Regarding breakers/fuses

Crystal · December 2009

I want to make sure that I have an understanding of the breakers/fuses that I plan to purchase. Any answers and advice will be helpful.

What size fuses will I need coming off 2 Evergreen 200 watt solar panels?
Will breakers work in the solar panel application?

I will be running #2 wire from the panels to a 30 amp charge control.
Rouge 30 amp charge control: requires a 30 amp breaker?

What size breaker would the Trimetric 2020 battery moniter and 100 amp shunt need? I will be using #16 wire.

IOTA 55 amp battery charger: requires a 45 amp breaker
I was unable to find this size at the NAWS store so should I go to a 50 amp?

What size breaker is required coming off four T-105 battery bank?

Does the Samlex 300watt inverter require a breaker?
If yes, would a 40 amp breaker be sufficient?

I will also be using a 5000watt generator to charge when battery bank is low. Is there a breaker in the wire between the generator and the charger? If yes, what size? Also, what size wire is recommended for a 50 foot run between generator and battery charger?

Thanks in advance for all the helpful advice!

Vic · December 2009

Re: Regarding breakers/fuses

Hello Crystal,

The function of a Fuse or Breaker is to protect wiring. At times, these protective devices also protect equipment.

In the case of the Rogue CC, you may be able to use a wire size appropriate for the Breaker that you can buy. Sometimes, hovewer, there are limits of the size wire that a device like a CC accommodate.

I am not a real Code expert, and the Code really dictates Wire and Breaker issues, but, the bottom line is that sizing of Fuses and Breakers in the Code is to keep the wiring from overheating and possibly causing a FIRE.

THe producer of the Rogue CC frequents this board, and there are numerous installers/Code experts here ... thery can chime in on the Code nuances.

Good Luck, Vic

hillbilly · December 2009

Re: Regarding breakers/fuses

What Vic said, and a bit more...
So to protect the wire the fuse/breaker needs to be sized up to the derated ampacity of the wire or smaller. The idea being that the breaker trips at a lower current than the wire is able to handle, so a wire that can handle 30amps would need a CB of 30amps or less. There are also different types of wire, which are rated higher or lower (and have specific intended applications, such as wet vs dry location). Then you need to derate that for other factors that can cause the wire to overheat; namely higher ambient temperatures and how many wires are in the same conduit.

Not being totally certain of the wire type you are using, #2 wire has ampacity ratings of 95amps to 130amps for example. So assuming that you're wire is rated at 115 amps (just for example's sake), and lets say that the ambient high temperature is 105F, that would derate your wire to 81 amps. If the ambient temperature is higher than 114F that wire would be rated down to 66 amps, just to give you an idea. Then you have the issue of where the wire is mounted, for example on a roof top the ambient temperature is much hotter and must be accounted for.

So you need all the specifics to make sure that your CB protection is adequate,
HTH, HB

GreenPowerManiac · December 2009

Re: Regarding breakers/fuses

This should help:

http://www.powerstream.com/Wire_Size.htm

Know your loads then add one size to be safe.

Regarding breakers/fuses

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