Can one lightning arrestor protect two charge controllers

beth · October 2010

I am wondering if I need to buy two lightning arestors. I have two PV arrays and each has its own charge controller. Is there a way to "wire in" one arrestor to protect both controllers? For example by branching the leads that come from the arrestor and then connecting one pair to the + and - of each array.

Thanks again for all the great help!

Ralph Day · October 2010

Re: Can one lightning arrestor protect two charge controllers

How much does an arrestor cost? How much does a charge controller cost?

Question asked and answered!

Ralph

JESSICA · October 2010

Re: Can one lightning arrestor protect two charge controllers

Ralph Day wrote: »

How much does an arrestor cost? How much does a charge controller cost?

Question asked and answered!

Ralph

I fully agree.
Buy TWO, and, if possible, buy a third one, and place it wherever you find 3 cables.

Addendum: Is there a way to know if my arrestors are in good conditions? Since my recent encounters with lightnings (in one, a breaker tripped; in the second one, a crater was caused in solid concrete), I have wondered whether my 2 arrestors are still functional and protect my cc and inverter. By the way, arrestors did not "explode" or open.

peterako · October 2010

Re: Can one lightning arrestor protect two charge controllers

Hi there a arrestor is shorting the lightning strike so it is always open, If it is a heavy strike it is permant shorted or is burnt.
If you have this type of heavy lighting then there is a first that you can do.

On a high part from your ground or behind ( to the north ) from your solar panels.
install a high metal pipe, higher than any thing else, the top with one or multi sharp metal peaks, in the ground a around the base a ring grounding or a maze.
The connection between them using bare copper or aluminum cable. The metal welding is still a high resistance.

On this way you start removing the ground - air charge before building to high. And if there is a strike it will hit this pipe first.

On this way i protect may property, the only problem that i have is the telephone cable above the ground, i replace every year 3 - 5 times my arrestor , filter and DSL modem.

Greetings from Greece

beth · October 2010

Re: Can one lightning arrestor protect two charge controllers

"How much does an arrestor cost? How much does a charge controller cost? Question asked and answered!"

Thanks for the replies, But No this doesn't answer the question.

That answer seems to say Instead of finding out the real answer since its only $30, just buy two and stay ignorant.

Or maybe it is just semantics and you are saying two offer more protection that one, but I would like to know why?

The question is about now the arrestor functions and how it may be wired.

BB. · October 2010

Re: Can one lightning arrestor protect two charge controllers

I think the idea is that you want to "suppress' at every point that lighting can enter and backfeed into your expensive electronics...

For example, each solar array (to each controller) would have its own arrestor because each solar a panel to charge controller is an independent circuit (you are not paralleling the panels into one controller for example).

Also, you look at your AC output of your inverter--presumably a long wire run that is susceptible to getting a strike and feeding back to your inverter--So a arrestor at the output of the inverter will protect it.

If you have some CFL lights, a simple fan and your laptop/workstation/computer/printer/etc. -- You would place some form of surge suppressor / lightning arrestor there to dump power/bypass feeding the induced current/surges into your expensive electronics--but you may not choose to protect your CLF lamps.

One interesting point was (a few years ago) Windsun (admin from our host NAWS) said that majority of the failures in off-grid systems (assuming solar PV based) was the at the AC inverter's output... I guess the battery banks, grounding and such did a pretty good job of protecting the other pieces of equipment (plus they may not be as susceptible as the AC inverter output was).

Buy the way, if you have lightning forecast for the area--disconnecting external cables to the solar array and moving them many feet a way from the home/charge controllers is not a bad solution either (no wire connection, little chance of surge / damage). Of course, you do that before the storm hits, not in the middle of the storm. Installing large DC connectors in your array wiring may not be cheap, and depending on how many days of lightning you have a year--it may not be practical option for you.

Does that answer your question--Or am I still not understanding it?

Perhaps some folks from Florida (lightning capital of the world) can give you some better answers than I.

