SEQUENCE OF OPERATIONS
1.1 1.1 Sequence Sequence of Operation: Chillers, Primary Chilled Water Water Pumps, Condenser water Pumps Pumps & Cooli ng Towers The primary chilled water system comprises of 3 chillers and 4 primary pumps ( 3 duty, 1 standby ). These primary pumps are constant speed pumps. Each chiller consists of isolating butterfly valves. Each cooling tower consists of cooling fan and butterfly valves for isolating the condenser water flow and individual condenser water temperature sensor. Cooling tower fan speed is controlled by variable speed drive comparing the condenser water temperature and condenser water temperature setpoint. The sequence of operation of the unit shall be as follows: The unit shall be operated by the BMS when: •
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The HOA switch of of the chillers, primary chilled water pumps, condenser water pumps and cooling water fans is in “Auto” position. The Trip signal of chillers, primary chilled water pumps, condenser water pumps and cooling water fans is in NORMAL state. Plant Enable Signal is enabled
Once chilled water plant enable sequence is enabled by the operator, BMS will start the process as per the following sequence: BMS will select the chiller with the least number of run hours and will issue a command to open the condenser water inlet motorised butterfly valve. BMS will select the cooling tower with the least number of run hours and will issue a command to open the condenser motorised butterfly valves at the inlet line of the cooling tower. When the butterfly valve status is open, BMS will start the condenser pump with the least number of run hours and start the Cooling Tower Fan. If condenser water pump and cooling tower fan status is not received within preset time delay of 30 & 60 seconds respectively after start command is issued then an alarm will be generated and latched on the BMS and the command to the pump & fan will be stopped. The condenser water temperature sensor installed in the cooling tower return line (leaving the cooling tower) will relay the measured signal (temperature) to the DDC controller. The DDC controller compares this signal with the set-point (adjustable by the operator from BMS central) and generates control output (based on Proportional Integral Control algorithm) which will modulate the speed of the cooling tower fan to achieve desired set point condition. The default set-point value of condenser water temperature leaving cooling tower is 34.0 °C (user adjustable).
When the condenser water flow is established, BMS will issue a command to open the chiller water inlet motorized butterfly valves of the chiller. Once the open status is received, BMs will issue a command to start the primary chilled water pump. If primary chilled water pump status is not received within preset time delay of 30 seconds after start command is issued then an alarm will be generated and latched on the BMS and the command to the pump will be stopped. Once the chilled water pump is started as noted by a volt-free contact (or differential pressure switch), BMS will issue a command to start the selected chiller after a predeternined time dealy. BMS will calculate the required number of chillers depending System Return Chilled water temperature. The calculated number of stages is incremented by one when the system return chilled water temperature is higher than the retun chilled water temperature setpoint (user adjustable). The calculated number of stages is decremented by one when the system return temperature is lower than the Chilled water return temperature set point and the flow through the chilled water bypass line is more than the flow of one one chiller. BMS will keep a delay of 15 minutes (adjustable operator) for incrementing or decrementing stages of chiller and checks whether the demand is still exists before next stage is switched ON or OFF. BMS shall monitor run hours of chillers, pumps and cooling tower fans and will start the next equipment with least number of run hours. BMS shall run at least one set of condenser water pump, primary chilled water pump and cooling tower fan even if there is no demand. If any pump or chiller or cooling tower fan fails, then BMS will first stop the command for the equipment and close the respective butterfly valves then it will command the standby equipment to start as per the earlier mentioned sequence. 1.1.1 1.1.1 Sto p Sequ Sequ ence When there is no demand or the when there is request to stop a chiller, BMS will initiate the stop sequence as follows. 1) Stop the chiller. 2) Stop the primary pump and close the respective butterfly valve after 2 minutes 3) Stop the condenser pump, cooling tower fan. 4) Close the respective condenser water butterfly valves. 1.2 1.2
Sequence Sequence of Operation: Secon Secon dary Chilled Water Water System
The Chilled Water Secondary Pumps shall be operated by the BMS when: The Hand-Off-Auto Hand-Off-Aut o switch is in “Auto” position, The Pump VFD trip signal is in “Normal” state. Plant Enable Signal is enabled • • •
