The purpose of this test is to verify the proper operation of distributed energy storage DX systems. Distributed energy systems (DES) 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. This applies to constant or variable volume, direct expansion (DX) systems with distributed energy storage (DES/DXAC).
Prior to functional testing, verify and document the following:
- The water tank is filled to the proper level.
- The water tank is sitting on a foundation with adequate structural strength.
- The water tank is insulated and the top cover is in place.
- The DES/DXAC is installed correctly (e.g., refrigerant piping, etc.).
- Verify that the correct model number is installed and configured.
The functional testing shall be in accordance with the following steps: Step 1: Simulate cooling load during daytime period (e.g., by setting time schedule to include actual time and placing thermostat cooling setpoint below actual temperature). Verify and document the following:
- Supply fan operates continually.
- Where the DES/DXAC has cooling capacity, DES/DXAC shall run to meet the cooling demand (in ice melt mode).
- Where the DES/DXAC has no ice and there is a call for cooling, the DES/DXAC shall run in direct cooling mode.
- Supply fan operates in accordance with the facility thermostat or control system.
- The DES/DXAC and the condensing unit do not run.
- The DES/DXAC is idle.
- The DES/DXAC runs in direct cooling mode.
Set the proper time and date in accordance with the manufacturer's instructions for approved installers.
Distributed energy storage DXAC system acceptance criteria shall be as follows:
- Verify night time 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 where there is no cooling demand during on-peak periods.
- Verify that the system does not operate during a morning shoulder period where there is no cooling demand.
- Verify that the system operates in direct mode (with compressor running) during the morning shoulder time period.