Wiring Your Solar Power System

Shop Solar Panel Wiring at altE: www.altestore.com/store/Cable...
This video will show you how to calculate the NEC compliant wire sizes for a photovoltaic (solar electric) system. We will include many of the de-rating calculations for temperature, conduit fill, distance off the roof, and others. These calculations are for both off-grid and grid tie solar system.

[@LoganCartwright]

Wow, absolutely clean and concise. Thank you!!

[@Edgardocelectric007]

I've been a electrician for 30plus years amazing how much you forget thanks for the refresher course

[@HappyfoxBiz]

glad to see Humble electricians are still around :)

[@aneesurrahman1086]

Edgar Acosta can we chat on whatsapp i am learning wiring diagram for grid tie solar so i really need your help please

[@williamjamesenkerwitz9495]

Thank you for showling im from South Africa

[@Rxtxb52gee]

00:22 ----- Objectives. 00:40 ----- Wire Types. 02:45 ----- Types and Use in PV. 03:49 ----- Extension Cables. 04:44 -----Wire Size.

[@iamfound74]

Hello Amy; as always great info and vids. Does the NEC have any guidelines on calculations for temperature conduit fill that is buried or grooved into concrete buildings and distanced off the roof? I'm installing in Mexico btw. Thanks and bests...

[@amyrbeaudet]

I used this voltage drop calculator in the video. www.rapidtables.com/calc/wire/voltage-drop-calculator.htm

[@nicolas230811]

Thanks, it was very useful

[@AltEStore]

@carultch Thanks for your great answers!

[@carultch]

10:06 - I've had trouble with this rule. See 110.14(C) in more detail. Derate factors apply to the wire rating, and not to the terminals. This is usually the advantage of 90C rated wire. Even though you can't take credit for its full ampacity at terminations, along the length of the wire it gives flexibility to adjust for conditions of use.

[@passedhighschoolphysics6010]

Well done.

[@bill767667]

thanks

[@rjas9192]

thank you so much for you help. can u do this also in an on grid system?

[@AltEStore]

This applies to both off and on grid. You can just skip some of the middle steps for grid-tie. For on grid, the PV Source Circuit is between the solar panels and the grid-tie inverter if you are not combining them on the roof. If you are using a combiner box, the PV Output Circuit is from the combiner box to the grid-tie inverter. Then you just need to jump forward to 18:18 to figure out the size of the Inverter Output Wires.

[@jamest.5001]

I have 16amps or less on 10 gauge, 100' or less, and doubled 2/0 , 5' with less than 250amps, welder cable, with fuses, breakers, and disconnects on everything! It's off grid, but I don't need it burning down either! 33kwh battery bank, I'm getting a larger inverter, and possibly going to 48v, from 24v being I only need to series my batteries, 7 series lithium now, so full would be just shy of 60v, but I stay under 28.8v. I have forced cooling from my basement, it's about 60°F mid summer, basically what I do is double what the wire is rated at, or half it, what ever! About 15.5 amps on 10 gauge upto 100' I'd rather have 8 gauge but it is only for about 4 hours a day, the panels are shaded, just under 1100w per 10 gauge run, in burried 1" conduit, with 4 strings, the rest is less than 25' with 600 watts, 42vmp, what ever that comes to, on 10 gauge use2. It may not be code, but its not going to burn my house down! (Knock on wood) great info,

[@bill767667]

that sounds great thanks for your help as soon as I can afford it I think I'll order an eight cubic foot refrigerator and have them install the ice cream thermostat at the factory that sounds really good that way I could use the refrigerator if I need a refrigerator or I can use the freezer if I need a freezer, do they have a very long service life Sundanzer??

[@AltEStore]

+bill767667 I'm not sure if it is possible to use the ice cream thermostat on their fridge. It is available with their freezer.

[@solareningenierias.a.s9592]

Very good explanation but I dont understand (18) in Breaker accepts18- 6AWG.

