Solar disconnect

[bluedog225]

I’m putting in a small 48 volt solar system for my shop. Starting small.

I think this will work as a DC disconnect for the solar panels if I keep it under 250 volt DC and 30 amps.

I got it at Restore. Pretty cheap. Cleaned out the insect nests. It snaps firmly.

Am I reading the specs correctly?

Thanks

 

[nadogail]

It looks to me as being good for 30 Amps at DC Voltages not exceeding 250.

 

[wyliesdiesels]

Keep in mind its not 3R rated meaning its indoor only

Also, continuous loads cannot exceed 80% of fuse rating. So 24a for 30a fuses

 

[BreeStephany]

What purpose does the disconnect serve in the photovoltaic system (i.e. is it intended as the main disconnecting means, is it serving as the rapid shutdown for the system, etc?)

Your disconnecting means shall comply with NEC 690.12 and 690.13.

My concern with the disconnect you have is that the device is not 3R / outdoor rated. The disconnect for the system needs to be READILY accessible and marked with its purpose as it serves with the photovoltaic system to ensure so that emergency personnel can readily isolate power sources when entering the building during a fire.

Emergency personnel look at the outside of the building to identify power sources before entering and if the deem it necessary to isolate power, need to isolate power sources BEFORE entering the building, hence the need for an exterior 3R rated disconnecting means which is readily accessible.

Personnel isolating power at the main disconnect of the building need to be able to readily identify that a secondary power source exists from the photovoltaic system and need to readily access that disconnect to isolate its power from the buildings internal wiring.

If the disconnect is installed within the structure at your main panel but not installed and identified at the main disconnect for the building, they may be unaware the photovoltaic system exists and assume that all power to the building has been isolated, leaving potential for the photovoltaic system to energize wiring within the building when the main disconnect to the building has been deenergized.

This is also true for maintenance personnel and electricians that may need to isolate power readily to the building.

If you havent already, I definitely suggest thoroughly reviewing and understanding NEC 690 in its entirety before proceeding on a photovoltaic system install.

Just my two cents.

 

[428PI]

My dc disconnect is in the inverter and ac disconnect after the inverter.

 

[reader2580]

You should have a disconnect on the AC side of the system the outside of the building, especially if grid connected.

 

[pembol]

You should have a disconnect on the AC side of the system the outside of the building, especially if grid connected.

That depends - some inverters are certified as 'rapid shutdown devices', in which case killing the AC power to the building also shuts down the solar. In this case you may not need an external AC disconnect. Our grid tie system does not have one.

 

[reader2580]

That depends - some inverters are certified as 'rapid shutdown devices', in which case killing the AC power to the building also shuts down the solar. In this case you may not need an external AC disconnect. Our grid tie system does not have one.

The AC disconnect is to kill the system in case of a fire, or if the utility wants to be certain their lineman can cut power. Turning off the AC will trigger the inverter to stop supplying power, and will trigger rapid shutdown if equipped.

I talked at length with the fire chief about electrical safety when designing my solar system. The fire department will not apply any water to a structure if there is any chance of contacting live electrical. They will shut off the main breaker if they can get to it. If not, they call the power company to come pull the meter. The FD will not pull the meter due to arc flash concerns.

The FD might as well pack up and go home if they have to wait 20 minutes for the power company to pull the meter. There will be nothing to save by the time thirty or forty minutes has passed since the fire started. I would rather have a complete burn at that point to make cleanup easy.

I installed the NEC 2020 required safety disconnect even under NEC 2017 so the FD can cut the power easily. I have a second disconnect for my solar since it is tapped off the meter and isn’t disconnected by the safety disconnect.

 

[wyliesdiesels]

That depends - some inverters are certified as 'rapid shutdown devices', in which case killing the AC power to the building also shuts down the solar. In this case you may not need an external AC disconnect. Our grid tie system does not have one.

disconnect is required on both sides here in california.