How do I connect 5 solar panels?

[PHoganDive]

Wouldn't the panels' blocking diodes protect against this?

As long as they're working properly, but I don't like betting on electronic devices proper operation for fire prevention, a fuse or circuit breaker is much safer. If you've ever had a personal encounter with a fire, you'd take every precaution as well.

 

[MisterSandals]

The reason is if any panel develops a problem, it can be back-fed the combined current from all the other parrallel panels

I will trust PHoganDive with regards to the back-fed issue.

But the current (amps) should be addressed and we have not done that for Santa. With 5 panels in parallel, which means the amps are added for all panels, it will require paying attention to the wire sizes!
What are the panel amps and how long will the longest point be from any panel and the SCC? And what wire gauge is Santa using?

Attached is the guide i use - i think one of these should be a sticky on this site somewhere.

 

[Santa]

I will trust PHoganDive with regards to the back-fed issue.

But the current (amps) should be addressed and we have not done that for Santa. With 5 panels in parallel, which means the amps are added for all panels, it will require paying attention to the wire sizes!
What are the panel amps and how long will the longest point be from any panel and the SCC? And what wire gauge is Santa using?

Attached is the guide i use - i think one of these should be a sticky on this site somewhere.

I was planning on using 10 Ga wire for the panels.
Specs for the (4) panels are:
100W
18.2 Vmp volts 18.2V x 5.5amps=100.1 watts (x 4 = 400.4 volts)
5.50Amps- Imp
Short circuit Isc 5.7A
Open circuit voltage Voc 21.4
Max system voltage 600 VDC
Fire rating class c

And for the suitcase:
100W
18 Vmp
2.78x2= 5.56 (amp) Imp=100.08watts
short circuit current Isc 3.24 A (6.48A total suitcase)
OPEN CIRCUIT Voc 21.83 v
Max system VDC 1000

 

[Santa]

and I am putting them in a van, down by the river, LOL.

 

[MisterSandals]

And for the suitcase:

And how long will that wire be from suitcase panel to the SCC?

 

[Santa]

And how long will that wire be from suitcase panel to the SCC?

Don't know yet...But can you estimate 10 feet maybe? Subject to change when installing...

 

[MisterSandals]

Don't know yet...But can you estimate 10 feet maybe? Subject to change when installing...

If your longest run is less than 20 feet then ~23 amps would require 12awg. Up to 30 feet 10awg. So you're good!
Longer than 30 feet you need 8awg.

 

[Santa]

If your longest run is less than 20 feet then ~23 amps would require 12awg. Up to 30 feet 10awg. So you're good!
Longer than 30 feet you need 8awg.

I got 28 amps...? but 10AWG is good. It won't be more than 15 feet I would assume.

 

[MisterSandals]

If your longest run is less than 20 feet then ~23 amps would require 12awg. Up to 30 feet 10awg. So you're good!
Longer than 30 feet you need 8awg.

oops, i see your suitcase is 2 panels. I got your total amps at 29.28.

Up to 30 feet you need 10awg. (still good)
Up to 50 feet you need 8awg. (same)

Just saw your post above, yep, you're right. You don't need us anymore!

 

[Santa]

oops, i see your suitcase is 2 panels. I got your total amps at 29.28.

Up to 30 feet you need 10awg. (still good)
Up to 50 feet you need 8awg. (same)

Just saw your post above, yep, you're right. You don't need me anymore!

Are you counting the Imp or the Isc?

 

[Justin Laureltec]

Attached is the guide i use - i think one of these should be a sticky on this site somewhere.

Very important to note (since I don't see it noted on that chart anywhere) that those length measurements must be for round-trip circuit length, not one-way. So if the panels are literally 30' away, round-trip distance is 60', and the wire must be sized accordingly.

 

[MisterSandals]

Very important to note (since I don't see it noted on that chart anywhere) that those length measurements must be for round-trip circuit length, not one-way. So if the panels are literally 30' away, round-trip distance is 60', and the wire must be sized accordingly.

Holy crap, i learned something very valuable today.

 

[Santa]

Very important to note (since I don't see it noted on that chart anywhere) that those length measurements must be for round-trip circuit length, not one-way. So if the panels are literally 30' away, round-trip distance is 60', and the wire must be sized accordingly.

