AC/DC Disconnects for Home Solar Power Systems

Adding AC/DC disconnects to your home solar power systems adds an element of safety and flexibility to your system. The first thing to note is that the AC disconnect is used on the AC side of your system and the DC disconnect is used on the DC side of your system.

Installing an AC/DC disconnect allows you to isolate the system on either side of the disconnect. Why would you ever want to do this? Well maybe not you, but your installer or maintenance person will eventually have to repair some part of your system over the course of your home solar power systems’life time.

The disconnects allow him to electrically isolate the part of your system that he/she needs to repair or troubleshoot without getting electrocuted from working on energized equipment.

To think of it another way you never screw a light bulb into a light fixture when the light is one right? Well its the same concept. The disconnect is a switch that stops the electricity flow at that point in the system.

More specifically the disconnect will open the circuit which ensures that no current is flowing past the disconnect from the source (your solar panels) to the load (your home appliances). This can also work when needing to isolate your home solar power systemsfrom the utility grid if you have a grid-tiedsystem installed or from your battery bank if installed.

Things to Think About

Now you can’t just go out and buy any old AC disconnect or DC disconnect for your home solar system. Now you would be hard pressed to find a AC/DC disconnect that wasn’t NEC(National Electric Code) Compliant, but you should always check.

Not only is this important because it ensures that the equipment meets specific national safety requirements but most systems will not be approved by your local building inspector or more importantly your local utility company might not let you connect your home solar power systemto the utility grid.

Your solar installer should know what equipment is NEC
compliant and more importantly what your local utility company requires in order for you to safely connect to your local utility grid, but it’s not a bad idea to ask :-)

Beyond the NEC compliancy you need to ensure that the AC/DC disconnect is “rated” for the current and voltage that will be passing through it. If your system is rated at 100A (i.e. 100 Amps of current flowing in your wires) and 600V (i.e. 600 Volts voltage differential) you can’t go by a disconnect
rated at 60A and 600V.

It just won’t be able to hold the current of your system and continue to blow fuses until the proverbial light bulb goes on in your head and you realize you purchased the wrong disconnect. So just make sure you get one that can carry the load of your system.

Some disconnects are waterproof, which means they are able to be placed outside. If you are going to install it indoors this is an unnecessary added feature, but if you plan on installing it outside you better make sure its waterproof, or poof there goes all that money.