The measurement devices used to verify the refrigerated warehouse controls shall be calibrated once every two years using a NIST traceable reference. The calibrated measurement devices to be used in these acceptance tests are called the "standard" and shall have the following measurement tolerances: The temperature measurement devices shall be calibrated to +/- 0.7°F between -30°F and 200°F. The pressure measurement devices shall be calibrated to +/- 2.5 psi between 0 and 500 psig. The relative humidity (RH) measurement devices shall be calibrated to +/- 1% between 5% and 90% RH.
NA7.10.1.1 Construction Inspection
Prior to functional testing, verify and document the following for all electric resistance underslab heating systems:
(a) Verify that summer on-peak period is programmed into all underslab heater controls to meet the requirements of Section 120.6(a)2.
NA7.10.1.2 Functional Testing
Step 1: Using the control system, lower slab temperature setpoint. Verify and document the following using an electrical test meter:
(a) The underslab electric resistance heater is off.
Step 2: Using the control system, raise the slab temperature setpoint. Verify and document the following using an electrical test meter:
(b) The underslab electric resistance heater is on.
Step 3: Using the control system, change the control system’s time and date corresponding to the local utility’s summer on-peak period. If control system only accounts for time, set system time corresponding to the local utility’s summer on-peak period. Verify and document the following using an electrical test meter:
(c) The underslab electric resistance heater is off.
Step 4: Restore system to correct schedule and control setpoints.
NA7.10.2.1 Construction Inspection
Prior to functional testing, document the following on all evaporators:
(a) All refrigerated space temperature sensors used for control are verified to read accurately (or provide an appropriate offset) using a temperature standard.
(b) All refrigerated space humidity sensors used for control are verified to read accurately (or provide an appropriate offset) using a humidity standard.
(c) All refrigerated space temperature and humidity sensors are verified to be mounted in a location away from direct evaporator discharge air draft.
(d) Verify that all fans motors are operational and rotating in the correct direction.
(e) Verify that fan speed control is operational and connected to evaporator fan motors.
(f) Verify that all speed controls are in “auto” mode.
NA7.10.2.2 Functional Testing
Conduct and document the following functional tests on all evaporators.
Step 1: Measure current space temperature or humidity. Program this temperature or humidity as the test temperature or humidity setpoint into the control system for the functional test steps. Allow 5 minutes for system to normalize.
Step 2: Using the control system, lower test temperature or humidity setpoint in 1 degree or 1% RH increments below any control dead band range until:
(a) Evaporator fan controls modulate to increase fan motor speed.
(b) Evaporator fan motor speed increases in response to controls.
(c) Verify and document the above.
Step 3: Using the control system, raise the test temperature or humidity setpoint in 1 degree or 1% RH increments above any control dead band range until fans go to minimum speed. Verify and document the following:
(d) Evaporator fan controls modulate to decrease fan motor speed.
(e) Evaporator fan motor speed decreases in response to controls.
(f) Minimum fan motor control speed (rpm or percent of full speed).
Step 4: Restore control system to correct control setpoints.
NA7.10.3.1 Evaporative Condensers and Condenser Fan Motor Variable Speed Control
Prior to functional testing, document the following:
(a) Verify the minimum condensing temperature control setpoint is at or below 70°F.
(b) Verify the master system controller saturated condensing temperature input is the temperature equivalent reading of the condenser pressure sensor.
(c) Verify all drain leg pressure regulator valves are set below the minimum condensing temperature/pressure setpoint.
(d) Verify all receiver pressurization valves, such as the outlet pressure regulator (OPR), are set lower than the drain leg pressure regulator valve setting.
(e) Verify all condenser inlet and outlet pressure sensors read accurately (or provide an appropriate offset) using a pressure standard.
(f) Verify all ambient dry bulb temperature sensors used by controller read accurately (or provide an appropriate offset) using a temperature standard.
