5 Best Practices for Drive Enclosures

So, you need to put a drive in a box. We can help with that.

These best practices for drive enclosures will save you time—and frustration. Drives are often used and specified for use in industrial applications. From conveyors to pumps, drives are an efficient piece of automation technology. This blog post will walk through a PowerFlex® 525 AC drive real-life example.

Best Practices for Drive Enclosures

This post will scratch the surface of the guidelines, best practices, and math used to take a known drive and find a suitable enclosure (aka box) to put that drive into. Our post will walk through five steps:

  1. Check the physical dimensions
  2. Check the clearance suggestions and guidelines
  3. Check the depth recommendations
  4. Check the wattage and BTU specifications on the device
  5. Double-check everything else in the control panel system

Step 1. Check the Physical Dimensions

Will your drive fit in the enclosure? In a very basic sense, most drives are three-dimensional boxes (a cube). They have a width, a height, and a depth. In reality, drives also have curves, notches, and other geometric abnormalities to their profiles; i.e., they’re not a perfect cube. But for the purposes of discussion, we take the largest value for any one dimension and use that as our parameter.

This step means: verify the width, height, and depth of your drive and then select an enclosure that will—at a minimum— encase that object.

Example:

25BD010N114 Rockwell Automation Drive

© Rockwell Automation®

The A30HS2508SSLP is a disconnect enclosure, and its approximate size is 30” high x 25.38” wide x 8” deep. We compare the width, height, and depth of your drive versus the corresponding dimension of the enclosure. All three dimensions fit, so we can move on to step two.

Check the Physical Dimensions - HOFFMAN

A30HS2508SSLP HOFFMAN Enclosure Dimensions

If we tried to put this drive into a Hoffman CSD12106, it wouldn’t work. That enclosure is wide enough and tall enough, but the depth is a mismatch. Depth of 6.77” (drive) versus a depth of 6.00” (enclosure).

Plus, the drive would mount to a back panel, which adds approximately 0.125”. The back panel stands off the actual mounting backplane of the enclosure about another 0.5”. Rule of Thumb: Typically, we assume 0.75” of depth when using a back panel within a standard enclosure.

Assume 6.77” + 0.75” = 7.52”. You might be able to fit drive 25BD010N114 into a CSD16128 (changing to 8” of depth), but you might not want to, which brings us to the next best practice for drive enclosures.

Step 2. Check the Clearance Suggestions and Guidelines

This step has to do with the actual square footage footprint, namely width and depth on the backplane of your control panel. Just because you can fit the drive into a box, doesn’t mean you should cram it in there—CAN doesn’t mean you SHOULD.

Most drive manufacturers will publish guidelines about how much space (in inches) to leave between drives and/or under each drive, or even in front of each drive. These clearances can be found online for most Rockwell Automation® drives. Our previous example had selected drive 25BD010N114.

Now, let’s say we want to put two of that same drive into an enclosure. Some folks might call this “ganging up,” and it is not uncommon to see six or ten or more drives all ganged up into one enclosure. For this, we want to review the minimum mounting clearances. In this case, a 270+ page user manual document exists covering these questions. Click here, skip ahead to chapter one, page 15.

Minimum Mounting Clearances

© Rockwell Automation

We have two drives. The work is already done for you! These diagrams show many ways to mount your drive or drives. Vertical, zero stack, with fan kits, sideways (horizontal). Each diagram includes suggested dimensions. In this case, almost always 2” on the top and 2” on the bottom of each drive. If you build electrical panels, these diagrams should make sense to you. They show where the wiring and/or duct would be.

Our expanded example is for two 25BD010N114 drives, and we’re mounting them vertically. That means side by side with 1” between them. That gives us a special footprint of (W+W+1) x (2 + H + 2) or calculated out to (3.43” + 3.43” + 1 = 7.86”) x (2” + 7.09” + 2” = 11.09”).

  • We compare W (width) of 7.86” versus 25.38”
  • We compare H (height) of 11.09” versus 30.0”

That will all still fit into enclosure A30HS2508SSLP. On to step three.

Step 3. Check the Depth Recommendations

In addition to the called out physical dimension of depth, there are also a couple of considerations for the overall depth of the installed system. Namely, there may be a consideration for depth to let the drive breathe or to account for cables that connect via the front face of the drive. This is more commonly seen in servo drives.

