Got a quick problem and looking for some feedback
Got a guy out in the field doing an air balance and trying to troubleshoot an overamping blower motor. He's fairly green so I'm having to walk him through everything. Running out of ideas here, and looking for that one thing I haven't thought of.
Here's the details.
480 v (495 actual)
2 hp blower motor (3.1 FLA / 3.6 SFA)
Initial airflow was measured at 136% of Engineers design airflow. (3000 cfm) (we find this a lot, so it's not unusual)
Motor initially operating at 4.1 amps (FLA = 3.1)
Tech adjusted pulley to minimum setting. This brought airflow to 125% of design, but amps only went down to 3.9.
Replaced blower pulley and brought airflow down to 100% of design, but amps only went down to 3.7.
RPM and pulley sizes are consistent with what we see on this concept, but the motor staying above FLA is not. No matter how far he slows the fan down, the amps are not dropping more than a 10th or two and the fan remains above FLA. Motor is not excessively hot.
This is the details of one system. There is also an 8.5 ton unit with the same problem. The motor will not go below FLA despite any adjustments. The remaining 4 units are all okay.
Right now he's checking for a short cycling roof curb.
I can provide any additional details if you need any.