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Old 06-23-2016, 02:21 PM   #1
friendofacatahoula's Avatar
Join Date: Mar 2016
Location: Alberta
Posts: 68
Do I need to add fuses - panels to controller

I stopped into my local solar shop today looking for some inline fuses for my solar set up and contrary to some of the information I have read the "solar guy" said I would not need fuses because the power cannot travel in reverse??? These guys have had some questionable advice already so I am looking for real world advice.

My set up is 3 100 watt panels in parallel connected by 3into1 MC4 connectors then two leads to the controller. I have a 30amp resettable breaker on the main power lead between the MC4 junction and the controller but that was left over from when I was going to run in series.

The controller to battery is protected.

I have read I should consider placing small fuses on each + lead of the panels. The LSC of my panels is 6 amps so a 7.5 amp fuse is really my best calculation. I am okay adding a inline mini fuse in a fuse holder but I can only find 12 gauge wiring. It is a very short run from the panel to junction, 2 feet, then less than 10 feet to the controller.

If the fuse is advisable on each panel, is my 7.5amp calculation correct, using the LSC*1.25?

Is the 12 gauge wiring on the inline fuse holders going to cause any noticeable loss? My leads are 10 gauge to the controller.

I have read pages and pages but much of it refers to electrical codes and in Canada our rv's are not bound by codes. I have also read Bob's and others pages but maybe I missed the part about "fuses" on the panels in parallel.


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Old 06-23-2016, 08:07 PM   #2
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Join Date: Mar 2014
Location: Mountain Foothills of Southern Alberta
Posts: 519
That local solar guy shouldn't be working where he is at if he is giving out such mis-information. He needs an education about fuses and diodes.
No need for individual fuses for each panel. The breaker you have in place between the the panels and controller will be just fine.


2007 Surveyor SV230
- 200 Watts Solar/MPPT Controller - 230 AH Battery Bank - 600 watt PSW Inverter - (2) 2000 watt Inverter Generators - LED Lighting - Boon Docking 99% of the time.
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Old 06-24-2016, 10:35 AM   #3
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Join Date: Mar 2016
Location: Alberta
Posts: 68
The only contrary info I have read mentioned concerns should a panel fail the other two could put more amperage into that panel and overload it's max fused limit. My panels do not mention what that limit is so I can only assume it's the same as the LSC.

Putting 12 amps into the failed panel could cause a fire as per the discussions.

That is my only concern. It's under $20 to get some in line fuse holders. If it isn't going to cause any minor loss by dropping down to 12 gauge for 4 inches then back to 10 I will do it. Over kill I guess

Wiring loss calculators do not get that specific.
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controller, fuse

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