(g) Verify all relative humidity sensor used by controller read accurately (or provide an appropriate offset) using RH standard.
(h) Verify all temperature sensors used by the controller are mounted in a location that is not exposed to direct sunlight.
(i) Verify that all sensor readings used by the condenser controller convert or calculate to the correct conversion units at the controller (e.g., saturated pressure reading is correctly converted to appropriate saturated temperature; dry bulb and relative humidity sensor readings are correctly converted to wet bulb temperature, etc).
(j) Verify that all fan motors are operational and rotating in the correct direction.
(k) Verify that all condenser fan speed controls are operational and connected to condenser fan motors to operate in unison the fans serving a common condenser loop.
(l) Verify that all speed controls are in “auto” mode.
Note: The system cooling load must be sufficiently high to run the test. Artificially increase evaporator loads or decrease compressor capacity (manually turn off compressors, etc.) as may be required to perform the Functional Testing.
Step 1: Override any heat reclaim, floating suction pressure, floating head pressure and defrost functionality before performing functional tests.
Step 2:
(a) Document current outdoor ambient air dry bulb and wet bulb temperatures, relative humidity and refrigeration system condensing temperature/condensing pressure readings from the control system.
(b) Calculate and document the temperature difference (TD), defined as the difference between the wet bulb temperature and the refrigeration system saturated condensing temperature (SCT).
(c) Document current head pressure control setpoint.
Step 3: Using the desired condenser fan motor cycling or head pressure control strategy, program into the control system a setpoint equal to the reading or calculation obtained in Step 2. This will be referred to as the “test setpoint.” Allow 5 minutes for condenser fan speed to normalize.
Step 4: Using the control system, raise the test setpoint in 1 degree (or 3 psi) increments until the condenser fan control modulates to minimum fan motor speed. Verify and document the following:
(d) Fan motor speed decreases.
(e) All condenser fan motors serving common condenser loop decrease speed in unison in response to controller output.
(f) Minimum fan motor control speed (rpm or percent of full speed).
(g) If the refrigeration system is already operating at minimum saturated condensing temperature/head pressure, reverse Steps 4 and 5.
Step 5: Using the control system, lower the test setpoint in 1 degree (or 3 psi) increments until the condenser fan control modulates to increase fan motor speed. Verify and document the following:
(h) Fan motor speed increases.
(i) All condenser fan motors serving common condenser loop increase speed in unison in response to controller output.
Step 6: Document the current minimum condensing temperature setpoint. Using the control system, change the minimum condensing temperature setpoint to a value greater than the current operating condensing temperature. Verify and document the following:
(j) Condenser fan controls modulate to decrease capacity.
(k) All condenser fans serving common condenser loop modulate in unison.
(l) Condenser fan controls stabilize within a 5 minute period.
Step 7: Using the control system, reset the system head pressure controls, fan motor controls and minimum condensing temperature control setpoint to original settings documented in Steps 3 and 6.
Step 8: Restore any heat reclaim, floating suction pressure, floating head pressure and defrost functionality. Reset the minimum condensing temperature setpoint to the value documented in Step #6.
NA7.10.3.2 Air-Cooled Condensers and Condenser Fan Motor Variable Speed Control
Conduct and document the following functional tests on all air-cooled condensers.
Prior to functional testing, document the following:
(a) Verify that the minimum condensing temperature control setpoint is at or below 70°F.
(b) Verify that the master system controller saturated condensing temperature input is the temperature equivalent reading of the condenser pressure sensor.
(c) Verify all drain leg pressure regulator valves are set below the minimum condensing temperature/pressure setpoint.
(d) Verify all receiver pressurization valves, such as the outlet pressure regulator (OPR), are set lower than the drain leg pressure regulator valve setting.
(e) Verify all condenser inlet and outlet pressure sensors read accurately (or provide an appropriate offset) using a pressure standard.
(f) Verify all ambient dry bulb temperature sensors used by controller read accurately (or provide an appropriate offset) using temperature standard.