-Bill

mike95490 · October 2010

Re: Can one lightning arrestor protect two charge controllers

An arrestor can protect only 1 wire. They wire into the feed wire from the PV array. If you try to protect 2 wires, with one arrestor, all you do is short the two arrays into one large array.
install instructions http://www.deltala.com/installa.htm

dwh · October 2010

Re: Can one lightning arrestor protect two charge controllers

beth wrote: »

The question is about now the arrestor functions and how it may be wired.

The way it functions is to "divert" electricity to ground.

Since ground wires are connected to ground, and neutral (or PV negative) wires are bonded to ground, then obviously you normally don't need lightning arrestors on those. You only need them to protect ungrounded lines - hot or positive.

To protect the line, the arrestor briefly connects the HOT (or positive) to GROUND.

That is normally a bad thing, since it would constitute a dead short to ground. So a lightning arrestor must be a switch which is only activated when the line is carrying some voltage above nominal (design spec) for the system.

Older styles used a spark gap, where the nominal voltage (say 120v -> ground) is not enough to cause the spark to jump the gap, but a high (lightning) voltage will jump the gap and be diverted to ground. And, since the conductors are never physically connected, it's not a dead short. The newer style uses a semi-conductor material which serves to insulate the conductors from each other at nominal voltage, but connects them together at higher voltages. A dead short yes...but only when required and much more efficient than a gap.

Since the switch does not act instantaneously, arrestors are often used in conjunction with a surge capacitor, which will briefly absorb the extra electricity for a few nanoseconds while the switch is activated.

Obviously, you don't use these devices to protect the antenna on a roof, or the frame of a PV - those you can just connect directly to ground. You only use them where you need to temporarily connect a hot wire to ground to DIVERT the extra energy.

Okay, that's how it works. Now, where do you need these gizmos?

You need them wherever you need (or *might* need) to divert excessive voltage. For a normal building connected to the grid, you might only use a single device if it's designed for a 3-wire (two hots) system.

For a solar system, you might use only one device for the entire array - in which case you would place it as near as possible to the array - AFTER the combiner - to protect the single hot wire coming FROM the combiner. That of course, will not protect the combiner, so you could choose to put one arrestor on each hot wire (string) feeding IN to the combiner.

You could then also place one between the combiner and the inverter or charge controller. Would you *need* that one? No, not as long as no excessive voltage got past the first arrestor - but it wouldn't hurt anything and it would give some redundancy and also protect the inverter or charge controller in case one of the "upstream" arrestors failed - OR protect the inverter or charge controller in case of a high "induced" current in the line caused by the nearby lightning strike.

(Maybe...it depends on if the voltage is high enough to activate the switch - it might be high enough to fry the inverter or charge controller but not high enough to activate the switch).

You could even place another one between the charge controller and batteries. Again, it won't hurt anything since the arrestor is basically inert until it gets hit with a voltage high enough to activate it.

Also, as with a fuse or breaker, you would want to install the device as near as possible to the source to protect the maximum amount of wiring and whatnot.

Generally, they are not used here and there and everywhere - they could be, but they are normally only used to keep excessive voltage from getting into the system in the first place. So normally, you would use ONE PER HOT FEEDING IN TO THE SYSTEM. This could be one per hot feeding IN to a combiner (best) or one per hot feeding OUT from the combiner (not as good, but better than nothing). Usually, there will only be one hot feeding OUT of a combiner - that's what a combiner does after all - so it's more economical to just use a single arrestor at that point.

How many do *you* actually need??

In your case, with two arrays feeding into two charge controllers, you would need *at least* two since there is no place where the positive wires from the arrays are connected together. If you combined them into a single hot, then yes, you could use just one arrestor, but since you have two different paths for excessive voltage to get in, you need an arrestor on each.

Depending on how your system is configured, you might want one per hot leg (string) feeding into a combiner box - that is, if you want to protect the combiner box.

