Appendix B:
Building Systems Sequence of Operations - Sample
The Building Systems Sequence of Operations outlines the as-operating sequence of operations
for all HVAC and lighting control systems, as well as integration of the fire/life safety and
HVAC systems. This document was developed in order to satisfy LEED-EB Energy &
Atmosphere prerequisite and credit requirements.
BEST BUILDING
SEQUENCE OF OPERATION
INDEX
Air Handling System Description and Control ............................................................................... 1
Cold-deck Air Handlers: AHU1 through AHU4 ........................................................................ 1
Fan OFF condition .................................................................................................................. 1
Fan Start-up or Shut-down ...................................................................................................... 1
Return Fan Volume Control.................................................................................................... 1
Discharge Air Temperature Controls ...................................................................................... 2
Static Pressure Controls .......................................................................................................... 3
Warm-up Control .................................................................................................................... 3
Night Low Limit ..................................................................................................................... 3
Night purge ............................................................................................................................. 3
Alarms and Safeties ................................................................................................................ 4
Manual smoke pressurization system ..................................................................................... 4
Dedicated Ventilation Air Fans: AHU7 through AHU10........................................................... 4
Hot deck air handlers: AHU 5 and AHU 6 ................................................................................. 4
Fan OFF condition: ................................................................................................................. 5
Fan Start-up or Shut-down: ..................................................................................................... 5
Discharge Air Temperature Controls ...................................................................................... 5
Static Pressure Controls .......................................................................................................... 5
Warm-up Control .................................................................................................................... 6
Night Low Limit ..................................................................................................................... 6
Alarms and Safeties ................................................................................................................ 6
VAV Box Description and Control................................................................................................. 6
Conference Room VAV Boxes ................................................................................................... 7
Conference Room is Occupied (during normal building operating hours)............................. 7
Conference Room is Unoccupied (during normal building operating hours)......................... 7
Building is Unoccupied........................................................................................................... 7
Dual Duct VAV Boxes ............................................................................................................... 7
Occupied Condition ................................................................................................................ 7
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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Unoccupied Conditions ........................................................................................................... 8
Cooling-only VAV Boxes........................................................................................................... 8
Occupied Condition ................................................................................................................ 8
Unoccupied Conditions ........................................................................................................... 8
Chilled Water System Description and Control.............................................................................. 8
Chillers and Primary / Secondary Pump Control ........................................................................ 8
The EMCS control points for Chillers 1, 2, and 3 .................................................................. 8
Chilled water supply (CHWS) temperature reset ................................................................... 9
Chilled Water System Enable ................................................................................................. 9
Chiller Staging ........................................................................................................................ 9
Primary Chilled Water Pumps .............................................................................................. 10
Secondary Chilled Water Pumps .......................................................................................... 11
Condensing Water and Cooling Tower Control ....................................................................... 12
Cooling Tower Operation ..................................................................................................... 12
Condenser Water Pumps for Chillers ................................................................................... 13
Condenser Water Pumps for the Heat Exchanger (cooling tower side) ............................... 13
Distribution Water Pumps for the Heat Exchanger (Liebert side) ........................................ 13
Heating Water System Description and Control ........................................................................... 14
General System Control ............................................................................................................ 14
System start-up...................................................................................................................... 14
System Shutdown.................................................................................................................. 14
Condensing Boiler Control ....................................................................................................... 14
Non-condensing Boiler Control ................................................................................................ 15
Distribution Water Loop Control .............................................................................................. 16
General Control Features .......................................................................................................... 16
Garage Exhaust Fan (EF-1) Control ............................................................................................. 17
General Exhaust Fan Control ........................................................................................................ 17
Lighting Control............................................................................................................................ 17
Parking Area ......................................................................................................................... 17
General Public and Jury Assembly Areas ............................................................................. 17
Office Spaces ........................................................................................................................ 17
Mechanical Rooms................................................................................................................ 18
Conference Rooms ................................................................................................................ 18
Fire/Life Safety System Control ................................................................................................... 18
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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AIR HANDLING SYSTEM DESCRIPTION AND CONTROL
Heating and cooling for the building is provided by dual duct variable air volume (VAV) air
handling systems, consisting of the following equipment:
AHU1 and AHU2: Cold-deck air handling units serving the B2 through 8th floors
AHU3 and AHU4: Cold-deck air handling units serving the 9th through 16th floors
AHU5 and AHU6: Hot-deck air handling units serving the B2 through 16th floors
AHU7 and AHU8: Ventilation air handling units serving AHU1 and AHU2, respectively
AHU9 and AHU10: Ventilation air handling units serving AHU3 and AHU4, respectively
Central exhaust for the building includes EF5 through EF9 and EF12, and operation of these
exhaust fans is interlocked with central air handling unit operation. Detailed sequence of
operations for each air handling system, and the central exhaust fans, is provided below.
