HVAC and Dehumidifying Systems_7

Chia sẻ: Thao Thao | Ngày: | Loại File: PDF | Số trang:17

Thêm vào BST

Báo xấu

57
lượt xem 9
download

Download Vui lòng tải xuống để xem tài liệu đầy đủ

Tham khảo tài liệu 'hvac and dehumidifying systems_7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả

Chủ đề:

Bình luận(0) Đăng nhập để gửi bình luận!

Lưu

Nội dung Text: HVAC and Dehumidifying Systems_7

MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com a) Keep the input and output points to the minimum number required for HVAC control and efficient building operation. Follow the recommended point guidance provided in par. 8.2. Follow the principle to "Keep it Simple." b) Use standard control sequences for similar HVAC control system applications. c) Show the following on control drawings as a minimum: (1) Flow diagram schematic of each mechanical system showing sensors, equipment, and operators. (2) Individual point list description for each mechanical system. (3) Electrical ladder diagram for each electrical circuit controlled. (4) Operating parameters - controller setpoints and time schedules. (5) Detailed sequence of operation. d) Use direct connection of temperature sensors when possible. Use only precision thermistors (10,000 ohms) for room sensing and 1000 ohm platinum RTDs for HVAC unit sensing. e) Use room zone temperature sensors with pushbutton override and setpoint adjustment integral to the sensor. f) Do not modify the chiller microprocessor system supplied with the equipment. Control and safety functions should be the chiller manufacturer's responsibility. The DDC system should only enable or disable the chiller, chilled water pump, condenser water pump, and in some cases chilled water and condenser water reset. For chillers 150 tons and larger, provide an RS-485 communication between the chiller microprocessor and the DDC system. g) Do not modify the boiler microprocessor system supplied with the equipment. Control and safety functions should be the boiler manufacturer's responsibility. Design hot water systems to maintain the boiler manufacturer's minimum temperature when in operation but vary the hot water supply temperature as required to meet the building's requirements. 106
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com h) Connect steam, high temperature hot water, gas, and electric meters to the DDC for remote monitoring of energy use of the building. 8.2 Standard Sequences of Operations 8.2.1 General Requirements. These requirements shall apply to primary HVAC systems unless modified herein. The sequences describe actions of the control system in one direction of change in the HVAC process analog variable, such as temperature, humidity, or pressure. The reverse sequence shall occur when direction of change is reversed unless specifically modified. 8.2.2 Operation of HVAC System. Equipment shall be operated in the optimized start, occupied, or unoccupied modes. a) The optimized start mode energizes the equipment at maximum capacity at the latest time required for heating up (or cooling down) the space to normal occupied temperature conditions. b) The occupied mode maintains the occupied conditions under all load variations while providing required ventilation. Supply fan operates continuously. c) The unoccupied mode cycles the equipment to maintain a minimum heating temperature (or a maximum cooling temperature) in the space while providing no ventilation. 8.2.3 Operation of Outside Air, Return Air, and Exhaust (Relief) Air Dampers a) Optimized Start Mode: Outside air and exhaust air dampers are closed and return air dampers are opened. b) Occupied Mode: Outside air dampers are opened to the minimum ventilation air position. If an economizer outside air cycle is provided, the outside air, return air, and exhaust air dampers are automatically controlled. An outdoor air dry bulb sensor disables the economizer cycle and maintains minimum ventilation air when the outside air dry bulb temperature exceeds the changeover point. c) Unoccupied Mode: Outside air and exhaust air dampers are closed and return air dampers are opened. 8.2.4 Operation of Filtration System. Differential pressure sensor measuring static pressure drop across the filter shall initiate alarm when pressure drop exceeds recommended value. 107
