Fuses For Solar Panels: Series and Parallel Fusing

[@cleversolarpower]

Update: if you have a single series string no fuse is required. If you have multiple series strings, then a fuse is required. 🎁Get FREE diagrams to kickstart your Off-Grid journey! View and get them here: cleversolarpower.com 🎁

[@spruce_goose5169]

I think you only need OCPD's when it is MORE THAN 2 series strings.

[@TexasRanger-b8j]

This is VERY VERY helpful. You answered all the questions I have in mind. Now, I'm more comfortable doing my project. You have a new subscriber here. Keep adding more videos man. Thanks!

[@cleversolarpower]

Thanks for the sub 🙏

[@HelloKLW]

your video is very informative. thank you.

[@cleversolarpower]

Glad it was helpful!

[@alanblyde8502]

Great review description mate👌🇦🇺

[@kaundabwalya7776]

Well explained 👏Thanks Sir 👍

[@bmbpdk]

A very nice and clear video, thank you!

[@samsonrobinson2392]

This was super helpful. thanks

[@cleversolarpower]

Glad you liked it!

[@dougiee6589]

I like simple math and this video is it

[@fujchi2172]

why did you use 6.2 amps in the calculations when the panels showed a rating of 5.8?

[@cleversolarpower]

I use the Isc, highest possible current.

[@Shane7son]

Love your videos this is a big help for me and you explain things real simple unlike the other guys You also get straight straight to the point I don’t like to reload my fridge all the time because I work outdoors. I have power tools like you that are battery power. So thank you. Can I run a refrigerator

[@cleversolarpower]

Thanks Shane! I try to keep my videos to the point so I don't waste people's time. I made a video about how much power my fridge consumes. Check it out on my channel page.

[@loganreynolds4396]

Thank you for you video - I have 4 550 W panels, with the following specs. What configuration would you recommend ? 2S2P? For Fuse 1 and Fuse 2 (14.01 x 1.56 = 21.86) would a 30a inline fuse work?? And then for the Fuse 3 - what type of fuse should be used?? Is there any benefit of doing a 2P2S configuration?? thank you! Series 1 & 2 = 100v and 14A = 100v 28A going to the charge controller. VMP: 41.96 IMP:13.11 ISC:14.01 VOC:49.9

[@johntheaccountant5594]

In your calculation 6.2A x 1.56 = 9.6A where did the 1.56 figure come from? OK; the 1.56 is a safety factor but before you were using 1.25

[@cleversolarpower]

The safety factor for being outdoors changes because it can get hotter outside. Imagine a black wire on a black roof at noon will get much hotter than a wire inside your house.

[@abitofeverything1985]

I still don't quite understand where 1.56 came from? Is it Maximum Series Fuse 15 A figure? My panel have (Ipm) 8.86 A, and Maximum Series Fuse 20 A. What fuse i need??

[@vellyyt3572]

Is the 1.56 safety factor written in NEC? Where is it come from?

[@hardeekpatel1944]

1.56 is standard value....give by NEC standard

[@cleversolarpower]

@@abitofeverything1985 1.25*1.25=1.56

[@thesolarpowerinstallersass635]

Very good information tks

[@qodaxdhuuni5332]

Thank you. What drawing program did you use?

[@cleversolarpower]

For the videos I use videoscribe. For the drawings edraw.

[@Khaztr]

if you're adding fuses on the positive line, doesn't that add some resistance, and therefore require you to add some extra wire on the negative side to equalize the resistance between both lines?

[@niallparker3655]

Can't think of a good reason to increase losses just so the voltage drops on each side are the same, what are you trying to achieve? The controller only cares about net differential voltage at its input.

[@adex2000ng]

Well appreciated video

[@FareFejzic]

Helpful explanation. I need instructions: How should I connect two solar panels that are on different sides of my mountain house of 450W each to a 12V 160Ah battery. Thank you very much

[@michaelrowland-us3he]

What exactly does the fuse you talk about look like??? A picture would be good.. also are they placed just before the branch connector?

[@cleversolarpower]

An inline MC-4 fuse for F1,2, and 3 and a DC breaker for F4.

[@FarqueKnowsWhere]

The 3 panels connected in series has an array amperage of 6.2, and a maximum series fuse rating of 15A, the array doesn’t need to be fused, the fuse won’t do anything.

[@shaynegadsden]

You are stupid right, did you not listen to the statement at the start

[@truesight91]

What if one of your panels is 20A fuse and the other is 15A ?

