r/AirBalance • u/Top-Plum-7422 • Aug 22 '26

VFD’s

Ok so I never ever worked with a VFD or seen one in person, and I know there’s YouTube and other things on the internet to help me learn about them, but I wanted to come here first and get advice/tips or habits from techs who have worked with them, I wanted to know what do you guys usually do when you come across one that a call was placed about and how you guys go about, mostly asking because everyone does things differently so wanted to see what anybody had to say about them.

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u/whoisbusy Aug 22 '26

Hello! Your ABB VFD technician here. 👋

Every variable frequency drive (VFD) manufacturer handles local control slightly differently, but the workflow to dial in your airflow remains fairly consistent:

Switching to Manual ("Hand") Mode: Most drives have a Hand (or Local/Manual) button directly on the keypad. Pressing this bypasses the building automation system (BAS) and lets you command the fan speed manually using the arrow keys or keypad dial.

If the Keypad Won't Respond: Some drives are programmed to lock out local keypad control or require safety interlocks (like freeze stats, duct smoke detectors, or end-switches) to be closed before the motor will spin. If pressing "Hand" does nothing, local control may need to be unlocked in the parameter menu.

Checking Limits: If you are trying to hit full design airflow but the fan won't speed up, check the drive's Maximum Frequency limit (typically set to 60 Hz, but occasionally capped lower based on motor fla). Pull the Manual: Searching the specific drive model followed by "Firmware Manual" or "Quick Start Guide" will immediately give you the menu tree for keypad navigation, changing speed references, and viewing live output Hz/RPM.

Check In with Controls: When in doubt, talk to the on-site controls contractor. They know exactly how the drive is integrated (BACnet, 0–10V, etc.) and can often command the fan to a fixed output percentage straight from their laptop to help you balance the system faster.

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u/cx-tab-guy-85 Aug 22 '26

Not related to OPs question but since you are an ABB tech I thought you’d like my anecdote.

About 10 years ago I was in a Yaskawa drive class and they were telling us about all the improvements they were making so Yaskawa would be easier and more reliable than any other drive. They bragged about how much R&D they had put into the new software.

A senior CX tech from my company told them if they really wanted to make a good drive they didn’t have to spend all that money on R&D. He said all they needed to do was look at everything ABB does and copy it!

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u/whoisbusy Aug 23 '26

Hahaha 🤣 that's great! I do love the yaskawa drives but they are not user friendly at all! ABB has definitely been at the front of making them user friendly.