AHU Bearing Failure
AHU Bearing Failure
(OP)
Has anyone seen a bearing failure on a rooftop air handler supply fan that is related to airflow problems? We have a McQuay air handler with a return and supply fan and have had several failures of the drive bearing on the supply fan. About four months ago an energy recovery ventilator was added to this system to supply conditioned outside air to the McQuay unit. Since then there have been two bearing failures. The McQuay vendor blames the ERV and said there are flow imbalances causing the bearing failures. The system was not balanced after installing the ERV, but I have never seen a bearing completely destroyed like this as a result of flow imbalance. The McQuay unit is a RAH047C. I can provide more info if needed. Any thoughts?





RE: AHU Bearing Failure
Vibration can be induced on a fan wheel. One way is to have air flowing predominantly on one side of ductwork. This can occur for example when a turn is placed too close to the fan. The off center airflow basically acts as a concentrated weight on the fan wheel causing it to vibrate because the wheel is not now in balance. The vibration then destroys the bearing. A vibration check should be done on the bearings to determine if the displacement levels are within tolerance.
RE: AHU Bearing Failure
RE: AHU Bearing Failure
RE: AHU Bearing Failure
Verify that the bearings have been lubricated with the proper grease.
Verify that the tension on the drive belts is proper, not excessive.
RE: AHU Bearing Failure
RE: AHU Bearing Failure
Sounds like we may be talking about the same building. I'm in Oak Ridge. I am supposed to get the failed bearing today so I can look at it. Repairs are being made today, and I would like to have some vibration readings taken as well.
Sounds like from the posts that most people see other causes for the failure than the addition of the ERV.
RE: AHU Bearing Failure
RE: AHU Bearing Failure
Flow is not directly injected into the fan cabinet, it is connected to the outside air make-up hood. I believe it goes through a preheat coil before it gets to the fan cabinet. The fan is a DWDI centrifugal, 40 hp motor, I have to find out about speed of fan, and it is a Dodge 212 bearing. Thanks for the input.
RE: AHU Bearing Failure