COLD-DECK AIR HANDLERS: AHU1 THROUGH AHU4
Each cold-deck air handling unit consists of two supply and return fans, each with separate
VFD’s and motors, economizer dampers, and chilled water cooling coils. Operation of each air
handling unit is based on the general schedule of 5:30 AM to 5:30 PM, Tuesday through Friday,
with Monday (or the first day after a holiday shutdown) start-up at 3:30 AM.
Fan OFF condition
 Normally open return air damper is open
 Normally closed economizer and relief dampers are closed
 Normally closed cooling coil valves are closed
 Isolation dampers on each supply fan are closed
Fan Start-up or Shut-down
 Fans start or shutdown upon signal from the EMCS. Basic system operating schedule is from
5:30 AM to 5:30 PM, Tuesday through Friday, with Monday (or the first day after a holiday
shutdown) start-up at 3:30 AM. The system is shut down on weekends and holidays.
 Upon an enable command from the EMCS, the supply fan isolation dampers are commanded
open. The supply fan VFD starts, along with the central exhaust fans (EF-5, EF-6, EF-7, EF8, EF-9, EF-12).
 Both supply fans ramp up and down at the same speed based on maintaining duct static
pressure setpoint.
 The operator can shut down any one of the fan motors from the EMCS. When a fan shuts
down, the respective isolation damper is closed as well to prevent recirculation of air through
the fan that is not operating.
Return Fan Volume Control
Due to envelope leakage, stack effect created a negative pressure in the lobby and lower floors,
allowing unconditioned air to infiltrate into the building. To alleviate building pressurization
issues, all return fans associated with AHU1, AHU2, AHU3, and AHU4 and have been
commanded OFF at the operator work station via a software override. If the lobby experiences
excessive positive pressure during warmer outdoor air conditions (i.e. negative stack effect),
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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facility operators should release the software override on the return fans associated with AHU1
and AHU2 only, allowing these fans to operate. The return fans associated with AHU3 and
AHU4, should remain OFF. Command AHU1 and AHU2 return fans back OFF at the end of the
day or when the lobby doesn’t experience excess positive pressure (typically when outdoor air
temperature is below 75F).
A future recommendation is to automatically control only the return fans associated with AHU1
and AHU2 based on outdoor air temperature. For example all return fans are OFF when outdoor
air temperature is less than 75F and AHU1/AHU2 return fans are commanded ON when
outdoor air temperature exceeds 75F (user adjustable value). This would eliminate the need for
manual control.
Discharge Air Temperature Controls
For AHU1 through AHU4, the economizer, relief air, and return air dampers are modulated in
sequence with the normally closed cooling coil valve to maintain discharge air temperature
setpoint. When the outdoor air dry-bulb temperature is less than return air dry-bulb temperature,
the economizer is enabled and the outdoor air dampers are modulated as necessary in
conjunction with the cooling coil valve to meet discharge air temperature setpoint. The
economizer is disabled and goes to 100% return air when the outdoor air dry-bulb temperature is
greater than return air dry-bulb temperature. In this condition, the cooling coil valve is
modulated as necessary to meet discharge air temperature setpoint.
