Solar to Charge Controller Disconnect Sizing

[thunderbeans]

I am trying to figure out the correct size breaker to add for my solar setup between my solar panels and charge controller. They are connected by 10AWG PV wire.

I have 3 175 Watt Solar Panels wired in Series.

Short Circuit Current: 10.35A

Optimum Operating Current: 9.75A

Maximum Series Fuse Rating: 15A

(https://ca.renogy.com/175-watt-monocrystalline-solar-panel/)

I have a 30A MTTP Charge Controller

Rated Battery Current: 30A	Rated Load Current:20A
Max. PV Input Short Current: 50A

(https://ca.renogy.com/rover-li-30-amp-mppt-solar-charge-controller/)


I was not sure whether I should size my breaker to match the max solar output (15A), or the wire gauge (30A) or the max input for my charge controller (50A).

Can anyone suggest the correct size? The size I am thinking this 32A 2P breaker - https://www.amazon.ca/gp/product/B0746DHZWT

Thanks in advance

 

[FilterGuy]

I am trying to figure out the correct size breaker to add for my solar setup between my solar panels and charge controller. They are connected by 10AWG PV wire.

I have 3 175 Watt Solar Panels wired in Series.

Short Circuit Current: 10.35A

Optimum Operating Current: 9.75A

Maximum Series Fuse Rating: 15A

(https://ca.renogy.com/175-watt-monocrystalline-solar-panel/)

I have a 30A MTTP Charge Controller

Rated Battery Current: 30A	Rated Load Current:20A
Max. PV Input Short Current: 50A

(https://ca.renogy.com/rover-li-30-amp-mppt-solar-charge-controller/)


I was not sure whether I should size my breaker to match the max solar output (15A), or the wire gauge (30A) or the max input for my charge controller (50A).

Can anyone suggest the correct size? The size I am thinking this 32A 2P breaker - https://www.amazon.ca/gp/product/B0746DHZWT

Thanks in advance

On a single series string, you don't need a breaker between the panels and the solar charge controller. However some people use a breaker for a disconnect. In your case, anything over 10A dc breaker would work as a disconnect.

Fusing & Wire Sizing guidelines for solar panels

To get the paper, click on the orange'' button at the top of the screen. This resource is intended to help the user understand when they need to add Over Current Protection Devices (OCPDs - Fuses or Breakers) to the solar panel array and what...

diysolarforum.com

 

[brewmatic]

From a safety point of view a breaker ampacity should nor exceed wiring capacity. Smaller breaker is OK. In your case anything between 15A and 30A is OK.

 

[rmaddy]

If you add a breaker to act as a disconnect then you must make sure it can handle the voltage. 3 of those panels in series will be about 66V @ STC. Figure close to 75V on a cold day. So the DC breaker must be rated for at least 75V. 100V would be better. 15 or 20A would be fine. Just be sure the voltage is supported by the breaker.

 

[FLD]

On the same lines as the OP, I was wondering what breaker, mainly for use as a disconnect, would work for my solar panel upgrade. Presently I have two 190 watt panels, connected in parallel to a 60-amp mppt controller, and will soon be adding two more in 2S2P configuration. 8awg wire from panels to controller.
Panel specs for all four are;

• Max Power at STC:190W
• Open Circuit Voltage:24.3v
• Short Circuit Current:10.15A
• Optimum Operating Voltage: 20.3V
• Optimum Operating Current: 9.3A
• Dimensions:60 x 26.8 x 1.4 in (1489 x 670 x 35 mm)
• Weight:24.2 lbs (11 kg)

I'm relatively new to solar and I'd rather ask folks instead of buying stuff, breaking it and buying more stuff, just because I was too stupid to ask folks that know about these things.
Any help is greatly appreciated.

 

[rmaddy]

Two 10.15A panels in parallel total 20.3A so your disconnect breaker should be 25A or 30A. The 8AWG wire can safely handle either. Adding two more panels as 2S2P doesn't change that calculation since you still have 20.3A. You just have twice the voltage.

One very important consideration when going from 2P to 2S2P is your Voc goes from 24.3V to 48.6V. And Voc increases in the cold. So it's important that the 25 or 30A breaker you choose also supports at least 55V. Many DC breakers are only rated for 36 or 48V.

 

[Just John]

I am trying to figure out the correct size breaker to add for my solar setup between my solar panels and charge controller. They are connected by 10AWG PV wire.

I have 3 175 Watt Solar Panels wired in Series.

Short Circuit Current: 10.35A

Optimum Operating Current: 9.75A

Maximum Series Fuse Rating: 15A

(https://ca.renogy.com/175-watt-monocrystalline-solar-panel/)

I have a 30A MTTP Charge Controller

Rated Battery Current: 30A	Rated Load Current:20A
Max. PV Input Short Current: 50A

(https://ca.renogy.com/rover-li-30-amp-mppt-solar-charge-controller/)


I was not sure whether I should size my breaker to match the max solar output (15A), or the wire gauge (30A) or the max input for my charge controller (50A).

Can anyone suggest the correct size? The size I am thinking this 32A 2P breaker - https://www.amazon.ca/gp/product/B0746DHZWT

Thanks in advance

That breaker you linked to is rated for 250v and should work, but would seem to high an amperage for the panels. Personally I use an in-line MC4 fuse, and a breaker as an on off switch. If you have a correctly rated fuse, you can use that breaker.