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 8.2.5 Operation of Freeze Protection. A freezestat with an extended surface sensing element, located ahead of the chilled water coil, shall stop the supply fan, return system components to their fail-safe position, and initiate a low-temperature alarm if the temperature at any point of the sensing element falls below the setpoint. Normal operation will occur only after the freezing condition is corrected and the freezestat is manually reset. 8.2.6 Operation of Smoke Detectors. Duct type smoke detectors located in the supply fan discharge air duct and in the return air duct (as required by NFPA) shall stop the supply fan, return system components to their fail-safe position, and shall activate the smoke alarm if either detector senses the presence of smoke. Normal operation will occur only after the smoke is cleared and the detector(s) is manually reset. 8.2.7 Operation of Chilled Water Coil Discharge Control. A dry bulb temperature sensor located in the chilled water coil discharge air shall, on a rise in temperature, first, gradually close the preheat coil valve, next, gradually open the outside air damper from its minimum ventilation air position while simultaneously gradually close the return air damper (ensure thorough mixing) and gradually opening the exhaust air damper, and then gradually open the chilled water coil valve. An outdoor air dry bulb sensor disables the economizer cycle and maintains minimum ventilation air when outside air dry bulb temperature exceeds the changeover point. 8.2.8 Operation of Preheat Coil Control. (Where required by outdoor design temperatures and ventilation air requirements.) A dry bulb temperature low limit sensor located in the mixed air (ensure thorough mixing) shall, on a fall in temperature, gradually open the preheat coil valve. Primary control shall be sequenced by the chilled water coil discharge sensor or supply air sensor. 8.2.9 Operation of Heating Coil Control. A dry bulb temperature sensor located in the heating coil discharge air shall, on a rise in dry bulb air temperature, gradually close the heating coil valve. 8.2.10 Operation of Space Control (Single Zone Unit). A room type dry bulb temperature sensor located in the most critical spot shall, on a rise in dry bulb temperature in the space, first gradually close the heating coil valve, next gradually close the preheat coil valve, then gradually open the outside air damper from its minimum ventilation air position while simultaneously gradually close the return air damper (ensure thorough mixing) 108
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com and gradually opening the exhaust air damper, and finally gradually open the chilled water coil valve. A dry bulb temperature low limit sensor located in the mixed air (ensure thorough mixing) shall, on a fall in temperature, gradually open the preheat coil valve. An outdoor air dry bulb sensor disables the economizer cycle and maintains minimum ventilation air when outside air dry bulb temperature exceeds the changeover point. 8.2.11 Operation of Space Control (Multizone Unit). A room type dry bulb temperature sensor located in the most critical spot shall, on a rise in dry bulb temperature in the space, gradually open the cold deck damper while simultaneously gradually close the hot deck damper. 8.2.12 Operation of Space Control (VAV Terminal Unit - Pressure Dependent). A room type dry bulb temperature sensor located in the most critical spot shall, on a rise in dry bulb temperature in the space, gradually open the VAV terminal box cold air valve. 8.2.13 Operation of Supply Duct Pressure Control. A supply duct static pressure sensor located two-thirds the distance from the fan of the length of the longest supply duct run shall, on a rise in static pressure, gradually reduce the speed of the electric motor variable speed drive and close the fan vortex damper. A high-limit duct static pressure sensor located at the fan discharge shall override the supply duct static pressure sensor to limit pressures to design values. 