Discharge air temperature (DAT) setpoint is reset based on loads within the building as
determined by the deviation of zone temperature from the active cooling setpoint for selected
zones. If the zone temperature of four (4) or more selected zones is warmer than the active
cooling setpoint by 2F, then discharge air temperature setpoint is lowered by 2F. If four (4) or
more selected zones remain warmer than the active cooling setpoint by 2F the next time the
control loop is executed (every 5 minutes), then the discharge air temperature setpoint is lowered
again by 2F. This process continues until either there are less than four (4) zones warmer than
the active cooling setpoint by 2F (at which point the discharge air temperature setpoint is held
steady at the current value) OR until a minimum setpoint value of 55F is reached.
The discharge air temperature setpoint is raised by 2F when two (2) or less selected zones are
warmer than the active cooling setpoint by 2F. If two (2) or less selected zones remain warmer
than the active cooling setpoint by 2F the next time the control loop is executed (every
5 minutes), then the discharge air temperature setpoint is raised again by 2F. This process
continues until either there are greater than two (2) zones warmer than the active cooling setpoint
by 2F (at which point the discharge air temperature setpoint is held steady at the current value)
OR until a maximum setpoint value of 70F is reached.
Note that the Excel spreadsheets AHU1&2.xls and AHU3&4.xls (located on the operator work
station under file folder C:\Project\BestBuilding) can be used to help troubleshoot discharge air
temperature reset controls. The spreadsheet documents all of the polled zones and their
respective deviation from setpoint. This can assist facility staff in identifying which zones are
driving the control strategy (either legitimately due to zone loads or as a “rogue” box that may
warrant further investigation or maintenance).
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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Static Pressure Controls
Variable frequency drives are used to control supply fan speed based on maintaining duct static
pressure setpoint. Static pressure setpoint is reset based on loads within the building as
determined by VAV box cold-deck damper position for selected zones. If the cold-deck damper
for four (4) or more selected zones is 100% open, then static pressure setpoint is raised by
0.2 in.wc. If the cold-deck damper for four (4) or more selected zones remain 100% open the
next time the control loop is executed (every 5 minutes), then duct static pressure setpoint is
raised again by 0.2 in.wc. This process continues until either there are less than four (4) zones
with cold-deck dampers 100% open (at which point duct static pressure setpoint is held steady at
the current value) OR until a maximum setpoint value of 2.5 in.wc. is reached. An alarm is sent
when duct static pressure is greater than 3.5 in.wc. and the system shuts down when the pressure
exceeds 4.0 in.wc. through a hard-wired safety.
The duct static pressure setpoint is lowered by 0.2 in.wc. when the cold-deck damper for two (2)
or less selected zones are 100% open. If the cold-deck damper for two (2) or less selected zones
remain 100% open the next time the control loop is executed (every 5 minutes), then duct static
pressure setpoint is lowered again by 0.2 in.wc. This process continues until either there are
greater than two (2) zones with cold-deck dampers 100% open (at which point duct static
pressure setpoint is held steady at the current value) OR until a minimum setpoint value of
1.5 in.wc. is reached.
Note that the Excel spreadsheets AHU1&2.xls and AHU3&4.xls (located on the operator work
station under file folder C:\Project\BestBuilding) can be used to help troubleshoot static
pressure reset controls. The spreadsheet documents all of the polled zones and their respective
cold-deck damper position. This can assist facility staff in identifying which zones are driving
the control strategy (either legitimately due to zone loads or as a “rogue” box that may warrant
further investigation or maintenance).
Warm-up Control
The warm-up control sequence is enabled when the discharge air temperature setpoint is greater
than or equal to 70F between 4 AM and 7 AM. During warm-up, the air handling units operate
in 100% return air mode with cooling locked out. Central exhaust fans (EF-5, EF-6, EF-7, EF-8,
EF-9, and EF-12) are commanded OFF during warm-up operating mode.
