Solar MC4 Junction Boxes

TheBatteries

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What are you guys using as junction boxes on your roofs? I know Peter mentioned having breakers on his roof too. What kind of enclosure did you use? All I can find is small ones on eBay that cost like $100. I'm looking to join 3 strings of panels with breakers, possibly more in the future then run one big cable down to my shed. Should I leave it as individual cables to the shed?

Just curious what others are doing...
 
I dont use any. I use MC4 junctions when needed and then all down to the cabinet.

But if i would do i woult go with IP65. Ie outdor cabinets that are made for outdoor use. Not sure what the equivallent is in your area.
 
Does this even work? Shorted solar panels will go up in voltage with very little current going through the short, if any, won't they? I would have thought the breakers consequently never would actually break the circuit.
 
The circuit breaker wont do much good for a normal setup where you tie 2 paralell strings together since in real life the max current will be 1 string if the other is shorted due to diode issues. And the breaker should be able to withstand the full current from 1 string :) So the breaker will only work if you have 3 or more strings together and I dont have that. Only 2 per wire going down and then breaker panel at the inverter side.

In sweden low voltage systems are not common at all. Normal is 300-800V :) And those are generally 1 string down and not combined.

Im not sure of the requirement though. There is nothing in the manuals I have followed regarding the junction more than it need to be weather proof.

Note that there are short-diodes in each panel and they should take out most cases if there are issues.
 
In Australia we have to have a disconnect on the roof by law
 
The pcm have 2p3s. Mc4 junction on the roof under the panels. 20A 2p dc breakers close to the charger. Then combined after the breakers.
 
Kind of but only for 2. They arent made for to high current so i guess those cheap ones are no good. For 100w panels it should be fine. Yes check ur area. They are fine here for non high volt.
 
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