Recently, our Control Products Group team had an inquiry from a customer who was asking how to view the status of the inputs on a Danfoss VFD, as they couldn’t quite figure out when the VFD system was on or off. While this may seem confusing at first, here at AirReps, we’re experts in HVAC, so of course we have advice on an easier way to check the status of your VFD system by utilizing the display.

First, head over to your HVAC system to your VFD and navigate to parameter 16-60, Digital Input. As a reminder, the display on the Danfoss VFD is binary, showing the status of all the inputs at that moment. Zero means the input is “off” and a one means that the input is “on”.

In order to decipher which digit corresponds to which input, we suggest you take a look at the chart below from the programming guide for the Danfoss VFD.

As a note, when utilizing this chart, input 18 is typically used for the start/stop. According to the chart, input 18 is “Bit 5”, and you count from the right starting with “Bit 0.” In summary, input 18 is going to be the sixth zero, for more help, see the picture below.

Here at AirReps, we know that these simple issues can cause major stress and frustration when not working properly. If you need any further assistance, please feel free to reach out to our team of experts today!

Here at AirReps, our Control Products Group division has an incredible legacy of creating blog posts to directly help customers and partners. This particular issue was impacting a customer named Ryan who was looking at his VFD one morning when he noticed an issue he had never seen before. When he reached out to our team, we were happy to help.

Ryan reported to the Control Products Group team that while looking at his VFD, he noticed that the analog input from the building control system looked “jumpy,” which obviously, doesn’t look too good!

Before we jump into this specific issue, for those who may not be aware, the most untilized definition of a Variable Frequency Drive in the HVAC industry would describe it as an electrical device, used as a fan accessory, to increase and decrease the rotations per minute, or RPM, of an alternating current, or AC, motor.

While seeing the analog input looking “jumpy” may seem like cause for alarm, this isn’t completely uncommon. This is something our team here at AirReps notices from time to time. In these cases, when looking at the VFD, we occasionally see that the 0-10v signal from the EMCS is moving around constantly by fractions of a volt. Again, while this may seem like cause for alarm when it comes to your VFD system, it truly doesn’t do any damage to your system, and won’t hurt anything long term either.

A VFD isn’t like a damper actuator, where hunting will wear it out. So, while it may be a bit annoying, the VFD isn’t harmed by this issue. However, in this case, our customer didn’t enjoy seeing the display constantly changing between “running on reference” and “ramping” like it didn’t make a setpoint. As mentioned above, we’ve seen this before, so we know that while it may not harm the system, it is something that customers would rather not have to deal with, with systems new or old.

While no one may know where these tiny voltage changes come from, we can help you to smooth them out, so your VFD input is back to running smoothly. Simply change the default filtering in parameters 6-16 from .001s to around 1s or so. Remember, if you set the filtering too high, it will slow down the VFD response to reference actual changes, so make sure to follow these instructions carefully. This should help to smooth out those little bumps and help to get your VFD system running perfectly again.

If you’re still struggling with your VFD system, or if you’re looking for even more help when it comes to your HVAC system, reach out to us here at AirReps! We’re happy to help, or to get started on your custom HVAC design today.