Night Low Limit
AHU1 through AHU4 stay OFF when night low limit control sequence is enabled.
Night purge
The building is flushed with outside air if the space temperature rises above 80F in any zone
and the outside air is below 65F. All supply fans are commanded ON and economizer dampers
100% open. Night purge is disabled when return air temperature drops to 75F.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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Alarms and Safeties
The following alarms and safeties are programmed as part of the operating sequences.
 Dirty Filter. A differential switch across the filter banks generates alarm at the operator
work station when the pressure drop exceeds the manual setpoint. This indicates the
filters need to be replaced.
 Freeze Stat. A low limit thermostat is used to stop the fan, return all dampers to their
normal positions, and alarm the EMCS upon detection of 40F at the mixed air low limit
thermostat.
 Supply Fan Failure. A fan failure alarm is sent to the operator work station if a supply
fan is commanded ON but a positive status signal is not received to verity fan operation.
Fan failure is detected via a current switch mounted on the electrical power leads to the
motor. Both supply fans within the respective air handling unit receive the same enable
and speed signal from the EMCS based on the static pressure control discussed above.
 Smoke Alarm. On a fire signal, as determined by smoke detectors or through the
building fire system alarm, all air handling units and exhaust fans are shut down and all
dampers return to “normal” positions (normally open return damper, normally closed
economizer and relief dampers, normally closed fan isolation dampers).
Manual smoke pressurization system
Each air handling unit can be controlled manually through the Fireman’s Command Center.
Supply and return fans, as well as outdoor, return, and relief dampers, can be commanded
independently in order to achieve the desired smoke control strategy.
DEDICATED VENTILATION AIR FANS: AHU7 THROUGH AHU10
Each cold-deck air handling unit has a dedicated ventilation fan unit which consists of a constant
volume supply fan, fan isolation damper, pre-heat coil, and a face-and-bypass damper. The
original intent of the system was to provide minimum ventilation to each central air handling unit
whenever it is enabled. However, it was noted during the retrocommissioning process that the
amount of ventilation air introduced by the dedicated fan systems far exceeded the ventilation
need for the building based on actual occupancy. Tests verified that adequate ventilation was
drawn in through the ventilation fan air handling units even if the ventilation fans were turned
OFF. Hence, these fans are commanded OFF, but the isolation dampers are commanded open to
allow ventilation air to be drawn into the central air handling unit by the supply fan.
The pre-heat coil valve is modulated as necessary to meet discharge air temperature setpoint.
The valve is commanded closed when there is a call for cooling (economizer and/or cooling coil
valve is modulating) and allowed to pre-heat ventilation air when the economizer is commanded
closed. The pre-heat coil tempers the ventilation air before it is mixed with return air to meet
discharge air temperature setpoint. The pre-heat valve is also commanded open whenever the
outdoor air temperature is below 35F.
HOT DECK AIR HANDLERS: AHU 5 AND AHU 6
Each hot-deck air handling unit consists of two supply fans, each with separate VFD’s and
motors, and hot water heating coils. Operation of each air handling unit is based on the general
schedule of 5:30 AM to 5:30 PM, Tuesday through Friday, with Monday (or the first day after a
holiday shutdown) start-up at 3:30 AM.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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Fan OFF condition:
 Normally open heating coil valves are closed
 Isolation dampers on each supply fan are closed
Fan Start-up or Shut-down:
 Fans start or shutdown upon signal from the EMCS. Basic system operating schedule is from
5:30 AM to 5:30 PM, Tuesday through Friday, with Monday (or the first day after a holiday
shutdown) start-up at 3:30 AM. The system is shut down on weekends and holidays.
 Upon an enable command from the EMCS, the supply fan isolation dampers are commanded
open and the supply fan starts.
 Both supply fan VFDs ramp up and down at the same speed based on maintaining duct static
pressure setpoint.
 The operator can shut down any one of the fan motors from the EMCS. When a fan shuts
down, the respective isolation damper is closed as well to prevent recirculation of air through
the fan that is not operating.
