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WHAT THE SPECIFICATIONS ASK WHEN TESTING CONTROL SYSTEM

WHAT THE SPECIFICATIONS ASK WHEN TESTING CONTROL SYSTEM. Gaylon Richardson Engineered Air Balance Co., Inc. SPECIFICATIONS. Does the specification cover what is required to test the control system? What is required for testing the terminal boxes?

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WHAT THE SPECIFICATIONS ASK WHEN TESTING CONTROL SYSTEM

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  1. WHAT THE SPECIFICATIONS ASK WHEN TESTING CONTROL SYSTEM Gaylon Richardson Engineered Air Balance Co., Inc. TESTING CONTROL SYSTEMS

  2. SPECIFICATIONS • Does the specification cover what is required to test the control system? • What is required for testing the terminal boxes? • What is required for verifying calibration of all sensors and that the correct sensors control the proper devices? TESTING CONTROL SYSTEMS

  3. SPECIFICATIONS • How will each sequence be verified and how should the test be written? Should all interlocks, alarms and safeties be identified? • Should the specification cover testing each point for its proper name and the point responds to a change in value at the main graphics? TESTING CONTROL SYSTEMS

  4. SPECIFICATIONS • BOTTOM LINE THE AIR FLOWS CAN BE SET, THE WATER FLOWS CAN BE SET, BUT IF THE CONTROL SYSTEM IS NOT VERIFIED TO BE CALIBRATED AND ALL SEQUENCES OPERATING IT ISN’T WORKING. TESTING CONTROL SYSTEMS

  5. What Should Be In The Specification? • Verify all control devices are properly connected and operated by the intended controller. • Observe all valves are properly installed in the piping system in relation to direction of flow. • Verify the proper application of all normally opened and normally closed valves and dampers. TESTING CONTROL SYSTEMS

  6. What Should Be In The Specification? • Observe the location of all sensors to determine whether their position will allow them to sense only the intended temperatures or pressures. If the sensor is in the wrong location the Control Contractor must be required to relocate the sensor. • Observe the calibration of all controllers. TESTING CONTROL SYSTEMS

  7. What Should Be In The Specification? • Verify the sequence of operation for all control modes, that each is in accordance with the specifications and that the approved shop drawings are correct. • Verify the operation of all interlock systems. • Verify all safeties and alarms. TESTING CONTROL SYSTEMS

  8. What Should Be In The Specification? • Verify on single zone systems there is a dead band between cooling and heating. • Verify the pressure set points in variable flow systems track from a full flow condition to a minimum flow condition. • Document all the above observations and verifications. TESTING CONTROL SYSTEMS

  9. How Can Everything Be Documented? • Start with the terminal box controls. • The flows must be established which involves testing all flows at maximum and minimum values and adjusting the terminal box software to provide the correct airflows. TESTING CONTROL SYSTEMS

  10. How Can Everything Be Documented? • The terminal box verification should list a controller number which identifies the application, the room number, DDC address, type of terminal, terminal size, cooling and heating primary maximum settings, TESTING CONTROL SYSTEMS

  11. How Can Everything Be Documented? • show the calibration of each control sensor (note some devices can not be calibrated and the control contractor will replace any device not within the specified tolerances). • Show control sequence verification. TESTING CONTROL SYSTEMS

  12. How Can Everything Be Documented? • Show trend logs for room sensors. • If specified verify all points back to the central data acquisition system by causing a change in value and seeing the correct point name have a change in value at the remote monitoring point. TESTING CONTROL SYSTEMS

  13. Terminal Box Verification TESTING CONTROL SYSTEMS

  14. Terminal Box Verification TESTING CONTROL SYSTEMS

  15. Sensor Calibration TESTING CONTROL SYSTEMS

  16. Control Sequence Verification SYSTEM DESCRIPTION The AHU is designed as a heating/cooling, dual duct, variable volume air handling system. The AHU consists of a single fan with coils located in the blow through configuration. The AHU has ducted return, 30% pleated pre-filters and 90% final filters. The cold deck has a reheat coil to avoid saturating the final filters with moisture. The AHU has a pressure independent terminal unit providing pre-treated outside air from AHU-AC-PH-01 and 02. The AHU unit serves dual duct air terminal units SAT 1 through SAT 80. High static control dampers have been added to the cold deck discharge and the inlet of the hot deck heating coil to prevent static pressure in either deck from exceeding 3.75”. The VFD serving the AHU has a bypass switch to allow the motor to operate when the VFD fails. A pressure relief damper has been installed to reduce the pressure in the discharge plenum when in bypass. TESTING CONTROL SYSTEMS

