Proper way to connect on/off switch for entire system

[pekka8]

I wan't to have an emergency switch, a big red knob, for an off-grid system I'm building (battery, mppt and inverter). I have heard that you should always connect mppt to battery before connecting panels to mppt. So how should the switch be connected? If you just cut off positive on battery, mppt will be connected to panels alone. Cutting of the panels and battery still don't work if battery needs to be connected to mppt before panels.

 

[MisterSandals]

So how should the switch be connected? If you just cut off positive on battery, mppt will be connected to panels alone. Cutting of the panels and battery still don't work if battery needs to be connected to mppt before panels.

You will definitely want a cutoff switch from your solar panels. Some folks use a breaker for a little added protection.

A switch between the battery and SCC is not all that important because if solar disconnected, there won't be much current, only what the SCC needs to power on.

A switch from your battery (after the fuse), is quite important for disconnecting your loads for safety and eliminating phantom power draw.

I think these 2 switches are the minimum one should have. There are times you will want loads on but solar off was well as solar on and loads off.

 

[pekka8]

You will definitely want a cutoff switch from your solar panels. Some folks use a breaker for a little added protection.

A switch between the battery and SCC is not all that important because if solar disconnected, there won't be much current, only what the SCC needs to power on.

A switch from your battery (after the fuse), is quite important for disconnecting your loads for safety and eliminating phantom power draw.

I think these 2 switches are the minimum one should have. There are times you will want loads on but solar off was well as solar on and loads off.

Makes sense. And with two switches you can connect battery first.

 

[OffGridInTheCity]

I understand that you are working to figure things out. Let me share where I've wound up with after 5 years of operation / working with a bigger system as just one example. Note: Midnite Classic Charge Controllers can be hooked to PV or Battery in any order but I agree that some Charge Controllers don't like this. However, the general concepts apply.


I have breakers to protect wire and so I can conveniently shut things off to work on the setup safely.
Here's where I have breakers....

1) PV Array -> (outdoor) Combiner Box within 10ft of array - Breakers/Quick-Disconnect
*Required by code / helps fire dept.
--------------- these are all within reach of each other at the 'solar power room' -------------------
2) Combiner Boxs --> Charge Controllers - Breakers at the Charge Controllers to shut off the PV current from different arrays.
*Useful so I can work on the Charge Controllers without going 150ft outside to the #1 above.
3) Charge Controllers -> Battery Bus Box - Breakers at the Battery Bus Box to shut off all Charge Controller current.
*Useful to stop current flowing to the master DC battery buss from the Charge Controllers
4) Battery -> Master DC buss Control Box - Battery Breaker/Shunt-Trip
* BMS can trigger if battery out of spec and manual trip useful to ensure the battery current is completely stopped to safely work on things.
* Use with #3 to make the master Battery box / bus 100% dead - safe to work on.
5) Battery Bus Box -> Inverter - Breaker to protect wire to the Inverter
* Useful to shut-off power to work on the Inverter

Some combine #3 with #4 - so a single 'master switch' will disconnect all current going to/from the battery bus and all the loads flowing from the master DC buss.

Here's a pic of #2 (other side of the area from battery)

Here's a pic of #3, #4, and #5


In the beginning of my journey, I ignored all this stuff... but as the system grew and the lethal potential grew (400a @ 48v) AND as I've had to work on things many times to expand and do maintenance - I find all all these breakers absolutely useful for safety.

 

[RV10flyer]

I wan't to have an emergency switch, a big red knob, for an off-grid system I'm building (battery, mppt and inverter). I have heard that you should always connect mppt to battery before connecting panels to mppt. So how should the switch be connected? If you just cut off positive on battery, mppt will be connected to panels alone. Cutting of the panels and battery still don't work if battery needs to be connected to mppt before panels.

For our two Sol-Ark 12K’s, I installed a big red emergency shutoff on the outside of power shed to shut everything down. They have two terminals for that purpose. Works great!

 

[OffGridInTheCity]

I understand that you are working to figure things out. Let me share where I've wound up with after 5 years of operation / working with a bigger system as just one example. Note: Midnite Classic Charge Controllers can be hooked to PV or Battery in any order but I agree that some Charge Controllers don't like this. However, the general concepts apply.


I have breakers to protect wire and so I can conveniently shut things off to work on the setup safely.
Here's where I have breakers....

1) PV Array -> (outdoor) Combiner Box within 10ft of array - Breakers/Quick-Disconnect
*Required by code / helps fire dept.
--------------- these are all within reach of each other at the 'solar power room' -------------------
2) Combiner Boxs --> Charge Controllers - Breakers at the Charge Controllers to shut off the PV current from different arrays.
*Useful so I can work on the Charge Controllers without going 150ft outside to the #1 above.
3) Charge Controllers -> Battery Bus Box - Breakers at the Battery Bus Box to shut off all Charge Controller current.
*Useful to stop current flowing to the master DC battery buss from the Charge Controllers
4) Battery -> Master DC buss Control Box - Battery Breaker/Shunt-Trip
* BMS can trigger if battery out of spec and manual trip useful to ensure the battery current is completely stopped to safely work on things.
* Use with #3 to make the master Battery box / bus 100% dead - safe to work on.
5) Battery Bus Box -> Inverter - Breaker to protect wire to the Inverter
* Useful to shut-off power to work on the Inverter

Some combine #3 with #4 - so a single 'master switch' will disconnect all current going to/from the battery bus and all the loads flowing from the master DC buss.

Here's a pic of #2 (other side of the area from battery)
View attachment 143371
Here's a pic of #3, #4, and #5
View attachment 143368

In the beginning of my journey, I ignored all this stuff... but as the system grew and the lethal potential grew (400a @ 48v) AND as I've had to work on things many times to expand and do maintenance - I find all all these breakers absolutely useful for safety.

Was just working on the control box to hookup wiring from the DC buss to generator based chargers. I turned off the main battery (shunt-trip) breaker and the charge controller breakers but forgot about the Inverter Breakers!

I forgot that the Inverter capacitors have a charge and caused some sparks which made me jump into the low ceiling. Not safe! So I want to amend my post above and add that Inverter's must be disconnected from the buss as well as even if they're 'off' they may still backfeed DC current. So that's another reason to have breakers to the Inverters.

Sigh - got lucky and avoided shock / all is working once again.