Today I arrived and checked in. There was a concern about a quiet knocking noise at the air handler located above grid. The blower compartment as well as any moving parts were checked for the source. The system was operated and still no noise detected. Eventually as it was operating one of the employees said that they heard the sound. What they heard was gurgling in the drain line. The system is functioning, the drain is not plugged and 5e condensation pump is operating. While above grid at the unit I did notice that there is not an emergency drain pan under the air handler, I spoke with Madison about this and I will be creating an estimate to install an emergency drain pan with a mechanical float switch to shut the A/C down if the pump ever fails or the system ices up. Thank you, Jon