[@carultch]

"The National Electrical Code establishes that if a conduit only contains 1 wire, the max fill percentage is 53%. If it contains 2 wires, the max fill percentage is 31%. And if it contains 3 or more wires, the max fill percentage is 40%." In general, it represents about 75% of the interior diameter of the conduit being filled. Good for an exam, but in practice this can be a lot tighter than you really want to go. Good for local pulls, but not when there is a lot of distance and bends. A practical approach when anticipating a difficult pull, is to start with largest size and total quantity, then add space for a hypothetical additional wire of the same size. Example: 3 #4 + 1 #8. Assume they are all #4, and size conduit for 5 #4, which would be 1 1/4" conduit.

[@ativaa4177]

Why did you "divided" 14.2 by 0.88 to get temperature correction. In the previous slide it was "multiplied". I believe ampacity should decreases.

[@markivanarididon862]

Hello there AltE. Would it work if i use PWM with a Series connection of pv arrays? What would be the possible outcome?

[@AltEStore]

Wiring in series increases voltage. A PWM charge controller needs the same voltage from the solar array as the battery bank. An MPPT charge controller can handle a higher voltage.

[@JoseGarcia-px9xj]

Looks, your ground connection is on the main electrical rod.l am not sure how far away your panels are from the charge control mines are about 110 foot. Do you think I need another electrical rod near the panels

[@AltEStore]

Yes. With the grounds so far apart, another grounding rod near the panel array is a good idea.

[@carultch]

18:17 - Should neutral count as a current-carrying conductor for PV inverters?

[@AltEStore]

carultch No, in normal configurations, the neutral is not current carrying. There are some exceptions for unusual cases, but in most instances, it is not.

[@thefaeryman]

you calculated 2/0 wire from batteries to inverter, what about battery to battery can that be smaller or the same being it not in conduit just open air?

[@AltEStore]

Rev John O'Toole You want to make sure that you use the same size cable for each of the interconnects to ensure the same resistance between batteries. But yes, you are right, if the interconnect cables are in free air, which is likely, you could calculate that wire size separately.

[@woodrobot8]

I like the way she says "aimps".

[@equanimousawareness]

Why not drill holes in the conduit to allow heat escape?

[@bill767667]

I just used a cheap Harbor Freight meter thing to check the wires on my four 100 watt each 12 volt solar panels and I got about 14.5 14.6 volts does that sound good or bad???

[@AltEStore]

+bill767667 It depends where in the system you were measuring, and if the wires were connected to the charge controller or not. If it is just the wires from the panels, not connected to anything but the meter, you should be reading 16 - 17V. If it is connected to the charge controller, that sounds about right.

[@bill767667]

My batteries are topped off and I think there at like 14 point something volts and my apps were I think 15 or 16 amps,,,, the last I checked them they were 12.4 and then I checked them again the Sun is moving across the sky I checked them a little bit ago and they were like 11.9 amps thats the Morning Star showing

[@joshsinykin5230]

I think you have a units problem on slide at time 13:40, you used F, but your tables are in C

[@GeorgeGardinier]

thanks for your answers this explains a lot so go bigger if you can ha ha thanks so very much

[@AltEStore]

+George Gardinier Go big or go home!

[@skyorc]

Thank you. My brain are hurts now!

[@AltEStore]

Mine hurt making this video.

[@vijay35215]

Hi. I have 2 solar panels of 150 watt each (8.5 + 8.5 ampere). Distance between solar panels and charge controller is 8 metres. The AWG table suggests 16 mm square cable. But in market there are only 4 mm square and 6 mm square cables. Is it possible to make 16 mm square cable by joining two 6 mm and one 4 mm (6+6+4 = 16 mm square)? ..................(12 v system)

[@AltEStore]

It is common to double up the wire to handle the current. I think it would be better to oversize the wire and use three of the 6mm, rather than including a 4mm. However, I'm not sure how code compliant that is. Are there any electricians out here who can help with the answer?

