4 string Combiner box build

[solarHandyman]

I rebuilt an older Midnight Solar combiner box and I was pleased with how it turned out. As my peak current is under 30 amps I like using recycled bus bars or ground bar kits from the store with polyester standoffs from Amazon rather than paying extra for oversized bus bars branded for solar. The old breakers were single pole LittleFuse breakers with 10 amp fuses. The new breakers are double pole Cbi 10 amp breakers. The Cbi breakers are smaller which allowed four double pole to fit. To save space inside the box I put the equipment ground on the outside utilizing an unused aluminum ground lug for a solar panel. I bonded the equipment ground to the solar array and the ground rod at the array with a white 10 awg stranded PV wire. (I have a rod at each array and one for the 48v battery rack on top of the two for the main panel in my house, all bonded). Red and black are my positive and negative PV conductors. The MC4 connectors are from Amazon. I'll be adding clear roofing sealant on the MC4 connectors for extra waterproofing, and more importantly to prevent pullout as this is a problem I've had in the past with inexpensive solar connectors.

 

[Brucey]

I rebuilt an older Midnight Solar combiner box and I was pleased with how it turned out. As my peak current is under 30 amps I like using recycled bus bars or ground bar kits from the store with polyester standoffs from Amazon rather than paying extra for oversized bus bars branded for solar. The old breakers were single pole LittleFuse breakers with 10 amp fuses. The new breakers are double pole Cbi 10 amp breakers. The Cbi breakers are smaller which allowed four double pole to fit. To save space inside the box I put the equipment ground on the outside utilizing an unused aluminum ground lug for a solar panel. I bonded the equipment ground to the solar array and the ground rod at the array with a white 10 awg stranded PV wire. (I have a rod at each array and one for the 48v battery rack on top of the two for the main panel in my house, all bonded). Red and black are my positive and negative PV conductors. The MC4 connectors are from Amazon. I'll be adding clear roofing sealant on the MC4 connectors for extra waterproofing, and more importantly to prevent pullout as this is a problem I've had in the past with inexpensive solar connectors.

Looks good. What standoffs did you use? And just cut the negative bus in half to get the positive and negative bus versus using the 300V/3 position bus bar? Any thoughts of adding a midnite 300V DC spd on a side?

 

[solarHandyman]

Looks good. What standoffs did you use? And just cut the negative bus in half to get the positive and negative bus versus using the 300V/3 position bus bar? Any thoughts of adding a midnite 300V DC spd on a side?

Standoffs from Amazon: https://www.amazon.com/dp/B0BMVNTDMX?psc=1&ref=ppx_yo2ov_dt_b_product_details

For solar, I've never had trouble with the 300 volt Midnite breakers as a two pole breaker for positive and negative rather than a single conductor breaker wired in series with the copper jumper as it's sold. I read somewhere they aren't affected by the direction in the flow of current. As most of our DIY inverters/charge controllers are non isolated and/or transformerless, I read you are supposed to have a disconnect on both the positive and negative wires.