PV Disconnect/Breaker

[rs14smith]

Hi,

I saw someone with a similar system as the one I plan to build use the following components to disconnect power from their solar panels to the rest of the solar system (charge controller, etc.):

Square D BY Circuit Breaker Box QO24L70S
Square D 40 Amp Circuit Breaker QO240CP
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When I looked up the items online, the circuit breaker is for a AC circuit, and I've read in some places that it's not a good idea to use AC breakers for a DC circuit. Does this circuit breaker have something different included that allows it to be ok for DC circuits?

My 12v system will only be producing about 23-24Amps.

[solarfrank]

you have to check the full specs , i read somewhere that QO breaker are listed for dc all the way to 48V , but you have to check .

[inetdog]

you have to check the full specs , i read somewhere that QO breaker are listed for dc all the way to 48V , but you have to check .

Neither the retail catalog page nor the specification sheet for the QO breakers list anything but AC voltages.
To know for sure you would have to contact their support staff.

[rs14smith]

Neither the retail catalog page nor the specification sheet for the QO breakers list anything but AC voltages.
To know for sure you would have to contact their support staff.

QO_Switches.JPG

Above is the spec sheet that does confirm I believe that the switch can be used in DC circuits. The guy in the video I was referencing used 1 that is "double" pole. Is a double pole switch required? I figured you only needed to break the hot (positive red wire) side of the PV system with a disconnect switch if you have a grounded system?

Thanks

[OceanArcher]

re: DC Circuit Breakers

Anytime I have to disconnect a DC circuit, I utilize breakers manufactured by Carling Technologies. They have a line of breakers specific for DC usage, and will fulfill most needs for small to medium home solar systems ....

[solarfrank]

Looks like the breaker it's listed for use up to 48V on DC circuits. If your inverter is grounded you need to have on the breaker just the red wire( + positive), if the inverter it's ungrounded you need both + and - to be on the breaker( fuse).

[rs14smith]

Looks like the breaker it's listed for use up to 48V on DC circuits. If your inverter is grounded you need to have on the breaker just the red wire( + positive), if the inverter it's ungrounded you need both + and - to be on the breaker( fuse).

Yes, eventually my inverter will be grounded once I upgrade it. I went ahead and hooked up both the positive and negative legs coming from my PV system to the circuit breaker to meet NEC code which requires a fused disconnect for the array output. At first I was somewhat confused if I had to use a disconnect that had actual fuses or if a circuit breaker would be enough. It looks like either works just fine.

[inetdog]

[ATTACH=CONFIG]6416[/ATTACH]

Above is the spec sheet that does confirm I believe that the switch can be used in DC circuits. The guy in the video I was referencing used 1 that is "double" pole. Is a double pole switch required? I figured you only needed to break the hot (positive red wire) side of the PV system with a disconnect switch if you have a grounded system?

Thanks

Yes, the models shown are good for 48V DC. Note that the higher voltages are "Certified By SquareD", which means to me that they will stand behind any failures when used at less than 125V DC, but that the electrical inspector is under no obligation to allow you to use them.