lighting and inverters

Dapdan

Hey all,

I had some lighting storms today and on my inverter was shut down 3 times. It is a pure sinvewave go power brand with the output going through a gfci outlet. On all occasions i had to reset the gfci outlet to get it going again but no damage to any equipment. Anyone have any ideas what was causing this. It is the first time this has happened since i have been running the house on the inverter. The lighting appeared to be taking place really close to the area but no actual evidence of strikes around the house or in the neighbourhood. Any thoughts anyone. It was very strange and worrisome at first.

Cheers...
Damani

nigtomdaw

Re: lighting and inverters

It looks like the GFCI was doing its job let us all know about what it is and where you purchased if from , Nigel

Dapdan

Re: lighting and inverters

hey nigel,

it is a gopower 1500w puresine wave inverter at 24v bought from rvandboataccessories.com last year july. Has been working well 24/7 service. It was a very strange occurence, I thought i had a direct hit and was thinking the worse (burnt out equipment etc) and was very relieved to find that it was the gfci outlet on the inverter that just needed reseting. It happen 3 times. It was very touch and go going out in the rain to the battery room to reset it 3 time while the storm was still taking place.

Cheers...
Damani

Cariboocoot

Re: lighting and inverters

The lightning is causing 'stray voltage' - triggers the GFCI. There's nothing that can protect equipment from a direct hit, of course - several million volts of electricity at a temp hotter than the surface of the sun can pretty much do what it likes!

Have you got any lightning arrestors on your PV's? How's the Earth grounding? If you can 'kill' the stray voltage before it triggers the GFCI all the better.

Dapdan

Re: lighting and inverters

Hey Carib,

no arrestor and no grounding to the panel ma brotha. Is that a bad thing?

Cheers...
Damani

Cariboocoot

Re: lighting and inverters

Yes, rather.

You want to give that stray voltage a path to ground that's not through your equipment. GFCI's aren't meant to be triggered repeatedly - they wear out. That's why they have a 'TEST' button on them.

The frame/mount of the array should be Earth grounded as should the AC ground line at the very least. Some installs recommend grounding the (-) DC as well. Look at some arrestors too:
http://store.solar-electric.com/deliar.html

Dapdan

Re: lighting and inverters

hmm....

Then i better at leas ground the panels since the ac side is grounded. Should i ground the panels directly to earth alone to effect the ground on the pv. If so I will ground the aluminium frame I have them mounted on to some rebars coming from some foundation reinforcement with say 6awg wire. Does that sound plausible?

Cheers...
Damani

BB.

Re: lighting and inverters

One of the reasons that GFI's should only be installed on circuits where there is a good expectation that some sort of human/ground fault can occur. And not a "central" GFI that cuts power to the entire home/facility.

Bascially, the GFI (as I understand them) is just looking for a 5+ mAmp current that is flowing in or out both the Hot and Neutral circuits at the same time (i.e., Common Mode Current--Diferential Mode Current is the current that flows out the "Hot" and back in on the "Neutral"; equal and oposite is everything working right).

5 mAmps is actually quite a small leakage current (sort of feels like bite to your hand)... And sometimes, larger equipment that has lots of filter caps in them (to earth/chassis ground) to keep emmissions down, can leak up to 2.5 mAmps of current--Plug several units in the same GFI outlet--and it may trip.

The following ground rant/discussion is not intended to tell anyone how to follow, or not follow code... Just an interesting point I have seen from my past design work.

I am not sure any grounding will do much to help a near or direct hit... From a pure circuit design point of view, grounding the neutral on an AC line is actually very bad from a lighting protection standpoint.

For example, any modern NEC approved/type equipment will take 1,800 volts minimum (each unit should be factory tested before shipment--this is from years ago--I think 1,800 is the minimum test voltage used) of common mode voltage on the AC power line (both Hot and Neutral are tied together and subjected to 1,800 VAC).

Remember, it is common mode current that "trips" the GFI. Differential mode current will not.

However, when you ground one leg of an inverter (which should take 1,800 VAC all day long--if designed for UL/NRTL with AC/DC Isolation)--Now tie the Neutral to Earth. All of a sudden, that 1,800 Volts AC is now 1,800 volts on the "Hot" and 0 (zero) volts on the "Neutral" leg. The inverter's output is designed to withstand a few hundred volts during normal operation, not an 1,800 volts (surge).

