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Topic: Lightning protection (Read 1070 times) previous topic - next topic

Lightning protection

We have been having thunderstorms around here for the last few days.
I'm installing solar panels on the roof and have a significant amount of metal, mostly aluminum up there now. I have concerns about lightning strikes.
Should I be nervous?
What would be a good way to install lightning protection?

Re: Lightning protection

Reply #2 –
What Roger said. We are in 'the monsoon belt' up in northern Arizona, and get lightning every few days. Noisy and sometimes scary, but never have heard of a dangerous 'hit'. One thing: I keep a very close eye on the weather, if it looks like a barnburner, I'll unplug from the pedestal. We also have a Progressive EMS that keeps me happy, just in case.  ^.^d

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Re: Lightning protection

Reply #3 –
Park near, but not under, something tall. A good choice would be a new Winnebago that towers over your coach by two feet. <grin>

Seriously, you want to make sure that each panel is properly grounded. Don't be the tallest object in the area. Unplugging the coach (both ends of the cord) well before the lightning appears and running on the generator or batteries may help.

Re: Lightning protection

Reply #4 –
Don't forget to unhook the coax cable from your portable dish receiver to the coach. Lighting can travel through the ground to the coax and into the coach.
We lost everything that had a HDMI cable and a few other things during a lighting storm in the Florida Keys storm a few years ago.

A large SOB 3 spots away took the direct hit. Lost all electronics, slides wouldn't work and had to be towed out of the park.

Re: Lightning protection

Reply #5 –
Quote from: kb0zke –
Park near, but not under, something tall. A good choice would be a new Winnebago that towers over your coach by two feet. <grin>

Seriously, you want to make sure that each panel is properly grounded. Don't be the tallest object in the area. Unplugging the coach (both ends of the cord) well before the lightning appears and running on the generator or batteries may help.

What would be a good method to ground the panels?

Re: Lightning protection

Reply #6 –
They should be electrically bonded to the chassis. IF there is a steel framework in the roof AND IF the panels are mounted to that AND IF that framework is electrically attached to the chassis then you are good. I believe, but do not know for sure, that Foretravels do have the steel framework attached to the chassis, and the framework covers the entire coach. If that is true, and I think it is, then if your panels are attached to that rooftop steel, then you are good.

I would think that attaching the panels to the steel frame would also make for a stronger attachment. I can imagine what sort of excitement and damage could be caused by a solar panel that comes loose at 65 mph.

Re: Lightning protection

Reply #7 –
The panel support structure is glued down. It would be easy to run a screw into a roof metal structure if that would solve the problem.
I could also run a ground wire from the panels along with the panel wiring and ground to the chassis, IF that is really needed or if Roger suggests its not needed.

Re: Lightning protection

Reply #8 –
Would the leveling jacks act as a ground?

Re: Lightning protection

Reply #9 –
Very little you can do if a DIRECT lightening strike.

But, the chances of a "nearby" strike are many, many times that of a direct hit.  Think of your surface area vs that of a one mile circle.

But, disconnecting from shore power will prevent NEARBY lightening strikes from causing a voltage spike that comes in via your shore power cord.

Re: Lightning protection

Reply #10 –
I agree. The unplugged coach is a Faraday cage, all metal framework, the safest place to be.

Re: Lightning protection

Reply #13 –
Yup, not much you can do if hit with a direct strike.  It will "let the smoke out" of most electronics.  Time to call the insurance company.

Re: Lightning protection

Reply #14 –
Quote from: Lon and Cheryl –
..............I'm installing solar panels on the roof and have a significant amount of metal, mostly aluminum up there now. I have concerns about lightning strikes.
Should I be nervous?
What would be a good way to install lightning protection?
OK Lon,

A few comments on the advice given thus far:

    • Lightning is a huge, elevated potential, a collection of electrons that is discharging through a path of least resistance to ground.
    • What is the perfect lightning protection?  It is a very tall, highly conductive spire, extending from the clouds, on the one end (where that huge collection of electrons; i.e. - bundle of energy is), to the other end of the spire, which is buried well into moist earth.
    • That spire has a "cone of protection" surrounding it, where , if you stand a good (air insulation) distance apart from the metal spire, any electrons that are discharging down through the spire to earth are not going to jump off of the metal spire, through some very high resistance air and then through you (you have some finite resistance too, but certainly much higher resistance than the metal), to get to ground.
    • Standing under a tall tree is not a good substitute for a metal spire. If a tree is tall, it is much more attractive, as a conductor, than air but it will have more resistance than you do and thus, when it gets to you, the lightning will readily jump off of a tree and go through you to ground.
    • Vehicles offer decent lightning protection, but there are some caveats:
    [/list]
      • As already stated, metal vehicles are like Faraday cages, meaning that the extremely high voltage of a lightning bolt (10's if not 100's of thousands of volts) contains electrons that are all powerfully repelled from one another. The electrons are so strongly repelled from one another that they conduct only through the extremities of the "skin" of a metal vehicle, eventually jumping off at the shortest air gap they can find, through air to get to earth ground (or through or across the surface of a rubber tire).  Jacks on earth ground would eliminate the need to jump any air gap at all.
      • So rubber tires insulating a vehicle from the ground is largely a myth — remember — lightning has traveled hundreds or even thousands of feet through air to get to your vehicle, so a few inches of distance through or across rubber represents a minuscule resistance when compared to the same distance through air.
      • Vehicles that have all fiberglass bodies, like a Corvette, afford little protection because the fiberglass has a much higher resistance, as a conductor, than your body does, so lightning will prefer going through you rather than through the fiberglass.
      • But you don't have to worry too much, because our coaches, with some caveats, are pretty good lightning protection, for people (not for equipment).  If the lightning bolt's energy can find a path to the metal frame up on the roof, the coach is still a rudimentary Faraday cage (the welded metal superstructure and mono-coupe subfloor frame)  that will conduct the electrons to within a few inches of ground.  And that gap is a relatively low resistance gap to jump as opposed to the 12 feet of air gap from the top of the coach to the ground.  There are plenty of ways for the lightning energy to find its way from outside the coach to the frame, through antennas, AC's, satellite gear, metal trim, solar panels, etc.
      • Think of it this way;  Anything with a wire on or in it is powered and the negative lead for all DC power is grounded to the frame eventually, somewhere.  All AC power is bonded to a ground rod through both the neutral and ground conductors somewhere at the entrance panel, whenever the coach is plugged into shore power.  So if a coach is struck by lightning, the Faraday cage (frame of the coach) is full of electrons, all strongly repelled by one another, until they jump a gap somewhere to earth ground.  When you and I are inside a Faraday cage, all we have to do is focus on not being that gap that represents the least electrical resistance path to ground:  i.e. - stay away from and don't touch anything metal, stay away from anything wet, don't try to get in or out of the Faraday cage (putting your foot on the ground while still touching the cage) during a thunder storm, etc.
      • But your question was whether to be worried about (and how to improve) lightning protection after adding solar panels.  Yes.  There are a number of things that you should do, but not just because you have added solar panels:
      • The very first thing to do is to unplug from shorepower and store the power cord inside the coach.  The neutral and ground wires are bonded to a ground rod at the power source's entrance panel.  Those wires make highly attractive lightning rods out of all of your AC powered equipment in the coach!  The bonding to a ground rod may be a short or a long distance away physically, but resistance wise, in Ohms, it is miniscule in comparison to the resistance of an air gap (think crows on 115,000 or 345,000 Vac transmission lines).  The crow is perfectly safe landing there, but if he dangles a bare copper wire from his beak to the ground, he gets evaporated!
      • The second thing to do is to disconnect and stow ALL other exterior cables you have connected to the coach (e.g.- satellite dishes on the ground, landline telephone, landline cable, etc.).
      • The third thing to do is to always use an EMS (or a far lesser choice, a surge protector) on your incoming shore power, either at the shorepower utility post breaker or at the shorepower/generator automatic bus transfer (ABT) switch.  The surge protection in these devices will interrupt lightning induced surges (essentially instantaneous, at 300 to 600 Volts, increasing, in either direction) in the hot or neutral or ground (or any combination thereof) paths.
      • The fourth thing to do is to shutdown and pull the power plug on any sensitive electronic equipment that you want to provide the highest protection for.  Why do that?  Well, as already stated, lightning strikes cause surges that can be in the thousands of volts, even within the nearby ground plane at ground zero of a lightning strike.  Those surges are more likely to be felt on neutral and ground wires than on hot wires that are breaker protected, slow, current, protection paths. Thus, a breaker or wall switch being open does not help you at all.  Remember that story about the coach that got hit by lightning, several spaces away from yours and it wiped out all of your non-surge protected appliances, electronics, HDMI and coax connected equipment because you just opened the shorepower breaker?  Well that coach affected you because the lightning surge had free access to your AC powered devices through the neutral and ground wires, which are not opened by the shorepower breaker, so power down and unplug your sensitive equipment.
      • The alternative to that is to invest in individual surge protectors or uninterruptible power supplies (UPS) with surge protection for valuable electronics.  That's what we use for our computers, tv's and hi-fi equipment.
      • As already discussed, the negative lead of your solar panel is already tied to the frame of the coach, through the controller I assume, so it is already as safe as it is going to get.  Tie the panel down with screws to the frame for mechanical reasons but it is not necessary from an electrical standpoint.