The pumps will be operated on Lead-Lag basis to equalize the run-time. BMS shall select and operate the pumps to achieve Runtime equalization. In case of lead pump fails the lag pump will operate. The sequencing of the pumps will be altered after every 200 hours (user adjustable). Once the command is issued form BMS the DDC will Command the Lead Pump to start. The BMS shall start the lead pump at low speed (40%, user adjustable). If the status of the Lead Pump is not received within preset time delay of 30 seconds after start command is issued then an alarm will be generated and latched on the BMS and DDC will issue start command to next available pump. In case of any of the running pumps fail, the DDC will command the stand-by pump in the sequence. The DDC shall monitor the differential pressure at the index line and generate an appropriate output (based on P +I algorithm) for the VFDs. The system shall attempt to maintain design conditions with the use of one pump. If after an adjustable/preset time limit of 15 minutes, the system pressure remains below the set point with one pump running, the BMS shall start the next pump at low speed. The speed of the second pump shall be increased and that of the lead pump shall be reduced till the set differential pressure value is attained. The BMS shall then increase or decrease the speed of all pumps simultaneously to maintain the system pressure set point. The addition of other pumps shall be as per the aforementioned sequence. The BMS shall continuously monitor the secondary pump speed and shall stop the lag pumps when the pump speed falls below 50%. The BMS shall then increase the speed of the lead pumps. The speed of the lead pumps shall be increased or decreased to maintain system pressure. If the chilled water demand decreases further and the pump speed goes below 40% and the differential pressure exceeds the set points then the decoupler valve, installed in the bypass line, will modulate to open to bypasses the chilled water flow to maintain the set point. 1.3
Plant Reset Reset
In the event of failure condition of equipment the operator must reset the latched failures by using the plant-reset button available on BMS graphic screen or by putting the respective equipment H/O/A switch status in OFF or HAND mode and bringing it back to AUTO mode from local control control panel panel (This provision provision is provided to facilitate facilitate the operator operator to reset respective equipment alarms in case graphic central communication fails with controllers).
1. Fire Fighting / Protection Protection Pumps System 1.1
System Overvi ew
The fire fighting pumps system is controlled by its local Control Panel. BMS does not have any control on the system it will just monitor the system. 1 .2 .2
Monitoring Points
The following points are monitored / displayed at the BMS central: Jockey Pump Status Jockey Pump Trip Alarm Jockey Pump Earth Leakage/Fault Alarm Electric Pump Status Electric Pump Trip Alarm Electric Pump Earth/Leakage Fault Alarm Diesel Pump Status Diesel Pump Trip Alarm Diesel Pump Engine Over speed Diesel Pump Low Oil Pressure Diesel Pump High Water Temperature Diesel Pump Engine Failed to Start Diesel Pump Battery Charger Fault Alarm Main Incomer Open Alarm Power Failure Alarm Fire Pumps Disconnect Switch Status Fire Pumps Disconnect OFF Alarm Fire Pumps Line Pressure – lowest level Fire Pumps Line Pressure – highest level Low Suction Pressure Alarm Sprinkler Water Pressure • • • • • • • • • • • • • • • • • • • • •
SMOKE MANAGEMENT – TYPICAL FLOORS
The typical floors lift lobbies of the project is provided with a smoke management installation. The operation principle is: In the event of a f ire within any service apartment, the lift lobby of the fire floor and the floors immediately above and below the fire floor shall be pressurized, in order to reduce the ingress of smoke into the lift lobby. The lift lobby shall be the safe exit exit route for the occupants of the offices. STAIRWELL PRESSURIZATION
Each staircase shall be pressurized in the event of a fire to prevent smoke ingress into the staircase. Each staircase shall have a dedicated fan at the roof with a shaft throughout the height of the staircase. Air supply supply shall shall be at each floor. The fan shall be signaled to run through a signal from the fire alarm panel. The fan shall be provided with a variable speed drive so as not to over pressurize the staircase. Pressure sensors located located within the staircase shall modulate the fan speed so as to limit the maximum differential differential pressure to 65 Pa. Pa. The fan and the connecting connecting ductwork shall be fire rated. The fan is sized to maintain a pressure differential of 12.5pa with 3 doors open, velocity of air through open door being 1.0m/s. The fan shall be sized based on 3 open door condition. However, for the G+3 buildings single injection fans were provided & the sequence of operation of the unit shall be as follows: The unit shall be operated by the BMS when: The HOA switch of the fans is in “Auto” position. The fan trip signal is in NORMAL state. Fire Condition exists and Motorize Smoke Damper Opened Once the above conditions are satisfied, unit is enabled to start in Auto mode or using a plant enable button on the graphics. Once the start command is issued then BMS shall monitor the run status of the fan from the differential pressure airflow switch. If the fan status from the differential pressure air flow switch is not proved ‘On’ within preset time delay of 60 seconds after the start command is being issued then an alarm will be generated and latched on the BMS and will stop the Fan.
