How do you inspect a rental VFD?

Renting a VFD can be a good option for customers looking for a short-term solution to control a motor’s speed and create a softer ramp up. One concern we’ve heard from customers before is knowing whether or not the rental VFDs are in good condition and can fulfill their needs.  

When we receive rental VFDs back at the end of a rental term, we thoroughly clean, inspect, and test them. The same inspections we perform could also be done for you when you receive a rental VFD on site.  

Match components to quoted system  

Most rental VFDs are enclosed in panels with additional components on top of just the VFD chassis. When receiving a rental VFD to your site, inspect the components in that panel. Verify the nameplate of the VFD matches the size of the VFD you need; undersizing it usually leads to problems. Rental VFDs are often slightly oversized based on what is available in the rental fleet. 

Panels often include breakers, capacitors, filters, reactors, and other components. To control harmonics or dV/dt, these may be crucial components. Check that all quoted components are included so your VFD accomplishes what is was specified to do.  

Inspect the condition  

The most easily detectable issues on a VFD panel are detected during a visual inspection. It’s important to inspect both the external and internal conditions. Look for damage that may have occurred during shipping or previous use. Dents, scratches, and broken components are good indicators of a possible issue. Warping or other heat-related damage is also a cause for concern.  

You also want to look for contamination. Look for dirt, dust, or other signs that the VFD was in a bad environment and has not had proper cleaning between uses. You should also look for water, condensation, mold, rust, or other signs of excessive moisture in the panel.  

Inspect connections  

Before you ever connect the motor leads, you can also inspect the other connections within the panel. Connections between the VFD, breaker, CPT, reactors, or capacitors can all be loose. It’s also possible they became loose during shipment. Look for any obvious connections that are undone or might be loose.  

You can inspect connections by hand and verify they are tight. We always recommend to torque connections to manufacturer specifications in order to ensure the best performance and lowest chance of problems.  

Verify parameters  

You usually don’t know the application that a rental VFD was last used in. Most often, the parameters on a VFD will have been reset to factory standards between use, but it’s possible that they weren’t or that this step was missed.

View the parameters and make sure that the settings for the VFD’s operation will work for your application. VFD applications are as diverse as the motors and driven loads they control, and what is optimal for one may not be appropriate for others. Setting parameters should be part of any commissioning process, but pay special attention to this step on rental equipment.

What not to do  

If there are any concerns that arise from the inspections above, it’s best to discuss these with the vendor you received the rental equipment from. Rental equipment should come to you in a condition where you feel comfortable using it.  

Avoid performing electrical testing or many major changes to the system that might put liability back on you as the end user. A good rule of thumb is that if it wouldn’t be included in a typical commissioning, avoid doing it without talking to the vendor.  

Work with a vendor you trust  

All of the inspections and processes listed above are great steps to verify that everything is the way it should be. However, the most important step is to partner with a vendor that you trust. When researching rental equipment, ask about the manufacturing processes. Make sure you know how it is cleaned, inspected, and tested between users.  

If you partner with someone who takes time to keep their rental fleet in good quality and is ready to serve a customer, you’ll be able to miss many of the issues that come with renting from someone who doesn’t prioritize quality experience.