PV Basics: Grounding and Surge Protection

[@Urge38]

Roland, I HAVE SAID THIS BEFORE, AND I WILL SAY THIS AGAIN, I dumbfounded as to why you don't dominate the Solar/off grid etc youtubers, your videos are by far the easiest to follow and you explain yourself and Solar so well. I thank you for all your time teaching us the less knowable many.

[@abednegomulwa6368]

Very well explained, good job. Thank you for the information.

[@wernergouws8609]

Thanks for your knowledge. I did not have a ac surge protector and no neutral eath bonding, my inverter got damaged. Now its fixed with the new improvements.

[@9111logic]

Thanks for the explanation which I followed with interest before I start assembling my PV system🙏 . . most people only use one surge protection box just after the strings but I can see how important it may be to be more cautious

[@JoseSantos-qx2sm]

Congratulations for the video. A question: DPS in DC protects between DC+/DC- and PE and not between DC+ and DC-. Suppose you have 450V solar string and a 550V mppt/inverter which you want to protect with fuse holder and 2 pole DPS like this video. If you install a 500V DPS, the protection between DC+ DC- will be 1000V and not 500V, therefore the DPS to be installed should be 250V to protect MPPT from surges and overvoltage. Do you agree? Thanks

[@RolandW_DIYEnergyandMore]

SPDs protect from external influences like lightning induced voltage surges on the PV power lines. External surges can only flow back to Earth, which is the opposite pole of the power source from which it was generated (lightning). The surge will be most likely equal on either of you DC+ or DC-. The SPD rating must be higher then your systems Idle Voltage otherwise current would flow from DC powerline to PE and as most solar equipment is transformer-less, then further via the AC-earthing back into the inverters DC side. That means you would have DC leakage on your AC-PE which in general is a fault condition for the inverter. SPDs are not used to take care overvoltage conditions between DC+ and DC-, as voltage control is a direct function inside the inverter itself. Example: 10 PV panels in series with a Idle voltage of 40V result in a Idle system voltage of 400V thus you need a 500V SPD. 5 PV panels in series would give you 200V so you can go with a 250V SPD. The maximum DC system voltage will depend on your used equipment. If you are using grid-tied inverters with a max input voltage of 550V then you can connect 13 panels as in this example and you will need a SPD which is rated for more than that voltage...

[@JoseSantos-qx2sm]

Thanks for excellent reply. To avoid overvoltage beween DC+ and DC- can I apply 1 pole SPD connecting DC+ (Solar) to DC+ (SPD) and DC- (Solar) to PE (SPD)?

[@RolandW_DIYEnergyandMore]

@@JoseSantos-qx2sm why would you want to do that? If a lightning is inducing a surge into you PV and it cannot release its charge to Earth, the voltage potential would rise regardless if that is DC+ or DC- as the DC is isolated from earth. So measured to Earth, both DC+ and DC- could reach thousands of Volts, but towards each other they will still have same voltage potentials as before the surge. The Mppt controller would even adjust loads to keep it that way :) The energy of the surge doesn't belong to the PV circuit, it belongs to the external circuit which is formed by the earth, clouds and lightning bolt. So any wiring must discharge the energy into earth if you don't want to create voltage potentials between power lines. If each of the poles get clamped to 600V by the SPDs, the differential voltage on the poles is Zero. Did you see someone to recommend this to do use SPDs between poles? If your system requires to earth bond for example the DC-, then you only need to put an SPD at the DC+ as DC- is connected to earth anyways...

[@JoseSantos-qx2sm]

Thanks! The idea would be a normal SPD (2 pole) and other (1pole) detailed on last message. However, I think the best idea is to use a 3 pole SPD DC, it will assure protection between DC+ and DC-, DC+ and PE, DC- and PE. Instead of a 2 pole, which do not protect between DC+ and DC-. Do you agree?

[@RolandW_DIYEnergyandMore]

@@JoseSantos-qx2sm Well, if you see a benefit in connecting DC+ and DC- then do it.

[@DanBurgaud]

From what I can see, you connected the SPD before the fuse?

[@RolandW_DIYEnergyandMore]

Hi. No, my PV plus output is first going through the fuse before it comes to the SPD and going further to a disconnect on the way to the inverter input...

[@AbuLeena]

Thanks for the valuable Information. I have a question please, how both the earthing rod of the pv modules frames and the earthing rod of main distrubtion panel MDB are interconnected? i. e. is it possible to interconnect the earthing of the 3 SPDs to one earthing rod?

