Fuses between solar panels? Panel>fuse>panel?

[Harmony5000]

...if only it were that easy.

Ok dude every time you make a wink now I have to question my whole reality... what am I apparently missing now or are you messing with me LOL

I ordered a sixth panel to do 3s2p without fuses if this is still wrong somehow someone pls stop me

 

[CamoGreg]

You'll be fine with 3S2P. You'll need a total of 3 pairs MC4 branch connectors. 2 pair to join each of the 2P strings and another pair to join that result into a single pair of +/- wire that will feed into your SCC.

Given what equipment you already have, this is the best optimized solution to get the most from your system.

 

[rmaddy]

You'll be fine with 3S2P. You'll need a total of 3 pairs MC4 branch connectors. 2 pair to join each of the 2P strings and another pair to join that result into a single pair of +/- wire that will feed into your SCC.

Only 1 pair of Y connectors is needed for 3S2P.

Take 3 panels and put them in series. No extra connectors needed. Repeat for the other 3 panels.

Now use 1 Y connector to connect the two positive wires (one from each series string) and use 1 Y connector to connect the two negative wires (one from each series string).

 

[CamoGreg]

Oops. Yep. 1 pair only.

 

[Harmony5000]

Cool, getting the project under way. Since it will only be a little over 11 amps I wonder if I need a 15a fuse between the array and scc?

There is a very slight curvature of the top of the van I think. Maybe I should lay down a rail to keep them all completely flat in comparison to each other or does that really matter? Planning to install in a single row like l l l l l l the length of the van.

Also I have a bit of room to space the panels at least 1” apart wonder if that works or if it’s recommended to do more?

 

[rmaddy]

Since it will only be a little over 11 amps I wonder if I need a 15a fuse between the array and scc?

If you are arranging them in 3S2P then you do not need a fuse. But it is helpful to have a disconnect. Many people use a 2-pole DC breaker for this. It is not meant to protect anything, just to act as a switch. Do make sure the breaker is rated for DC and rated to handle the full Voc of the panel arrangement.

There is a very slight curvature of the top of the van I think. Maybe I should lay down a rail to keep them all completely flat in comparison to each other or does that really matter? Planning to install in a single row like l l l l l l the length of the van.

Panels in series should be in the same plane or you will lose a lot of performance. The two series strings that are in parallel do not need to be in the same plane as each other.

Also I have a bit of room to space the panels at least 1” apart wonder if that works or if it’s recommended to do more?

1/2" is enough space between each panel. You want some airflow to help with cooling.

 

[12VoltInstalls]

deleted

 

[Harmony5000]

Hi all, I just tested the 3s2p setup

Getting a reading of 64v 6.5 amps

Does that ratio seem correct? It’s around noon and partly cloudy.

When I first got them I did 5p and if I remember correctly that only read around 6 something amps.

Is this making sense or did I get bum solar panels??

 

[Harmony5000]

Maybe my test is off with the multimeter? This is the setup I’m using for testing amps

 

[Harmony5000]

Reading 7.20amps now cloud cover went away.

 

[Harmony5000]

delete

 

[12VoltInstalls]

Getting a reading of 64v 6.5 amps

Seems normal for clouds to me

 

[foggysail]

Based on environment I wonder when parallel vs series or whatever combinations make most sense. Ppl seem to have their preferences but they don’t tend to say ‘becaaauuse, it’s always sunny’ or ‘because, I get shade from ****’ etc. difficult to draw conclusions.

Yeah, many times it happens to be guess work BUT IMHO, the best way to connect is to us a combo depending on the number of panels. For example, one should try to get the voltage as high as possible between the panels and an MPPT controller. Now the limit would be determined by the controller so maybe not all panels (if you are wiring a bunch together) can be wired in series making a case for combos of both parallel and series connection.

The driving reason for getting the voltage high is to minimize the wire drop from a panel to the controller.
OH and be careful, REMEMBER voltages above 40 can be lethal! But so is the voltage in a normal wall outlet. Consider 6 so called 24V panels where Vmp is usually around 18 VDC. If all are connected in series you will have you will have 144V. Been awhile since looking at low voltage panel spec sheets but 24V would be Voc (open circuit voltage with Vmp about 18).

For exampe-- 2 groups, each with 3 connected in parallel and then connected in series will give you a reasonably safe output votage. I have 2 groups of 30 volt panels, 2 connected in parallel in those groups connected in series on my boat. Works well for me.

In an earlier post someone said that #12 wire is only good for 20 amperes............that is mixing oranges with apples! That rule is based on a 3% voltage drop in a 100' length of wire operating at 120V. You can pump 40 amperes through #12 BUT YOU DO NOT WANT TO because the voltage drop in the wires will be a considerable percentage of 12V if you were trying to run panels at so called 12V

 

[Omkar]

If your total array current is greater than the fuse rating of an individual panel, why would you choose a fuse of the same rating as the panel? The current will exceed the fuse rating and blow it out. Ref: https://youtu.be/s1P31hxlD3I?t=129 Thank you.






REPLY

 

[foggysail]

If your total array current is greater than the fuse rating of an individual panel, why would you choose a fuse of the same rating as the panel? The current will exceed the fuse rating and blow it out. Ref: https://youtu.be/s1P31hxlD3I?t=129 Thank you.






REPLY

Why would you fuse individual panels??? Sure, fuses to protect wiring but panels are current sources and have no trouble at all working into a short circuit

EDIT: I just watched your referenced youtube. There he describes multiple panels in parallel and although a single panel OR a number of panels in series have no problems working into a short without fuses as I see it. But yes... if multiple panels are connected in parallel and one shorts then that shorted panel will have to be able to carry the entire available currents produced by other panels in parallel with the shorted panel.

OK, so a damaged shorted panel could be further damaged by the increased current produced by other panels. So what? A damaged panel with an internal short is junk anyway. My contention is fuses/circuit breakers in solar systems provide wiring protection and that is about it. And for certain, a circuit breaker provides an easy way to shut down a string of panels as does a fuse although pulling fuses is a PITA.