Circuit Breaker on Solar question.

[Vintage465]

I'm putting in some circuit breakers on my solar upgrade. Question is...on the breaker one side is Battery and one side is Auxiliary. My thought would be that the "input" or solar side would go on the "battery" post side of the breaker and the Auxiliary would then be hooked up to the side that goes to the battery. Now this is backward to the actual, "this is the battery and this is battery post". My thought is the power or higher amount is coming from the solar and it seems to me like that should get the "battery" post on the breaker. What are your thoughts?

[Randy the sly old fox]

I have never seen a CB that is directional. Can you post some more details on that CB. Perhaps there is something that I am missing.

[Vintage465]

One says Aux and the other says Bat.

Originally Posted by Randy the sly old fox

I have never seen a CB that is directional. Can you post some more details on that CB. Perhaps there is something that I am missing.

[Reka]

Does not matter closed current flows open no flow

[Randy the sly old fox]

Those look like marine type thermal CBs meaning that the open based on temperature. Personally I prefer Magnetic Breakers where the over current drives a coil that opens the circuit. Thermal breakers can be affected by external temperatures, so to avoid unwanted trips the breakers are designed to be very slow to open often requiring 600% over current to trip.

but as for the Bat and Aux markings - they can be ignored.

[twinboat]

Circuit breakers protect wires from overloading, melting and causing fires.

Batteries have huge energy reserves and can output 1000s of amps in a direct short.

You put the breaker " Batt. " terminal on the item that has the greatest potential of overloading and burning up the wires. That's the battery !!!
You also place the breaker close to that energy source, for the best protection.

If your system is wired correctly, your solar output will never be higher then the breaker rating. You don't want a breaker tripping on a sunny day.

[Vintage465]

Originally Posted by twinboat

Circuit breakers protect wires from overloading, melting and causing fires.

Batteries have huge energy reserves and can output 1000s of amps in a direct short.

You put the breaker " Batt. " terminal on the item that has the greatest potential of overloading and burning up the wires. That's the battery !!!
You also place the breaker close to that energy source, for the best protection.

If your system is wired correctly, your solar output will never be higher then the breaker rating. You don't want a breaker tripping on a sunny day.

All sounds good what you're saying. Both my breakers are 10-15% above the usage

[twinboat]

Originally Posted by Vintage465

All sounds good what you're saying. Both my breakers are 10-15% above the usage

Your wiring should be above the solar output also.

Unless your running 3 or more parallel panels, breakers are not needed on the solar input side. The energy producers, ( panels ) will never make more energy then you wire them for. A short will not overload the wiring and cause a fire. Actually nothing will happen except no charging. Same reason a auto alternator doesn't fuse its output wire. It can only output so much.

A switch type breaker is useful for turning off the system though.

Once you get to multiple, parallel panels, breakers are needed to protect one panels wiring from being overloaded by the other panels output. The breakers need to be in the junction box.

[Vintage465]

Originally Posted by twinboat

Your wiring should be above the solar output also.

Unless your running 3 or more parallel panels, breakers are not needed on the solar input side. The energy producers, ( panels ) will never make more energy then you wire them for. A short will not overload the wiring and cause a fire. Actually nothing will happen except no charging. Same reason a auto alternator doesn't fuse its output wire. It can only output so much.

A switch type breaker is useful for turning off the system though.

Once you get to multiple, parallel panels, breakers are needed to protect one panels wiring from being overloaded by the other panels output. The breakers need to be in the junction box.

So what you’re describing here is all likely in my scenario. Three 150w panels. In parallel to start with. Plan on putting a 40a switch type breaker like pictured in the combiner box.
If I don’t get the results I’m looking for in parallel I may go series and an mppt type controller. Good info!

[twinboat]

Originally Posted by Vintage465

So what you’re describing here is all likely in my scenario. Three 150w panels. In parallel to start with. Plan on putting a 40a switch type breaker like pictured in the combiner box.
If I don’t get the results I’m looking for in parallel I may go series and an mppt type controller. Good info!

You would actually want 3, 15 amp breakers. One on each panel, before the junction.

That way if one panel shorts, where it comes from the panel, the other 2 panels combined amps don't back feed to the short and overload its wiring.

In your situation, because panels use 10 gauge wiring, the two panels won't produce enough amperage to overload ones panels wiring.

Bigger panels or more panels can produce more amperage then 10 gauge wiring can carry.

Pick up 3 of these and 15 amp fuses and then combine the wires after the fuses. Then your set for adding more panels in parallel, if you want.

[Vintage465]

Originally Posted by twinboat

You would actually want 3, 15 amp breakers. One on each panel, before the junction.

That way if one panel shorts, where it comes from the panel, the other 2 panels combined amps don't back feed to the short and overload its wiring.

In your situation, because panels use 10 gauge wiring, the two panels won't produce enough amperage to overload ones panels wiring.

Bigger panels or more panels can produce more amperage then 10 gauge wiring can carry.

Pick up 3 of these and 15 amp fuses and then combine the wires after the fuses. Then your set for adding more panels in parallel, if you want.Attachment 266037

This is great info. I've just ordered up the fuse holders and connectors in fifteen amp to address this. This sound like the solid plan.

[Vintage465]

Originally Posted by twinboat

You would actually want 3, 15 amp breakers. One on each panel, before the junction.

That way if one panel shorts, where it comes from the panel, the other 2 panels combined amps don't back feed to the short and overload its wiring.

In your situation, because panels use 10 gauge wiring, the two panels won't produce enough amperage to overload ones panels wiring.

Bigger panels or more panels can produce more amperage then 10 gauge wiring can carry.

Pick up 3 of these and 15 amp fuses and then combine the wires after the fuses. Then your set for adding more panels in parallel, if you want.Attachment 266037

This is the new plan since getting the info on prioritizing the fusing on individual PV runs. Renogy recommends doing this too. I like the idea. Hopefully this will view correctly with the attachment. At some point I may upgrade to a MPPT controller. Right now I'll clean up the wiring, add the third panel, new combiner box etc. I'll post some pic's by Tuesday.
Solar.pdf

[astrocamper]

I use a disconnect switch between the panels and the controller. I use a DC breaker between the controller and the batteries. I open the disconnect from the panels before and opening the breaker when I want to isolate the controller. I have an MC4 fuse on the positive side of each panel before combining them down to the disconnect before the controller.

[Vintage465]

Originally Posted by astrocamper

I use a disconnect switch between the panels and the controller. I use a DC breaker between the controller and the batteries. I open the disconnect from the panels before and opening the breaker when I want to isolate the controller. I have an MC4 fuse on the positive side of each panel before combining them down to the disconnect before the controller.

I think what you’re describing is what my plan is though I forgot to show the breaker between the controller and the batteries on my drawing