[@junbaclay3871]

Hi Kumar, since your system is already 300 Wp (total), another option is to increase the system voltage, from 12V to 24V dc.. this would reduce the required wire size from PV array to charge controller. For 12 V system, voltage drop is critical, which means you would need bigger cable to reduce voltage drop. For 12 V system, allowable voltage drop between PV and charge controller is 0.5V. If voltage drop is high, the output current of PV is reduced due to the PV's IV curve characteristic

[@jamest.5001]

Just imagine, someone sometime had to do all the testing to figure all this out! And in 1890's they used copper bar covered in wood and wrapped in tar soaked rope! Running DC about a mile! That don't fly anymore? Ha-ha...

[@JoseGarcia-px9xj]

should I connect both rods with a cable

[@AltEStore]

Some people do. I recommend reading this article by John Wiles. He talks a lot about grounding. africanenergy.com/new/wp-content/uploads/2012/08/grounding-the-south-forty.pdf

[@aneesurrahman1086]

i dot not understand why when using tables 310.15b2a and 310.15b3a why you divide factors i think you should multiply that .

[@kybishop]

***** hey Amy, I was wondering why you didn't calculate voltage drop from each array to combiner box

[@kybishop]

Also, why put the PV output circuit into conduit? Could one avoid the ambient-temp increase from table 310.15(B)(3)(c) if simply using bare wire?

[@carultch]

Kyle Bishop You have to have some kind of a structure, to mechanically support it and protect it from physical damage. Conduit is usually the practical solution. "Bare wire" means non-insulated wire, which shouldn't be used for current-carrying. Good for an equipment ground, not good for power. Open air wiring methods can still be subject to the air temp increase, when in close proximity to the roof in direct sunlight. I haven't found an official NEC calculation for it, but intuitively, I wouldn't ignore the temperature adder just because you hang the wire on your racking system instead of run it in a conduit. Open air wiring methods also require more robust insulation. Such as USE-2 instead of THWN-2.

[@carultch]

Probably because it is the same calculation strategy for the source circuit wiring, as it is for the DC feeder, so she only needed to show one calculation to demonstrate the concept. It certainly is correct that both voltage drops matter, and do add up.

[@kybishop]

carultch Thanks! Misnomer on my part when saying "bare wire", really just mean insulated wire out of conduit.

[@kybishop]

I noticed you continue using the 75 degree column (for max amperage) from charge controller to batteries, batteries to inverter, and inverter to AC socket. Am I right to assume you're no longer using a breaker at that point? If so, why not use the 90 degree column? Are charge controllers, inverters, or batteries ever rated to a maximum temperature?

[@AltEStore]

+Kyle Bishop Remember that the 75 degree column is Celsius, not Fahrenheit. It's 167F. If my charge controller and inverter are exposed to higher than 167F in my basement, I have got some other problems going on ; ).

[@kybishop]

+altE Store Hah, indeed. I just realized you're using the 75 degree column because of the wire type selected. So unless the charge controller, battery, inverter, or AC output has a temperature rating associated with it, you could use the 90 degree column if using one of the wires listed for that column. (please do correct me if I'm wrong about that!)

[@AltEStore]

+Kyle Bishop Bingo. Good old NEC Table 310.15(B)(16). Allowable ampacity of copper conductors. The type of wire used has the temperature associated with it. Nothing else was pushing me into a different column.

[@thefaeryman]

this is calculated for 3500 watt/24 volt inverter, what if I plan to add at a later date another of same inverter in a tandem, would the cable size still be the 2/0 cable?

[@AltEStore]

+Rev John O'Toole That can be a tricky one. Since the current from the the DC Load Center to the second inverter would be 175A, 2/0 cable can be added to wire the inverter in. But the wire from the battery bank and the battery interconnect cables would need to be looked at. You've increased the wattage pull from the battery from 3500W to 7000W, so it's now 350A. When we divide the 350A by 1.05 because of the cool temperature, we need cable that can handle 333A. Per NEC 310.15(B)(16), 2/0 cable is only rated for 175A, and 4/0 is only good for 230A. So you'd need to either get even bigger wire, or more likely, add a second set of 2/0 cable to increase the current capability.

[@AltEStore]

If you were designing the system from scratch, and planning on eventually going up to 7000W, you should consider starting out with a 48V system instead of 24V to keep the current down.