Discharge Air Temperature Controls
Discharge air temperature setpoint is reset based on outdoor air temperature per the following
schedule:
 70F DAT setpoint when outdoor air temperature is greater than 60F (basically use
return air to meet the load)
 110F DAT setpoint when outdoor air temperature is less than 48F.
Static Pressure Controls
Variable frequency drives are used to control supply fan speed based on maintaining duct static
pressure setpoint. Static pressure setpoint is reset based on loads within the building as
determined by VAV box hot-deck damper position for selected zones. If the hot-deck damper
for four (4) or more selected zones is 100% open, then static pressure setpoint is raised by
0.2 in.wc. If the hot-deck damper for four (4) or more selected zones remain 100% open the next
time the control loop is executed (every 5 minutes), then duct static pressure setpoint is raised
again by 0.2 in.wc. This process continues until either there are less than four (4) zones with
hot-deck dampers 100% open (at which point duct static pressure setpoint is held steady at the
current value) OR until a maximum setpoint value of 2.5 in.wc. is reached. An alarm is sent
when duct static pressure is greater than 3.5 in.wc. and the system shuts down when the pressure
exceeds 4.0 in.wc. through a hard-wired safety.
The duct static pressure setpoint is lowered by 0.2 in.wc. when the hot-deck damper for two (2)
or less selected zones are 100% open. If the hot-deck damper for two (2) or less selected zones
remain 100% open the next time the control loop is executed (every 5 minutes), then duct static
pressure setpoint is lowered again by 0.2 in.wc. This process continues until either there are
greater than two (2) zones with hot-deck dampers 100% open (at which point duct static pressure
setpoint is held steady at the current value) OR until a minimum setpoint value of 1.5 in.wc. is
reached.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
5
Note that the Excel spreadsheet AHU5&6.xls (located on the operator work station under file
folder C:\Project\BestBuilding) can be used to help troubleshoot static pressure reset controls.
The spreadsheet documents all of the polled zones and their respective hot-deck damper position.
This can assist facility staff in identifying which zones are driving the control strategy (either
legitimately due to zone loads or as a “rogue” box that may warrant further investigation or
maintenance).
Warm-up Control
The warm-up control sequence is enabled when the return air temperature is less than 70F and
AHU5/6 are in occupied mode. The air handling units will remain in warm-up mode until the
return air temperature raises above 70F. Once warm-up mode is disabled, it will not be reenabled regardless of return air temperature until the air handling unit reaches the next
“occupied” cycle. During warm-up, the air handling units are commanded to meet maximum
discharge air temperature setpoint (110F) and normal duct static pressure setpoint as determined
by the reset schedule.
Night Low Limit
The night low limit control sequence is intended to prevent the building from getting too cold
during unoccupied hours. If the zone temperature for more than six (6) selected zones falls
below the unoccupied setpoint of 55F, then the air handling units and boiler plant are
commanded ON. During night low limit, the air handling units are commanded to meet
maximum discharge air temperature setpoint (110F) and normal duct static pressure setpoint as
determined by the reset schedule. The system is disabled when zone temperature exceeds
setpoint by 3F.
Alarms and Safeties
The following alarms and safeties are programmed as part of the operating sequences.
 Dirty Filter. A differential switch across the filter banks generates alarm at the operator
work station when the pressure drop exceeds the manual setpoint. This indicates the
filters need to be replaced.
 Supply Fan Failure. A fan failure alarm is sent to the operator work station if a supply
fan is commanded ON but a positive status signal is not received to verity fan operation.
Fan failure is detected via a current switch mounted on the electrical power leads to the
motor. Both supply fans within the respective air handling unit receive the same enable
and speed signal from the EMCS based on the static pressure control discussed above.
 Smoke Alarm. On a fire signal, as determined by smoke detectors or through the
building fire system alarm, all air handling units and exhaust fans are shut down and all
dampers return to “normal” positions (normally closed fan isolation dampers).
