Lightning Surge Supression

srhill

Hi everybody,
I am looking for advice on surge (lightning) protection for my solar system. I recently got hit and my SB8000 was fried ! Even though I am properly grounded (I think), I have no protection devices. My array is about 400 feet from the inverter. I have been looking at the Midnite Solar MNSPD-600 Surge Protector Device and the Delta LA302DC Photovoltaic Surge Arrestor 500 VDC Max for the DC run. I am also planning on covering the AC side. So, does anyone have a favorite suppression device or advice on the best way to get protected.
Thanks !!!

Mountain Don

Re: Lightning Surge Supression

We got hit this summer too. We now have several of both the MN-SPD and the Delta on both the AC and DC sides. We had toasted equipment all over the place.

We now also have air terminals (lightning rods) along the ridges of the roof and the chimney top. Large diameter (7/16") wires from the terminals to the earth grounds. There are two down wires at opposite diagonals leading to earth grounds. The grounds are multiple rods and two 2 ft sq copper plates, buried.

We also have a long run between the PV array and the CC. I made the end near the cabin easy to disconnect from the CC. We have a lightning season in summer. The sun never shines when we have thunderstorms. If we are on sire we disconnect the lines and pull them back leaving a ten foot gap between the CC and the incoming wires. The idea is to help prevent a surge that may be induced in the DC lines from getting too close to the CC. If we are away we then hope all the other precautions work.

Note, the grounding rods / plates for the air terminals are completely separate from the electrical earthing of the AC/DC power system.

Organic Farmer

Re: Lightning Surge Supression

At least one Surge Protector at each component, and lightning rods above every component [each individually grounded].

srhill

Re: Lightning Surge Supression

thanks for the help, I will order the devices ASAP, new inverter on the way.

vtmaps

Re: Lightning Surge Supression

srhill wrote: »

I recently got hit <snip> My array is about 400 feet from the inverter.

Mountain Don wrote: »

We got hit this summer too. <snip> We also have a long run between the PV array and the CC.

I'm curious... do either of you have your array ground rod connected to your ground rod at the house? If so, are they connected by a buried bare copper wire?

--vtMaps

niel

Re: Lightning Surge Supression

forget the deltas as midnite solar has proven them to be junk. go with the midnite spds.

mike95490

Re: Lightning Surge Supression

niel wrote: »

forget the deltas as midnite solar has proven them to be junk. go with the midnite spds.

I think the Deltas & Midnights serve 2 different purposes, and I use both. The Midnights activate at much lower (reasonable) voltages and will lots of saving of systems. But one bolt of lightning, and I'm pretty certain they will be totally toasted, MOV's can only dissipate so much power before they vaporize. That's where the Deltas can save the rest of the day. It may take several thousand volts before they conduct, but I believe they will handle much more power before they too, vaporize. Hopefully by then, that lightning bolt has finished, the protection has sacrificed itself, and the main gear may still be alive. Each lightning bolt has as many as a dozen "strokes" in rapid fire succession, that our eyes see as just one.
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niel

Re: Lightning Surge Supression

in theory that sounds reasonable mike, but the point of flashover in the deltas is so high that the damage will occur in wires and equipment long before the deltas arc over. your deltas won't hurt anything being there, but don't help much either.

srhill

Re: Lightning Surge Supression

Thanks for the discussion. Although I don't expect a SPD to survive (or stop) a major strike, the Midnight Solar u-tube videos have convinced me to go with them. Not cheap, but neither was my inverter.
Steve

oil pan 4

Re: Lightning Surge Supression

I have a ton of 40 volt MOVs.
They have proven them selves in welding machine applications. They would work for solar panels too.

niel

Re: Lightning Surge Supression

oil pan 4 wrote: »

I have a ton of 40 volt MOVs.
They have proven them selves in welding machine applications. They would work for solar panels too.

hmmm. i hope it wasn't the 40v movs that had welding applications as they would short to ground with 120vac and 240vac applied. those 40v movs would be good for 12v pvs and may work for some 24v type pvs, but you are cutting it very close for 24v as some movs may not be at 40v for their activation and may be lower as tolerances aren't that critical on them causing some variation swings. you don't hear of 40v movs as most are much higher and makes them a bit rarer to come by.

how'd you get a bunch of them?

oil pan 4

Re: Lightning Surge Supression

They would be used on 12, 24 volt DC side. Or stick 2 of them in series for voltages in excess of 40v, but no more than 80 volts. If you want 120v MOVs radio shack has them for fairly cheap. I use radio shack MOVs on the high voltage input side of my welders wired Line to Neutral to protect the machine its self, power factor correction capacitors, input volt meter and other electronics on the same service.
The max suppression voltage is actually 40.2v and break down voltage is 44.7v. I use them in a mig welder that puts out 30 volts.

Since a 36 volt system can see a little over 40v they wouldn't work there.

I only needed like five of those 40v MOVs and I ordered 100 of them, because that was the minimum order so there are a few left over.