We have been having a spell of rainy humid weather here in the northeast and I came in this morning to find my Haakon AHU with about 4" of water throughout the bottom of the air handler.
I have 2 drains on the unit. One in the humidifier compartment and one after the cooling coil in the blower fan compartment.
I found that due to the vacuum created by the blower running it was not allowing my compartments to drain properly. Once I popped the doors and allowed the pressures to stabilize in the compartments, the water began to drain. Water was flowing freely through the drain pipes. They are not clogged.
My situation is this:
This AHU supplies an ISO 7 clean room and our SOP states that if for any reason the unit has to be shutdown and discharge air pressures fall below allowable tolerances then we need to perform a cleaning of the room. Fortunately my room was out of service at this time, however we plan to be bringing the room into service and our operations can not afford to have production stop so they can reclean the room if I have to shutdown the AHU to drain it out again.
Picture Below. The two yellow arrows are pointing to the drains.