[@thefaeryman]

+altE Store originally I built with 4 awg for smaller inverter and not fully understanding the math. so going with the 2/0 would cover me for upgrades in future. right now I just wish to get through some power outages with my aimes 3000 w/24v on 4 t-105 re's. but replacing those 4 cables with 2/o cables, would be a good idea. interesting that aimes shipped 1/0 with the inverter a few years ago. best

[@AltEStore]

+Rev John O;Toole I had to leave out some wire sizes in the 310.15(B)(16) table to fit onto the page. 1/0 can handle 150A. 3000W / 20V = 150A

[@thefaeryman]

+altE Store actually I was using a different source for same table. the price difference is close and you don't have 1/0 cables. I'm good at making my own cables but a bit cold for it. I'm putting in an order now. thanks

[@premkumar-nz5uq]

need a 10-hour battery backpack, how much is a solar plant

[@AltEStore]

I assume you mean 10 amp hour (Ah) battery. If you use half of it, that means you have to put 5Ah back in. If it is in good sunlight all day, a 10W solar panel might be able to do it. But if it is on the backback as you are hiking, a bigger panel would be needed to make up for less than perfect conditions.

[@solareningenierias.a.s9592]

Ati Vaa and mi question? Why did you "divided" 14.2 by 0.88 to get temperature correction. In the previous slide it was "multiplied". I believe ampacity should decreases. Ambiental temp increase, Current decrease in wiring

[@AltEStore]

When you divide by a decimal point, like 0.88, the number increases. So 14.2A becomes 16.13A.

[@epedrego]

You multiply when determining the wire capacity, but divide when you are working with the current. Is that right altE?

[@epedrego]

I thought more about this. Why would you derate the wire by 0.88 to find the proper wire that can handle 14.2A? Instead of "uprating" the current to find the wire. I can see how either way works, but they are not exactly the same. For example in the PV Output Wire section, you are working with a current of 35.5A. To find the correct 75deg wire you uprate the current by 0.58 (35.5 / .58 = 61.2A) and select the 6AWG wire. I would think you would approach from the other end, which is to find the wire gauge and derate to a value higher than your working current of 35.5A, so 65*.58 = 37.7A which is greater than 35.5A. This still requires that you use the 6AWG wire, but the calculations are a little different. Any thoughts?

[@epedrego]

Great video by the way!!

[@bill767667]

I have 4, 6 volt 188 amp hour golf cart batteries old school flooded lead acid I've got them all wired up to essentially make one big 12 volt battery and series and parallel,,, I also have a Honda eu2000i inverter generator and a knock off of the Honda manufactured by champion by the way the kids actually really good for the however what I want to know it's an overcast day is any snow eccentric I'm going to need to charge my Bank, what type of battery charger do I need to use for this so I don't destroy my batteries so I can charge all four of the batteries all at once what type of charger would you use for that, and if you know of a good one for that do you sell it??? also Amy are you from New Hampshire by any chance? I live in Ohio now but years ago I lived in Franklin New Hampshire ,we had some beautiful girls up there that looked just like you ,I was kinda of wondering if you mighta been related to email.

[@jmdelapp]

3:02 Says THW is "dry locations only". That is wrong. See NEC table 310.104(A)

[@HillCumorah1]

13:25 - your ppt shows the temp calcs in F. Really I think you meant Celsius.

[@AltEStore]

+Gloria Riker Nice catch! Thanks, we'll fix that. Because of our international audience, I try to use both C and F, and occasionally get them mixed up.

[@akramal-khazzar5450]

at 13:27 ambient was 38 degrees while at 14:19 it became 36??

[@AltEStore]

Good catch. I think I had changed the temperature when I was writing it, and missed correcting it on that page. Fortunately, 38C + 22C= 60C, still keeping it in the correct temperature range. Thanks for the correction.

[@AkramAlKhazzar89]

please I will need these slides as a pdf can you provide'em

[@AltEStore]

Sorry, we are not able to do that.