[@JerryMartins-vh9vc]

Good day , this safety factor 1.56 is it common/ constant to all countries ?. How can we find this safety factor ??

[@cleversolarpower]

It's a standard factor for cables that are outside under the sun. Indoors safety factor is 1.25

[@ThomasNowicki-m5s]

there is no factor. a panel I max is a absolut number a panel can produce only this or lower currents!! so to prtect against a 100% limited current is pure nonsens in any aspect. so on panles no fuses theyx are for nothing existing. on the battery side coz a battery is a umlimited power source a fuse will be needted and this is best set below your wire limits without factor nonsens !!! lets say you you a wire that can handle ~40 Amps current max, on this conditons it get war, over time so the best way to set a real protection to it set from battery to charger a 35 Amp fuse to wire never will run on its limits and you protect the wire from this. no mgic factor or nonsens theories from youtubes use your brain. make yxour build with bigger wires then you really need maximium the set the fuse below this wire maximum to give this wire a real protection. that is all the magic.

[@smvsspould]

Where do you get the 6.2amps and the 1.56 from?

[@rdd8094]

I didn't understand either ...

[@cleversolarpower]

6.2A is the Isc (short circuit of the panel) and 1.56 is a safety factor for calculating current in a conductor for outdoor wiring.

[@JohnDoe-pn3qu]

where is the '1.56' in your formula ISC x 1.56 = minimum fuse size coming from? I ask because my solar panels have Isc 8.75A. So 8.75 x 1.56 = 13.65A minimum fuse size, but the panel indicates: 'max series fuse = 12A'.

[@manonfire7675]

yeah, i don't get this too.

[@cleversolarpower]

Hello John, good question. This is because the cabling is mounted outside. We need to apply an additional 125% safety margin. So it becomes 8.75A x 1.25 x 1.25= 13.67A. if you look on my website, the article about 'how to calculate fuse size for solar system' it's explained there.

[@narotica1]

@@cleversolarpower so why 1.56 not 1.25?

[@cleversolarpower]

@@narotica1 check my previous answer

[@narotica1]

@@cleversolarpower yeah it was a shit explanation, 1.25 * 1.25 is 1.56 for everybody else

[@Torumees0]

my isc A show 6.68, should i use 10A and 30A or i need to go 15 and 40?

[@ThomasNowicki-m5s]

nothing. to put ona limit powwer source a fuse in pure nonsens. if you panel makes 6.68 Amps max iin a short this number will never be higher so to protect your panel / wire against 10 Amps, where thsi 10 amps will come from? for what? where this 10 Amps will came from if your panle have a absolut limit that is 6,68 A in best conditions and only can be this or lower???? there are alot of youtuber telling trash in videos and dont explain how this fuse will work or exactly against what it will protect.

[@sheldonlampson6368]

Where do you get the number 1.56?

[@cleversolarpower]

Safety factor for outdoor wiring. This is because the cable can get very hot in the sun.

[@pasheatsi]

Thank you very much for clarifying this. I want to connect only two 200 watt panels in parallel to a portable power station (Ecoflow Delta 2 Max). Do I still need 3 fuses, or can I just use one for each panel?

[@cleversolarpower]

I would use a fuse for every panel because they are placed in parallel.

[@tembonemon]

Hi. Can i use a fuse and a dc circuit breaker at the same time

[@cleversolarpower]

Yes, but why would you do that?

[@nnamdi.ohaegbuchi]

Which size of wire should I use in 3 pieces of 350w solar panels system

[@cleversolarpower]

Check my video about wire sizing for charge controllers.

[@naveencruise1559]

How did you get that 1.56 value ??

[@cleversolarpower]

1.56 is the safety factor considering wires that are outside. The sun will influence the temperature of the cable, so thats why the safety factor is 1.25x1.25=1.56

[@jonnytacooutdoors]

So where do you fuse the panels ? Did I miss that

[@cleversolarpower]

The fusing happens as close to the power source as possible. This can be an inline MC-4 fuse. You can also add the fuse next to the charge controller right before it enters the input of the charge controller. You can also use a combiner box if you have parallel strings.

[@jonnytacooutdoors]

@@cleversolarpower I’m using a PV shut off switch. As close to the power source as in the panel or the battery? So if you meant the panel then just clip it onto the panel mc4 output cable right?😎

[@cleversolarpower]

@@jonnytacooutdoors To the panel. Yes, if that is physically possible. If you have parallel strings, then you can do it after the combiner box.

