Solar fuse ( breaker) in Main distribution box sizing

[Jim Edwards]

Hi, I am adding some solar panels to my coach. 3 panels in totaling 420 watts. I have the original heliotrope rv45d controller that is capable of 500 watts so I am OK there but there is a fuse in the main distribution box ( see attachment ) for the solar panel rated at 15 Amps. AM solar recommended that this should be at least 25 amp. Has anyone run across this as an issue? What has been done as a solution? Please advise.

Thanks   

[Steve Huber Co-Admin]

Jim,
Assuming your original setup had a single panel, the 15A fuse would have been correct. Panels put out 17-18v DC and 100-140 watts, depending on type of panel. 140W would yield about 8 amps. Going to 3 panels, the current triples to about 24 amps so a 25A fuse is minimum. Keep in mind that panels will seldom reach their rated output which is probably why the 25A fuse was recommended rather than a 30A. If you are adding the 3 to the existing panel, the 25 a fuse would need to be increased
Steve

[Jim Edwards]

With the change in fuse, would you know if there is anything that needs to be changed in the support wiring? I have added heavier wire from panels to controller during residential fridge install for voltage drop but is heavier wire needed between controller and fuse or fuse and where ever? They seem to be 10 ga. or heavier which should be OK but gage on wires are not marked.  I was always taught that the fuse was sized to protect the wiring. Perhaps not the case here. Photo of breaker and wires attached.  Thanks

[Steve Huber Co-Admin]

Jim,
You should be OK. 10 awg cu will handle 30A.
Steve

[Jim Edwards]

Just for anyone reading this. After a bit of research there appears to be 3 types of breaker of the given size and shape to fit this application. They vary by how they reset after a fault. The original installed by Beaver was a type II but seems to be a rare find and no longer manufactured by some. The type I  that is commonly available, continuously resets until the fault is cleared. The type II resets after a power shutdown cycle (which I don't know ever happens because of the direct connection to the batteries). The type III is a physical reset. (button on the breaker). I spoke to some solar guys that specialize in RV solar and they recommended the type III.

Finally sourced 30A on Amazon (beaver portal!)