8.3 Single Zone Unit Sequence of Operations (Sample). See Figure 33 and Table 15. a) General: Sequences describe actions of the control system in one direction of change in the HVAC process analog variable, such as temperature, humidity, or pressure. Reverse sequence shall occur when direction of change is reversed unless specifically modified. b) Optimized Start Mode: Energize equipment at maximum capacity at the latest time required for heating up (or cooling down) the space to normal occupied temperature conditions. Outside air and exhaust air dampers are closed and return air dampers are opened. c) Occupied Mode: Maintain occupied conditions under load variations while providing required ventilation. Supply fan operates continuously. Outside air dampers are opened to the minimum ventilation air position. If an economizer outside air cycle is provided, the outside air, return air, and exhaust air 109
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com dampers are automatically controlled. An outdoor air dry bulb sensor disables the economizer cycle and maintains minimum ventilation air when outside air dry bulb temperature exceeds the changeover point. d) Unoccupied Mode: Cycle the equipment to maintain minimum heating temperature (or maximum cooling temperature) in the space while providing no ventilation. Outside air and exhaust air dampers are closed and return air dampers are opened. e) Maintenance and Safety Mode: A differential pressure sensor measuring static pressure drop across the filter shall initiate an alarm when the pressure drop exceeds the recommended value. A freezestat with extended surface sensing element located ahead of the chilled water coil shall stop the supply fan, return system components to their fail-safe position, and initiate a low-temperature alarm if the temperature at any point of the sensing element falls below the setpoint. Normal operation shall occur only after the freezing condition is corrected and the freezestat is manually reset. f) Room Control Mode: A room type dry bulb temperature sensor located in the most critical spot shall, on a rise in dry bulb temperature in the space, first gradually close the heating coil valve, next gradually close the preheat coil valve, then gradually open the outside air damper from its minimum ventilation air position while simultaneously gradually close the return air damper (ensure thorough mixing) and gradually opening the exhaust air damper, and finally gradually open the chilled water coil valve. A dry bulb temperature low limit sensor located in the mixed air (ensure thorough mixing) shall, on a fall in temperature, gradually open the preheat coil valve. A dry bulb temperature low limit sensor located in the supply air shall, on a fall in temperature, gradually open the heating coil valve. An outdoor air dry bulb sensor disables the economizer cycle and maintains minimum ventilation air when outside air dry bulb temperature exceeds the changeover point. 8.4 Multizone Unit Sequence of Operation (Sample). See Figure 34 and Table 16. a) General: Sequences describe actions of the control system in one direction of change in the HVAC process analog variable, such as temperature, humidity, or pressure. Reverse sequence shall occur when direction of change is reversed unless specifically modified. 110
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 111
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 112
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Table 15 Equipment for Single Zone HVAC Control System XX LOOP CONTROL DEVICE DEVICE ADDITIONAL FUNCTION NUMBER FUNCTION SETPOINT RANGE PARAMETERS ROOM ZONE DA-XX01, DAMPER -- 4-20 ma MIN.O.A. TEMPERATURE 02, 03 ACTUATOR XXXX CFM OUTDOOR AIR 65O F -- -- SOFTWARE DB HI LIMIT POINT 55O F 30-130o F TS-XX01 MIXED AIR -- LOW LIMIT TEMPERATURE SENSOR VLV-XX01 PREHEAT COIL -- 4-20 ma CV-10 VALVE CLOSE AGAINST 16 PSIG 55O F 40-140o F TS-XX02 SUPPLY AIR -- VLV-XX02 HEATING COIL -- 4-20 ma CV-12 VALVE CLOSE AGAINST 16 PSIG VLV-XX03 COOLING COIL -- 4-20 ma CV-20 VALVE CLOSE AGAINST 20 PSIG H-70O F 50-100o F WITH TS-XX03 ROOM ZONE TEMPERATURE C-76o F SETPOINT N-55o F SENSOR ADJUST- MENT & OVERRIDE SWITCH 35o F SAFETY & TSL-XX01 LOW -- -- MAINTENANCE TEMPERATURE PROTECTION THERMOSTAT SD-XX01 SUPPLY AIR -- -- -- SMOKE DETECTOR SD-XX02 RETURN AIR -- -- -- SMOKE DETECTOR DP-XX01 FILTER STATUS 0.5 IN. 0-2 IN. -- DIFFERENTIAL W.G. W.G. PRESSURE 113