  17. Control Sequence Verification PREREQUISITE TEST PRIOR TO CONTROL SEQUENCE VERIFICATION All return, supply terminals and OSA terminals must be balanced. The Terminal Box Control Verification Forms must be complete. The AHU will be traversed with all terminal boxes set for maximum cooling, maximum heating, and total submittal airflow (if the AHU does not have a connected airflow to equal the submitted airflow the cold deck terminal boxes in the flexible zone will be set to 2000 fpm inlet velocity to verify the maximum airflow of the AHU). All water flows must be balanced and coil capacities established. TESTING CONTROL SYSTEMS

  18. Control Sequence Verification Des Max Cooling CFM 36920 Act Max CFM 38455 Des Max Heating CFM 14660 Act Max CFM15625 Heating Max CFM 20920 Act Cool CFM 21570 Sub Max Cool CFM 42000 Act Cool Max 40210 Des RA CFM 28655 Act RA CFM 30545 Des OSA CFM 8255 Act OSA CFM 8255 Minimum Speed Set point 20HZ TESTING CONTROL SYSTEMS

  19. Control Sequence Verification AHU SEQUENCE START The fan will be enabled through a signal from the BAS with the VFD in the “auto” position. Upon a fan “start” command the variable frequency drive (VFD) will operate at a preset minimum speed. The BAS will monitor the discharge static pressure sensors. The pretreated outside air terminals will open to their airflow setpoint. Minimum Speed Set point 20HZ TESTING CONTROL SYSTEMS

  20. Control Sequence Verification STATIC PRESSURE CONTROL The hot and cold decks are monitored with static pressure sensors located 2/3 down the ductwork. The static pressure control loops senses the static pressure in the hot and cold decks and sends a signal to the VFD to modulate the fan speed to satisfy the lower of the two static pressure signals being monitored. Full Cooling Cold Deck SP 1.40” @ 58.8 HZ Full Heating Hot Deck SP 1.40” @ 46.3 HZ TESTING CONTROL SYSTEMS

  21. Control Sequence Verification With the terminal boxes in control the static pressure set point will be raised 0.20” above set point and lowered 0.40” below set point. The VFD response to change will be shown by recording the static pressure maintained and the operating hertz. After all adjustments are made the system will be returned to its original operating conditions. Raise SP 1.60” @ 43.5 HZ Lower SP 1.00” @ 39.1 HZ TESTING CONTROL SYSTEMS

  22. Control Sequence Verification The hot and cold deck static pressure sensors located 2/3 down the ductwork are also used to control the discharge static pressure loops that will modulate the discharge damper in the hot or cold duct. The duct having the highest static pressure of the two will be controlled at 2.0”. The static pressure control will be tested from full cooling to full heating by placing terminal boxes to full heating two at a time. The static pressure sensors located 2/3 down the duct and at the fan discharge will be observed after each box is set for heating until all terminal boxes are at full heating. TESTING CONTROL SYSTEMS

  23. Control Sequence Verification The same test will be performed by returning each terminal box to full cooling until all boxes are at full cooling. The static pressures and VFD HZ will be recorded with terminal boxes set for 100%, 75%, 50%, 25% of maximum cooling airflow and 100%, 75%, 50%, 25% maximum heating airflow. 100% Cooling Discharge 1.40 CD 3.67 HD 58.8 HZ 75% Cooling Discharge 1.40 CD 2.61 HD 49.1 HZ 50% Cooling Discharge 1.40 CD 1.64 HD 40.0 HZ 25% Cooling Discharge 1.40 CD 2.01 HD 42.3 HZ 100% Heating Discharge 2.22 CD 1.40 HD 46.3 HZ 75% Heating Discharge 2.18 CD 1.41 HD 43.0 HZ 50% Heating Discharge 1.99 CD 1.40 HD 39.1 HZ 25% Heating Discharge 1.39 CD 1.64HD 36.0 HZ TESTING CONTROL SYSTEMS

  24. Control Sequence Verification HOT DECK TEMPERATURE CONTROL The hot deck temperature control loop is enabled by the fan status proof through the BAS. The control loop will modulate the hot water control valve to maintain a discharge air temperature set point at the temperature sensor. The hot deck temperature set point is reset through the BAS. Heating Valve Control Verification Heating Coil Discharge Air > Set point Hot Water Valve Will Modulate Closed Heating Coil Discharge Air < Set point Hot Water Valve Will Modulate Open Heating Coil Valve will close when the AHU is disabled from the BAS TESTING CONTROL SYSTEMS

  25. Control Sequence Verification Hot Deck Reset As the Outside Temperature falls below 70F the hot deck temperature will increase 0.3F for every 1F drop in outside temperature. At 30F the hot deck temperature will be 95F. Adjust the virtual outside air point to 85F,50F,30F and verify the hot deck temperature. The reset schedule is as follows: Outside Air Temperature Hot Deck Temperature 30F 95F 70F 80F Test #1 85F OSA 80F HDT Test #2 50F OSA 87.5F HDT Test #3 30F OSA 95F HDT TESTING CONTROL SYSTEMS