Thank you! I too learned something new. It won't be over 30 feet roundtrip.

 

[Justin Laureltec]

Holy crap, i learned something very valuable today.

It's amazing how many wire gauge calculators don't tell you that, particularly given how bloody critical of a consideration it is...

 

[MisterSandals]

Very important to note (since I don't see it noted on that chart anywhere)

I'm not a fan of my chart anymore. Do you have one you recommend, one for dummies like me?

It won't be over 30 feet roundtrip.

Here in California, we like to (need to?) park in the shade so having your carry out panels 25+ feet from your RV is not uncommon. Just consider your real world use case.

 

[Santa]

I'm not a fan of my chart anymore. Do you have one you recommend, one for dummies like me?


Here in California, we like to (need to?) park in the shade so having your panels 25+ feet from your RV is not uncommon. Just consider your real world use case.

I will be mounting 4 on the roof. The suitcase will only come out sometimes. So, for argument's sake, I will be connecting them with the mc4 Y 1-4 combiner and then connect the suitcase with a MC4 1-2 combiner. If I use 10AWG to connect the 4 panels, and let's say I have to move my suitcase panel 25 feet (50 feet roundtrip). Would I need to get 8AWG wire for the suitcase panel to the combiner?

 

[Justin Laureltec]

I'm not a fan of my chart anymore. Do you have one you recommend, one for dummies like me?

I mean, the chart is still good (albeit a little optimistic in my view), you just have to remember that "circuit length"=ALL wire used in the system. Alternatively, we have a decent calculator and some relevant charts on our site, but you still have to remember to input round-trip length (although at least ours mentions that). I've found, in practice, that our calculator tends to spec heavier-gauge wire than Blue Sea's, which I personally like because I'm a big believer in overkill when it comes to wiring, but I suppose that could be argued.
Bottom line, the chart you posted is perfectly valid, it's just someone needs to put CIRCUIT LENGTH IS ROUND-TRIP in big bold letters across the top of it :D

 

[MisterSandals]

I will be mounting 4 on the roof. The suitcase will only come out sometimes. So, for argument's sake, I will be connecting them with the mc4 Y 1-4 combiner and then connect the suitcase with a MC4 1-2 combiner. If I use 10AWG to connect the 4 panels, and let's say I have to move my suitcase panel 25 feet (50 feet roundtrip). Would I need to get 8AWG wire for the suitcase panel to the combiner?

I'm feeling really unqualified to answer this now...
I "think" that with the addition of 50 foot round trip you would require ALL of the wires to be 8awg. (Justin?)

Alternatively, if you disconnected the roof panels when you add the suitcase, you would be 6.48 amps and good to 100' roundtrip.

What is the use case for the suitcase? To augment the rooftop panels or for use when rooftop not in use? (parked in shade for example).
For the latter, i think you'd be disconnecting the rooftop panels to be safe (trees do fall and shadows move...)

 

[Santa]

I'm feeling really unqualified to answer this now...
I "think" that with the addition of 50 foot round trip you would require ALL of the wires to be 8awg. (Justin?)

Alternatively, if you disconnected the roof panels when you add the suitcase, you would be 6.48 amps and good to 100' roundtrip.

What is the use case for the suitcase? To augment the rooftop panels or for use when rooftop not in use? (parked in shade for example).
For the latter, i think you'd be disconnecting the rooftop panels to be safe (trees do fall and shadows move...)

In my OP, I explained the reason for only sometimes using suitcase. I want as much power as possible, when stealthly possible. Disconnecting the roof panels defeats why I would even mount them in the first place.

 

[Justin Laureltec]

Ahhhhhh worse than all that... 30A at 50' needs 2AWG to keep the voltage drop under 3%, though 4AWG puts you at 3.2%, which... eh... could be lived with I guess.
8AWG at that distance puts your voltage drop at 8.08%, which is simply untenable. Then again, running 2ga wires 25' out is also pretty untenable... I strongly recommend just not putting your suitcase that far away, @Santa .

EDIT: I'm an idiot... what voltage are your panels running at? I was using 12v as the voltage in my calculator and on the panel side of the controller, that's obviously not the case.