(g) Verify all temperature sensors used by the controller are mounted in a location that is not exposed to direct sunlight.
(h) Verify that all sensor readings used by the condenser controller convert or calculate to the correct conversion units at the controller (e.g., saturated pressure reading is correctly converted to appropriate saturated temperature, etc.)
(i) Verify that all fan motors are operational and rotating in the correct direction.
(j) Verify that all condenser fan speed controls are operational and connected to condenser fan motors to operate in unison the fans serving a common condenser loop.
(k) Verify that all speed controls are in “auto” mode.
Note: The system cooling load must be sufficiently high to run the test. Artificially increase evaporator loads or decrease compressor capacity (manually turn off compressors, etc.) as may be required to perform the Functional Testing.
Step 1: Override any heat reclaim, floating suction pressure, floating head pressure and defrost functionality before performing functional tests.
(a) Document current outdoor ambient air dry bulb temperature and refrigeration system condensing temperature/condensing pressure readings from the control system.
Step 2: Calculate and document the temperature difference (TD), defined as the difference between the dry bulb temperature and the refrigeration system saturated condensing temperature (SCT).
Document current head pressure control setpoint.
Step 3: Using the desired condenser fan motor cycling or head pressure control strategy, program into the control system a setpoint equal to the reading or calculation obtained in Step 2.
(b) This will be referred to as the “test setpoint.” Allow 5 minutes for condenser fan speed to normalize.
Step 4: Using the control system, raise the test setpoint in 1 degree (or 3 psi) increments until the condenser fan control modulates to minimum fan motor speed. Verify and document the following:
(c) Fan motor speed decreases.
(d) All condenser fan motors serving common condenser loop decrease speed in unison in response to controller output.
(e) Minimum fan motor control speed (rpm or percent of full speed).
(f) If the refrigeration system is already operating at minimum saturated condensing temperature/head pressure, reverse Steps 4 and 5.
Step 5: Using the control system, lower the test setpoint in 1 degree (or 3 psi) increments until the condenser fan control modulates to increase fan motor speed. Verify and document the following:
(g) Fan motor speed increases.
(h) All condenser fan motors serving common condenser loop increase speed in unison in response to controller output.
Step 6: Document current minimum condensing temperature setpoint. Using the control system change the minimum condensing temperature setpoint to a value greater than the current operating condensing temperature. Verify and document the following:
(i) Condenser fan controls modulate to decrease capacity.
(j) All condenser fans serving common condenser loop modulate in unison.
(k) Condenser fan controls stabilize within a 5 minute period.
Step 7: Using the control system, reset the system head pressure controls, fan motor controls and minimum condensing temperature control setpoint to original settings documented in Steps 3 and 6.
Step 8: Restore any heat reclaim, floating suction pressure, floating head pressure and defrost functionality. Reset the minimum condensing temperature setpoint to the value documented in Step 6.
NA7.10.3.3 Adiabatic Condensers and Condenser Fan Motor Variable Speed Control
Conduct and document the following functional tests on all adiabatic condensers.
Prior to functional testing, document the following:
(a) Verify the control system minimum Saturated Condensing Temperature (SCT) setpoint is at or below 70°F.
(b) Verify the control system maximum SCT setpoint (if used) is at or near the system design SCT.
(c) Verify accuracy of refrigerant pressure-temperature conversions and consistent use of either temperature or pressure for the controlled variable setpoint in the control system.
(d) Verify the discharge pressure sensor (or condenser pressure if used) reads accurately, using a National Institute of Standards and Technology (NIST) traceable reference pressure gauge or meter. At the minimum, the discharge pressure sensor accuracy shall be verified at two different pressures within the typical operating range. Calibrate if needed. Replace if outside manufacturers recommended calibration range.
(e) Verify the ambient dry bulb temperature using a NIST traceable instrument, including verification of at least two different ambient readings. Calibrate if needed. Replace if outside manufacturer’s recommended calibration range.
