Solar Panels - Where Does the Fuse Go?

[redsky49]

Trying to comply with ABYC requirements, as well as proper standards and practices.


ABYC Sec. 11.10.1.1.1 requires overcurrent protection (fuse or circuit breaker) device placed within 7" of power source. How can you possibly comply with this for solar panels? Even the exception(s) allowing placement further away seems impossible to meet.


And does this 7" requirement also pertain to the charge controller? I would like to consolidate all the fusing to avoid (user) confusion. What is kosher, and what is done in the real world?

[BillKny]

Solar panels are inherently current limited. You can dead short the wires, on the output and if the wires are sized properly, everything is just fine. No fuse is needed to protect the wires from the solar panels.

You fuse these wires to protect them from the BATTERY. As far as the wires are concerned that is the unlimited source of power in the system.

A controller isolation failure followed by some kind of short could result in a dead short across the battery terminals and the essentially unlimited current available there from the battery.

The fuse needs to be close to the battery protect wires between the controller and the battery from a short. If the wires going out to the solar panels are significantly smaller in ampacity (not unusual) another fuse might be needed at the outlet of the controller, again to protect the wires from the battery.

[Uncle Bob]

Originally Posted by redsky49

Trying to comply with ABYC requirements, as well as proper standards and practices.


ABYC Sec. 11.10.1.1.1 requires overcurrent protection (fuse or circuit breaker) device placed within 7" of power source. How can you possibly comply with this for solar panels? Even the exception(s) allowing placement further away seems impossible to meet.


And does this 7" requirement also pertain to the charge controller? I would like to consolidate all the fusing to avoid (user) confusion. What is kosher, and what is done in the real world?

Follow the requirements of the controller manufacturer.
In my case, a fuse no more than seven inches from the battery. That's it.
When this question has come up previously responses have been to fuse at the battery as well as at the controller with a circuit breaker between the controller and panels and then to add individual fuses at each panel.
Imagine trying to troubleshoot that one.
Follow the equipment manufacturer's instructions.

[SunPoweredYachts]

Good questions. Solar panels are what the ABYC refers to as 'self limiting devices' but it's still recommended to put an appropriately sized fuse/circuit breaker after the charge controller and before the battery bank.

Some installs also like to put an appropriately sized fuse/circuit breaker after the combined solar panels and before the charge controller. Or you might put an inline MC4 fuse after each solar panel (on the positive wire)

(Worth noting there's also likely going to be a fuse in the charge controller.)

[smac999]

the battery is the source. fuse at battery. the panels are current limited.

panels need fuses if you are putting a bunch in parallel and the combined amps of all pannels exceds the cables of any one of them. then the group of panels becomes a source greater then the wires can handle if one panel shorted.

[Manateeman]

Littlefuse? Not sure of spelling, has special solar fuses. All my panels go to a DIN rail with solar fuses then to Ferez Shaumet ? Blocks which lets you join different size wires ...then one large Circuit Breaker before the controller and another Circuit Breaker after the controller.
I also have a Midnight Solar lightning protector thing before the controller.
I try to follow what protection the solar people are using. I have a Schneider controller and it’s fantastic.
DIN rail makes everything easy and neat looking and it’s a snap to pull down the fuses to inspect or change or disconnect just one panel.
Six 285 panels Rolls batteries 24 volt and 700 AH.
Happy trails to you
Mark and a manatee crew who exist solely on pizza and cold beer.