[@RolandW_DIYEnergyandMore]

That depends on where your array, mount, equipment is located. If all is at one place, then you need to ground all components at the same main grounding bar which can go to one single rod. But if your array is somewhere in your garden and the rest is in the house, you need to ground the PV at the place and do not interconnect grounds as you will not be able to touch 2 different potentials during a surge.

[@AbuLeena]

@@RolandW_DIYEnergyandMore actually, it is a four-floor building(8 apartments) , the array is on the roof and the inverter is in the ground floor apartments. one only electode for the whole building

[@RolandW_DIYEnergyandMore]

@@AbuLeena yes. then ground all at the main grounding bar.

[@JustaCuriousity]

Hi Roland, can i have your advise? I have growatt SPF5000ES inverter, it has output of Grounding, Line, Neutral and Input of Grounding, Line, Neutral. When i tried to measure continuity between Output of Grounding and Neutral, it was connected, but not on the Input Grounding and Neutral while Input and Output Groundings are connected. Do you think its safe? I just think Input and Output Grounding and Neutral have to be disconnected all the time.

[@RolandW_DIYEnergyandMore]

Hi. As there is only one Earth, and PE is typically connecting all internal metal parts of an electric device, most inverters do only have one single PE terminal for input and output grounding. I don't know why the Growatt has two separate. There should never be the chance of possibly shocking yourself just because someone is touching two with different parts of a device. So, yes. Ground should be connected on input and output but power lines L/N just under certain conditions.

[@JustaCuriousity]

@@RolandW_DIYEnergyandMore thank you Roland for such great videos and reply 👍🏼

[@emad6534]

Hello Roland. My solar panels and combiner box are installed on the 3rd floor of my house, and I don't have a ground wire running from the combiner box as it is very far from the ground. My combiner box came with a surge protector installed already. Since I cannot have a ground, should I disconnect the surge protector, or can I just leave them connected?

[@RolandW_DIYEnergyandMore]

Hi Emad, just leave them inside. They cannot do anything to your system.

[@nestyplus]

Hello @Roland W, oh I forgot one more question if you dont mind... while connecting the ground wires and pv wires in the rails at the rooftop. Is it allowed to combine the ground wires and pv wire(pos, neg) inside a single conduit tube from roof going down to house panel? thanks

[@RolandW_DIYEnergyandMore]

I don't know if your country's electrical code will say something about it, but I would keep it separate until the SPDs, where then the ground wire is going to the earthing point. So basically yeah, keep them separate if you can :). That way there will be just a little inductive crosstalk on the wires.

[@nestyplus]

@@RolandW_DIYEnergyandMore , I also have reservation of running the grounding wire with the dc pv wires in one conduit because if the is a lightning voltage leakage and passes thru the ground wire which is adjacent to the pv wires I'm concern of the arcing that might penetrate in the dc wires. I guess in your setup you also separate the ground wire in a separate conduit away from the pv wires until it reaches the spd box. That is how I understand it..

[@RolandW_DIYEnergyandMore]

@@nestyplus yes, that is correct. In my set ups DC wires are entering the junction boxes with the SPDs and the PE is going straight to earthing rods underneath them by separate conduits. There are no grounding wires running next to active DC. On your AC side it doesn't matter. Run the Grounding with all the others.

[@BlazeByte21]

Is your SPD ground wire connected to ground rod of solar panel frame?

[@RolandW_DIYEnergyandMore]

Yes

[@BlazeByte21]

@@RolandW_DIYEnergyandMore What's the VDC size of your solar panel system spd?

[@RolandW_DIYEnergyandMore]

@@BlazeByte21 my system voltage is somewhere between 250 and 350V on my PV, so i am using SPDs with around 500-600V Uc. Clamping voltage should always be well over your system voltage to avoid unwanted leakage.

[@BlazeByte21]

@@RolandW_DIYEnergyandMore My 60A SCC max PV voc is around 150volts.Will still be protected by an SPD 500v uc in case of a lightning strike? Or I should use Spd 150v uc but i can't find spd below 500v uc here.

[@RolandW_DIYEnergyandMore]

@@BlazeByte21 500v is ok. Most important is to prevent the thousands of volts coming into your device. But keep the SPD as close as possible to your device which should be protected.

[@kcir3r3av3r]

can I parallel the ground wire of a dc spd and an ac spd?

[@RolandW_DIYEnergyandMore]

yes you can, as SPDs are only creating momentary connections to ground.

