I have been asked to see why an A500 VFD is not changing Hz despite the fact that I am getting the 4-20ma signal from our Honeywell loop controller on one of our boilers. I am completely unfamiliar with Mitsu drives and have reviewed the documentation yet am unclear on the setting range of 0-99,9999 for activation of the AU signal. This VFD is controlling an Overfire blower on one of our boilers so I am hesitant to just go changing things as one might imagine. My suspicion is that someone has clamped the max Hz or inadvertently turned off the Analog current signal in Par. 184 of the drive.