Hi all 

I have 6 x solar panels of 450w each 4 in series amd 2 in parallel as shown in the diagram.

How do I calculate the fuse size I need . please

If i had to make an educated guess based on what i run  i would say 30amp fuses with 4mm PV wire. i run strings of 455w panels on 15A fuses so it would basically be double that. The formula is Isc x 1,2.

I am still learning What does Isc x1.2 mean ?

Can you show me how it is calculated  

1 minute ago, jason compo said:

I am still learning What does Isc x1.2 mean ?

Can you show me how it is calculated  

The short circuit current of the panels x 1,2 is the size of the fuse required in a series string , so for parallel you double that.

So if I have 4 x panels I multiple that by 1.2amps which is 4.8 amps

If I have 4x panels in parallel it would then be 9.6 amps 

 

2 minutes ago, jason compo said:

So if I have 4 x panels I multiple that by 1.2amps which is 4.8 amps

If I have 4x panels in parallel it would then be 9.6 amps 

 

No that does not sound right , what panels are they ?

16 minutes ago, jason compo said:

I have 6 x solar panels of 450w each 4 in series amd 2 in parallel as shown in the diagram.

That doesn't make sense.  If you have 6 panels you should connect them all in series.  Or make two strings of 3 panels each and then connect in parallel.  You need to tell us what your inverter's solar charger as well as your solar panel specifications are.  From that one can determine how the panels need to be connected without breaching your inverter's maximum input voltage.  There is also a minimum voltage spec.  You must make sure you work within those limits.

Just now, Nexuss said:

No that does not sound right , what panels are they ?

These are the panels

5 minutes ago, jason compo said:

These are the panels

Isc 11.6A x1,2 x2 (strings in parallel) =27,84A so a 30 A fuse will do.

From your pictures from your other post I see this:

Your MPPT has an input range of 90 - 450VDC.  240VDC recommended input.

Your panels have a nominal voltage of 41.5V (Vmp).  So if you connect all 6 panels in series you will get 41.5x6 = 249VDC  which would be perfect for your MPPT.

From your other post I gather that you have a total of 12 panels?  So make 2 strings of 6 panels each.  Then connect the two strings in parallel.

It might be good to fuse the two strings separately before paralleling.

Separate strings need a 15 or 16A fuse.  Once paralleled, you will have double the available current and will need a fuse double the rating, i.e. 30A as Nexuss mentioned.

Your panels actually state the max fuse rating. And you do not need an additional fuse between the 4  and 2 panels that you will connect as a 6 panel series string.

The drawing in the first post shows six solar panels in series. You don't need any fuses, although they make nice isolation points and create a false sense of safety.

So if I fully understand  I can connect 6 panels in series and connecting a 30A fuse to the combiner box would work perfect for the inverter

2 hours ago, Modina said:

From your pictures from your other post I see this:

Your MPPT has an input range of 90 - 450VDC.  240VDC recommended input.

Your panels have a nominal voltage of 41.5V (Vmp).  So if you connect all 6 panels in series you will get 41.5x6 = 249VDC  which would be perfect for your MPPT.

From your other post I gather that you have a total of 12 panels?  So make 2 strings of 6 panels each.  Then connect the two strings in parallel.

It might be good to fuse the two strings separately before paralleling.

Separate strings need a 15 or 16A fuse.  Once paralleled, you will have double the available current and will need a fuse double the rating, i.e. 30A as Nexuss mentioned.

Could you draw me a diagram so that I can get a better picture of what I havw to do.

The strings go into a combiner box before they go into the inverter. 

Only I am lost on the 2 string in parallel 

Thank you

2 hours ago, jason compo said:

So if I fully understand  I can connect 6 panels in series and connecting a 30A fuse to the combiner box would work perfect for the inverter

Could you draw me a diagram so that I can get a better picture of what I havw to do.

The strings go into a combiner box before they go into the inverter. 

Only I am lost on the 2 string in parallel 

Thank you

The first drawing posted is adequate. Someone then wrote on the two seperate panels the word parallel, but all panels are drawn in series. You can forget about the combiner box, surge arrestor and fuses. The PV negative on the inverter must be connected to the first panel's negative, all panels are connected positive to the next one's negative, the last panel's positive goes to the inverter's PV positive. If you want to add a 20A fuse for isolation, you can.

Edited April 14, 20233 yr by frivan

Would you or someone one draw a diagram so that I can understand better as I am now confused with so much information please 

7 hours ago, jason compo said:

Would you or someone one draw a diagram so that I can understand better as I am now confused with so much information please 

You owe me

Note that you will have a few hundred volt DC on the panels. So, you want to finish all wiring with the inverter off and the MC4 connectors disconnected. It will also be good to check polarity before plugging in to the inverter.

Thank you very much

@jason compo  I think it would have been better if you kept your fuse query under your Solar Panel Setup heading.  In that other thread you mentioned that you have a total of 12 panels.  So this is how you would connect to a single MPPT

Note, I did not show any circuit breakers here.  In practice one would add CBs to disconnect the one or other string.

Edited April 15, 20233 yr by Modina

44 minutes ago, Modina said:

@jason compo  I think it would have been better if you kept your fuse query under your Solar Panel Setup heading.  In that other thread you mentioned that you have a total of 12 panels.  So this is how you would connect to a single MPPT

Note, I did not show any circuit breakers here.  In practice one would add CBs to disconnect the one or other string.

Take note there are 2 x MPPTS on the said inverter. 

12 panels exceed the current to a MPPT as well as the 4000W input. 

Edited April 15, 20233 yr by Scorp007

Would it be best to place 6 x panels IN PARALLEL on each MPPT ?

Thank you I finally understand this part of the solar system 

Thank you every one for your help

9 minutes ago, jason compo said:

Would it be best to place 6 x panels IN PARALLEL on each MPPT ?

No thats a terrible idea and will blow your MPPT. If your MPPT is 18 A you should wire one series string of 6 panels per MPPT.

Edited April 15, 20233 yr by Nexuss

You have two MPPT, thus use both, one for each string

PLEASE READ THE FULL TOPIC.AS

Why is everyone giving me different answer to my question 

This is becoming very very confusing.PLEASE STOP

I would ask if you are not 100% sure on that is going on please do not commit  as I do not want to destroy my system 

Thank you