LIFT WELL PRESSURIZATION
The lift shaft of the fireman’s fireman’s elevator is provided with a pressurization installation. installation. In the event of a fire, the lift shaft pressurization fan shall run through a signal from the fire alarm panel. Fan duty is based on air leakage through lift doors. Based on EN 12101-6, leakage through each lift door at a pressure differential of 25 Pa is 0.25 m³/s.
BASEMENT CAR PARK VENTILATION
The basement of the project is used as car car parking facility. This floor is provided provided with mechanical ventilation for operation in three modes: -
Normal ventilation
@ 3 ACH (up to 50 PPM CO concentration)
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High CO concentration levels @ 6 ACH (exceeding 50 PPM CO concentration)
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Smoke extract.
@ 9 ACH. (Fire) Mode.
The ventilation system provided is a ducted installation with extract and make up air fans. The smoke extract fans and ducts are fire rated construction suitable to handle high temperature smoke upto 400°C for a period of two hours. Carbon monoxide detectors are provided to sense the CO concentration and to alter the fan speed through a carbon monoxide monitoring and control panel.
1. FAHU with wi th Fixed Speed Speed Suppl y & Exhaust Fan with wi th Heat Heat Recov Recovery ery Wheel Wheel & Heat Pipe 1.1
System Overvi ew
The Fresh Air Handling Unit with Heat Recovery Wheel is used to provide treated fresh air, which is distributed through medium and low pressure duct systems and supplied to the space through FCU units. The air-handling unit will be started and stopped by signal from the BMS. The unit is comprised of: •
Supply air fan.
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Exhaust air fan
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Heat recovery wheel, to pre-cool the fresh air supply at the point of entry to the AHU.
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Fresh air ON/OFF damper.
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Exhaust air ON/OFF damper
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2-way modulating cooling valve.
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Heat pipe across cooling coils
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Bag & Pre Filter
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A temperature sensor installed downstream of the cooling coil.
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1.2 1.2
Temperature and Humidity Sensors on the supply and extract air duct at the upstream and downstream of the heat recovery wheel. Common set of sensors to monitor ambient air conditions at each service floor/plant room. Temperature and humidity sensor at supply air duct Differential Pressure Switches for establishing establishing air flow of Supply Supply & Extract Extract Air Fan. Sequence Sequence of Operation
The sequence of operation of the unit shall be as follows: 1.2. 1.2.1 1 Supp ly Ai r Fan Fan Control The AHU Supply air fan shall be operated by the BMS when: The Auto / Manual switch of the supply fan is in “Auto” position, The Occupancy Schedule is in “Occopied” state, The supply air fan trip signal is in “Normal” state. • • •
If above conditions are satisfied AHU will be enabled to start in Auto Mode based on Occupancy Schedule or using a Plant Enable button on the graphics in manual mode by operator. Once enabled, BMS will automatically command the Fresh and Exhaust Air Damper to open. If fresh air and exsaust air damper status is not received within preset time delay of 90 seconds after start command is issued then an alarm will be generated and latched on the BMS and the AHU start sequence will be stopped. Once the dampers opened (confirmed by damper open status), the DDC controller will give the start command to the supply air fan. Once the start command is given, BMS shall monitor the airflow switch of the fan via the differential pressure switch installed across the fan. If the airflow switch signal is proved “ON” then BMS will enable Exhaust Air Fan control, control, Heat Recovery Recovery Wheel control, Temperature Temperature & Humidity control Loop. Loop. If Supply fan status is not received within preset time delay of 60 seconds after start command is issued then an alarm will be generated and latched on the BMS and the AHU supply air air fan will be stopped. stopped. Based on the run status, BMS will also display the run hours of the unit. 1.2. 1.2.2 2 Exhaust Air Fan Control The AHU Exhaust Fan shall be operated by the BMS when: The Auto / Manual switch of the exhaust fan is in “Auto” position. The exhaust air fan trip signal is in “Normal” state The supply air fan run status is in “On” state. • • •