You could theoretically use a 3-wire lightning arrestor, with one leg connected to each hot coming from the arrays, but that would a bit of a dodgy way to go. Better to use (at least) one per array and put them at the array end to dump the excessive voltage to ground ASAP.

beth · October 2010

Re: Can one lightning arrestor protect two charge controllers

Thanks once again for some really educational responses !!!

Your sharing of your knowledge is so appreciated.

JESSICA · October 2010

Re: Can one lightning arrestor protect two charge controllers

beth wrote: »

I am wondering if I need to buy two lightning arestors. I have two PV arrays and each has its own charge controller. Is there a way to "wire in" one arrestor to protect both controllers? For example by branching the leads that come from the arrestor and then connecting one pair to the + and - of each array.

Thanks again for all the great help!

Beth:

Your original question was this: "I am wondering if I need to buy two lightning arestors..." You did not ask for "a really educational response". I think Ralph (and myself) did answer your original question: Yes, you need to buy two of them.

Now, the question that was not answered was mine: "Is there a way to know if my arrestors are in good conditions? Since my recent encounters with lightnings (in one, a breaker tripped; in the second one, a crater was caused in solid concrete), I have wondered whether my 2 arrestors are still functional and protect my cc and inverter. By the way, arrestors did not "explode" or "open".

BB. · October 2010

Re: Can one lightning arrestor protect two charge controllers

One additional discussion point... As I understand:

The new NEC code requires a ground fault detection circuit which adds a 1-5 amp fuse or circuit breaker in the (typically) negative wire of the solar panel to ground.

Fuses and breakers are not that fast--perhaps the first lightning strike will still short out through the fuse/breaker before they trip... But with this NEC ground fault requirement now "breaks" the circuit path to ground.

I would propose that for dc solar charge controllers (at least) that now both the positive and negative legs from the solar array now need lightning arrestors on the solar PV array input for charge controllers equipped with GF detection.

Thoughts?

-Bill

mike95490 · October 2010

Re: Can one lightning arrestor protect two charge controllers

JESSICA wrote: »

Now, the question that was not answered was mine: "Is there a way to know if my arrestors are in good conditions? Since my recent encounters with lightnings (in one, a breaker tripped; in the second one, a crater was caused in solid concrete), I have wondered whether my 2 arrestors are still functional and protect my cc and inverter. By the way, arrestors did not "explode" or "open".

http://www.deltala.com/installa.htm 1/3 of the way down:
(DELTA brand ONLY )
The arrestor remains good and functions properly as long as its enclosure is intact. Should the arrestor ever be damaged the enclosure will burst.

dwh · October 2010

Re: Can one lightning arrestor protect two charge controllers

BB. wrote: »

I would propose that for dc solar charge controllers (at least) that now both the positive and negative legs from the solar array now need lightning arrestors on the solar PV array input for charge controllers equipped with GF detection.

Thoughts?

-Bill

Aye, makes sense. Good point and I agree.

tokso · August 2011

Re: Can one lightning arrestor protect two charge controllers

mike90045 wrote: »

An arrestor can protect only 1 wire. They wire into the feed wire from the PV array. If you try to protect 2 wires, with one arrestor, all you do is short the two arrays into one large array.
install instructions http://www.deltala.com/installa.htm

I must be dense, for I don't really see any thing specific for PV panels in these instructions.

I am putting together a kyocera 130w 12v PV panel with junction box, the Morningstar Sunkeeper 12v and I wish to add the Delta LA302-DC Lightning Arrestor for protection. The junction box has two knockouts, so one can be used with the Delta LA and one for the wires out.

I want to double check how the Delta LA is wired in with the Sunkeeper.

The Delta LA DC has three wires:

Positive = Red
Black = Negative
Green = Ground

The Sunkeeper has three main wires:

Solar+ = Yellow (normally going to the kyocera's "+" connector)
Battery + = Red (goes straight to "+" battery terminal)
Common Ground/Negative = Black (normally going to the Kyocera's "-" neg. connector and to the battery neg. terminal).

So, if the Delta LA DC protects the Sunkeeper/downstream feed, then it would be?

