build surge protectors for PV arrays and I was just wondering how important everyone feels these are to a solar system? Would it be just as effective to flip the breaker to the panels off when a storm comes through? Also, can someone confirm with me the correct procedure for shutting down a solar system. I’m guessing that to run completely off the batteries with no input, I would simply flip the breaker between the batteries and the charge controller. After that, I could flip the main to the panels and I’m guessing if I were to want to pull the batteries, I would need to throw the main AC breaker and then shut off the inverter.

BB.

The 1/4 to 1/2 inch gap in a circuit breaker is no big deal to lightning that just traveled a mile or more through air. A few people in lighting prone areas have a ~6 foot disconnect plug and cable between the solar array and the home. When lightning is predicted or reported, they disconnect the cable and move it away from the home to protect the in-home system/loads/devices. Obviously, you don't want to be out in an active lightning storm while doing the disconnect.

More or less what is happening with surge suppressors--The lightning energy gets in the wiring, however wiring has higher impedance than the air--And tends to reduce current flow. Put a suppressor on the end of the wiring next to the load, and the surge suppressor "shorts out" the high voltage current to ground before it can damage your equipment.

If you have power lines in the area (or simply are grid connected), the surge suppressors are after the main breaker and will draw enough current to trip the breaker if there is a line cross (1x,xxx volts to 120/240 VAC) to dump surge current until the utility fuses/breakers trip.

No surge suppressor is going to be able to mange the current from a direct strike--You are sort of just taking care of any stray energy the best you can.

Interestingly, more often than not, it is the output of an off grid AC inverter that fails during a lighting storm and not the DC side of the solar power system. The DC side is usually negative grounded to a water pipe/ground rod (good lighting path) and (I believe) the battery bank behaves like a surge suppressor between + and - leads. And other than the line to the solar array, DC power is usually kept in a small area. Whereas, the AC output from the inverter goes all over the home and possibly outside for lighting, well pump, out building--And it is easier for lightning to find a way in or simply couple in like an antenna receiving the energy.

Regarding cycling power to your solar array/charge controller... Almost always, the best way is to shut down the Solar Array DC connection (combiner box breakers/array on-off switch) first, then shut down the charge controller to Battery Bank connection. And in reverse, connect the charge controller first and a few moments later, connect the solar array. Solar charge controllers generally get their operating power from the battery bank and need their "brains" to boot first, before the solar array is connected. Also, many charge controllers set their output voltage based on measured battery bank voltage (12/24/48 volt bank). If you connect the solar panels first, if the controller does power up, it may get confused about what the battery bank voltage is.

-Bill

rp3703

That's why I posted this thread. This system will be completely off grid. So it would have to be either a direct shot or in the vicinity of the grounding rod location.