How to Troubleshoot Fan Performance Issues

5 Steps to Find and Fix Industrial Fan Performance Problems

Troubleshooting and addressing fan performance issues can feel overwhelming, but with the five steps outlined below and the help of a trusted application engineer either remotely or on-site, you can find the solutions you need for your operations.

Whether you’re a producer of products or materials with a system or an original equipment manufacturer of a system, you have a system that requires a fan to operate. If the system is not working properly or at all, for example, you’re not getting the output you need, you need a solution fast. We’re starting with the assumption that you consider the fan part of the problem and need help identifying what’s going wrong.

Our Process for Troubleshooting Industrial Fan Performance Issues

We’re happy to help when we get calls about fan performance issues, even if we didn’t make the fan in question. We always start simple and go deeper from there. You can handle several things on your own before giving us a call, or you can connect with us from the start and let us walk through the process with you.

Our basic process is here, with further details below:

Check fan rotation and speed
Collect key measurements and information
Plot the ideal fan curve and horsepower curve
Compare ideal to actual readings and review installation photos
Have an application engineer inspect the fan and system directly

Check Fan Rotation and Speed

These seem like very basic elements of fan performance, but we often find that we can resolve issues quickly by double-checking them and addressing any errors or inaccuracies.

Fan Rotation: It’s important to know which way your fan wheel rotates, and the outlet of the fan or blower always indicates the direction the fan wheel needs to spin to move the air or gas from the inlet to the outlet. If you’re not getting the pressure you need, reversing the rotation might be all you need to do.

Fan Speed: We ask to verify speed because you’re probably getting your speed reading off of digital output. Most of the time, it’s correct. In order to be sure, we ask you to turn the fan off, remove the guard, put a tachometer (tach) on the shaft that’s driving the fan wheel, and put the guard back on before turning the fan on. There should be a hole in the guard so you can read the tach with a laser to verify the operating speed and ensure there’s no connection issue in your electrical readout. If there is, you might find that fixing the reading will enable you to resolve the issue easily.

Collecting Measurements & Information to Calculate Curves

In order to get to the root of deeper issues, you’ll need a bit of a roadmap in the form of an ideal fan performance curve and horsepower curve for your actual system. To construct that, we need to know key information and readings.

Horsepower: The horsepower the motor is consuming doesn’t lie. Plotting it against the ideal fan curve can help pinpoint fan performance issues and solutions. We use a calculation to figure out what your motor horsepower is and relate it to the fan curve. To do that, we ask you for the following:

Voltage: Input to the motor
Amperage: Power coming off the three legs on a three-phase motor
Motor Nameplate Photo: To provide other key info

Temperature: We need to verify the air temperature at the fan inlet, assuming it’s only air. If you’re working with a gas that is not just air, we also need you to calculate and send us the density of the gas or give us all the properties of the gas and let us calculate it.

Static Pressure: This is fairly easy to read in the field using a gauge through a hole at the inlet and the outlet. Give us those two numbers so we can look at the differential.

Volumetric Flow: This is extremely difficult to measure accurately. We can use the other information provided to calculate it.
Plotting the Ideal Fan Curve and Horsepower Curve to Assess Fan Performance
We (or you) start by creating the ideal fan curve at your conditions. This may vary from the manufacturer’s fan curve because your actual system conditions make a difference.

A fan engineer plots your fan curve with calculations using the above information, with the volume on the x-axis (horizontal) and the static pressure on the y-axis (vertical). As volume grows, static pressure drops. We also plot a horsepower curve on the same grid, which crosses the fan curve.

Compare Ideal to Actual Readings and Review Installation Photos

Once you have your ideal/expected curves, you’ll find your specific horsepower and static pressure with your given conditions. To do that, we draw a vertical line from the point on the horsepower curve to find where it crosses the ideal fan curve and determine the related static pressure.

Now see if those points on the ideal fan curve match your actual calculations. They might. If they don’t, the fan performance issue is likely related to system effects like duct length/constraints or a 90-degree turn close to the inlet or outlet. To help us identify the system effects, we’ll ask for photos of your installation so we can compare the ideal system to the actual one.

Have an Application Engineer Inspect the Fan and System Directly

If you’ve checked fan rotation, motor speed, and potential systems effects and things still don’t make sense based on your curve calculations and comparisons, there might be something else going on or other actions you can take.

You’ll want to look beyond the fan and check the system thoroughly for things like leaks bringing unwanted air in. These can masquerade as fan issues. Once you resolve those, go back to the beginning to see if your fan performance is back on track.

If that’s not it or it does not resolve the issues, you could have a faulty fan design that must be corrected. This is unlikely if you’re working with a reputable fan manufacturer, but not impossible. If you’re working with AirPro, you know you have a 3-year warranty, so any design-related fan performance issues should be addressed well within that time frame.

Finally, don’t forget that you can always ask a fan engineer to investigate fully and identify the appropriate solution. There’s nothing wrong with starting here – they might get to the solution faster. But we can do much of this work with you remotely, and we’re here for you at any stage when you need assistance to get your system operating optimally.

Hear About Troubleshooting Fan Performance from an Application Engineer

Chet White, Senior Application Engineer / Sales & Marketing Manager, outlines how to troubleshoot fan performance issues using a detailed whiteboard drawing in this 15½-minute video.

Note, the information above is based on 11 years of experience of one fan engineer. It does not necessarily cover all possible fan problems or represent all possible solutions.

To ask questions, get more details, or discuss your application, reach out and connect with one of our application engineers.

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