Delta LA DC RED to POSITIVE lug in Kycera junction box
Delta LA DC BLACK to Sunkeeper Solar+/yellow
Sunkeeper Battery + = Red (goes straight to "+" battery terminal) [no change]
Sunkeeper Black/common ground to PV Panel "-" lug [no change]

Where does the GREEN/ground on the DELTA go? To the PV Panels "-" lug or to the frame ground (where a lightning rod ground wire will be hooked up)?

???

Cariboocoot · August 2011

Re: Can one lightning arrestor protect two charge controllers

Green wire connects to Earth ground.
The idea is that any high Voltage present on the black or red wires can "jump the gap" (so to speak) to the green wire, making that the shortest route to ground and earthing it before it can travel through other parts of the system and fry components.

niel · August 2011

Re: Can one lightning arrestor protect two charge controllers

tokso,
i'm not 100% sure of how you are wiring the delta, but hopefully this will clarify even if just for general reading. the delta should not be pressed into protecting after the controller, but only before it. the negative pv line needs protected too and should have one of the leads from the delta protecting it. technically spds are not polarized with the exception that one lead has to go to earth ground. this means one delta lead to the pv + and one lead to the pv - and the ground lead to ground. the reasoning for this is that the pv - lead can be viewed as a wire that can pick up emp either from the air or another wire and it would have a potential above ground and therefore can carry potentially damaging if not dangerous voltages if not diverted to ground. to only place one delta lead on the + pv would only protect that + pv wire leaving the - pv wire with possible emp voltage potentials. to protect a cc output lead is somewhat moot as the cc would've been already blown out by the potential hitting it from the pv input.

to be sure you are doing this correctly the delta is paralleled with the pv + and - leads with the 3rd going to earth ground and is not wired in series as i read is possible you may be configuring it. if wired correctly this means 2 wires are actually protected and not 1.

techntrek · August 2011

Re: Can one lightning arrestor protect two charge controllers

Cariboocoot wrote: »

Green wire connects to Earth ground.
The idea is that any high Voltage present on the black or red wires can "jump the gap" (so to speak) to the green wire, making that the shortest route to ground and earthing it before it can travel through other parts of the system and fry components.

Not really. Voltage potential (in this case over-voltage potential) travels at the speed of light. So your entire system is fully energized instantly. The potential has already passed the arrestor, it is just a race between how fast the arrestor can clamp down and how long all the equipment attached to that conductor can hold out. This is why in a standard home you can install just one whole-house arrestor at the service panel.

Not to mention that in a direct hit all bets are off and you get weird results, like maybe frying everything in the house except your TV, or frying almost nothing except the pad transformer and the alarm system. Which is what happened at my church recently. Four buildings attached to the transformer, one person witnessed lightning arcing across a room in one building, yet only the alarm system in another building was harmed. And the transformer fried.

boB · August 2011

Re: Can one lightning arrestor protect two charge controllers

techntrek wrote: »

Not really. Voltage potential (in this case over-voltage potential) travels at the speed of light. So your entire system is fully energized instantly.

Pretty much this is the case, but don't forget the inductance of the lines from energy source to electronics, which can sometimes be quite a bit. If so, that can help slow the current down.... some. Way better for the protection to come into effect at lower than 6000 or 7000 volts.

boB

tokso · August 2011

Re: Can one lightning arrestor protect two charge controllers

niel wrote: »

tokso,
...

to be sure you are doing this correctly the delta is paralleled with the pv + and - leads with the 3rd going to earth ground and is not wired in series as i read is possible you may be configuring it. if wired correctly this means 2 wires are actually protected and not 1.

OK, just to make sure, you are saying that:

The charge controller yellow/PV+ AND the Delta red/positive both attach to the PV Panel's "+" lug.

The charge controller black/common ground AND the Delta black/negative both attach to the PV panel's "-" lug (and the negative wire for the battery is attached here as well).

And the delta's green/ground attaches to the Earth Ground lug.