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Table 15 (Continued) Equipment for Single Zone HVAC Control System XX LOOP CONTROL DEVICE DEVICE ADDITIONAL FUNCTION NUMBER FUNCTION SETPOINT RANGE PARAMETERS 50-100O F SAFETY & TS-XX04 RETURN AIR -- -- MAINTENANCE TEMPERATURE (CONT’D) SENSOR SUPPLY FAN R-XX01 SUPPLY FAN -- -- -- START RELAY CS-XX01 SUPPLY FAN -- -- -- CURRENT SENSOR 114
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 115
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Table 16 Equipment for Multizone HVAC Control System XX LOOP CONTROL DEVICE DEVICE ADDITIONAL FUNCTION NUMBER FUNCTION SETPOINT RANGE PARAMETERS COLD DECK DA-XX01, DAMPER -- 4-20 ma MIN.O.A. TEMPERATURE 02, 03 ACTUATOR XXXX CFM -- OUTDOOR AIR 65 deg F -- SOFTWARE DB HI LIMIT POINT TS-XX01 MIXED AIR 55 deg F 30-130 deg F -- LOW LIMIT TEMPERATURE SENSOR 116
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Table 16 (Continued) Equipment for Multizone HVAC Control System XX LOOP CONTROL DEVICE DEVICE ADDITIONAL FUNCTION NUMBER FUNCTION SETPOINT RANGE PARAMETERS COLD DECK VLV-XX01 PREHEAT COIL -- 4-20 ma CV-10 TEMPERATURE VALVE CLOSE (CONT’D) AGAINST 16 PSIG 55O F 40-140o F -- TS-XX02 COLD DECK TEMPERATURE SENSOR VLV-XX02 COOLING COIL -- 4-20 ma CV-20 VALVE CLOSE AGAINST 20 PSIG 180o F 40-240o F HOT DECK TS-XX03 HOT DECK TEMPERATURE TEMPERATURE SENSOR VLV-XX03 HEATING COIL -- 4-20 ma CV-12 VALVE CLOSE AGAINST 16 PSIG O o ROOM SENSORS TS-XX04 ROOM H-70 F 50-100 F WITH C-76o F (MULTIPLE) TEMPERATURE SETPOINT N-55o F SENSORS ADJUST- MENT & OVERRIDE SWITCH DA-XX04 ZONE DAMPER -- 4-20 ma ONE PER ACTUATORS ZONE 35o F SAFETY & TSL-XX01 LOW -- -- MAINTENANCE TEMPERATURE PROTECTION THERMOSTAT SD-XX01 SUPPLY AIR -- -- -- SMOKE DETECTOR SD-XX02 RETURN AIR -- -- -- SMOKE DETECTOR DP-XX01 FILTER STATUS 0.5 IN. 0-2 IN. -- DIFFERENTIAL W.G. W.G. PRESSURE 50-100O F -- TS-XX04 RETURN AIR -- TEMPERATURE SENSOR 117
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Table 16 (Continued) Equipment for Multizone HVAC Control System XX LOOP CONTROL DEVICE DEVICE ADDITIONAL FUNCTION NUMBER FUNCTION SETPOINT RANGE PARAMETERS 50-100o F SAFETY & TS-XX04 RETURN AIR -- -- MAINTENANCE TEMPERATURE (CONT’D) SENSOR SUPPLY FAN R-XX01 SUPPLY FAN -- -- -- START RELAY CS-XX01 SUPPLY FAN -- -- -- CURRENT SENSOR b) Optimized Start Mode: Energize equipment at maximum capacity at the latest time required for heating up (or cooling down) the space to normal occupied temperature conditions. Outside air and exhaust air dampers are closed and return air dampers are opened. c) Occupied Mode: Maintain occupied conditions under all load variations while providing required ventilation. Supply fan operates continuously. Outside air dampers are opened to the minimum ventilation air position. If an economizer outside air cycle is provided, the outside air, return air, and exhaust air dampers are automatically controlled. An outdoor air dry bulb sensor disables the economizer cycle and maintains minimum ventilation air when outside air dry bulb temperature exceeds the changeover point. d) Unoccupied Mode: Cycle the equipment to maintain minimum heating temperature (or maximum cooling temperature) in the space while providing no ventilation. Outside air and exhaust air dampers are closed and return air dampers are opened. e) Maintenance and Safety Mode: A differential pressure sensor measuring static pressure drop across the filter, shall initiate an alarm when the pressure drop exceeds the recommended value. A freezestat with extended surface sensing element located ahead of the chilled water coil shall stop the supply fan, return system components to their fail-safe position, and initiate a low-temperature alarm if the temperature at any point 118
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com of the sensing element falls below the setpoint. Normal operation will occur only after the freezing condition is corrected and the freezestat is manually reset. f) Chilled Water Coil Discharge Air Mode: A dry bulb temperature sensor located in the chilled water coil discharge air shall, on a rise in temperature, first gradually close the preheat coil valve, next gradually open the outside air damper from its minimum ventilation air position while simultaneously gradually close the return air damper (ensure thorough mixing) and gradually open the exhaust air damper, and then gradually open the chilled water coil valve. A dry bulb temperature