VAV BOX DESCRIPTION AND CONTROL
Zone loads throughout the building are served by a variety of variable air volume (VAV) boxes,
as described below:
 Series fan-powered dual duct (serving conference rooms)
 Cooling-only (serving interior zones)
 Dual duct (serving perimeter zones)
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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Detailed sequence of operations for each VAV box is provided below.
CONFERENCE ROOM VAV BOXES
Each conference room is served by either two or three series fan-powered VAV boxes depending
on the size of the conference room. The series fan is enabled based on the operating schedule for
the central air handling units (approximately 5:30 AM to 5:30 PM, Tuesday through Friday, with
Monday (or the first day after a holiday shutdown) start-up at 3:30 AM). The main lighting
circuit for each conference room is monitored by a current relay that sends an “occupied”
command to the EMCS when the lights are on and an “unoccupied” signal when the lights are
off. The occupied/unoccupied signal is used to control the VAV box dampers and temperature
setpoints as detailed below.
Conference Room is Occupied (during normal building operating hours)
 Series fan operates continually during normal building operating hours to circulate air into
the conference room regardless of conference room occupancy status
 Cold-deck damper modulates between minimum and maximum cooling flow rate (per
design values) as necessary to maintain zone temperature setpoint. The boxes maintain a
minimum cold-deck flow rate to provide ventilation to the conference room during heating.
 Hot-deck damper modulates between minimum and maximum heating flow rate (per
design values) as necessary to maintain zone temperature setpoint. For most boxes, the
minimum and maximum heating flow rates are the same value.
 Occupied zone temperature setpoint on average is 70F for all conference rooms.
Conference Room is Unoccupied (during normal building operating hours)
 Series fan operates continually during normal building operating hours to circulate air into
the conference room regardless of conference room occupancy status
 Unoccupied zone temperature cooling setpoint is 75F and heating setpoint is 65F.
 Both the cold-deck and hot-deck dampers are commanded closed unless zone temperature
exceeds setpoint, at which time they are modulated as necessary to maintain unoccupied
zone temperature setpoint.
Building is Unoccupied
 Series fan is commanded OFF
 Both the cold-deck and hot-deck dampers are commanded closed
DUAL DUCT VAV BOXES
All perimeter zones are served by dual duct VAV boxes that provide both cooling and heating to
the respective zone as necessary to maintain zone temperature setpoint as detailed below.
Occupied Condition
 Cold-deck damper modulates between minimum and maximum cooling flow rate (per
design values) as necessary to maintain zone temperature setpoint. The boxes maintain a
minimum cold-deck flow rate to provide ventilation to the respective zone during heating.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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

Hot-deck damper modulates between minimum and maximum heating flow rate (per
design values) as necessary to maintain zone temperature setpoint. For most boxes, the
minimum and maximum heating flow rates are the same value.
Occupied zone temperature setpoint can vary depending on occupant preference. But on
average the zone temperature setpoint ranges between 70F and 74F.
Unoccupied Conditions
 Both the cold-deck and hot-deck dampers are commanded closed
 If the VAV box is selected for polling, zone temperature is monitored and used to trigger
night low limit or morning warm-up control sequences if conditions are met (refer to Air
Handler Unit for detailed control sequences).
COOLING-ONLY VAV BOXES
All interior zones are served by cooling-only VAV boxes that provide just cooling to the
respective zone as necessary to maintain zone temperature setpoint as detailed below.
Occupied Condition
 Cold-deck damper modulates between minimum and maximum cooling flow rate (per
design values) as necessary to maintain zone temperature setpoint. The boxes maintain a
minimum cold-deck flow rate to provide ventilation to the respective zone.
 Occupied zone temperature setpoint can vary depending on occupant preference. But on
average the zone temperature setpoint ranges between 70F and 74F.
Unoccupied Conditions
 The cold-deck is commanded closed
 If the VAV box is selected for polling, zone temperature is monitored and used to trigger
night low limit or morning warm-up control sequences if conditions are met (refer to Air
Handler Unit for detailed control sequences).