Our two 25BD010N114 drives do not require additional mounting depth considerations. But, to take an example, consider servo drive 2097-V33PR5. This is a totally different type of automation product than the aforementioned 25BD010N114 drive, but they are both called “drives” by some users. So, let’s just take a quick look.

This is a good example for the world of servo drives. Returning to earlier example, the two PowerFlex 25BD010N114 drives that we put into enclosure A30HS2508SSLP. There are no additional requirements for our selected drive(s) at this step.

Step 4. Check the Wattage and BTU Specifications on the Device

If you’ve made it this far, you have a good mechanical fit. Your drive should fit in your enclosure, and you should be able to make all connections and still close the door. But it’s important to know that drives create heat. In general, too much heat inside an enclosure runs a very serious risk of damaging key electrical and electronic components like circuit boards. This step delves into electrical heat load.

We approach this step by finding two bits of information:

  1. How much heat could this drive create?
  2. At what temperature can this drive safely run?

Those two pieces of information can be found in the user manual for the drive. Then, we need to use about ten more known technical inputs to run this build through a calculator. The other information includes the width x height x depth of enclosure (for a contained cubic volume), ambient temperature, and more. We can also provide input as to whether we have fans on each drive, which is a commonly added option. We can also provide input as to whether we have a fan or an AC unit on the enclosure itself, or even an air exchanger or heat exchanger. These calculations involve BTU (thermal unit of measurement) and CFM (cubic feet per minute). You can get started here.

Cool Selection Tool - HOFFMAN

Honestly, we don’t have enough time or space on this blog to explain ALL those calculations. To keep step four simple, we’ll check:

  1. How much heat could this drive create? This is a 5 HP drive, AC current, 4 kW Normal Duty. That means (and this is the shorthand version) Total Watts Loss = 133 W. In this example, two drives create 266 W. Our calculations show that our enclosure system is a fit.
  2. At what temperature can this drive safely run? Per the published environmental specifications, surrounding air temperature with a range = -4…122 °F, known as “without derating.” Further temperatures are possible with derating, and there are published current derating curves and guidelines. For brevity, we’re saying as long as we keep this drive in an enclosure less than 122 °F we should be fine.

Step four can get quite complex and involve other considerations. For example, some folks might assume that 10% of the energy is dissipated as heat. Some might not. Your applications are unique. Your local Horizon Solutions contact can work with the manufacturer to help you with these calculations on your next project.

Step 5. Double-Check Everything Else in the Control Panel System

I know, just everything else. For a large and complex control panel, this step could be a 50-hour project in and of itself. Each item in your system has the capability of generating heat, and each item in your system has three dimensions of space to consider. Even a terminal block takes up width, using a bit of available DIN rail real estate. New, unplanned, and unexpected components sometimes have depths you haven’t yet factored. If the depth of a network switch prevents you from closing the door to your enclosure, that is a very bad thing.

What about where your finished control panel is going? Inside? Outside? We didn’t have space above to delve into enclosure type or a required NEMA rating. Those are two very important topics to discuss. Meaning, if you have an electrical enclosure in a space on a factory floor that gets washed down with water and/or cleaning chemicals, you’ll very likely need to explore options like NEMA 4X and stainless-steel enclosures. We’ve covered that before, here and here.

We Can Help with Everything

These best practices for drive enclosures take on the relatively small scope of putting one or two drives into an enclosure. Your systems may be quite complex and interrelated, so the maxim of “check everything else” isn’t meant to be covered by this post. This post was intended to introduce the guidelines, best practices, and math used to take a known drive and find a suitable enclosure to put that drive into. Our team of specialists can help you navigate all the factors. Contact us today!

What size drives do you use? What types of enclosures do you put them into? Do you have design and sizing issues with your drives?

About the author

Will Cole
Will Cole

Will is the Manufacturing Services Project Coordinator at Horizon Solutions, based out of Rochester, NY. His focus is on modified enclosures and custom control panel builds. He brings organization and enthusiasm to all stages of your project, including design, build, fabrication, customization, testing, and shipping. In his free time, Will likes to binge-watch the television show "How It's Made" and identify the Rockwell Automation controllers used.