Lightning arrestor for inverter

Tonygreen
Tonygreen Registered Users Posts: 15 ✭
in Solar Beginners Corner #1
Hi:

Recently, I bought an Exeltech xp inverter, and I want to protect it from lightning strikes. I was thinking of buying this product: Delta LA-302DC DC Lightning Arrestor [http://www.solar-electric.com/deldcphotsur.html ]

Will it do the job?

Since this arrestor has three (3) cables, how do I connect it to the inverter, in order to maximize protection?

Thanks,

Antonio

Exeltech inverter; 4 solar panels; outback controller; deep cycle marine batteries.:confused:
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Lightning arrestor for inverter

    Welcome to the forum.

    You know that page you linked to? Click on the lower small picture to the right of the main image; it's the wiring diagram! :D
    On the DC side the (+) goes to red, the (-) goes to black, and the green connects to Earth ground. On an AC connection the two AC lines go to red and black (either way) and green goes to Earth ground.

    The Delta products are fine, but some people prefer the slightly more expensive MidNite solar suppressor/arrestors: http://www.solar-electric.com/suprde.html
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  • Tonygreen
    Tonygreen Registered Users Posts: 15 ✭
    #3
    Re: Lightning arrestor for inverter
    Cariboocoot wrote: »
    Welcome to the forum.

    You know that page you linked to? Click on the lower small picture to the right of the main image; it's the wiring diagram! :D
    On the DC side the (+) goes to red, the (-) goes to black, and the green connects to Earth ground. On an AC connection the two AC lines go to red and black (either way) and green goes to Earth ground.

    The Delta products are fine, but some people prefer the slightly more expensive MidNite solar suppressor/arrestors: http://www.solar-electric.com/suprde.html

    Cariboocoot:

    I saw the diagram, but it was not clear to me.
    Do you mean: red cable to positive battery terminal of inverter, and black cable to negative battery terminal of inverter?

    The question may sound silly to an expert, but I am just a beginner!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Lightning arrestor for inverter
    Tonygreen wrote: »
    Cariboocoot:

    I saw the diagram, but it was not clear to me.
    Do you mean: red cable to positive battery terminal of inverter, and black cable to negative battery terminal of inverter?

    The question may sound silly to an expert, but I am just a beginner!

    Yes, but; mostly one of these would be connected to the output of the solar panels which feed the charge controller as they and their related wiring are what is most likely to pick up the stray Voltage from nearby lightning strikes. The whole thing would be mounted outside and have its own grounding rod.
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  • Tonygreen
    Tonygreen Registered Users Posts: 15 ✭
    #5
    Re: Lightning arrestor for inverter

    Thanks!
    And thanks again, for the reglamentary length.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,660 admin
    #6
    Re: Lightning arrestor for inverter

    It is always a good idea to use a volt meter to check connections (before connecting and before throwing the switch)... Many DC devices can be toast when miss-wired.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Volvo Farmer
    Volvo Farmer Solar Expert Posts: 209 ✭✭✭✭✭
    #7
    Re: Lightning arrestor for inverter
    Cariboocoot wrote: »

    The Delta products are fine, but some people prefer the slightly more expensive MidNite solar suppressor/arrestors: http://www.solar-electric.com/suprde.html

    Hmm, Maybe I have been drinking too much Midnite Kool-aid, but I got the impression that the Delta products were not "fine" when tested in the Midnite labs. Have there been any independent tests of these types of arrestors or does anyone have a story about equipment that was saved or not saved with them?
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #8
    Re: Lightning arrestor for inverter
    Volvo Farmer wrote: »
    I got the impression that the Delta products were not "fine" when tested in the Midnite labs.
    That was definitely my impression as well. Some of the "arrestors" were nothing more than spark gaps. Scary,, considering the delicate electronics they are supposed to protect. I thus ended up getting a couple of the Midnights, very impressed with their apparent quality.
    One note however, many people seem to be concentrating on protecting the DC input side of their inverters. From what I've recently been reading, and it makes sense, it's the AC output stage of the inverter that lightening usually takes out, not the DC input side. The long AC runs act as great antennas for collecting induced high voltage spikes from nearby lightening, and feeding it into the inverter, and it's output FETs, blowing them. Most inverters have only a short run to the batteries, where the potential difference is less than 60 volts between + and - and the battery would soak up anything beyond that, far better than any lightening arrestor ever could. For all of these reasons, I wired my Midnights to the AC outputs of the inverters.
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #9
    Re: Lightning arrestor for inverter

    The AC side, especially if you have AC grid connected, should also have protection. The DC side, (i.e. batteries) shouldn't need any protection since that circuit is inside and no outside wires are there to act as antennas.