So--grounding one leg of a 120 VAC inverter may take a "minor" lightning event and turn it into an inverter destroyer event--Obviously, a direct hit; nothing is going to help.

I wonder... IIRC, a few years ago Windsun (NAWS Admin) said that most of the off-grid lightning induced inverter failures he had seen had the failure in the AC output stage--I wonder if the Neutral bonding/grounding was part of that issue or not?

-Bill

Cariboocoot

Re: lighting and inverters

Better you should take the 6 AWG straight from the frame all the way down to a good grounding post - you never know quite what path a piece of rebar follows.

You get lots of lightning there? 'Cause it sounds like your AC is getting charged enough to make the GFCI think the grounding has failed.

Lightning can be fun. I used to have a fluorescent tube desk lamp that was 'starter less': you turned it on by holding down a push button until the ends glowed, then released it. You shut it off by pushing another button that broke the AC circuit. During a lightning storm, the stray voltage could be high enough to excite the gases in the tube to where the light would come on!

mike95490

Re: lighting and inverters

Cariboocoot wrote: »

During a lightning storm, the stray voltage could be high enough to excite the gases in the tube to where the light would come on!

That stray voltage is enough to trip your GFI circuits. You really should have lightning arresters on your Array wires and maybe on your AC side, if the close strikes keep tripping. You will likely NOT prevent the GFI from tripping, but you may save your gear from a fatal zap.

Cariboocoot

Re: lighting and inverters

Bill -

I'll 'second' that "don't tie neutral to ground" recommendation. We used to have a lot of trouble with that, even though it is common practice and in some places code, in agricultural applications. The 'other' kind of stray voltage would come from the energized neutral line feeding the ground and charging it and whatever it was connected to. This is often the cold water pipe, which feeds all the drinking bowls for dairy cows et cetera. Bossy would take a sip and get a shock.

If there's supposed to be three separate wires, why tie two of 'em together?

Not much different than in the old days when there was NO third 'ground' wire at all!

Dapdan

Re: lighting and inverters

Ok guys,

ground and arrestor for the panels as a minimum...right. I pretty much know all my rebar since I installed them myself. In brief all are connected together since I instpected them before the concrete footing was cast and was there while it was being cast. Basically I have at lease 40ft fo 2' * 8" deep RC footing that contains 3 1/2 rebars running longitudinally and u-bars at 12" c/c running perpendicular to the bars and then starter bars(running verticaly for the 8" solid filled cider blocks that are tied to the bottom most 1/2" rebars running the entire length of the wall.

Cheers...
Damani

Kamala

Re: lighting and inverters

Cariboocoot wrote: »

I used to have a fluorescent tube desk lamp that was 'starter less': you turned it on by holding down a push button until the ends glowed, then released it. You shut it off by pushing another button that broke the AC circuit.

Gosh, I forgot about those old FL fixtures. My grandparents had several. Almost like an igniter. And a kill. Hmmm...

K

mike95490

Re: lighting and inverters

Kamala wrote: »

Gosh, I forgot about those old FL fixtures. My grandparents had several. Almost like an igniter. And a kill. Hmmm...

K

uh, I've got a couple myself. Old ones, from the 60's. In daily use.

Cariboocoot

Re: lighting and inverters

Thanks for making me feel old, guys! Oh wait; I am old.

To Dapdan: re-bar still isn't a good idea for grounding. Steel doesn't conduct as well as copper, and it does actually go into the ground, does it? Concrete isn't a good conductor either. The idea here is to construct a path for the voltage to go deep into the (preferably) damp ground where is dissipates.

Yes an arrestor on your panel wiring is a good idea. You are also getting your AC lines charged, though; that's what's tripping the GFCI. You may want to seriously consider an arrestor on them as well. They provide a high voltage path to Earth - that's the whole idea here; give it a lower resistance alternate grounding path rather than running through your expensive equipment and frying it.

BB.

Re: lighting and inverters

A couple of threads on "Ufer Grounding" (using concrete+re-bar for grounding):

Ufer Grounding
Outback Inverters/ X-240 Transformer Causing Generator Damage?

-Bill

Cariboocoot

Re: lighting and inverters

A properly installed concrete foundation would be waterproofed. Therefor the concrete would stay dry and not be a good conductor.

Mind you, an awful lot of foundations have been installed without so much as builder's plastic 'round them.