If the AHU is commanded to start and the supply air fan running condition is ON (monitored by the differential airflow switch), then BMS will automatically start the exhaust air fan. Once the start command is issued then BMS shall monitor the differential pressure airflow switch of the fan. If exhaust fan status is not received within preset time delay of 60 seconds after start command is issued then an alarm will be generated and latched on the BMS and the AHU shall be stopped. Based on the run status, BMS will also display the run hours of the unit. 1.2.3 1.2.3 Heat Reco Reco very Wheel Operati on Heat recovery wheel is used to pre-cool the fresh air supply to the AHU. Heat recovery Wheel shall be operated by the BMS when: The Auto / Manual switch of the HRW is in “Auto” position. •
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The HRW trip signal is in “Normal” state The supply & exhaust exhaust air fan run status is in “On” state. The Outside air The Outside air temperature (or enthalpy) is higher than the Return air temperature (or enthalpy).
The HRW operation is interlocked with the FAHU supply air fan i.e., the HRW will run only when the supply air fan is proved running. Once the AHU is commanded to start and the fan running condition is ON (monitored by the differential airflow switch), then BMS will automatically start the HRW. Once the start command is issued, then BMS shall monitor the HRW run status. If HRW run status is not received within preset time delay of 30 seconds after start command is issued then an alarm will be generated and latched on the BMS and the HRW will be stopped. 1.2. 1.2.4 4 Temperature Temperature Control Loop The supply air temperature sensor installed in the supply air duct will relay the measured signal (temperature) to the DDC controller. The DDC controller compares this signal with the set-point (adjustable by the operator from BMS central) and generates control output (based on Proportional - Integral Control algorithm) which will modulate 2way modulating cooling valve to achieve desired set point condition. The default setpoint value for the supply air temperature is 13.0 °C (user adjustable). 1.2.5 Heat pipe Heat pipe operation is independent of the BMS system. BMS shall not have any control on it. The temperature & humidity between the heat pipes will be monitored by BMS. 1.2. 1.2.6 6 Fire Alarm Interlock The whole plant unit operation shall be interlocked with the fire alarm signal. In the event of fire being detected in the building BMS will automatically switch off AHU equipments. 1.2.7 Plant Reset In the event of failure condition of AHU equipments the operator must reset the latched failures by using the plant-reset button available on BMS graphic screen or by putting the respective equipment H/O/A switch status in OFF or HAND mode and bringing it back to AUTO mode from local control panel (This provision is provided to facilitate the operator to reset respective equipment alarms in case graphic central communication fails with controllers).
1 .3 .3
Monitoring Points
The following points monitored by BMS will have no action on the operation of the airhandling unit. Outside Air Temperature & Humidity. On & Off-HRW Coil Temperature & Humidity On -Cooling Coil Temperature On Heat Pipe Humidity & Temperature Return Air temperature and Humidity • • • • •
FCU –Standalon –Standalon e Thermost at 1. FCU 1.1
System Overvi ew
The fan coil units shall be controlled by a dedicated Thermostat.
1.2 1.2
Control Sequence Sequence
Standalone Thermostat with built in temperature sensor will compare the room temperature with the desired temperature setpoint and modulate the 2-way chilled water valve to maintain the room temperature at the preset conditions (e.g. 23 ºC +/- 1ºC) while the 3-speed fan will will be running at the low low speed. If the temperature is not attained at low speed, the speed of the supply fan will be increased in steps to the High speed. Once the speed is achieved, the speed will be decreased in steps to the low speed. The occupant will be able to change the set point to his requirement & select the fan speed (Low, Medium, and High) and switch On/Off the system (FCU) from Thermostat.