  26. Control Sequence Verification COLD DECK TEMPERATURE CONTROL The cold deck temperature control loop is enabled by the fan status proof through the BAS. The control loop will modulate the cold water control valve to maintain a discharge air temperature set point at the cooling coil discharge air temperature sensor. The control loop will also modulate the hot water control valve serving the reheat coil to maintain a discharge air temperature at the reheat discharge air sensor. Cold deck Discharge Set point 52F Reheat Discharge Set point 54F TESTING CONTROL SYSTEMS

  27. Control Sequence Verification Cooling Valve Control Verification Cooling Coil Discharge Air > Set point Chilled Water Valve Modulate. Open Cooling Coil Discharge Air. < Set point Chilled Water Valve Will Modulate Closed Cooling Coil Valve will close when the AHU is disabled from the BAS Set point 52F TESTING CONTROL SYSTEMS

  28. Control Sequence Verification Re-heat Valve Control Verification Re-heat Coil Discharge Air > Set point Hot Water Valve Will Modulate Closed Re-heat Coil Discharge Air < Set point Hot Water Valve Will Modulate Open Re-heat Coil Valve will close when the AHU is disabled from the BAS Set point 54F TESTING CONTROL SYSTEMS

  29. Control Sequence Verification Dehumidification Control The BAS will monitor the relative humidity in the return air duct. If the return air relative humidity exceeds 60% the cold deck discharge air temperature will be lowered 1F per 5% humidity above 50%. The cold deck will be proportionally lowered from 52F to 50F. When 50% relative humidity is obtained the cold deck temperature set point will return to 52˚. Return relative humidity > 60% cold deck temperature 50F. Return relative humidity < 50% cold deck temperature 52F. Set point 60% Set point 50F TESTING CONTROL SYSTEMS

  30. Control Sequence Verification SAFTIES A high static pressure sensor is located in the hot deck and the cold deck. If the set point of either sensor is exceeded the VFD will stop the fan. Set point 3.75” Fire smoke detector (FSD-1) located in the return duct will signal the VFD to stop the fan Fire smoke detector (FSD-2) located in the hot duct will signal the VFD to stop the fan Fire smoke detector (FSD-3) located in the cold duct will signal the VFD to stop the fan. TESTING CONTROL SYSTEMS

  31. Control Sequence Verification ALARMS Discharge Air Temperature- If the discharge air temperature in the cold deck is below 45˚ F or above 65˚ F for more than 5 minutes an alarm will be initiated at the BAS workstation. If the final filter in either the hot deck or cold deck differential pressure exceeds 1.20” WG for more than 10 minutes an alarm will be initiated at the BAS workstation. If the pre-filter differential pressure exceeds 0.5”WG for more than 10 minutes an alarm will be initiated at the BAS workstation. If the VFD is not in the “auto” position an alarm will be initiated at the BAS workstation. If the fan commanded value does not match the status proof condition an alarm will be initiated. TESTING CONTROL SYSTEMS

  32. Control Sequence Verification Alarm when cold deck < 45˚ F for 5 minutes Alarm when cold deck > 65˚F for 5 minutes Alarm when CDl filter ∆P > 1.2” WG for 10min Alarm when HDl filter ∆P> 1.2” WG for 10 min Alarm when pre- filter ∆P> 0.5” WG for 10 min Alarm when VFD not in “auto” position Alarm when fan commanded value does not match the status proof condition TESTING CONTROL SYSTEMS

  33. Control Sequence Verification STOP –BMS DISABLED (VFD IN AUTO) Unit Disabled Fan Stop - AHU status off OA terminal disabled Controls disabled TESTING CONTROL SYSTEMS

  34. Control Sequence Verification VFD FAILS-ENABLE AHU WITH THE BYPASS SWITCH When the bypass switch enables the AHU fan the relief damper will be driven open to a pre set position and remain in place for three minutes. The damper will be released to control the discharge plenum to 5.0” WG. The control system will function as described above. TESTING CONTROL SYSTEMS

  35. Control Sequence Verification Test the relief damper with all dual duct terminal boxes set for full cooling and the VFD in bypass. Test the relief damper with all dual duct terminal boxes set for full heating and the VFD in bypass. Measure the SP in the discharge plenum and downstream of the discharge dampers during both tests. Full Cooling Static Pr Discharge 2.01 CD 2.68 HD Full Heating Static Pr Discharge 1.98 CD 1.65 HD TESTING CONTROL SYSTEMS

  36. Point to Point TESTING CONTROL SYSTEMS

  37. Point to Point TESTING CONTROL SYSTEMS

  38. Conclusion • When writing control sequence verifications the main source should be the specifications. • As changes are made to the system because of job conditions the specification must be changed to reflect the change. TESTING CONTROL SYSTEMS

  39. Conclusion • As changes are made the shop drawings, control sequence verification and commissioning plan must be updated. • All systems have some differences and a verification used on the last system probably will not work on the next. TESTING CONTROL SYSTEMS

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