LOVELY VIDEO, Ive attended many solar courses and not one has covered this aspect in such detail! Lastly, When you mention 'fusing' ,does that specifically refer to the SLOW BLOW FUSE type or does that also refer to a DC CIRCUIT BREAKER aswell ? They both perform the same function??
Thanks for that. I am specifically referring to slow blow fusing. Honestly, now days with a plethora of inverter options that have multiple MPPT with just 2 x inputs, if you select one of these inverters, sort of don’t need fusing ( less work for the installer).
This was a great video. I worry about how much non sense and wrong information is out there. I have 2 stings in parallel each has 3 solar panels in series. this is the back panel info ( Isc 13.41A, Voc 20.52, the max fuse rating of a panel is 15 Amp) I have also 100V / 40 Amp charge controller. With that I am combining 2 x 13.41 = 26.82A (with 61.56V) going to the charge controller. 13.41 is less and I should not need the 15Amp fuse. This is what I have got in one of the Newpowa representative in the email: "We still recommend you to use a 15A fuse in the series connection of your solar panels. It is important to note that under certain conditions, such as when the solar panels are exposed to full sunlight, the current output of the solar panels can exceed their rated Isc. Therefore, using a 15A fuse in the series connection can help protect your solar panels and prevent damage from overcurrent conditions." Isc is 13.41 Amp and that is it...that is why they list it in the specifications.... less sun or full sun....I mean rather in full sun. How they can provide you with such a information. I am happy to see good info. Thank you again for your time and good explanation. michael
This may be obvious, but please confirm this is for parallel strings into one MPPT. In the case where you have 3 strings into 3 separate MPPTs, would you still need fusing? Nice choice of tunes, BTW. Very reminiscent of Blue Sky.
As of Dec 2022 if there are individual strings going to individual MPPT’s, no string fusing required. See examples below: EXAMPLE 1 Does the string contain a DCU NO What is the Isc of the panels used, see data sheet 9.8 Are you using bifacial modules No How many strings 4 What is the Reverse current of the panels used in A 30 KI multiplier is 1.1 Multiplier 1.25 Inverter backfeed current ( from data sheet) is? 3 IBF TOTAL in Amps is 39.75 Do I need string fusing? YES Can I use this panel though? YES, maybe String overcurrent protection sizing results Where there are no DCUs: 1.2 × ISTRING MAX < In ≤ IMOD MAX OCPR I string max is 17.7 Multiplier 1.2 In must be more than >>> 21.24 In maximum is 30 Select a fuse > 21.24 but < = to 30 25 EXAMPLE 2 Does the string contain a DCU NO What is the Isc of the panels used, see data sheet 9.8 Are you using bifacial modules No Put zero here > > > > > > > 0 How many strings 3 What is the Reverse current of the panels used in A 30 KI multiplier is 1.1 Multiplier 1.25 Inverter backfeed current ( from data sheet) is? 3 Results IBF TOTAL in Amps is 27.5 Do I need string fusing? No string fusing required Can I use this panel though? YES, maybe
Thank you for sharing but I do have a question on the Formula 3 - 1 why am I minusing one string? In my case I just have two panels I want to wire in parallel so that is one string in parallel my short circuit is 9.05 * 2 which is 18.1 Which is less than my 20 amps Max fusing is that correct? I just don't understand why if you're having three strings why are you subtracting one string in your equation I'm lost
It comes down to this. If there is a short circuit in one string the other strings will send their ‘energy’ to the the short-circuited string and that’s when the max reverse current rating of the panel comes into play. That’s why the calculation is for example ( 3 - 1) Note: If in Australia the current AS5033:2021 standard has a slightly different, less forgiving calculation: According to AS/NZS 5033:2021, string overcurrent protection is required if: IF STRING + IBF TOTAL > IMOD MAX OCPR Which becomes: (SA - 1) × ISTRING MAX + IBF TOTAL > IMOD MAX OCPR Which becomes: (SA - 1) × 1.25 × KI × ISC MOD + IBF TOTAL > IMOD MAX OCPR (3 - 1) × 1.25 × 1.1 × 9.8 A + 3 A > 20 A 26.95 A + 3 A > 20 A → TRUE, so string overcurrent protection is required. The changes from AS/NZS 5033:2014 to AS/NZS 5033:2021 are inclusion of a 1.25 factor, inclusion of the KI factor, and inclusion of the back feed current. In this example, the changes are significant enough to alter the result of the calculation. Hope this helps!
I am a bit confused because there was no explanation of what a "string" is. Am I correct in assuming that in this case the SA is 3 means that there is one string of 3 panels connected in parallel? In other words, if there were 4 panels connected in parallel, it would be a string of 4?