    The DC side, if PV or wind turbine should be protected, both positive and negative to ground.

    As for the LA series, you would be better off hooking up a donut. It would do you just as good as the Delta or maybe even better !

    You might want to watch the video of the test of the Midnite SPDs and Deltas. The video also shows what is inside of a Delta LA.

    They are a complete scam and have been for many years now.

    boB
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #10
    Re: Lightning arrestor for inverter

    i'm going to elaborate on what boB said here and say that the dc side may actually need protected too because the pvs and their associated wire runs make excellent antennas to pick up lightning surges. sometimes, like in off grid systems, the dc side is actually more prone to blowout than the ac side, but make no mistake about it that it can happen on either the ac or dc side of things and generally both sides should have the spd protection. with lightning, there aren't any guarantees as lightning is fairly powerful and it does whatever it wants to, but the midnite spd protection will increase your odds of survival.
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  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    #11
    Re: Lightning arrestor for inverter

    I have a delta on the AC side of my invertter and a whole house inverter on my main panel. My inverter still got cooked when the utility managed to "dance" the high voltage line onto the 240 lines. Its on my list to upgrade to midnight solar arrestors. I do have a misnight solar on my DC side.
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  • Tonygreen
    Tonygreen Registered Users Posts: 15 ✭
    #12
    Re: Lightning arrestor for inverter
    boB wrote: »
    The AC side, especially if you have AC grid connected, should also have protection. The DC side, (i.e. batteries) shouldn't need any protection since that circuit is inside and no outside wires are there to act as antennas.

    The DC side, if PV or wind turbine should be protected, both positive and negative to ground.

    As for the LA series, you would be better off hooking up a donut. It would do you just as good as the Delta or maybe even better !

    You might want to watch the video of the test of the Midnite SPDs and Deltas. The video also shows what is inside of a Delta LA.

    They are a complete scam and have been for many years now.

    boB

    First of all: Where can I watch the video?
    Second: If they are a "complete scam", why NAWS doesn't retire them from their shelves?

    Third (and most important for me): The AC "side" of my Exeltech inverter has two (2) screws: positive and negative/ground (negative is bonded to the ground screw). So, how do I connect the 3 wires of the arrestor to that side of the inverter?
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #13
    Re: Lightning arrestor for inverter
    Tonygreen wrote: »
    Where can I watch the video?
    http://www.midnitesolar.com/video/spd/spd.php
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #14
    Re: Lightning arrestor for inverter
    Tonygreen wrote: »
    First of all: Where can I watch the video?
    Second: If they are a "complete scam", why NAWS doesn't retire them from their shelves?

    Third (and most important for me): The AC "side" of my Exeltech inverter has two (2) screws: positive and negative/ground (negative is bonded to the ground screw). So, how do I connect the 3 wires of the arrestor to that side of the inverter?

    The Deltas are not a "complete scam" (and this is probably the only thing I've ever disagreed with boB on). BUT they are only for lightning protection and definitely do not have the "range" of protection the MidNite units have. I was trying to gently hint that the MidNites are better. Especially on the AC side.

    The output of your Exeltech or any other 120 VAC inverter has two hots (one of which functions as neutral) and a ground. The arrestors have a green for going to Earth ground, a black and a red (usually) which connect to the AC hot wires - doesn't matter which is which because its only trying to conduct very high Voltage off the leads and to ground.

    BTW, NO form of lightning protection is 100%. This is NOT possible. All you can do is minimize the potential from damage caused by elevate stray Voltage (HV static electric) in the area where lightning occurs. The bolts are billions of Volts, millions of Amps, hotter than the sun, and a direct hit will blow everything to smithereens. Trust me.
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  • Tonygreen
    Tonygreen Registered Users Posts: 15 ✭
    #15
    Re: Lightning arrestor for inverter
    Cariboocoot wrote: »
    ...The output of your Exeltech or any other 120 VAC inverter has two hots (one of which functions as neutral) and a ground. The arrestors have a green for going to Earth ground, a black and a red (usually) which connect to the AC hot wires - doesn't matter which is which because its only trying to conduct very high Voltage off the leads and to ground.
    ... Trust me.

    Ok. I do trust you.
    However, my question/doubt remains: In my inverter, the neutral (white) terminal is bonded to the ground terminal, so it is not absolutely correct to speak about 2 terminals "and a ground"... In other words, there is NO separate ground terminal.
    Then: Do I connect red and black, each to the positive and the negative terminals of my inverter and connect the green wire directly to my ground bar?

