At-A-Glance
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NA7.5.13 Distributed Energy Storage DX AC Acceptance |
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Use Document NRCA-MCH-14-A |
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Purpose of the Test |
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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. |
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Instrumentation |
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Distributed energy storage acceptance tests require no additional instrumentation for testing. |
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Test Conditions |
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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. Verify refrigerant piping connects and the system is charged with refrigerant. |
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Estimated Time to Complete |
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Construction Inspection: 0.5 hours |
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Acceptance Tests: 2 hours |
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Acceptance Criteria |
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Verify nighttime ice making operation. |
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Verify that tank discharges during on-peak cooling periods. |
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Verify that the compressor does not run and the tank does not discharge when there is no cooling demand during on-peak periods. |
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Verify that the system does not operate during a morning shoulder period when there is no cooling demand. |
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Verify that the system operates in direct mode (with compressor running) during the morning shoulder time period. |
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Potential Problems and Cautions |
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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. |
A. Test Application
Newly Constructed and Additions/Alterations: Applies to constant and variable volume, direct expansion systems with distributed energy storage (DES/DXAC). This acceptance requirement is an addition to economizer and packaged equipment acceptance.
B. Construction Inspection
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 document NRCA-MCH-14-A:
1 The water tank is filled to the proper level.
2 The water tank is sitting on a foundation with adequate structural strength to support the weight of the filled vessel
3 The water tank is insulated and the top cover is in place.
4 The DES/DXAC is installed correctly (refrigerant piping, etc.).
5 The correct model number is installed and configured.
C. Functional Testing
Step 1: Simulate cooling load during daytime period.
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.
Verify and document
Supply fan operates continually.
If the system has ice storage, 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.
•This is done by setting the cooling setpoint above the current space temperature, and set the system time during the daytime period.
Verify and document
Supply fan operates as per the facility thermostat or control system.
The DES/DXAC and the condensing unit do not run.
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.
Verify and document
•The DES/DXAC system remains idle.
Step 4: Simulate a cooling load during the morning shoulder time period (between 6 am and noon).
•Set the space setpoint below the current space temperature.
Verify and document
•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.
Calibrating Controls
•Set the date and time back to the current date and time after completion of the acceptance tests, following manufacturer’s instructions.