[@jonnytacooutdoors]

@@cleversolarpower am I just fusing the positive line? I plan on just plugging in the fuse to the positive line coming out of the first panel and then have that wire go down into the truck

[@SetchiPaunda]

great video ! Very clear

[@slr617hp]

If the short circuit current is 13.58A; open circuit voltage is 38.95V with max fuse at 25A: For a 3S2P setup, 13.58A x 1.56 x 2 = 42.3A is that correct? Would I be able to get a 45A fuse?

[@cleversolarpower]

You should fuse every series string first with 25A. So you need two MC-4 connectors fuses. Then have one DC circuit breaker so you can turn off the whole solar system. This is can be a 64A DC circuit breaker suited for solar (1000VDC).

[@clintoncoker6]

I've never understood the reason for fusing solar panels. Even if you rub through a solar wire and it shorts to earth, the fuse will not blow as a) it is sized lower than the solar current (as it has to be), and b) the fuse would be near the charge controller, so your short would typically be after the fuse, and c) typically the charge controller would stop any battery current trying to flow back through the panels in case of any wiring fault.

[@cleversolarpower]

In a series configuration, yes. But in a parallel configuration, you need it. If one panel is shorted, the other panels will back feed into the broken panel, sending lots of current to it. In order for the panel not to melt, the fuse of the broken panel melts. However, I think it's still useful and good practice to fuse a series connection.

[@Ibian666]

Houses catch on fire from unfused parallel panels, is why.

[@susiejrgensen7041]

@clewersolar I need to paralel, because my panel give 12,2 Amp Isc, and 41 Voc volt, and my controller max 75 volt, I have 2 panels, shall I use 12,2 Amp x 1,25 = 15/16 Amp ? Thanks

[@marcvandaele1878]

⁠​⁠​⁠@@susiejrgensen7041you need *1.25=32 Amps breaker

[@nnamdi.ohaegbuchi]

Can i use a combination of fuse and diode in 3 pieces of 350w solar panels

[@cleversolarpower]

No, a diode only prevents backwards flow of electricity.

[@nnamdi.ohaegbuchi]

@@cleversolarpower thanks

[@nnamdi.ohaegbuchi]

Can i use a diode rather fuse?

[@cleversolarpower]

No

[@nnamdi.ohaegbuchi]

@@cleversolarpower thanks

[@croomcas]

For me in series 11.4A x 1.56 = 17.784A Do I use a 20A even though my panels Max series fuse rating is 20A? Thanks

[@cleversolarpower]

Yes.

[@cardinhamkilligrew9712]

I have two 120 watt solar panels (ss 6.8 amps) in parallel. was planning on 12 awg wire from panels to mppt and 10 awg from mppt to batteries. before combiner was going to use 15 amp inline fuse and a 20 amp MPPT. will that work? i assume the combined power was 21.6 volts at 13.6 amps. Thoughts?

[@cleversolarpower]

6.8*1.56*2 panels in parallel = 21A. 20a fuse is on the edge but ok.

[@dheller777]

I have three 300 watt panels that will be wired in parallel due to shading. Each has a short circuit current of 18.1 amps. So I woll need 3 20 amp fuses one for each panel. How big of fuse will I need forthe iotput end of my 3 into one adapter? Thank you

[@cleversolarpower]

No, isc x 1.56

[@johntheaccountant5594]

Can you use an MCB instead of a Fuse?

[@cleversolarpower]

An MCB from a reputable brand is more expensive. MCB's are used in AC switchboards because they can be switched off often. For DC, it's cheaper to have fuses. If you look at the end of the video you can see a popular MCB which is unbranded. It's known to cause problems and heat up under use.

[@DomainUltra]

Is a fuse required if only one 100w panel is plugged directly into a solar generator with built in MPPT?

[@cleversolarpower]

No, but a breaker could be depending on your local code.

[@awesomedee5421]

Great summary. Is there a device to boost up voltage after the combiner so don't have to have such a thick cable, and then on the other side of the run bring the voltage back down?

[@cleversolarpower]

Not that I am aware of. A solution is to wire your panels in series.

[@HariPLTS]

Nice info

[@bestillandknowthatuaregod]

What Fuse Size for 150W Solar Panel - ISC Amps 8.76 should I use? THANKS

[@cleversolarpower]

8.76x1.56=13.6 so a 15A fuse is ok. But you don't need a fuse for one panel.

[@bestillandknowthatuaregod]

Im only using 2 150Wats Panels in parallel. Still need fuse?@@cleversolarpower

[@СергейВиноградов-м9ъ]

Why you don't need a fuse for one panel? @@cleversolarpower

[@hollygrinstead7252]

Why no fuse needed for one panel?

