NA7.5.1.2 Constant Volume Systems Outdoor Air Acceptance

Use Form NRCA-MCH-02-A

Purpose of the Test

The purpose of the test is to ensure that adequate outdoor air ventilation is provided through the constant volume air handling unit to the spaces served under all operating conditions. The intent of the test is to verify that the minimum volume of outdoor air, as required per §120.1(b)2, is introduced to the air handling unit and is within 10% of the required volume during typical space occupancy.

Note that systems requiring demand ventilation controls per §120.1(c)3 must conform to §120.1(c)4E regarding the minimum ventilation rate when the system is in occupied mode.

Related acceptance tests for these systems include the following:

•      NA7.5.2 Constant-Volume, Single-zone, Unitary Air Conditioners and Heat Pump Systems

•      NA7.5.4 Air Economizer Controls (if applicable)

•      NA7.5.5 Demand Controlled Ventilation Systems Acceptance (if applicable)

Instrumentation

Performance of this test will require measuring outdoor air flow. The instrumentation needed to perform the task may include, but is not limited to:

•      A means to measure airflow (typically either a velocity pressure probe or hot wire anemometer)

•      If the system was installed with an airflow monitoring station (AFMS) on the outdoor air it can be used for the measurements if it has a calibration certificate or is field calibrated.

•      A watch or some equivalent instrument to measure time in minutes

Test Conditions

To perform the test, it may be necessary to override the control system of the air handling unit. The control system of the air handling unit must be complete.

All systems must be installed and ready for system operation, including:

•      Air economizer controls

•      Duct work

•      Control sensors (temperature, flow, thermostats, etc.)

•      Electrical power to air handling unit and control system components

•      Completion of air handling unit start-up procedures, per manufacturer’s recommendations

•      Document the initial conditions before overrides or manipulation of the setpoints and schedules. All systems must be returned to normal at the end of the test.

Note: Systems requiring demand ventilation controls per §120.1(c)3 must conform to §120.1(c)4E regarding the minimum ventilation rate (refer to NA7.5.5 Demand Controlled Ventilation Systems Acceptance Test).

Estimated Time to Complete

Construction inspection: 0.5 hours

Functional testing: 1 hour (depending on difficulty in measuring outdoor air flow)

Acceptance Criteria

System has a means of maintaining the minimum outdoor air damper position.

Minimum damper position is marked on the outdoor air damper

Measured outdoor air flow is within 10 percent of the total value found on the Standards Mechanical Plan Check document NRCC-MCH-03-E Column M.

Potential Issues and Cautions

Do not attempt to set the minimum damper position and perform the acceptance test at the same time. The acceptance test verifies the outdoor airflow of the system after calibration and system set-up is complete. Testing costs can be reduced by conducting the acceptance test immediately after set-up is concluded.