Bishara

The following building pressure SOO has been tried and true over several various sizes and types of buildings with a mechanical air distribution system consisting of an air handling unit with a relief fan and a damper at the relief fan discharge.  The SOO below is for one relief fan, and I will address having multiple fans in the sections to follow.

1. Relief Fan Speed – Pressure Control Loop

a. Relief fan speed controlling to space pressure using a PI variable of a control loop

b. Setpoint 0.03 in wc.

c. Set the fan VFD minimum speed to 6 Hz with maximum at design airflow using fan    selection

d. Bldg pressure feedback value into the Pressure Control Loop shall be a rolling average over 15 minutes.

2. Pressure Control Loop Enable & Disable

a. Enable Condition: Bldg actual pressure => 0.07 in wc for 20 minutes

b. Disable Condition: Bldg actual pressure =< 0.01 in wc for 20 minutes

3. Relief Air Damper Control

a. Two position damper control

b. Damper at 100% open position anytime relief fan enabled to run

c. Damper at 0% open position anytime relief fan is disabled

The following addresses if the air handling unit has multiple relief fans with each dedicated relief damper at the discharge of each fan

4. Relief Fans Staging Control

a. Lag Fan Stage Up Condition: Pressure Control Loop output =>90% for 10 minutes

b. Lag Fan Stage Down Condition: Pressure Control Loop output =<40% for 10 minutes

c. All operating fans shall receive the same Pressure Control Loop output

General Section

1. Make all setpoint values adjustable for tuning purposes.

Any suggestions or feedback sharing your experience would be greatly appreciated.