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Lightning protection location?
#11
(03-01-2020, 06:23 PM)Maniac_Powerwall Wrote: 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 the positive line from a PV array (e.g. only 1 line) and will 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 the PV 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 Smile
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#12
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.

(03-01-2020, 07:48 PM)OffGridInTheCity Wrote: 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 ;-)
Running off solar, DIY & electronics fan :-)
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#13
(02-29-2020, 04:49 AM)Redpacket Wrote: 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
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#14
I agree having the dc surge-lightning protection after pv panels-before equipment is a good idea.., but isn’t lighting going to take the easiest path to ground which would be directly to a ground rod that’s connected to pv panels
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#15
(03-04-2020, 12:47 AM)Doin it Wrote: I agree having the dc surge-lightning protection after pv panels-before equipment is a good idea.., but isn’t lighting going to take the easiest path to ground which would be directly to a ground rod that’s 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.
Doin it likes this post
Running off solar, DIY & electronics fan :-)
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