Lightning protection location?

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Dec 20, 2018
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Where should I locate lightning protection for my solar panels? Before the breaker, to the panels? Or behind them, to the inverter side?
 
Maniac_Powerwall said:
Where should I locate lithning protection for my solar panels? Before the breaker, to the panels? Or behind them, to the inverter side?
A common place is at the combiner box / outside. Panels ------> combiner-box/quick-disconnect/lightning-arrestor(outside) ------> Charge Controller (usually inside)

image_wuhslx.jpg


There are 4 arrestors because there are 4 independent pv sub-arrays (e.g. 4 seperate + / - wires)feeding into the house from this combiner box. I always see them outside and I presume it because its better to deal with lighning surge outside where fire is less likely to burn anything up :)

Maybe someone can give the actual recommendations on this.
 
You also need a good earth cable connected to the arresters.

The important thing with lightning is to bond all the cables (eg with arrestors, etc) to a common earth point to stop/calm voltage differential.
Eg lightning hits array, whole system gets voltage on it, Ethernet cable leaving towards house goes PC, PC > house ground
Ethernet cable gets voltage on it, damages gear at each end of the cable because house ground is different to shed system.
 
We will ground the PV array and all the gear. But for now I need to find the right spot to install the lightning protection. Any idea?
 
Just found a installation manual that tells me to put them before and behind the breakers. I think I will install the one I got before the breakers. That makes more sense to me somehow...
 
I'd put one set on the side of the breaker towards the charge controller/battery, etc, thinking, easier to work on, close to the gear is better than on the roof (easier access & better protection).
 
My thought is that a lightning would most likely pop the breaker and the protection is useless afterwards if placed behind the breaker to the gear.
 
Maniac_Powerwall said:
My thought is that a lightning would most likely pop the breaker and the protection is useless afterwards if placed behind the breaker to the gear.
I believe the ideais a lightning (or other) surgewill 'fry' (melt) a breaker before it can tripand that's why you wire it upstream from the breaker.

However, here's what I consider a 'legitimate'discussion by Midnite Solar on their SPD(s) (its what I show in my picture above) and their different uses / recommended hookup -MidNite Solar - Introduction to the Surge Protection Devicehttps://youtu.be/-B64V_FZBFQ Checkout 6:18 into the youtube - talks about PV array -> Charge Controller specifically.
 
But it will be still available if the breaker is melt. I do understand why two of them would be better. But still think having only one on the panel side of the breaker is better, right?

BTW those midnite SPDs look really fancy :)
 
Maniac_Powerwall said:
But it will be still available if the breaker is melt. I do understand why two of them would be better. But still think having only one on the panel side of the breaker is better, right?

BTW those midnite SPDs look really fancy :)
The Midnite Solar youtube suggested (and showed behind they guy) that you can have them 'at the charge controller' - e.g. inside and downstream of the breaker out at the combiner box. On the other hand, he discussed having it 'first thing' (ahead of the breakers)at the main house panel for surges from lightning hitting the power line near your house - and sending a surge into your house wiring.

I still believe the idea is that up stream of the breaker would help you avoid replacing a 'melted breaker'. He also said(at the 6:13'ish area of youtube) that a breaker os typically on thepositive linefrom a PV array (e.g. only 1 line) andwill not stop a surge down the negative line (the other line)to ground... e.g. the surge will bypass the breaker as a surge can go down either + or - line from thePV array... Their Midnite lightning arrestor blocks the surge on both lines.

>SPDs look really fancy :)
Agree and expensive - like $100 each.

So I think there are multiple ways to skin the cat here - e.g. more than 1 correct way. A surge suppressor (in addition to circuit breaker) sounds like a common/strong recommendation for solar PV arrays because they can attract lightning. BUT - there are other surge suppressor(s) than Midnite and they probably have their own specs/recommendations :)
 
Lightning is typically so fast that breakers don't have time to react.
Even if the breakers did trip & open, the lightning will immediately arc over the opening contacts & blast right on through anyway.
If you get a direct hit with enough energy to melt a breaker, you're going to have lots of problems & very few surge protectors will cope with that much energy.

OffGridInTheCity said:
The Midnite Solar youtube suggested (and showed behind they guy) that you can have them 'at the charge controller' - e.g. inside and downstream of the breaker out at the combiner box. On the other hand, he discussed having it 'first thing' (ahead of the breakers)at the main house panel for surges from lightning hitting the power line near your house - and sending a surge into your house wiring.

Agree having protection on all incoming lines to an installation is a good idea.
There's an IEEE guide on it here:
http://lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf

Basically you want protection from differential voltages across your gear from lightning entering here, then exiting there, with your gear in the middle getting fried ;-)
 
Redpacket said:
You also need a good earth cable connected to the arresters.

The important thing with lightning is to bond all the cables (eg with arrestors, etc) to a common earth point to stop/calm voltage differential.
Eg lightning hits array, whole system gets voltage on it, Ethernet cable leaving towards house goes PC, PC > house ground
Ethernet cable gets voltage on it, damages gear at each end of the cable because house ground is different to shed system.

Thanks for your reply, my doubts are now cleaned
 
I agree having the dc surge-lightning protection after pv panels-before equipment is a good idea.., but isnt lighting going to take the easiest path to ground which would be directly to a ground rod thats connected to pv panels
 
Doin it said:
I agree having the dc surge-lightning protection after pv panels-before equipment is a good idea.., but isnt lighting going to take the easiest path to ground which would be directly to a ground rod thats connected to pv panels

Trouble is the panels & close cables are very likely to have the lightning voltage on them especially with a direct hit.
Hopefully most of the energy of a hit takes the easiest path, but....
A ground rod doesn't stay at "0V" when there's a hit (compared to ground somewhere distant), it has resistance & impedance - & lightning is massive energy.
So the panels, etc go up/down several thousand volts at least.
The ground around the lightning rod ground location also has voltage induced too & makes a bit of a voltage "hill" getting lower/less with distance.
The house mains earth, & other wires like mains feed from the street, your cable TV coax, your phone line connect with your place but the other end is "way down the hill" at a lesser voltage.
So whatever is between the panels & any of these other cables is at high risk of getting blasted.
The IEEE guide recommends clamping all these cables to a local common point to stop/reduce the differential across the gear.
 
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