solar fuses

Ok great info. Thanks guys.

Muddydogs wrote:
Ken
What happens as both the controller and battery are both energy sources?

The controller is an energy source for the battery and needs a fuse sized according to its output current and cable size.

The battery acts as an energy source for the DC panel and other DC loads so it needs a fuse at its output to these loads and the fuse is sized according to the cable size.

The converter acts as a source to the DC panel, loads, and battery so it needs a fuse sized according to its output current and cable size.

Each of these fuses protect excessive energy from being passed through a cable that isn't designed to handle the heat that is generated from a shorted fault condition.

EDIT: Oh and the reason the solar panels under some conditions do not need to be fused is because they act as a constant current source which means a finite amount of current is generated.

So, if the cable can handle this finite, short circuit current indefinitely without overheating, a fuse sized for this cable would never open anyway.

Ken
What happens as both the controller and battery are both energy sources?

mena661 wrote:

2oldman wrote:
Fuses are not required for series PV installations, as mine is. Go ahead, tear me apart.

NEC only requires fuses when you have 3 or more parallel strings. That's a minimum of 6 panels wired series/parallel. Anyone here have that kind of setup? When I get my solar setup, there will be no fuses on the panels to controller side. A hint on why: solar panels are designed to be shorted. You're not protecting those, you are protecting the wire and only when you have X number of panels connected will you ever stand a chance of going over a wires current limit.

To clarify you need a fuse on each string for more than three strings in parallel

http://www1.cooperbussmann.com/pdf/9df1f7ec-8c62-4210-8cf8-9504927394f0.pdf

Muddydogs wrote:
Seems like if something happens in the confines of a trailer a fuse isn’t going to help much, the battery or controller will still be pumping juice through the line up to the fuse block most likely melting wire and starting a fire. On my trailer near as I can tell the main lines off the battery to the converter are not fused.

Doesn't work that way. DC requires a circuit. Think of a circle. If you break the circle (circuit), nothing happens. A popped fuse stops current (amps) flow.

Muddydogs wrote:
So here is a question.
So say I have a 30 amp fuse on the line between my battery and controller and either the battery shorts or the controller does and blows the fuse what good is the blown fuse since there is still a hot line active? Seems like if something happens in the confines of a trailer a fuse isn’t going to help much, the battery or controller will still be pumping juice through the line up to the fuse block most likely melting wire and starting a fire. On my trailer near as I can tell the main lines off the battery to the converter are not fused.

Fuses are designed to protect the wiring and they should be place as close as possible to the energy source.

If they are, then you are protected...

So here is a question.
So say I have a 30 amp fuse on the line between my battery and controller and either the battery shorts or the controller does and blows the fuse what good is the blown fuse since there is still a hot line active? Seems like if something happens in the confines of a trailer a fuse isn’t going to help much, the battery or controller will still be pumping juice through the line up to the fuse block most likely melting wire and starting a fire. On my trailer near as I can tell the main lines off the battery to the converter are not fused.

I have said it a million times,....many heavy cables are not fused or CB from OEM. I would guess they figure, "what are the odds of it shorting"
If thats good enuff for them, its good enuff for me.


Living life on the cutting edge ! :)

pianotuna wrote:
Hi Twomed,

Yes, but how many watts?

Twomed wrote:
40a on the roof, disconnect box with 40a in 30a out after Tristar60

Fuses are cheap... fire is expensive, pretty simple. ??

Sorry for late reply...running MT to FL. 600 watts

TechWriter wrote:

Me. Breakers also serve another purpose -- breakers make it easy to service your system by just flipping a few switches.

Nothing wrong with that.