I am attaching a picture of what I think you are saying is the way to wire this up:

Cariboocoot · August 2011

Re: Can one lightning arrestor protect two charge controllers

tokso;

Your description and drawing look right to me. (My netbook screen is awfully small, though.)

niel · August 2011

Re: Can one lightning arrestor protect two charge controllers

it doesn't look right to me from what i see. wire your controller and pv up normally as if the delta wasn't there and then parallel one lead of the delta to the pv + and one lead of the delta to the pv - and the delta ground to the earth ground. there would not be any breaks in the wiring that would normally have been for the pv and controller as that is what parallel means for this. you put the pv in series with the + wire of the controller and it won't even electrically work that way. show us that you even know how to wire the pv, controller, and battery first.

now if you can't seem to get it right then maybe you should see if delta has some advice for you so you can understand this. either that or get somebody who knows what they are doing to wire it. it really isn't difficult or complicated, but to an individual not familiar with it it can be detrimental or even dangerous if done wrong.

Cariboocoot · August 2011

Re: Can one lightning arrestor protect two charge controllers

Let's see if this picture is any good (playing with drawing program).

niel · August 2011

Re: Can one lightning arrestor protect two charge controllers

thank you coot as that's the way it is supposed to be. i guess for accuracy you should've shown the pv frame at earth ground too, but if he can't get it from this then he shouldn't do it and let somebody else do it for him. i do hope that it was only our difficulty in being able to read your diagram and good luck.

tokso · August 2011

Re: Can one lightning arrestor protect two charge controllers

Cariboocoot wrote: »

Let's see if this picture is any good (playing with drawing program).

I believe it basically shows the same thing as my diagram...

That is, if your removed the Delta LA302DC, you would still have the charge controller hooked up to the positive and negative (common ground) of the PV panel and going out to the positive and negative battery terminals.

Please note that my diagram is basically to scale. If you have never seen a Sunkeeper 12 charge controller, it is about the size of an iphone and is meant to attach to the junction box on the back of the PV panel and hook directly to the PV panel's plus/minus lugs. So physically, I actually do have a junction box on the back of the PV panel with a Sunkeeper and a Delta hanging off of it.

tokso · August 2011

Re: installing a Delta LA

niel wrote: »

it doesn't look right to me from what i see...

now if you can't seem to get it right then maybe you should see if delta has some advice for you ...

Delta's OFFICIAL advice was the same as what they indicate on the product:

Red to Positive
Black to Negative
Green to Ground

Beyond that, you are on your own.

However, when I showed them both diagrams (parallel vs "serial" install) a Delta rep indicated that the "parallel" install seemed to be the "best" of the two.

The rep did add the comment that "some systems deliberately ground the negative DC conductor and some do not. [We] think that neither DC conductor should be grounded."

tokso · August 2011

Re: installing a Delta LA

niel wrote: »

... but if he can't get it from this then he shouldn't do it and let somebody else do it for him. i do hope that it was only our difficulty in being able to read your diagram and good luck.

I am not sure if this comment is directed at me (the original questioner) or someone else.

In my case, the PV frame is grounded to Earth (with a grounding lug and copper wire running down the pole and attached to an 8ft grounding rod). Which is why in my diagram I show the green/ground lead from the Delta going over to the grounding lug on the frame which leads to a copper wire, which leads to a grounding rod...

ggunn · August 2011

Re: installing a Delta LA

tokso wrote: »

The rep did add the comment that "some systems deliberately ground the negative DC conductor and some do not. [We] think that neither DC conductor should be grounded."

What did he mean by that? Some (most?) inverters ground the PV negative DC conductor through ground fault detection circuitry; is he saying that they don't think they should? One should never externally ground the DC negative conductor because that will defeat the ground fault detection; is he saying that some installers do that? Or is he talking about the battery negative DC conductor?

BB. · August 2011

Re: Can one lightning arrestor protect two charge controllers

My guess...

Think differential and common mode signals (two wires, either the voltage moves different on both wires, or the voltage moves together).

