TAB Update #1

We are currently working on a Performing Arts addition to a local high school. The addition is served by one 36,000 CFM air handling unit. The unit has a supply and return fan along with hot and chilled water coils and mixing dampers for the economizer. Also at the discharge at the supply fan, there are sound attenuators. Also located in the air handling unit is a 5,900 CFM exhaust fan that provides general exhaust ventilation in the restrooms in the addition. A dedicated 6,500 CFM outside air fan is also located in the air handling unit . The partitions in the air handler prevent mixing of the supply/return air, exhaust air and outside air. An energy recovery heat wheel transfers heat between the exhaust & outside air streams. Air distribution is via 40 VAV boxes and 10 fan powered boxes with hot water re-heat. The air is delivered into the rooms via standard 2 x 2 ceiling diffusers. An Andover DDC control system maintains space temperature and air handler operation.

The project was done in two phases, the 1st phase was completed in September of 2008 and we are currently 80% done with the 2nd phase. We are planning on completing the balance of the return air grilles tomorrow and will finalize the air handler by the end of the week.

Currently, the exhaust fan VFD is operating at 51 hertz. The owner has requested that we perform a sheave change to slow down the fan so that the fan will operate at design flow at 60 hertz. Also, the outside air fan sheave will be changed due to damage. The manufacturer did not tighten the set screw that holds the keyway for the adjustable pulley. As a result, a portion of the sheave separated causing the damage. As for the supply fan, during the course of the balancing of the VAV boxes, the supply duct static pressure set point was established at 1.3"wc.

Also on our list of things to do is to move the supply duct static high limit sensor. Currently, it is located in the discharge plenum of the air handler in a place where air turbulence is causing nuisance trips. It will be relocated in the discharge duct near the plenum connection. Currently, the high limit set point is set at 3"wc.

That's all for now. Have a mabuti araw. Mabuhay!