If you read Amp Authority with any regularity, you know two things:
- We like to keep things simple
- We like local motor disconnect switches
Keeping with both themes, we are going to explore a rather technical piece of electrical code but with our own twist. NEC Article 430 is actually one of the longest and most complex sections of the code. While technically called “Article 430: Motors, Motor Circuits, and Controllers”, we will call it by its shorter name of NEC Article 430.
For those feeling extra brave, feel free to read the entire Article here. For everyone else, let’s get started!
Where NEC Article 430 Fits In the Big Picture
Here’s a great picture from Rockwell that helps put the motor control circuit into proper context:
As you can see, NEC Article 430 presupposes that you are in a facility, there are machines present, industrial control panels are involved, and there’s at least one motor powering a machine.
Major Sections of NEC Article 430
Before we jump into Disconnecting Means, it’s important to understand the sections of NEC Article 430. Here are the main sections of the Article:
Motor Control Circuits
Feeder Short-Circuit and Ground-Fault Protection
There’s also a nice visual representation of the steps included below which shows various considerations when dealing with any element of NEC Article 430:
Now we can finally get to disconnecting means. As NEC Article 430 states, you need a disconnect for each motor controller. Here’s a really simple digram showing where the disconnecting means must fall within the motor control circuit:
You must locate it within sight of the controller (see below). “Within sight” means visible and not more than 50 ft from each other. Under certain circumstances, exceptions are allowed to this requirement:
There are also several other key points to know:
- The controller disconnect must open all circuit conductors simultaneously.
- The controller disconnect can serve as the disconnect for motor control circuit conductors and the motor
- The disconnecting means for the motor controller and the motor must open all ungrounded supply conductors simultaneously
- The disconnecting means must be legibly marked to identify its intended purpose
- When operated vertically, the “up” position corresponds to the “on” state
- The controller disconnect or motor disconnect required by must be readily accessible
Products Used To Disconnect
Now that we understand the major components of disconnecting means within NEC Article 430, let’s take a quick look at the products used to meet code.
In other posts, we’ve broken down the difference between UL 98 and UL 508 disconnect. For the most part, the disconnects used to accomplish the objectives set out above are UL 98 disconnects. In the field, these are commonly referred to as local disconnects. Here’s an example of what one looks like:
You can look at this and see that it satisfies many of the items from the section above. When you walk the floor of a food plant, you’ll see dozens (if not hundreds) of these local disconnects scattered throughout the facility and NEC Article 430 is the reason why.
Summing It Up
In conclusion, we hope you enjoyed our breakdown of one of the toughest pieces of NEC code. Let us know if you want us to cover other sections of Article 430 in future posts!