Solar panel disconnect switch question

[bshackcreative]

I purchased a battery disconnect switch to disconnect the solar panels from my solar charge controller. (see attached image) I am not sure I purchased the correct thing.

It is a 'Battery Disconnect Switch 12V 24V 48V Master Isolator Cut Off Switch'. It states it has a 275 Amp continuous rating for 1 hour. My solar charge controller is a 'Victron SmartSolar MPPT 100/15 Solar Charge Controller 100V 15A with Bluetooth'. Should I be looking at volts or amps in the rating of the switch?

Can someone tell me if this switch is safe to do the job? If not what would a better compact alternative be. I have a very small camper.

I am not using the hardware that came with the switch.

Thanks!

 

[rmaddy]

Should I be looking at volts or amps in the rating of the switch?

Both.

If your panel array Voc is over 48V do NOT use that switch. In fact, don't use it all. You have a 100V SCC therefore you need a disconnect that is rated for at least 125V to be safe.

The more typical PV disconnect is done with a 2-pole DC breaker rated with sufficient DC voltage and amperage for your panel array.

 

[bshackcreative]

Ok cool thanks for the direction. I will checkout 2-pole DC breakers.

 

[rmaddy]

While not a specific product recommendation, here is an example of what I mean:

https://www.amazon.com/Miniature-Circuit-Isolator-Magnetic-Disconnect/dp/B095YFQWHK

 

[bedpan]

Can I ask why a 2 Pole and not a single on the Positive only? I am sure there is a reason I just don't know!

 

[rmaddy]

Apparently the NEC states that PV disconnect should be on both negative and positive PV wires. I don't recall the specific reasoning.

 

[bedpan]

Interesting.. I will have to read.. thanks for pointing it out.

Apparently the NEC states that PV disconnect should be on both negative and positive PV wires. I don't recall the specific reasoning.

 

[bshackcreative]

Thanks I order this:

AIMS Power Solar PV DC Quick Disconnect Switch 1200V 32 Amp https://a.co/d/hSyXu9a

 

[z_zk_z]

You already got one, anyway this is the one I am using

IMO DC Disconnect Rooftop Isolator Switch

IEC 60364-7-712, dc disconnect, imo, ul listed, DC AC, DC DISC

signaturesolar.com

 

[HRTKD]

If the final voltage of the solar panels exceeds the 48 volts rating of the switch in the original post then that switch is not rated for what you plan to use it. The AIMS switch is the correct option.

+1 to rmaddy's suggestion to use a two-pole breaker. For most of us in the mobile environments, an outdoor rated disconnect isn't necessary as we usually have the disconnect inside the vehicle.

 

[STW]

I recommend the circuit breaker be 25amps. I did that with mine because the 10ga wires going to panels, and the mc4 connectors are rated at 30 amps. So the 25 amp breaker should help protect them.

 

[rmaddy]

I recommend the circuit breaker be 25amps. I did that with mine because the 10ga wires going to panels, and the mc4 connectors are rated at 30 amps. So the 25 amp breaker should help protect them.

The PV disconnect breaker is only meant to act as a switch. It is not there to protect the wiring. You actually want to ensure the disconnect switch is rated higher than the possible current coming from the panels.

If you have panels in parallel and you have 3 or more strings in parallel then you must fuse each parallel string. This is separate from the use of a PV disconnect.

 

[STW]

The PV disconnect breaker is only meant to act as a switch. It is not there to protect the wiring. You actually want to ensure the disconnect switch is rated higher than the possible current coming from the panels.

If you have panels in parallel and you have 3 or more strings in parallel then you must fuse each parallel string. This is separate from the use of a PV disconnect.

Yes, obviously it’s there as a disconnect, but there is nothing protecting those PV wires if too many panels are connected and the amps are too high. Choosing a CB lower than the wiring/mc4 limit will add another level of protection.

 

[Shimmy]

Apparently the NEC states that PV disconnect should be on both negative and positive PV wires. I don't recall the specific reasoning.

All ungrounded conductors over 60V are supposed to have a disconnect and overcurrent protection. Logic is a ground fault would be unprotected if both conductors are not disconnected.

 

[rmaddy]

Yes, obviously it’s there as a disconnect, but there is nothing protecting those PV wires if too many panels are connected and the amps are too high. Choosing a CB lower than the wiring/mc4 limit will add another level of protection.

If you have that much amperage then you have enough panels in parallel that each string should be fused. If you have enough amperage to be too much for the MC4 limit then you need to be using a combiner box which won't have any MC4 connectors. If you have too much amperage for the wire then you screwed up choosing too small of a wire. You don't fix that by adding a lower amperage breaker. You fix it by choosing the correct wire and building your system correctly. Using the lower amperage breaker just means the breaker will trip on regular use leaving you with a non-functional solar setup.

 

[STW]

If you have that much amperage then you have enough panels in parallel that each string should be fused. If you have enough amperage to be too much for the MC4 limit then you need to be using a combiner box which won't have any MC4 connectors. If you have too much amperage for the wire then you screwed up choosing too small of a wire. You don't fix that by adding a lower amperage breaker. You fix it by choosing the correct wire and building your system correctly. Using the lower amperage breaker just means the breaker will trip on regular use leaving you with a non-functional solar setup.

I agree with all points. I was simply stating if you are going to put in a CB as a disconnect, might as well make it also useful to protect wiring. I see the possibility where somebody adds additional panels without considering the existing wiring.

 

[SolarStudent]

Thanks I order this:

AIMS Power Solar PV DC Quick Disconnect Switch 1200V 32 Amp https://a.co/d/hSyXu9a

I have three of those that came with my kit for my house. While waiting on my last few components to arrive, I'm struggling to design how I'll mount these outside my home.

Was your application for mobile RV, or a home?

I'm thinking of building a custom box to mount all three in...

I'd love to see pictures of how these Aims have been installed outside... anyone have photos to share?