[@nestyplus]

Hi Roland, I hope you can read this... my question is the dc input range of my hybrid inverter is 550VDC, can I use an SPD with spec of Uc 600VDC? Also would you recommend placing a string fuse also before the SPD as my inverter can accomodate 1string for each mppt.. thanks

[@RolandW_DIYEnergyandMore]

Choose the SPD closest to the planned max string voltage, because if your inverter can take 550V but you maybe only connect panels which would reach 350V in idle, you can as well use a lower then the 550V SPD. Otherwise if you plan to max out your channel, 600V SPD is perfect. Yes, always add a string fuse to each channel at the SPD as well.

[@RolandW_DIYEnergyandMore]

Choose the SPD closest to the planned max string voltage, because if your inverter can take 550V but you maybe only connect panels which would reach 350V in idle, you can as well use a lower then the 550V SPD. Otherwise if you plan to max out your channel, 600V SPD is perfect. Yes, always add a string fuse to each channel at the SPD as well.

[@nestyplus]

Hello @@RolandW_DIYEnergyandMore , thank you for the response. My total of 8 panels 3kW for mppt1 results to 320VDC series voltage. However upon checking I can not find an SPD of lower than 550V. In the market I can only find 600V SPD and 1000V SPD... I will not max out my channel. Would 600V SPD still be fine even if my actual is 320V ?

[@dendricknonso4327]

Did you connect the dc and ac ground wire to same ground rod

[@RolandW_DIYEnergyandMore]

Hi, that depends of the place where you panels are and where the inverter is. if all is at one spot, then just use same ground. if the mount is a distance away from the other equipment, then use a rod right at the mount and ground the DC there. In my example it is a different rod for DC and AC...

[@gimiandtarascott8496]

should the ground rod for SPD in the combiner box be a different one to the main load centre ground/earth used for all the other ground/earth connections? And Can the SPD share the chassis ground rod for the panel frames? It seems in an off grid system you will have at least two ground rods. One near the panels for the panel chassis. And one for the main panel/consumer unit/load centre. I wonder does it matter If you have both AC and DC flowing into the same ground rod, especially when the since neutral is bonded to the ground. In certain scenarios it feels like you could potentially have both AC and DC returning to the neutral of the inverter output. Thanks for your knowledge. You explain things very clearly and simply

[@RolandW_DIYEnergyandMore]

hi. if you olar array is away from other elements of you system (more then 5m), use a separate rod right at the array. if all is just at the same place, dont bother with 2 rods. SPDs only let high voltage surges through, so they dont care about AC or DC.

[@RolandW_DIYEnergyandMore]

current can only flow from source to source. in the event of a lightning, the source is ground. only a voltage surge can reach the inverter, but that surge will happen in either part of the electric system, as it is build up by induction. most important is to use a rod with a large surface to get the energy into the ground quickly. so please dont use a tiny rod

[@ntechsolutions1071]

Sir,are ground wires from spd and panels connected to the same ground rod?

[@RolandW_DIYEnergyandMore]

yes. a surge at the panel array will always originate from a lightning, so it needs to go directly to a ground source there.

[@ntechsolutions1071]

@@RolandW_DIYEnergyandMore so, you didn't connected both wires(from spd and panels) to a busbar and from that busbar one wire goes to ground rod or you directly connected both wires to a ground rod, combined, twisted?

[@RolandW_DIYEnergyandMore]

@@ntechsolutions1071 in my case i went on separate wires straight to the rod.

[@ntechsolutions1071]

@@RolandW_DIYEnergyandMore did you twisted both wires before you connected it?

[@RolandW_DIYEnergyandMore]

@@ntechsolutions1071 no. just squeezed into the rod connector by its screw, but you can twist it, don't see a problem with that

[@sabilza]

Can I connect the SPD ground to the pole that used for lightning rod?

[@RolandW_DIYEnergyandMore]

Yes, you can. The shorter the way to ground, the better.

[@tanishqbhaiji103]

Absolutely not, if you do that everytime the Lightning rod gets a strike it will raise earth voltage on the conductor will trigger the SPD and cause lightning current to flow to your inverter and panels, please use a seperate earth pit and earth conductor for the lightning rod.

[@lhffan]

Hi there.... how many panels in kwh and number... on your carport?

[@RolandW_DIYEnergyandMore]

Hi. 58 panels, 19 kWp

[@chris2011ireland]

What are the yellow connectors on your pv cables going into the spds?

[@RolandW_DIYEnergyandMore]

Hi, those are crimp lugs to hold the stranded wire together...

[@chris2011ireland]

@@RolandW_DIYEnergyandMore could you link some for me please as only ones I can find are for battery connectors. Many thanks Roland

[@RolandW_DIYEnergyandMore]

@@chris2011ireland this kind of ferrules: a.aliexpress.com/_mtk62oE Or this type works too (only use male part): a.aliexpress.com/_mN2BdiE ...random examples. Use you favourite suplier!

