Fuse needed
- Thread starter NikonRon
- Start date
rayra
Expedition Leader
Typically no but you could. Depends how fixed, protected or exposed your installation is. IF the wiring is sealed up in conduit, nah. If it's a loose extension cord sort of arrangement, having an in-line fuse would probably be a good idea.
as for sizing it, figure out what either the safe carrying capacity of the wiring that came attached to the panel. But if you are wiring it yourself, then size the wire and fuze to something that can comfortably handle the peak power of the panel that's energizing the circuit. 150W panel at 12v is ~13A. Depending on the capacities and efficiencies and needs of your system you could fuse it down to 10A (on the theory that most panels rarely do better than 80% of their (peak) rating anyway, so you won't be cutting anything off, but might be blowing fuses at peak output, OR you go 15A on the fuse and wire capacity and lose some fractional power to the increased resistance of the thicker wire.
Beyond a basic safety level, it's all tradeoffs and compromises, depending on your own preferences or comfort levels.
And the whole thing is predicated on how drawn down your batteries get overnight and how much power your charge controller allows to pass, anyway. Your system may never even come close to sucking in enough juice to need maximal fusing and wire gauge on your panel. But that also presumes there's never a failure mode or cut / damaged / shorted wire and maximum amp flow. In which case you are again back to fusing to protect ignition of the wire (or anything else downstream of your power source, the panel).
Think of a fuse as a throttle limiter. Your wire has a max safe capacity. The fuse keeps the current flow BELOW that. And at the same time you don't want that set so low that you can't get the most out of your panel.
And panel space being at a premium on a vehicle-mounted or -borne system, you want to make that max flow possible to eke out all you can get from the panels, for the times you really need it. Ideally your panels system's total rated output is say double your anticipated power consumption. That gives you buffer for ACTUAL panel performance vs its factory rating, gives you buffer for poor panel positioning / capture angles, loss of efficiency in transmission, conversion, partial shade on the panels, loss of performance over lifespan of the panel, etc etc.
And then all the compromises start. Size, space, placement, COST, etc etc.
as for sizing it, figure out what either the safe carrying capacity of the wiring that came attached to the panel. But if you are wiring it yourself, then size the wire and fuze to something that can comfortably handle the peak power of the panel that's energizing the circuit. 150W panel at 12v is ~13A. Depending on the capacities and efficiencies and needs of your system you could fuse it down to 10A (on the theory that most panels rarely do better than 80% of their (peak) rating anyway, so you won't be cutting anything off, but might be blowing fuses at peak output, OR you go 15A on the fuse and wire capacity and lose some fractional power to the increased resistance of the thicker wire.
Beyond a basic safety level, it's all tradeoffs and compromises, depending on your own preferences or comfort levels.
And the whole thing is predicated on how drawn down your batteries get overnight and how much power your charge controller allows to pass, anyway. Your system may never even come close to sucking in enough juice to need maximal fusing and wire gauge on your panel. But that also presumes there's never a failure mode or cut / damaged / shorted wire and maximum amp flow. In which case you are again back to fusing to protect ignition of the wire (or anything else downstream of your power source, the panel).
Think of a fuse as a throttle limiter. Your wire has a max safe capacity. The fuse keeps the current flow BELOW that. And at the same time you don't want that set so low that you can't get the most out of your panel.
And panel space being at a premium on a vehicle-mounted or -borne system, you want to make that max flow possible to eke out all you can get from the panels, for the times you really need it. Ideally your panels system's total rated output is say double your anticipated power consumption. That gives you buffer for ACTUAL panel performance vs its factory rating, gives you buffer for poor panel positioning / capture angles, loss of efficiency in transmission, conversion, partial shade on the panels, loss of performance over lifespan of the panel, etc etc.
And then all the compromises start. Size, space, placement, COST, etc etc.
Last edited:
IdaSHO
IDACAMPER
It is always recommended to have it fused between panel and controller.
See here for some tips:
https://www.windynation.com/jzv/inf/how-properly-fuse-solar-pv-system
There is no off switch for panels.
An inline fuse ( I use re settable) is a good way to cut power from the panel at the controller to safely install/service it.
I use these guys. From array to controller, and controller to battery bank.
They are rated at 20A for my system, act as a breaker, and are inexpensive.
See here for some tips:
https://www.windynation.com/jzv/inf/how-properly-fuse-solar-pv-system
There is no off switch for panels.
An inline fuse ( I use re settable) is a good way to cut power from the panel at the controller to safely install/service it.
I use these guys. From array to controller, and controller to battery bank.
They are rated at 20A for my system, act as a breaker, and are inexpensive.
Last edited:
loonwheeler
Adventurer
Agreed that having a way to cut the power from the panels to the controller is very convenient as shown in this example.
However having the fuse or breaker so close to the controller doesn't really protect the main feed wire from the panels would it? Typically you see fuses or breakers installed in the combiner box (as close to the power source as possible) on the roof for this very reason. While less convenient - having them at the combiner box (or as close to the panel as possible, depending on how many panels and what panel configuration you have) seems like best practice. What are your thoughts?
IdaSHO
IDACAMPER
I do agree that closer to the panel the better from a safety standpoint.
Technically fuses are used to protect wires.
The array side traditionally does not need to be fused as the wiring always exceeds the panels maximum rated amperage by a great deal.
Most 100watt panels that have the potential to provide 6-8 amps are wired with 14g conductors. Super overkill from a safety standpoint, but great from a (lack of) voltage drop standpoint.
If you happen to have an array that has the potential to exceed the wire's capacity, then by all mean, fuse it close to the panel(s)
But if you are that close to the wires capacity, then your wiring is undersized and should be increased anyhow simply to minimize voltage drop
Technically fuses are used to protect wires.
The array side traditionally does not need to be fused as the wiring always exceeds the panels maximum rated amperage by a great deal.
Most 100watt panels that have the potential to provide 6-8 amps are wired with 14g conductors. Super overkill from a safety standpoint, but great from a (lack of) voltage drop standpoint.
If you happen to have an array that has the potential to exceed the wire's capacity, then by all mean, fuse it close to the panel(s)
But if you are that close to the wires capacity, then your wiring is undersized and should be increased anyhow simply to minimize voltage drop
pugslyyy
Expedition Vehicle Engineer Guy
I use a Blue Sea circuit breaker, so that I can take the panel out of circuit if I need to. (Mainly if I need to ensure that the house system is de-energized while I am working on it.)