(f) Verify all ambient dry bulb temperature sensors are not mounted in direct sunlight or is provided within a suitable solar shield.
(g) Verify that all sensor readings used by the condenser controller convert or calculate to the correct conversion units and are displayed at the controller (e.g., observed pressure reading is correctly converted to appropriate saturated temperature, etc.)
(h) Verify that all fan motors are operational and rotating in the correct direction.
(i) Verify that all condenser fan speed controls operate automatically in response to changes in both pressure (SCT) and ambient temperature.
Note: The system cooling load must be sufficiently high, and ambient conditions sufficiently below design, to operate with all condenser fans in operation and observe controls in average conditions. Be cognizant of weather conditions in scheduling testing and, if necessary and possible, arrange to artificially increase or decrease evaporator loads in order to perform the Functional Testing at typical system conditions. The functional test shall be performed in dry mode.
Step 1: Verify mechanical controls and other strategies will not affect tests.
(a) Verify condenser pressure low-limit holdback and/or bypass regulating valves, if any, are set below the minimum SCT setpoint. Condenser pressure controls valves will cause fans to operate at 100% speed if they are not set below the minimum SCT value. In warm weather, this may require setting out of range, and deferring valve settings until cold weather allows valves to be adjusted.
(b) Turn off any heat reclaim controls and any intermittent defrost pressure offset strategies that would affect condenser setpoint control.
(c) Document adiabatic mode switching setpoints, if necessary for test temporarily change the adiabatic mode setpoint such that the condenser operates in dry mode. Verify that the adiabatic pads are completely dry before beginning tests.
Step 2: Operate in control range and verify
(a) Verify the condenser control value is operating in the variable setpoint control range, i.e. above the minimum SCT setpoint and below the maximum SCT setpoint.
i. If necessary, increase or decrease the system load.
ii. If necessary, during low load or low ambient conditions with system observed at the minimum SCT, temporarily adjust the minimum SCT to a lower value, if the refrigeration system design will allow, or increase the control TD to result in a higher control value.
(b) Observe control operation for at least 30 minutes to confirm stable control operation, as shown by condenser fan speed varying as compressor capacity changes, and not ranging from maximum to minimum fan speed or constant “hunting”. If required, adjust control response setpoints to achieve stable operation. Since condenser control settings require fine-tuning over time, this is often accomplished using control system history or visual trends, showing one hourly and daily operation.
Step 3: Identify control Temperature Difference
(a) Record the current outdoor ambient air dry bulb and refrigeration system condensing temperature/condensing pressure readings from the control system. Note whether discharge pressure or a dedicated condenser pressure sensor is used for condenser pressure control.
(b) Document current head pressure control setpoints, including the Temperature Difference (TD) setpoint.
(c) Calculate and record the actual observed TD, defined as the difference between the dry bulb temperature and the refrigeration system SCT.
(d) Confirm agreement between the current control system TD setpoint and the observed TD. If values are different, address and correct controls system methods.
Step 4: Test adjusted control Temperature Difference (Setpoint1).
(a) Enter a smaller TD value into the control system sufficient enough to cause an observable response, such as 1 to 2 degrees smaller, but not small enough to cause the system to operate continuously at 100% fan speed. Record this value as TD Test Setpoint 1.
(b) Observe change in control system operation which should include an increase in fan speed and a decrease in condensing temperature.
(c) Allow time for the control system to achieve stable operation.
(d) Document current head pressure control setpoints, including the TD setpoint.
(e) Calculate and record the actual observed TD, defined as the difference between the wet bulb temperature and the refrigeration system SCT.
(f) Confirm agreement between the current control system TD setpoint and the observed TD. If values are different, address and correct control system methods.
Step 5: Test adjusted control Temperature Difference (Setpoint2) Enter a TD value into the control system that is different from TD Test Setpoint1, sufficient enough to cause an observable response. Record this value a TD Test Setpoint2.