CHILLED WATER SYSTEM DESCRIPTION AND CONTROL
CHILLERS AND PRIMARY / SECONDARY PUMP CONTROL
EMCS control points for Chillers 1, 2, and 3
1. Chilled water setpoint control
2. Demand limiting control (time delays between stages are adjustable to limit demand)
3. Start/stop control
4. General alarm
5. Indication of kW or Amps (and % of full load amps)
The chilled water system consists of one, 116 ton unit (CH3) and two, 450 ton units (CH1 and
CH2). The EMCS system provides lead/lag selection that allows the small chiller to act as the
lead machine, with either of the two larger units staged as necessary as the 1st lag and 2nd lag
machines. Selection of CH1 and CH2 for 1st lag/2nd lag operation is rotated automatically by
the EMCS.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
8
Chilled water supply (CHWS) temperature reset
Chilled water supply temperature setpoint ranges between 42F and 48F. The CHWS
temperature is reset based on maintaining cooling coil valve position > 90% open at AHU1,
AHU2, AHU3, and AHU4 per the following schedule:
3 or 4 valves greater than 90% open = 42F CHWS temperature setpoint
2 valves greater than 90% open = 44F CHWS temperature setpoint
1 valve greater than 90% open = 46F CHWS temperature setpoint
0 valves greater than 90% open = 48F CHWS temperature setpoint
Chilled Water System Enable
The chiller system is enabled upon these conditions:
1. Chiller system is scheduled ON
2. Outside air temperature greater than 56F
3. Any cooling valve open 15%
4. Chiller sump temperature greater than 40F
5. Emergency stop switch is Normal (OFF)
Chiller Staging
Chiller operation is separated into 5 stages, as outlined below, to maximize system performance
and match building loads more closely. Note that individual chillers are not allowed to start until
a positive status signal is received to verify operation of the respective primary chilled water and
condenser water pumps.
Stage 1
CH3 is enabled.
Stage 2
CH3 is disabled. CH1 or CH2 is enabled depending on which unit is selected by
the EMCS as the 1st lag unit.
Stage 3
CH3 and CH1 or CH2 are enabled.
Stage 4
CH3 is disabled. CH1 and CH2 are enabled
Stage 5
CH3, CH1, and CH2 are enabled.
The chillers are staged up when the following operating parameters are met:
 Stage 1 is enabled when the chilled water system is enabled, as outlined above.
 Stage 2 is enabled when measured CH3 %FLA exceeds setpoint (100%) OR secondary
loop supply water temperature is greater than CH3 chilled water temperature setpoint
AND the stage-up timer has expired (20 minutes).
 Stage 3 is enabled when measured %FLA for CH1 or CH2 exceeds setpoint (90%) OR
secondary loop supply water flow is greater than primary water flow AND the stage-up
timer has expired (20 minutes).
 Stage 4 is enabled when measured %FLA for CH3 and CH1 or CH2 exceeds respective
setpoint OR secondary loop supply water flow is greater than primary water flow AND
the stage-up timer has expired (20 minutes).
 Stage 5 is enabled when measured %FLA for CH1 and CH2 exceeds setpoint (90%) OR
secondary loop supply water flow is greater than primary water flow AND the stage-up
timer has expired (20 minutes).
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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The chillers are staged down when the following operating parameters are met:
 Stage 5 is disabled when the secondary water flow is less than 1215 gpm (approximately
90% of water flow from CH1 and CH2) AND the stage down timer has expired
(20 minutes).
 Stage 4 is disabled when the secondary water flow is less than 770 gpm (approximately
90% of water flow from CH1 or CH2 and CH3) AND the stage down timer has expired
(20 minutes).
 Stage 3 is disabled when the secondary water flow is less than 608 gpm (approximately
90% of water flow from CH1 or CH2) AND the stage down timer has expired
(20 minutes).
 Stage 2 is disabled when the secondary water flow is less than CH3 chilled water flow
AND the stage down timer has expired (20 minutes).
