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Open Roads Forum  >  Tech Issues

 > Tripping solar panel breaker

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2oldman

NM

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Posted: 05/12/22 07:19am Link  |  Quote  |  Print  |  Notify Moderator

I don't know why you have to fuse panels.

StirCrazy

Kamloops, BC, Canada

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Posted: 05/12/22 07:51am Link  |  Quote  |  Print  |  Notify Moderator

EMD360 wrote:

Last fall I installed two Solarland 180w PERC panels. I had ordered three 100 watt but changed my mind and bought the two 180’s. Unfortunately I didn’t resize my order for the panel breaker which is 15 amps. The 100 watt panels were rated for five amps each but these are at 9.42 each. So now that we are getting really sunny days my panel breaker is tripping. I thought ok I’ll have to replace it with a 20. But I was watching the power when I was trouble shooting and thought I might have briefly seen more than 20 amps. Would a 30 amp fuse of these two panels be too high? The MPPT controlller is Victron. The system side breaker is 40 amps.


can you change the wiring to a series setup instead? this will keep your incoming amprage low but raise the voltage, so you'll be able to get a bit better efficency out of that MPPT controler. I have a old PWM controler on my three 180 watt panels on my 5th wheel and I see 22amps quite often, I am looking at changing the controler to a MPPT so I can put them in series. in parralel with a 8 ga wire you are looking at losing up to 0.38V over 10 feet, in series that would be a voltage drop of 0.19. doesnt sound like much but it adds up..

Steve


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EMD360

Arvada, CO

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Posted: 05/12/22 09:21am Link  |  Quote  |  Print  |  Notify Moderator

As I understand it series wiring means the panels have to both be working at the same efficiency to get maximum power from them. So partial shading impacts the total power available more. Most campsites have at least partial shade. So I opted for parallel wiring. Am I wrong about that? I believe I read that was the case.


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Posted: 05/12/22 09:28am Link  |  Quote  |  Print  |  Notify Moderator

StirCrazy wrote:

I am looking at changing the controler to a MPPT so I can put them in series. in parralel with a 8 ga wire you are looking at losing up to 0.38V over 10 feet, in series that would be a voltage drop of 0.19. doesnt sound like much but it adds up..
Series also has greater shade tolerance/power with panels that have bypass diodes (most have them).

My 3 series 30V panels have 3 bypass diodes, so 10V per panel section. I've seen charging at 20V increasing in 10V increments to 90V due to a leafy shade tree. ie The 20V can be from 2 different panels. Parallel would require sun on the entire panel and hence charging would occur with 1, 2 or 3 panels with sun.


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2oldman

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Posted: 05/12/22 10:08am Link  |  Quote  |  Print  |  Notify Moderator

EMD360 wrote:

So partial shading impacts the total power available more... So I opted for parallel wiring. Am I wrong about that?.
Depends on the panel. Bypass diodes allow for shading by shutting down that part of the panel. If no diodes are in the panel, then yes, a series setup will shut it all down.

I have 6 panels in series and I don't really notice that much of a degradation of power with partial shade. YMMV

EMD360

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Posted: 05/12/22 02:20pm Link  |  Quote  |  Print  |  Notify Moderator

2oldman wrote:

I don't know why you have to fuse panels.


Apparently you don’t if wired in series. The amps are not high enough to damage the wires if there is a short circuit.
That’s what the windynation site that was shared explained.

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Posted: 05/12/22 07:35pm Link  |  Quote  |  Print  |  Notify Moderator

2oldman wrote:

I don't know why you have to fuse panels.
Serial and 2 parallel panels don't need a fuse. 3 or more panels can cause a fire in a shorted panel and hence each panel should be fused at the combiner box to prevent excessive amps to the defective panel.

LittleBill

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Posted: 05/12/22 07:40pm Link  |  Quote  |  Print  |  Notify Moderator

how do u find out how many bypass diodes are in a panel? I don't think I have ever seen that listed?





EMD360

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Posted: 05/12/22 09:46pm Link  |  Quote  |  Print  |  Notify Moderator

I could not find any reference to bypass diodes in the specs for my panels but in a general explanation of bypass diodes I read that most panels have three. They are located in the junction box on the panel. Here is the diagram of the Solarland box. I’m assuming the three sections are bypass diodes.

[image]

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Posted: 05/12/22 11:02pm Link  |  Quote  |  Print  |  Notify Moderator

LittleBill wrote:

how do u find out how many bypass diodes are in a panel? I don't think I have ever seen that listed?
It should be in the specs or panel information. Opening the junction box will reveal the diodes.

It's common for 1 diode per 2 rows. So a 60 cell panel is 10x6 cells with a diode for every 10x2 section, so 3 diodes.

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