(a) Observe change in control system operation which should include an increase in fan speed and a decrease in condensing temperature.
(b) Allow time for the control system to achieve stable operation.
(c) Record the current outdoor ambient dry bulb temperature.
(d) Record the current refrigeration system condensing temperature/condensing pressure readings from the control system.
(e) Document current head pressure control setpoints, including the TD setpoint.
(f) Calculate and record the actual observed TD, defined as the difference between the dry bulb temperature and the refrigeration system SCT.
(g) Confirm agreement between the current control system TD setpont and the observed TD. If values are different, address and correct control system methods.
Step 6: Document current minimum condensing temperature setpoint. Using the control system change the minimum condensing temperature setpoint to a value greater than the current operating condensing temperature. Verify and document the following:
(a) Condenser fan controls modulate to decrease capacity.
(b) All condenser fans serving common condenser loop modulate in unison.
(c) Condenser fan controls stabilize within a 5 minute period.
Step 7: Using the control system, reset the system head pressure controls, fan motor controls and minimum condensing temperature control setpoint to original settings documented in Steps 3 and 6.
Step 8: Restore any heat reclaim, floating suction pressure, floating head pressure and defrost functionality. Reset the minimum condensing temperature setpoint to the value documented in Step 6.
Conduct and document the following functional tests on all variable-speed screw compressors.
NA7.10.4.1 Construction Inspection
Prior to functional testing, document the following:
(a) Verify all single open-drive screw compressors dedicated to a suction group have variable speed control.
(b) Verify all compressor suction and discharge pressure sensors read accurately (or provide an appropriate offset) using a standard.
(c) Verify all input or control temperature sensors used by controller read accurately (or provide an appropriate offset) using temperature standard.
(d) Verify that all sensor readings used by the compressor controller convert or calculate to the correct conversion units at the controller (e.g., saturated pressure reading is correctly converted to appropriate saturated temperature, etc.).
(e) Verify that all compressor speed controls are operational and connected to compressor motors.
(f) Verify that all speed controls are in “auto” mode.
(g) Verify that compressor panel control readings for “RPMs,” “% speed,” “kW”, and “amps” match the readings from the PLC or other control systems.
(h) Verify that compressor nameplate data is correctly entered into the PLC or other control system.
NA7.10.4.2 Functional Testing
Note: The system cooling load must be sufficiently high to run the test. Artificially increase or decrease evaporator loads (add or shut off zone loads, change setpoints, etc.) as may be required to perform the Functional Testing.
Step 1: Override any heat reclaim, floating suction pressure, floating head pressure and defrost functionality before performing functional tests.
Step 2: Measure and document the current compressor operating suction pressure and saturated suction temperature.
Step 3: Document the suction pressure/saturated suction temperature setpoint. Program into the control system a target setpoint equal to the current operating condition measured in Step #2. Allow 5 minutes for system to normalize. This will be referred to as the “test suction pressure/saturated suction temperature setpoint.”
Step 4: Using the control system, raise the test suction setpoint in 1 psi increments until the compressor controller modulates to decrease compressor speed. Verify and document the following:
(a) Compressor speed decreases.
(b) Compressor speed continues to decrease to minimum speed.
(c) Any slide valve or other unloading means does not unload until after the compressor has reached its minimum speed (RPM).
Step 5: Using the control system, lower the test suction setpoint in 1 psi increments until the compressor controller modulates to increase compressor speed. Verify and document the following:
(d) Any slide valve or other unloading means first goes to 100 percent before compressor speed increases from minimum.
(e) Compressor begins to increase speed.
(f) Compressor speed continues to increase to 100 percent.
Step 6: Using the control system, program the suction target setpoints back to original settings as documented in Step 3.
Step 7: Restore any heat reclaim, floating suction pressure, floating head pressure and defrost functionality.