    Sorry if I am a pain in the neck!

    Tony
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #16
    Re: Lightning arrestor for inverter
    Tonygreen wrote: »
    Ok. I do trust you.
    However, my question/doubt remains: In my inverter, the neutral (white) terminal is bonded to the ground terminal, so it is not absolutely correct to speak about 2 terminals "and a ground"... In other words, there is NO separate ground terminal.
    Then: Do I connect red and black, each to the positive and the negative terminals of my inverter and connect the green wire directly to my ground bar?

    Sorry if I am a pain in the neck!

    Tony

    Which Exeltech do you have, exactly? They make a very wide range of models adapting input and output to customer needs (frequency and Voltage for instance).

    The normal neutral-ground bond is to the electrical safety ground, and this terminal can be considered "hot" for purposes of connecting the arrestor. The ground rod it goes to should not be the same as the electrical safety ground. And I'll say right now someone is going to disagree with me on that. People like to disagree with me for some reason. ;) Do not connect the arrestor's green wire to your electrical safety ground, as this could just send the high Voltage back into the system via the ground conductors. You want to take it out and sink it to Earth as quickly as possible.

    As has been mentioned before you don't really need an arrestor on the battery side of the inverter as the wires are short and unlikely to pick up any charge. One on the PV output is good and another one on the AC out is good (the MidNite units are MUCH better for the AC side of things as they react to a wider range of surge).

    Incidentally, there are "surge protector outlets" (bars) which have MOV's (the component usually used for HV protection) from hot to ground, hot to neutral, and neutral to ground. At a glance one might think that is useless as the neutral and ground are bonded at the electrical box and so are "the same wire". Except there can be a lot of wire between the box and the outlet, and that wire length is what picks up the stray Voltage in the air. The sooner you can "grab" it and get rid of it the better. HV has a "skin effect" and can travel "harmlessly" along conductors until it finds a convenient "earthing path" which it will then fry to bits.
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  • Tonygreen
    Tonygreen Registered Users Posts: 15 ✭
    #17
    Re: Lightning arrestor for inverter

    xp 1100 24 volts ( http://www.solar-electric.com/exxp24vol11w.html )
    I can connect loads via a regular extension cord, or directly to AC terminals in the back of the inverter (It is there that neutral and ground are bonded.)

    Now, when you say "Do not connect the arrestor's green wire to your electrical safety ground, as this could just send the high Voltage back into the system via the ground conductors..."; Do you mean I should nail another copper rod 10 feet into the ground just for that purpose alone????
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #18
    Re: Lightning arrestor for inverter
    Tonygreen wrote: »
    xp 1100 24 volts ( http://www.solar-electric.com/exxp24vol11w.html )
    I can connect loads via a regular extension cord, or directly to AC terminals in the back of the inverter (It is there that neutral and ground are bonded.)

    Now, when you say "Do not connect the arrestor's green wire to your electrical safety ground, as this could just send the high Voltage back into the system via the ground conductors..."; Do you mean I should nail another copper rod 10 feet into the ground just for that purpose alone????

    Yes. Lightning arresting systems should have their own separate grounding rod. Preferably a good deal away from the electrical ground as the earth can become energized too and send some HV back through the ground system.

    The trouble with lightning protection is: you never know if it works until it doesn't. :roll:
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #19
    Re: Lightning arrestor for inverter

    in cases of where the neutral is grounded at the inverter and assuming the spd is near the inverter, i see no reason to connect a spd hot lead to the neutral/ground of the inverter as the spd is of the function of shorting to ground when presented with high enough surge voltage. just put both of the hot leads of the spd to the inverter hot lead to double up on the protection on that leg.

    as to why naws carries things it is because people ask for and buy them.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #20
    Re: Lightning arrestor for inverter
    peakbagger wrote: »
    I have a delta on the AC side of my invertter and a whole house inverter on my main panel. My inverter still got cooked when the utility managed to "dance" the high voltage line onto the 240 lines. Its on my list to upgrade to midnight solar arrestors. I do have a misnight solar on my DC side.

    in a case like this the spds may not be enough to protect you and can be worse than a nearby lightning strike as this is continuous high voltage with high amperage being fed in from the utility. the spd will go into a short circuit state and pass power at the parts ratings in the spd which would be easily exceeded and blow out the spd. lightning, as you know, we say there aren't any guarantees with and this is a short duration event when talking of lightning. the utility is simply at fault and has to make good on replacing everything that was connected to that line.

    there may be one chance of salvation in a severe case like that and that may be to take advantage of the high current that may flow through the spd so that it will pop a breaker or fuse. high voltage can still jump the gaps presented by breakers/fuses and even an spd so one will need to cross one's fingers in this case. as for the power flow of such an accident means it will have the utility ac connection, then the fuse/breaker, then the spd, and finally the inverter.
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #21
    Re: Lightning arrestor for inverter
    Cariboocoot wrote: »
    The Deltas are not a "complete scam" (and this is probably the only thing I've ever disagreed with boB on). BUT they are only for lightning protection and definitely do not have the "range" of protection the MidNite units have. I was trying to gently hint that the MidNites are better. Especially on the AC side.


