Proper cutoff/fuse for Solar Panels to MPPT in a van

[downhilltrucker]

I am setting up a big solar setup in a van I'm building. I noticed most folks seem to use a cutoff/fuse in between the panels and the MPPT like the left fuse. In my previous solar setups, I have used fuses like the one on the right. Should I be using something like the left setup?



For background, I have 400w (2 200w panels in series going to a Victron 100/30 MPPT. Here are the specs for each 200w panel:

• Max Operating Voltage (Vmpp): 18.90Volts Max Operating Current (Imp): 10.58Amps Open Circuit Voltage (Voc): 21.86Volts Short Circuit Current (Isc): 10.99 Amps

I think I should be good with the breaker on the right (48v and 40amp max) but wondering if I'm wrong or if there is advantage to the left breaker.

 

[MaikaiLife]

The breaker on the left is a dual-pole breaker, meaning it will disconnect both the positive and negative lines. This ensures a complete disconnection between the connected devices, which is especially useful if there's an unexpected current feed on one side. The breaker on the left is also compatible with a rail system, making it easier to mount in various electrical boxes available on the market.

Both options will work, so the choice comes down to personal preference once the specifications are matched.

 

[HarryN]

Just get a different brand of dual pole breaker. There are a lot of failures with those. They might be worse than having nothing.

There are some discussions of options for breakers in this section.

Wire/Connectors/Junction Boxes

diysolarforum.com

 

[0truck0]

I use the one like on the right. Just get an amp rating close to your panels unless you are only looking for an on/off switch.
I have had no issues in a few years of using them.
I have also use the ones that look more cylinder shape, common for audio systems, on eBay you will see them listed next to the right side one. I like them because the bare cable ends gets closed up under a cap, unlike the one you picture here.

 

[42OhmsPA]

Just get a different brand of dual pole breaker. There are a lot of failures with those. They might be worse than having nothing.

There are some discussions of options for breakers in this section.

Wire/Connectors/Junction Boxes

diysolarforum.com

I thought Chtaixi were known to be a good option.
I have MWh's through a few of them with no issues.

 

[HarryN]

I thought Chtaixi were known to be a good option.
I have MWh's through a few of them with no issues.

A lot of people did - including me.

But they don't seem to be tripping correctly - an increasing number of reports - especially in mobile applications.

The requirements for lower voltage systems is just "disconnect on both poles" and some people are just going back to using a connection and some fuses instead.

I personally don't see a big advantage for breaking both poles with the breaker vs just one pole and then pulling the plug / MC-4 for occasional disconnect - especially for sub 40 volt panel Voc. I am going to verify that no current is flowing before maintenance anyway.

But I am also looking at one of the original suppliers of double pole breakers for solar use - midnight solar.

Still studying their products, but am headed in this general direction.

MNDC-GFP80 midnight solar double pole breaker

This breaker looks interesting for some applications that need both DC poles switched with one handle.

diysolarforum.com

MNEDC-300 30A thru 80A NON POLARIZED Midnight solar dual pole breakers

Possible breakers for dual pole, DC applications 300 VDC

diysolarforum.com

 

[42OhmsPA]

A lot of people did - including me.

But they don't seem to be tripping correctly - an increasing number of reports - especially in mobile applications.

The requirements for lower voltage systems is just "disconnect on both poles" and some people are just going back to using a connection and some fuses instead.

I personally don't see a big advantage for breaking both poles with the breaker vs just one pole and then pulling the plug / MC-4 for occasional disconnect - especially for sub 40 volt panel Voc. I am going to verify that no current is flowing before maintenance anyway.

But I am also looking at one of the original suppliers of double pole breakers for solar use - midnight solar.

Still studying their products, but am headed in this general direction.

MNDC-GFP80 midnight solar double pole breaker

This breaker looks interesting for some applications that need both DC poles switched with one handle.

diysolarforum.com

MNEDC-300 30A thru 80A NON POLARIZED Midnight solar dual pole breakers

Possible breakers for dual pole, DC applications 300 VDC

diysolarforum.com

Thanks for the info.
Yes, always verify with a meter.

I'm using the dual pole mainly as a disconnect and a fused positive after.
Some thermal shots here

I'm using 100A single pole Midnite breakers for my battery disconnects. They are solid.

 

[meetyg]

The one on the left should have both short-circuit protection (fast acting) and overcurrent protection (slow acting). This is done by two mechanisms internally: One is a magnetic coil (for the short circuit protection) and the other is thermal (for overcurrent).
The one on the right is only thermal.

Also, the one on the left should have an arc extinguishing chute. This is important for higher voltage DC such as in PV panels.
This is also important should you need to disconnect the PV under load. This is generally not recommended, but should you need to do that, the left one should be safer.

See this for example:

I personally use the kind on the left for my PV panels.

Do note that the dual pole is polarized, meaning that you must connect it the correct way, otherwise you might get burn the breaker.

Input (PV panels) go on the top, output on the bottom.