[@plattenstrom4916]

Won't multiple grounding rods (even with RCDs?) be converting to shortcuts for the lightning path through sensitive equipment?

[@RolandW_DIYEnergyandMore]

Lightning always want's to take the shortest path to earth. The only thing to consider when there are more rods installed, is that other rods would pick up voltages which are building up in the ground before they disapead at the activated rod from lightning. Thats why it is important to keep a minimum distance of 5m between rods.

[@gigel99324]

@@RolandW_DIYEnergyandMore distance between rods should be twice their height here. So 5m if they are 2.5m tall

[@Michael-he2pw]

Does this also apply if all the ground rods are connected together?

[@gigel99324]

@@Michael-he2pw are you asking me?

[@Michael-he2pw]

@@gigel99324 I'm asking anyone that may know , currently we have a large offgrid system with multiple batteries and inverters. We have earthed the solar panels , solar array stand , inverters, distribution panels , house panels all on the same bonded earth . We probably have about 10 earth rods in total spread over a area of about 30m radius

[@MrIonutz2008]

Will it be a problem if i put 1000v spd instead of 500v ? Thank you

[@RolandW_DIYEnergyandMore]

it is of course better to be closer to system voltage. but high voltage SPD will still protect as lightning surge is far higher then 1000V.

[@nicholas3913]

Could connect multiple panel strings to a single SPD?

[@RolandW_DIYEnergyandMore]

Yes, you can put a SPD after combining parallel strings. It should be just one SPD for each MPPT channel

[@dougiee6589]

i learnt sumfing tjank you

[@simonazulay4781]

Hello..I wouldn't put DC source and AC source in same fuse box..

[@sreejeshpvofficial]

just want to know what is the thickness of the earth wire from spd to ground rod

[@RolandW_DIYEnergyandMore]

Typically, by code, such main earthing connections are done with 10mm2 Copper wires. If you don't have that by hand but you have a 6mm2, use that one. It will do well enough if the wire is not too long...

[@sreejeshpvofficial]

@@RolandW_DIYEnergyandMore thanks for your quick & valuable reply.

[@sreejeshpvofficial]

@@RolandW_DIYEnergyandMore can I use the same 6mm2 dc cable for the same ?

[@RolandW_DIYEnergyandMore]

@@sreejeshpvofficial yes, if your PV wire is 6mm2, then you can use the same for grounding too, but not smaller...

[@sreejeshpvofficial]

@@RolandW_DIYEnergyandMore sure .. i will use 10mm2 dc cable for the same ..Thanks for your advise

[@itsmattmp]

Why do you need a surge protector if you have a circuit breaker?

[@RolandW_DIYEnergyandMore]

Circuit breakers do not constrain voltage spikes. They are designed to protect against current anomalies and are much to slow to trip. A circuit breaker might eventually trip at a lightning hit, but then parts of your inverter will already be burned trough...

[@lozanibrahim6109]

nice video , appreciated could you please share the electrical wiring diagram thanks in advance

[@kafilkafish2152]

Could I use the structural Column as an earth instead of the rod?.

[@russdlhmedia1993]

No because then the structure will be live

[@SylwerDragon]

Nice video. I will be honest here all what you are talking is good for charge on panels..for this grounding is very important. to ground panels/construction is good idea and should be used in metal constructions. But if you are unlucky and lighting will strike that construction you can be sure of one thing.. you can throw away probably all your panels. you can change all your cables , your inverter, your charger and probably all appliances in your house. Reason is it doesn't matter how good your system is protected all electronic will be dead. That is why I and you as well pray that it will never strike. Check what happen when lighting will strike directly house...all cables in wall are black and it doesn't matter if you had lighting rod or not..lighting will melt any cable.It is scary truth

[@klaviantsigetur3027]

Those protections are for indirect near lightning hits. Any direct hit is, as you wrote, a disaster. Unless your cabling is like 2 inches thick, your grounding is like on Wardenclyffe Tower, and your house is in a complete Faraday cage.

[@mudislander864]

I might sound stupid here, my aray will put out 400 volts dc, with no isolated switch between panel output and surge protection don't you run the risk of getting socked. Thats alot of volt

[@RolandW_DIYEnergyandMore]

Hi. I don't understand where you want to get shocked. At with place can you touch the 400V? Or you want to install a surge protector to a existing system? If yes, then you need to open one of the MC4 connectors which is connecting the panel once it gets dark. Turn off the DC switch on your inverter if it has one. Then you cannot have a closed circuit and current flowing.