FCU Blower pulling in water

alvinccfei,

A couple of observations/questions:

If I understand the situation, You are operating a clean room with a supplemental fan-coil unit that recycles air from the room itself.

What ducts are being flooded?

Does this FCU have a ducted supply of air in addition, or is it operating solely to provide thermal comfort, by constantly recycling the air in the room?

Is it possible that the fan is operating at too high a speed, causing condensed moisture to blow off the coils, or out of the condensate pans?

What is the temperature of the chilled water serving the FCU? If too cold, it could cause excessive condensation.

What is the moisture content of the air being supplied to the clean room via the primary HVAC/HEPA air filtration system ?

Is the R.H. in the clean room controlled to manage ESD?

restricted air flow.

Hi JMAN,

Thanks for the reply.

Yes, the FCU is use for the return air (recycled air). The ducts that were flooded were the ones after the FCU where the recycled air is directed to the plenum.

The FCU does not have other air supply apart from the reycled air. I'm not sure if the fans are running at too high a speed but from what i see the fans are pulling condenstate into the duct.

The room RH should be quite high as we are running a wet process in the cleanroom.

Hi ozzb,

May i know what you meant by restricted air flow?

up-flow coil in a down-flow application? or the other way around... The fins on the coil are slanted in the wrong direction. The air flow causes the water to blow into the ducts instead of dripping down to the pan.