[@Bendy509-cz8vz]

Do one about circuit breaker dc and ac please

[@aysensvoboda2274]

Great video. May I ask which tool you use for those drawings? Thank you

[@cleversolarpower]

Thanks. I use Edraw.

[@tembonemon]

Lovely

[@expeditionchef222]

Where do you get the 1.56 from?

[@cleversolarpower]

It's a safety factor.

[@The_Resistance_1961]

OK, I bought two solar panels and don't plan on linking them at all. I'll be running both control boxes that came with each panel. Now, the wires, control box etc can all be handled easily by the wires and by the control box itself, so would I need a fuse between each panel and the control box? The solar panels are rated at 15 Amps each, control boxes are 30 Amp.

[@cleversolarpower]

No need for a fuse if there is only one solar panel per controller.

[@The_Resistance_1961]

@@cleversolarpower Yeah I watched a couple more vids and got around adding solar panels by simply running each panel (350W) on the controller that came with them, but I might add a busbar to minimise the number of rings around the battery terminals. Yeah, then I figure it can't go wrong given that SLA batteries give off a ''resistance'' which each controller reads and moderates, although one must apparently make one of them the master controller so that the batteries don't ''equalise'' more than once a month. Nevertheless I've added 30 amp circuit breakers between panels and controllers, and put 200 ah fuses between each of the four batteries in my bank. It's not that hard when you watch videos such as your own.I've had a simple philosophy all my life - if you don't know something just ask someone who does.

[@chansuihing1416]

Where can I buy the book

[@cleversolarpower]

You can check the link in the description.

[@SweetFLGuy1]

cleversolarpower What size fuses should I use when connecting four 180w solar panels in 2series2parallel. Each panel is rated 10.5 amps max with a series 15 max rating on each panel going into a 15 amp max rated portable solar generator. I'm guessing the formula is 10.5 x 1.56 = 16.38 amps so would I need two 15 amp fuses going into a 30 amp fuse or two 20 amp fuses going into a 40 amp fuse after that before it goes into the solar generator rated at 15 amps max. Will it work and safely to protect my panels and solar generator without constantly blowing fuses? Let me know. Thanks

[@cleversolarpower]

You need two 15A fuses and one 30 amp fuse.

[@joeking3966]

Hello, thank you for the informative videos, love the content! I have a stupid question, at 3:46 when you are explaining the voltage drop across different wire sizes, I was wondering how did you come into the conclusion that the 14awg wire is sufficient? Or at 4:17, 12awg is sufficient voltage drop for the 2 strings? Is there a rule of thumb on the % drop is acceptable? Thank you in advance!

[@joeking3966]

Haha, nevermind, i just saw your other video that explained the voltage drop of 3%. Thank you!

[@nickchlapanas2987]

Great video, great analysis. I have a question though, what is the difference between mc4 fused connector and mc4 diode connectors?

[@nickchlapanas2987]

I also would like to ask what fuse should I use for a 7.75a panel? 10 a or 15a?

[@cleversolarpower]

The max fuse size will be indicated on the back of the panel. I recommend watching the video again. MC4 fuses is just a fuse holder which fit MC-4 connectors. I suspect that MC4 diode connectors are the same. Why would you use a diode?

[@netrocker9990]

​@@cleversolarpoweryou're wrong,mc4 diode is used as blocking diode to avoid shading issues between two parallel strings/parallel panels

[@Greg65]

There is no reason to place a "combined current" fuse (F4 @ THE 1:38 mark) after the normal parallel fuses (F1, F2 & F3) as it serves no purpose, if anything goes wrong after these fuses they will blow anyway (before fuse F4 can blow).!

[@cleversolarpower]

It's a solar disconnect breaker (resettable fuse). Maybe I should have made it more clear what it is. The breaker is there to isolate the solar panels from the system. It is required to do so.

[@Greg65]

@@cleversolarpower Thanks for the reply, yes that makes 100% sense of things!

[@MrHanzeeman]

@@cleversolarpower yes, maybe you can add a caption to clarify that. It certainly didn't come across in the video like that.