[@refusoagaino6824]

You can use Window's Prnt Scrn function, paste the image into MS Paint or any image editing software, and pick out what you need and save it as a *.jpg, png or some other picture formats. Not a PDF (yet) but the info you want in printable form. I grabbed a straight line diagram of a system that's almost the same as mine, saving me a whole lot of trouble on the permit application, from another video. Is that copyright infringement? If it is, people have been infringing mine all my life so it doesn't bother me. Publish something to the Internet, and you lose all ownership rights in a practical sense, not just a legal sense.

[@bill767667]

well that last post didn't make 100% sense I'm using the microphone feature on my cell phone and it likes to write words that you're not actually speaking ,,,well,,, that pretty part about Amy was right,,, what I was trying to ask is on overcast days can I use my generator with a really good quality battery charger to charge up my battery bank ?and if so which charger do I need,and do you sell it?

[@AltEStore]

+bill767667 You can get a quality AC charger like the IOTA DLS. Probably the 30A or 45A model. Ideally, you don't want to charge a flooded battery bank faster than 10% of its capacity. For your battery bank, you have 188Ah x 2 strings in parallel, which equals 376Ah. 10% of that is 37 amps. You can see details of the Iota chargers here. www.altestore.com/store/Charge-Controllers/AC-Battery-Chargers/IOTA-Engineering-DLS-30-30A-12V-AC-ConverterCharger/p696/ You should also get the optional IQ add-on, that converts the charger into a 3-stage charger for even better battery life. www.altestore.com/store/Charge-Controllers/AC-Battery-Chargers/Accessories-for-the-AC-Chargers/IOTA-IQ4-Smart-Controller-for-DLS-Series/p703/

[@akramal-khazzar5450]

at 16:41 it is table 310.15-B-2-a not -16???

[@AltEStore]

That table used to be 310.16 in older versions of NEC, I don't remember which year. I don't have 2011 on me, but I know it is 310.15 in both 2014 and 2017.

[@bill767667]

which Morningstar MPPT charge controller will allow me to increase my 12 volt solar set up to 600 Watts safely ,,,,I have 4 100 watt each Renorgy mono crystalline solar panels now eventually I would like to add 2 more 100 watt each panels for an A total 600 watt set up,,, I am currently using a Morningstar Prostar PS 30 m charge controller and it works really good

[@AltEStore]

+bill767667 The Morningstar TS-MPPT-45 can handle an input up to 600W. www.altestore.com/store/Charge-Controllers/Solar-Charge-Controllers/MPPT-Solar-Charge-Controllers/Morningstar-MPPT-Solar-Controllers/Morningstar-Tristar-TS-MPPT-45-45A-MPPT-Charge-Controller/p7727/

[@bill767667]

Thank you

[@bigfatpear]

as clear as mud.

[@AltEStore]

This was a tough one to make as it requires a lot of calculations and code references. It is definitely the most technical video we've made. Some find if they watch the video a couple of times, and pause when needed, it starts to become clearer.

[@refusoagaino6824]

I need a nap now.

[@AltEStore]

Yah, this was a rough one. Lots of technical stuff to get through. But it is important.

[@stefano1488]

Started crying at 11:20 😞Ok, I'll call an expert electrician. Better poor than incinerated 😀

[@ChileExpatFamily]

I left the Usa because of bureaucracy gone wild.

[@ooddy24]

very complicated issue; should provide video into a series of 4 or 5 videos rather than one. need to include pictures of cables and wires and related solar elements.

[@AltEStore]

I agree this is one of our more advanced videos. We have over 100 videos on different solar topics, at different technical levels, and are adding more weekly. We'll look at how we can create some additional videos to break this down a bit more.

[@ooddy24]

For DIY like me, it would help if it's a dumb down kind of video, with a lot of accompanied pictures of real equipments, tools, or elements. It might be hard to do, considering a range of DIY folks that you have to satisfy.

[@AltEStore]

I wonder if it would make sense for us to have a technical rating, like 1 wrench to 5 wrenches for basic to very technical. You've definitely given us something to work on, thank you so much for your feedback.

[@AltEStore]

The good thing about making solar videos is, we'll never run out of topics.

[@ooddy24]

thank you. Overall, your video session is well made and good reliable and accurate source of information. Keep up your good work...