UpCodes logo
Jump To Full Code Chapter
The purpose of this test is to ensure that the supply fan in a variable air volume application modulates to meet system airflow demand. In most applications, the individual VAV boxes serving each space will modulate the amount of air delivered to the space based on heating and cooling requirements. As a result, the total supply airflow provided by the central air handling unit shall vary to maintain sufficient airflow through each VAV box. Airflow shall be controlled using a variable frequency drive (VFD) to modulate supply fan speed and vary system airflow. The most common strategy for controlling the VFD is to measure and maintain static pressure within the duct.
E 805.7.1 Test Procedure
The procedure for performing a functional test for supply fan variable controls shall be in accordance with Section E 805.7.1.1 and Section E 805.7.1.2.
E 805.7.1.1 Construction Inspection
Prior to functional testing, verify and document the following:
  1. Supply fan controls modulate to increase capacity.
  2. Supply fan maintains discharge static pressure within plus or minus 10 percent of the current operating set point.
  3. Supply fan controls stabilize within a 5 minute period.
E 805.7.1.2 Functional Testing
The functional testing shall be in accordance with the following steps:
Step 1: Simulate demand for design airflow. Verify and document the following:
  1. Supply fan controls modulate to increase capacity.
  2. Supply fan maintains discharge static pressure within plus or minus 10 percent of the current operating set point.
  3. Supply fan controls stabilize within a 5 minute period.
Step 2: Simulate demand for minimum airflow. Verify and document the following:
  1. Supply fan controls modulate to decrease capacity.
  2. Current operating setpoint has decreased (for systems with DDC to the zone level).
  3. Supply fan maintains discharge static pressure within plus or minus 10 percent of the current operating setpoint.
  4. Supply fan controls stabilize within a 5 minute period.
Step 3: Restore system to correct operating conditions.
E 805.7.2 Acceptance Criteria
Supply fan variable flow controls acceptance criteria shall be as follows:
  1. Static pressure sensor(s) is factory calibrated (with calibration certificate) or field calibrated.
  2. For systems without DDC controls to the zone level, the pressure sensor setpoint is less than one-third of the supply fan design static pressure.
  3. For systems with DDC controls with VAV boxes reporting to the central control panel, the pressure setpoint is reset by zone demand (box damper position or a trim and respond algorithm).
At full flow:
  1. Supply fan maintains discharge static pressure within plus or minus 10 percent of the current operating control static pressure setpoint.
  2. Supply fan controls stabilizes within a 5 minute period.
  3. At minimum flow (not less than 30 percent of total design flow).
  4. Supply fan controls modulate to decrease capacity.
  5. Current operating setpoint has decreased (for systems with DDC to the zone level).
  6. Supply fan maintains discharge static pressure within plus or minus 10 percent of the current operating setpoint.

Related Code Sections

E 804.2 Sustainable Practices, Tests
installed and tested (Form MECH-5A). Demand-controlled ventilation control systems (Form MECH-6A). Supply fan variable flow controls (Form MECH-7A ...
E 805.1 Sustainable Practices, Variable Air Volume Systems (Form Mech- 2A)
be performed in conjunction with supply fan variable flow controls test procedures to reduce the overall system testing time as both tests use ...
E 805.8 Sustainable Practices, Valve Leakage (Form MECH-8A)
The purpose of this test is to ensure that control valves serving variable flow systems are designed to withstand the pump pressure over the full ...