Hi JR, A string is a series connection of solar panels. For example, have 20 x panels connected in series, each panel has a VocMax of 40 volts, VocMax of the string is 20 x 40 = 800 volts. Hope this helps!
It depends on the number of strings involved. If you are in Australia just check out the latest standards because soem of the calculations are a bit different now.
Hi Kerry We are assuming 18,19, 20 panels in series connection indicative of commercial solar voltages commonly used. Then these strings are paralleled to each other with obvious restrictions. If there is a fault in one of the strings, the fusing is there to protect the other strings that are paralleled to it.
Hi Rashid Remember string fusing is based on the reverse/short circuit current rating of the module in question and the number of parallel strings and the Isc of the module in question. Let’s assume the following: 1. Module reverse current rating is 20A 2. With one string with module Isc of 11 amps no string fusing 3. With two strings no string fusing 4. But three strings in parallel yes as ((3-1) x 11 = 22A > 20A! Now have to select the rating of the fuse. so the fuse has to > than 1.5 x Isc which is 16.5A AND has to be less than 2.4 x Isc which is 26.4A so, in this case, would use a 20A fuse. So first determine the reverse current rating of the module, then the Isc, the number of parallel strings and in the case of the Australian Standards the min 1.5 rule and the max 2.4 rule. Apply the following formula, ((SA - 1) x Isc MOD) > IMODMAX OCPR where: 1.SA is the number of parallel strings, 2. Isc MOD = Short circuit current of the module in question, 3. IMODMAX OCPR, Max fuse rating in Amps/ reverse current rating.
Excellent!! All of the info and calculations were extremely clear - Thank you
LOVELY VIDEO, Ive attended many solar courses and not one has covered this aspect in such detail!
Lastly, When you mention 'fusing' ,does that specifically refer to the SLOW BLOW FUSE type or does that also refer to a DC CIRCUIT BREAKER aswell ? They both perform the same function??
Thanks for that. I am specifically referring to slow blow fusing. Honestly, now days with a plethora of inverter options that have multiple MPPT with just 2 x inputs, if you select one of these inverters, sort of don’t need fusing ( less work for the installer).
Excellent video .
Cheers
Excellent information.
Cheers.
Great video, thanks!
This was a great video. I worry about how much non sense and wrong information is out there. I have 2 stings in parallel each has 3 solar panels in series.
this is the back panel info ( Isc 13.41A, Voc 20.52, the max fuse rating of a panel is 15 Amp) I have also 100V / 40 Amp charge controller.
With that I am combining 2 x 13.41 = 26.82A (with 61.56V) going to the charge controller. 13.41 is less and I should not need the 15Amp fuse.
This is what I have got in one of the Newpowa representative in the email:
"We still recommend you to use a 15A fuse in the series connection of your solar panels. It is important to note that under certain conditions, such as when the solar panels are exposed to full sunlight, the current output of the solar panels can exceed their rated Isc. Therefore, using a 15A fuse in the series connection can help protect your solar panels and prevent damage from overcurrent conditions."
Isc is 13.41 Amp and that is it...that is why they list it in the specifications.... less sun or full sun....I mean rather in full sun. How they can provide you with such a information. I am happy to see good info. Thank you again for your time and good explanation. michael
No worries.
great video..could i also select a 20amp fuse as well?
Hey Adam, you can't select a 20amp fuse. This is because the 20A rating of the fuse does not satisfy the requirement of In
This may be obvious, but please confirm this is for parallel strings into one MPPT. In the case where you have 3 strings into 3 separate MPPTs, would you still need fusing?
Nice choice of tunes, BTW. Very reminiscent of Blue Sky.
As of Dec 2022 if there are individual strings going to individual MPPT’s, no string fusing required.