    OK,, sorry for the length, but I felt the need to comment on some of the advice given thus far.
    HTH,
    Neal

    Re: Lightning protection

    Reply #15 –
    Hi Lon,

    The Foretravel roof structures (all that I know of anyway) are aluminum not steel.

    Each of my panels is held in place with 72 sq in of VHB tape at 91 psi tensile strength.  6552 lbs per panel.  many installations used much smaller mounts.

    I did some follow up on this.  What I have been told by more than one solar panel installer that on RVs there is no ground wire to the frames of the panels.

    The installation instructions for the ReneSola Panels (yours and mine) says...
    13、 Grounding
    1) PID (Potential Induced Degradation) due to combined effects of high temperature,
    high humidity and high voltage, is most likely to be observed in similar climates and mounting surroundings such as India, Southeast Asia, floating designs. Except for equipment grounding, negative system grounding is strongly recommended as the basic solution for PID phenomenon.
    2) Grounding method shall be consistent with the local standard and regulations. Any grounding system/method, which is designed in accordance with relevant international and local standards and regulations, such as UL2703, UL467, IEC60335, NEC article 250 and section 690.V.43, etc. could be attached to the Modules.
    3) In order to prevent electrochemical corrosion, materials in contact with module frames, should be properly selected and galvanic isolation provided where necessary.
    4) Grounding wire shall be the bare copper wire with simple surface treatment and no insulation sleeve. Wire cable with cross-sectional area of 4~6 mm2 (10~12 AWG) and ground clamp (such as Tyco, identification of product: 1954381-2)are recommended.

    On an RV this is not done.  AM Solar told me this morning that they do not ground the RV solar panel frames. 

    If you are determined to do this it is kind of hard to say what to do.  So if you run a 10 ga copper wire from each panel down through the refrigerator bay and into the basement what are you going to hook it to?  And even if to the coach frame then what?  Are you going to run some big grounding strap from somewhere near the engine and pound in a 4 ft grounding rod into the ground and flood the area around the rod with water? 

    Your coach is not attached to any ground especially if it is not plugged in to anything.  If you have a Travl'r Satellite Dish there is no ground wire and that sticks up higher than (most) solar panels.  If grounding the solar panel frames is something you want to do the a screw through the mount into the aluminum roof structure will be insufficient.  My solar panel frames are not grounded with a separate ground wire. I wouldn't know what to connect the to. 

    The plus power cables from each panel are fused. There is a switch between the fuse panel and the solar charge controller and the output from the solar charge controller is also fused.  All of the ground sides are connected to the batteries and to the coach frame as is the solar controller itself.

    I hope that helps. 

    Roger

    Re: Lightning protection

    Reply #16 –
    Good job guys.  ^.^d

    Re: Lightning protection

    Reply #17 –
    Many thanks for the GREAT advice and education on this subject, that was the main point of my post.
    I now see no reason to try and do any preventive work, there is nothing I can really do as far as grounding the panels, they are good to go.
    I will add the EMS system and install surge protection on many outlets. I will also follow the advice and disconsolate from any outside sources.
    THANKS!!!!!!!

    Re: Lightning protection

    Reply #18 –
    EMS's are worth .001% for lightening.

    Again, DISCONNECT FROM SHORE POWER.