    I believe that if you knew what was inside them and at what voltage they "arc" over at, you might tend to be more apt to agree with me.

    Their literature says they clamp at 250V or so, depending on the model, when in reality, they arc over at around 7,500 volts with a very small
    electrode surface area and no fusing. At high current and voltage they just break open and spill their sand out.... And way before their current rating.

    Absolutely right on about lightning arrestors (SPDs) not being 100% effective, especially with a very very close strike or direct hit.

    boB
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  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    #22
    Re: Lightning arrestor for inverter

    Strange thing was with my problem was that nothing else in the house was impacted, including an older Advanced Energy Inverter sitting right next to it.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #23
    Re: Lightning arrestor for inverter
    peakbagger wrote: »
    Strange thing was with my problem was that nothing else in the house was impacted, including an older Advanced Energy Inverter sitting right next to it.

    That is the whole problem with lightning protection: it works in the lab under controlled conditions, but lightning itself is not controlled or controllable. Complete roll of the dice. You can minimize the risk, but you cannot eliminate it.

    Delta must have fallen into unscrupulous hands as their arrestors worked fine in the old days. Silicon oxide varistor much the same as the power companies use. My uncle had them to protect his ham equipment (his house was on a hill) forty years ago. Occasionally one would fry, but he never had any damage beyond that.

    I guess I'll stick with my "hundreds of trees" system. Doesn't work for everyone, of course. :p
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #24
    Re: Lightning arrestor for inverter
    Cariboocoot wrote: »

    I guess I'll stick with my "hundreds of trees" system. Doesn't work for everyone, of course. :p

    I got a big surprise last Summer. A neighbor of mine had (past tense) baby barn, in between his triple story house and a tall hedge of spruce trees. about 50 feet between the house and trees, with the baby barn between. Lightening storm. Bog bang. Baby barn burned to the ground taking rider mower and snow blower with it. Trees and house untouched. What are the chances? It did happen, against everything I thought I knew about lightening.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #25
    Re: Lightning arrestor for inverter
    waynefromnscanada wrote: »
    I got a big surprise last Summer. A neighbor of mine had (past tense) baby barn, in between his triple story house and a tall hedge of spruce trees. about 50 feet between the house and trees, with the baby barn between. Lightening storm. Bog bang. Baby barn burned to the ground taking rider mower and snow blower with it. Trees and house untouched. What are the chances? It did happen, against everything I thought I knew about lightening.

    You need lodge pole pines at least 100 feet tall. :p

    But that's the problem with lightning; it does what it wants to do, not what it's supposed to do.
    Just like children. Same sort of resulting damage too. :p
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #26
    Re: Lightning arrestor for inverter
    Cariboocoot wrote: »
    That is the whole problem with lightning protection: it works in the lab under controlled conditions, but lightning itself is not controlled or controllable. Complete roll of the dice. You can minimize the risk, but you cannot eliminate it.

    Delta must have fallen into unscrupulous hands as their arrestors worked fine in the old days. Silicon oxide varistor much the same as the power companies use. My uncle had them to protect his ham equipment (his house was on a hill) forty years ago. Occasionally one would fry, but he never had any damage beyond that.

    I guess I'll stick with my "hundreds of trees" system. Doesn't work for everyone, of course. :p


    I like the tree method of lightning rods ! That will work.

    As for "silicon oxide varistor" being a standard method of lightning protection, that is what I thought for a long time. After googling that term,
    all of the links I could find that referenced that went back to Delta. I believe they coined that phrase. I would be very interested to see any
    links that talk about a "silicon oxide varistor" other than Delta.

    If you can find any respectable links regarding that, that would be great, but even if it is true and I just happened to miss it, Delta doesn't
    make anything that will clamp at anything under 7 thousand volts. If the Delta does prevent lightning strike faults, it's only because 7500
    volts was low enough... It's just an arc. Like I say, you might as well put two wires into a donut and space them so that they arc over
    at 7000 volts or so. Or maybe just twist a couple of wires together. It will work just as well.

    boB In John day Oregon for solwest this weekend.
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