[@Floyd112007]

Yes, this is now clear. Exactly like in my combiner box. @@cleversolarpower

[@davidjosephhansen8555]

I'm installing twelve 400w panels at my cabin. The EG4 3000w MPPT/inverter has an input limit of 500w and 80a max charging current. These panels are 36.8v and 13.85A. short circuit current 13.55A, Pmax -0.34%/C. I was first going to make two strings of 6 and put them in parallel for 27.7A, but you made me reconsider and think about putting them all in series. 36.8v x 12 =441.6 V for the series, less than the 500v the inverter can handle. In Wisconsin, it is possible to get a -37C event in winter, so using the Pmax I figure that could be a voltage increase of 13% to 499V. I don't know if that Pmax uses the panel's temperature or ambient temperature, but is that cutting it too close? Should I stick with two strings in parallel for 27.A or try for all in a series at 13.85A? I have a fairly long cable run of 120', so I figure I'd be much better off with the lower amperage and fusing would be simpler.

[@cleversolarpower]

You need two series strings to make 6S2P. Your voltage will be over 500V. Voc*12*1.25=max 500V. In your case this is: 36.8V*12*1.25=552V. Your charge controller can get damaged on cold sunny days. 1.25 is a safety factor.

[@expeditionchef222]

My panels have a maximum fuse rating of 20A. I have 22 panels in seri parallel with 2 strings. 495 wats per panel. What would you suggest regarding the fuse’s?

[@cleversolarpower]

Fuse every series string, and then the combined array for a total of 3 fuses.

[@expeditionchef222]

@@cleversolarpower thank you very much. And what fuse rating you suggest? 20amp for individual and 32 amps for combined? Thank you

[@bogdan.dobrowolski]

Do I need a fuse for a single solar panel, for example 300W. ???

[@cleversolarpower]

No

[@bogdan.dobrowolski]

@@cleversolarpower THANKS !!

[@ΔημητριοςΑραβιδης]

What about Solar DIODE connector fuse. Is it the same ?

[@cleversolarpower]

The diodes are already on the back of the panel in the small box. You need to add the fuse with an MC-4 connector fuse holder.

[@josegarcia-th3pj]

it has to be a fuse or can be a breaker

[@cleversolarpower]

Can be both, a fuse will be cheaper.

[@danieleercole9973]

Hi…thank you for your video is amazing …I have a question …I have 2 solar panel 200w 18.2v 11.7 amp and 1 100w 20.4v 5 amp …the question is …what tipe of fuse do I need for the 200w panels ? And one more question …the fuse that will go string after the 3to1 adapter will a need a 50amp fuse and if so is going to make any problems with the mc4 connector due that they are rated only for 30amp …thank you for your help

[@jacqalas]

Hi. Will the fuse be helpful for lightning in any way or is the fuse just for over current and not high voltages?

[@cleversolarpower]

a fuse will not help with lightning, you should consider it a loss when it hits your panels. Don't ground the panels and bring it inside of your house where it can destroy more equipment.

[@БојанКостић]

👍👍👍👍👍👍👍👍

[@ronhanish]

Formula ISC? You lost me on that. Can you explain the formula.

[@cleversolarpower]

Isc * 1.56 -> 1.56 is 1.25*1.25 which are two safety factors multiplied with each other for outdoor temperatures.

[@USA-GreedyMenOfNoIntegrity]

No fuse needed paralleling two series strings or two individual panels. Fuse each when three or more in parallel.

[@cleversolarpower]

Every parallel string needs a fuse. And for simplicity reasons I recommend fusing solar panels.

[@davebenz8271]

@@cleversolarpower Is that required, or just you being overly cautious?

[@cleversolarpower]

@@davebenz8271 Fusing is required for parallel strings. I do recommend fusing series solar panels if the combined Isc of the panels goes over the rated current of the wire.

[@MrHanzeeman]

I think rv10flyer has a point... Please correct me if I'm wrong. If the first of two panels in parallel, has a short, it's fuse may blow or may not, depending on how much over Isc you installed. Now say it didn't blow, and the second panel in parallel starts to back feed it... It also won't blow it because it can only provide 1 times the Isc. 3 or more panels in parallel... Different story. Edit: Or do you still add in the being produced by the shorted panel?

[@cleversolarpower]

@@MrHanzeeman No need to have a fuse when you have one or two parallel strings. You need to calculate the Isc though. If you have three parallel strings or parallel panels, then you need to fuse because the combined ISC is higher than the 1.25xIsc of the panel. Hope this helps.

[@Swenser]

The solar panels can't provide anymore current in series than rated. No need for fuse in series.

[@cleversolarpower]

Correct. If you have multiple series strings, then a fuse is required.

[@manfredkuminski5448]

Use fuses only for 80% of their nominal value.

[@cleversolarpower]

That's why we multiply by 1.25