13.79 NA7.5.13 Distributed Energy Storage DX AC System Acceptance

NA7.5.13 Distributed Energy Storage DX AC Acceptance

Use Form NRCA-MCH-14-A

Purpose of the Test

This test verifies proper operation of distributed energy storage DX systems. Distributed energy systems reduce peak demand by operating during off peak hours and storing cooling, usually in the form of ice. During peak cooling hours the ice is melted to avoid compressor operation. The system typically consists of a water tank containing refrigerant coils that cool the water and convert it to ice. As with a standard direction expansion (DX) air conditioner, the refrigerant is compressed in a compressor and then cooled in an air-cooled condenser. The liquid refrigerant then is directed through the coils in the water tank to make ice or to air handler coils to cool the building.

Benefits of the Test

The test will ensure that the distributed energy storage system is able to charge the storage tank during off-peak hours and discharge the storage tank during on peak hours to reduce peak demand. Since the DX air conditioner can operate more efficiently at night when ambient temperatures are lower, the system may save cooling energy in some climates.

Instrumentation

Distributed energy storage acceptance tests require no additional instrumentation for testing.

Test Conditions

The DX equipment should be installed and operational. Perform pre-startup installation procedures as specified by the manufacturer. Verify that the building cooling is controlled by a standard indoor HVAC thermostat and not by factory installed controls. Verify that ice making is not controlled by the thermostat. The water tank should be filled to the proper level as specified by the manufacturer prior to the start of the test. All refrigerant piping field connections should be made and the system should be charged with refrigerant.

Estimated Time to Complete

Construction Inspection: 0.5 hours

Acceptance Tests: 2 hours

Acceptance Criteria

Verify nighttime ice making operation.

Verify that tank discharges during on-peak cooling periods.

Verify that the compressor does not run and the tank does not discharge when there is no cooling demand during on-peak periods.

Verify that the system does not operate during a morning shoulder period when there is no cooling demand.

Verify that the system operates in direct mode (with compressor running) during the morning shoulder time period.

Potential Problems and Cautions

These tests only apply to systems with storage capacity less than 100 ton-hours. Systems with storage above 100 ton-hours should be modeled using the thermal energy storage compliance option. Be sure the water tank is filled to the proper level indicated by the manufacturer prior to the start of the tests. The tests require override of the system controller programming. Be sure to record the system settings prior to the start of the testing, and restore the system settings to their original values upon completion of the tests.

The distributed energy storage system third party submittal form should be verified, which contains the following information: testing laboratory, address, phone number, contact person, date tested, tracking number, model number, and manufacturer. The following performance information should be recorded and reported on the form NRCA-MCH-14-A:

• The water tank is sitting on a foundation with adequate structural strength.

• The intent of this test is to verify that during on-peak conditions the tank will discharge and the compressor will remain off.

• Set the time clock to on-peak hours (typically between 12 noon and 6 PM), or change the on-peak start time control parameter to be earlier than the current time. Set the space cooling setpoint to be below the current space temperature.

• If the system has storage of ice, verify that the DES/DXAC runs in ice melt mode and that the compressor remains off. The supply fan operates continuously to provide cooling to the space. The refrigerant pump operates to circulate refrigerant to the evaporator coil(s).

• If the DES/DXAC system has no ice and there is a call for cooling, verify that the DES/DXAC system runs in direct cooling mode, with the compressor running. Verify that cooling is provided to the space.

• Step 2: Simulate no cooling load during daytime conditions by setting the cooling setpoint above the current space temperature, and set the system time to be within the daytime period.

Step 3: Simulate no cooling load during the morning shoulder time period(before noon).

Set the space temperature setpoint to be above the current space temperature and set the system time clock to be between the hours of 6AM and noon.

• Step 4: Simulate a cooling load during the morning shoulder time period (between 6 am and noon) by setting the space setpoint below the current space temperature.

Verify that the DES/DXAC system runs in direct cooling mode, with the compressor running. Verify that the tank does not discharge during this period.

Set the date and time back to the current date and time after completion of the acceptance tests, following manufacturer’s instructions.