Common mode signals are relatively easy to protect and block against surge current... And the equipment at the end of a common mode signal is not (usually) as sensitive to common mode spikes... Basically, if you have a 24 volt charge controller and put 100 volts on both wires together and move the voltage up and down (i.e, think both wires shorted together), the charge controller sees "zero volts" across the +/- leads.

If you have a differential mode surge... Think +100 volts on + and zero volts on -... Now the electronics/input circuits "see" 100 volts across and input designed for 24 volts--very likely to blow something up.

When you "Ground" on lead of your +/- wiring, you pretty much are guaranteeing that you will change a common mode voltage/energy spike (say lightning) which is relatively a "don't care" for the input to a differential spike (+ has voltage surge and - has zero volts) which will probably "take out" the input electronics.

For other issues, hard grounding (local ground rod, grounding metal cabinets, etc.) has safety value to limit the maximum voltage that would normally be present on wiring (say grounding the 120/240 VAC neutral on North American Home wiring). This is a cheap and easy way to, for example, protect against high voltage line cross (12,000 volt distribution wire falls onto a 120/240 utility drop to home). The grounded neutral (and "near ground" 120/240 hot leads) will "safely" short the excessive voltage (high voltage, relatively low current) to earth/common ground.

With safety and costs thrown into the mix--this stuff gets real confusing real fast. And, many times, doing "A" will cause problems with "B" (i.e., DC grounding for short circuit and human touchable voltage, is more likely to enhance damage from lightning).

I forgot, but the "Cheap" Delta Lightning Arrestors clamp at something like 200-1,000 volts (for AC depending on model; DC appears to be 240-3,000 VDC depending on model and current)... Obviously not near low enough voltage to really protect differential low voltage solar DC components from getting "fried" if there is enough energy behind the voltage surge.

From what I can tell--the DC Battery Bank is one of the major components that limit surge damage.

-Bill

niel · August 2011

Re: Can one lightning arrestor protect two charge controllers

tokso,
if i misread your diagram then sorry. i do hope you understand how to wire it though. these surge arrestors really are just a bunch of metal oxide varistors tied between +, -, and ground.

bill is quite right in that the voltages get very high depending on the model before it is allowed to channel this surge. sometimes it's enough to stop damage and sometimes it's not for nothing is foolproof. everything you do is certainly a help being it's a step in the right direction.

i have utilized diodes to help lower the trigger point of protection as they have a piv value that almost acts like a zener regulating diode. a high enough voltage (the piv point) will reverse conduct when that point is hit and diodes have lower trigger points than most surge arrestors do. example: a 1n4001 diode has a 50v piv 1a rating and roughly 50v will cause it to conduct in the reverse direction. it will be limited in it's current carrying ability so this will not take the place of the movs or even a good gas discharge tube, but a diode is cheap and readily available to most people.

i guess i better explain how it's wired in a bit. it will not be in series with the + pv lead as that would only make it an under rated blocking diode. it is a parallel connection as the + connection of the diode would be on the positive pv wire and the negative side goes to the - pv lead or optionally to ground. if wired backwards the diode could blow if using the pv- as the other connection point.

tonygcan · August 2011

Re: Can one lightning arrestor protect two charge controllers

Related question to this topic (or stupid question so apologies in advance), for lightning protection - I've noticed that most thunderstorms in my country (Philippines) happen at night when the PV panels are of no use.

Would it be a good idea to disengage the breaker before the CC to prevent any damage from a lightning strike during a thunder storm?

Or to install a safety switch before the CC that you could disengage?

BB. · August 2011

Re: Can one lightning arrestor protect two charge controllers

The "ideal" method would be to unplug the solar array from the home and pull the cables 6 feet or more from the side of the home.

Opening a circuit breaker (or knife switch) is not going to really stop a lightning bolt that just came through a mile or so of air.

Would you want to be hanging on to the end of a cable that may get hit by lightning in the near future--Hmmm.... Perhaps not.

-Bill

Can one lightning arrestor protect two charge controllers

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