low limit sensor located in the mixed air (ensure thorough mixing) shall, on a fall in temperature, gradually open the preheat coil valve. An outdoor air dry bulb sensor disables the economizer cycle and maintains minimum ventilation air when outside air dry bulb temperature exceeds the changeover point. g) Heating Coil Discharge Air Mode: A dry bulb temperature sensor located in the heating coil discharge air shall, on a rise in dry bulb air temperature, gradually close the heating coil valve. h) Room Control Mode: A room type dry bulb temperature sensor located in the most critical spot shall, on a rise in dry bulb temperature in the space, gradually open the cold deck damper while simultaneously gradually close the hot deck damper. 8.5 Variable Air Volume (VAV) Unit Sequence of Operation (Sample). See Figure 35 and Table 17. a) General: Sequences describe actions of the control system in one direction of change in the HVAC process analog variable, such as temperature, humidity, or pressure. Reverse sequence shall occur when direction of change is reversed unless specifically modified. b) Optimized Start Mode: Energize equipment at maximum capacity at the latest time required for heating up (or cooling down) the space to normal occupied temperature conditions. Outside air and exhaust air dampers are closed and return air dampers are opened. Fans of series type VAV terminal units shall start. c) Occupied Mode: Maintain occupied conditions under all load variations while providing required ventilation. Supply fan operates continuously. Outside air dampers are opened to the minimum ventilation airflow by the air monitoring unit for all 119
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com values of supply fan flow. If an economizer outside air cycle is provided, the outside air, return air, and exhaust air dampers are automatically controlled. An outdoor air dry bulb sensor disables the economizer cycle and maintains minimum ventilation air when the outside air dry bulb temperature exceeds the changeover point. Fans of series type VAV terminal units shall run continuously. d) Unoccupied Mode: Cycle the VAV terminal units at maximum heating capacity to maintain minimum heating temperature in the space while providing no ventilation. Outside air and exhaust air dampers are closed and return air dampers are opened. e) Maintenance and Safety Mode: A differential pressure sensor measuring static pressure drop across the filter shall initiate an alarm when the pressure drop exceeds the recommended value. A freezestat with extended surface sensing element located ahead of the chilled water coil shall stop the supply fan, return system components to their fail-safe position, and initiate a low-temperature alarm if the temperature at any point of the sensing element falls below the setpoint. Normal operation will occur only after the freezing condition is corrected and the freezestat is manually reset. f) Supply Fan Discharge Air Mode: A dry bulb temperature sensor located in the supply air fan discharge air shall, on a rise in temperature, first gradually close the preheat coil valve, next gradually open the outside air damper from its minimum ventilation air position while simultaneously gradually close the return air damper (ensure thorough mixing) and gradually open the exhaust air damper, and then gradually open the chilled water coil valve. A dry bulb temperature low limit sensor located in the mixed air (ensure thorough mixing) shall, on a fall in temperature, gradually open the preheat coil valve. An outdoor air dry bulb sensor disables the economizer cycle and maintains minimum ventilation air when the outside air dry bulb temperature exceeds the changeover point. g) Supply Duct Static Pressure Mode: A supply duct static pressure sensor located two-thirds the distance from the fan of the length of the longest supply duct run shall, on a rise in static pressure, gradually reduce the speed of the electric motor variable speed drive and close the fan vortex damper. A high-limit duct static pressure sensor located at the fan discharge shall override the supply duct static pressure sensor to limit pressures to design values. 120
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 121
MIL-HDBK-1003/3 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 122