See examples below:
EXAMPLE 1
Does the string contain a DCU NO
What is the Isc of the panels used, see data sheet 9.8
Are you using bifacial modules No
How many strings 4
What is the Reverse current of the panels used in A 30
KI multiplier is 1.1
Multiplier 1.25
Inverter backfeed current ( from data sheet) is? 3
IBF TOTAL in Amps is 39.75
Do I need string fusing? YES
Can I use this panel though? YES, maybe
String overcurrent protection sizing results
Where there are no DCUs: 1.2 × ISTRING MAX < In ≤ IMOD MAX OCPR
I string max is 17.7
Multiplier 1.2
In must be more than >>> 21.24
In maximum is 30
Select a fuse > 21.24 but < = to 30 25
EXAMPLE 2
Does the string contain a DCU NO
What is the Isc of the panels used, see data sheet 9.8
Are you using bifacial modules No
Put zero here > > > > > > > 0
How many strings 3
What is the Reverse current of the panels used in A 30
KI multiplier is 1.1
Multiplier 1.25
Inverter backfeed current ( from data sheet) is? 3
Results
IBF TOTAL in Amps is 27.5
Do I need string fusing? No string fusing required
Can I use this panel though? YES, maybe
Thank you for sharing but I do have a question on the Formula 3 - 1 why am I minusing one string? In my case I just have two panels I want to wire in parallel so that is one string in parallel my short circuit is 9.05 * 2 which is 18.1 Which is less than my 20 amps Max fusing is that correct? I just don't understand why if you're having three strings why are you subtracting one string in your equation I'm lost
It comes down to this. If there is a short circuit in one string the other strings will send their ‘energy’ to the the short-circuited string and that’s when the max reverse current rating of the panel comes into play.
That’s why the calculation is for example ( 3 - 1)
Note: If in Australia the current AS5033:2021 standard has a slightly different, less forgiving calculation:
According to AS/NZS 5033:2021, string overcurrent protection is required if:
IF STRING + IBF TOTAL > IMOD MAX OCPR
Which becomes: (SA - 1) × ISTRING MAX + IBF TOTAL > IMOD MAX OCPR
Which becomes: (SA - 1) × 1.25 × KI × ISC MOD + IBF TOTAL > IMOD MAX OCPR
(3 - 1) × 1.25 × 1.1 × 9.8 A + 3 A > 20 A
26.95 A + 3 A > 20 A → TRUE, so string overcurrent protection is required.
The changes from AS/NZS 5033:2014 to AS/NZS 5033:2021 are inclusion of a 1.25 factor, inclusion of the KI factor, and inclusion of the back feed current. In this example, the changes are significant enough to alter the result of the calculation.
Hope this helps!
Sir diode PV input reverse-polarity protection?
I am a bit confused because there was no explanation of what a "string" is. Am I correct in assuming that in this case the SA is 3 means that there is one string of 3 panels connected in parallel? In other words, if there were 4 panels connected in parallel, it would be a string of 4?
Hi JR,
A string is a series connection of solar panels. For example, have 20 x panels connected in series, each panel has a VocMax of 40 volts, VocMax of the string is 20 x 40 = 800 volts. Hope this helps!
What Fuse Size for 150W Solar Panel - ISC Amps 8.76 should I use? THANKS
It depends on the number of strings involved. If you are in Australia just check out the latest standards because soem of the calculations are a bit different now.
I have 30 panels 15 and 15 of 2 string panel short AMP 13.77 Max model 25 AMP
20 amp fuse good or not
What if the panels were connected in series, is the calculation different for parallel?
Hi Kerry
We are assuming 18,19, 20 panels in series connection indicative of commercial solar voltages commonly used. Then these strings are paralleled to each other with obvious restrictions.
If there is a fault in one of the strings, the fusing is there to protect the other strings that are paralleled to it.
love it.
Sir 535watt 15panel 1string =740voc and 13A ISC total 3string fuse rating 25A
20A fuse single string?
Hi Rashid
Remember string fusing is based on the reverse/short circuit current rating of the module in question and the number of parallel strings and the Isc of the module in question.
Let’s assume the following:
1. Module reverse current rating is 20A
2. With one string with module Isc of 11 amps no string fusing
3. With two strings no string fusing
4. But three strings in parallel yes as ((3-1) x 11 = 22A > 20A!
Now have to select the rating of the fuse.
so the fuse has to > than 1.5 x Isc which is 16.5A AND has to be less than 2.4 x Isc which is 26.4A so, in this case, would use a 20A fuse.
So first determine the reverse current rating of the module, then the Isc, the number of parallel strings and in the case of the Australian Standards the min 1.5 rule and the max 2.4 rule.
Apply the following formula, ((SA - 1) x Isc MOD) > IMODMAX OCPR where:
1.SA is the number of parallel strings,
2. Isc MOD = Short circuit current of the module in question,
3. IMODMAX OCPR, Max fuse rating in Amps/ reverse current rating.
Thank you,and how to calculate thé size of a câble ?
Do 10 AWG or 8 AWG
Best bet is to use something like Jcalc or similar. www.jcalc.net/cable-sizing-calculator-as3008
www.jcalc.net/cable-sizing-calculator-as3008
I have a question with u
What's the question?
🇹🇭Thanks you ❤️ธรรมชาติคือชีวิต หยุดทำลายโลกกันเถอะ fc thailaned❤️👺🥰🇹🇭
why 3-1??