NA7.5.2 Constant Volume, Single-zone, Unitary Air Conditioner and Heat Pumps Systems Acceptance

Use Form NRCA-MCH-03-A

Purpose of the Test

The purpose of the test is to verify the individual components of a constant volume, single-zone, unitary air conditioner and heat pump system function correctly, including: thermostat installation and programming, supply fan, heating, cooling, and damper operation.

Testing of the economizer, outdoor air ventilation, and demand-controlled ventilation are located in the following sections of the Reference Appendices:

•      NA7.5.1.2 Constant Volume System Outdoor Air Acceptance

•      NA7.5.4 Air Economizer Controls (if applicable)

•      NA7.5.5 Demand Control Ventilation (DCV) Systems (if applicable)

 Instrumentation

Temperature meter, amp meter

 Test Conditions

Unit and thermostat installation and programming must be complete.

HVAC system must be installed and ready for system operation, including completion of all 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.

 Estimated Time to Complete

Construction inspection: 0.5 to 1 hour (depending on familiarity with thermostat programming)

Equipment test: 1 to 2 hours

 Acceptance Criteria

The following are verified through inspection:

•      Thermostat is located within the space-conditioning zone that is served by the respective HVAC system

•      Thermostat meets the temperature adjustment and dead band requirements of §120.2(b).

•      Occupied, unoccupied, and holiday schedules have been programmed per the facility’s schedule

•      Pre-occupancy purge has been programmed to meet the requirements of §120.1(c)2

The following modes of operation function correctly:

•      Occupied heating mode operation: The supply fan operates continuously, all heating stages operate, cooling is not enabled, and the outdoor air damper is at minimum position.

•      Occupied operation with no heating or cooling load: The supply fan operates continuously, heating or cooling is not enabled, and the outdoor air damper is at minimum position.

•      Occupied cooling mode operation: The supply fan operates continuously, all cooling stages operate, heating is not enabled, and outside damper is at minimum position.

•      Unoccupied operation with no heating or cooling load: The supply fan shuts off, heating or cooling is not enabled, and the outdoor air damper is closed.

•      Unoccupied operation with heating load: The supply cycles ON, heating is enabled, cooling is not enabled, and the outdoor air damper is at minimum position.

•      Unoccupied cooling mode operation: The supply cycles ON, cooling is enabled, heating is not enabled, and the outdoor air damper is  at minimum position.

•      Manual override mode: System reverts to occupied mode, the supply fan turns ON for duration of override, heating or cooling is enabled as necessary, outdoor air damper opens to minimum position.

Potential Issues and Cautions

Ensure that the supply fan runs continuously in occupied mode and cycles appropriately in unoccupied mode. Cycling refers to the supply fan running only when heating or cooling is enabled.

When testing the manual override, it may be necessary to adjust the length of the override period to minimize test time. Be sure to reset the override period back to the correct length of time.

Overall test time may be reduced (especially for rooftop HVAC units controlled by thermostats) if two people perform the test - one to manipulate the thermostat while someone else verifies operation at the packaged unit.

The Standards do not mandate the actual differential between occupied and unoccupied setpoints, only that the system must be adjustable down to 55°F for heating and up to 85°F for cooling and that the thermostat can be set for a 5°F deadband.

Setback control is only required for climates where the winter median of extremes is less than or equal to 32°F.

Setup control is only required for climates where the 0.5 percent summer design dry-bulb temperature is greater than or equal to 100°F.