 Stage 1 is disabled when the Chilled Water System is disabled based on:
1. Outdoor air temperature is less than 56F
2. Any cooling coil valve is less than 15% open
3. System is scheduled OFF
Primary Chilled Water Pumps
The primary chilled water pumps are constant volume. Operation and staging of the primary
chilled water pumps is executed as described below.
1. On a Chilled Water System Enable command calling for mechanical cooling and a
positive status signal to verify operation of the secondary pump(s), primary chilled water
pump CHWP4 or CHWP5 is commanded ON. CHWP4 and CHWP5 are dedicated to
CH3 (stage 1 chiller) and are configured in lead/stand-by operation. Selection of
CHWP4 and CHWP5 for lead/stand-by operation is rotated automatically by the EMCS.
The stand-by pump is automatically commanded ON if a positive status signal is not
received to verify operation of the lead pump. A positive pump status signal is necessary
before the chiller will be allowed to start.
2. Upon calls for stage 2, 3, 4, and 5 mechanical cooling, the primary chilled water pump
associated with the respective chiller is commanded ON as required per the chiller
staging sequences described above. CHWP1 and CHWP3 are dedicated to CH1 and
CH2, respectively, and both pumps are configured in lead/stand-by operation with
CHWP2. If the lead pump fails to start, an alarm is generated at the operator work
station. In this case, the isolation valve(s) in the distribution piping associated with
CHWP2 must be opened manually and the stand-by pump must be commanded ON by
the facility operator. A positive pump status signal is necessary before the chiller will be
allowed to start.
3. A pump failure alarm is sent to the operator work station if a pump is commanded ON
but a positive status signal is not received to verity pump operation. Pump failure is
detected via a current switch mounted on the electrical power leads to the motor.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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Secondary Chilled Water Pumps
The secondary chilled water loop pumps are variable volume and controlled via variable
frequency drives to match system load requirements. Operation and staging of the secondary
chilled water pumps is executed as described below.
1. On a Chilled Water System Enable command calling for mechanical cooling, secondary
chilled water pump CHWP6, CHWP7, or CHWP8 is commanded ON depending on
which pump is selected as the lead pump. All three pumps are configured in lead,
1st lag and 2nd lag operation, with pump selection rotated automatically. The 1st lag
pump is commanded ON if a positive status signal is not received to verify operation of
the lead pump. A positive pump status signal is necessary before the primary chilled
water pump(s) are commanded ON.
2. Flow control of all secondary pumps is based on maintaining differential pressure
setpoint across supply/return header serving all of the pumps. As load within the
building increases and cooling coil valves begin to open, the differential pressure in the
secondary distribution loop decreases. In response, the VFD increases the speed of the
lead pump to maintain DP setpoint. If the secondary flow exceeds near-design flow
rate for the lead pump (700 gpm), the first lag pump is started and the speed of both
pumps are modulated in unison to maintain DP setpoint. If the loop differential
pressure continues to drop and secondary flow continues to increase until chilled water
flow exceeds near-design flow of both the lead and 1st lag pumps (1400 gpm), the
2nd lag pump starts and the speed of all pumps are modulated in unison to maintain DP
setpoint.
3. As load within the building decreases and cooling coil valves begin to close, chilled
water demand decreases and the differential pressure in the secondary distribution loop
increases. In response, the VFD slows down the speed of the three pumps that are
operating to maintain DP setpoint until the secondary flow equals near-design flow of
just two pumps (1400 gpm). At this point the 2nd lag pump will be commanded OFF.
The speed of the remaining two pumps are modulated in unison to maintain DP
setpoint. If the DP continues to increase as the chilled water demand decreases, the
VFD slows down the speed of the two pumps that are operating until the secondary
flow equals near-design flow of just one pump (700 gpm). At this point the 1st lag
pump will be commanded OFF. Then the VFD modulates the speed of the lead pump
as necessary to maintain DP setpoint. The lead pump is shut off when the Chilled
Water Enable command is OFF.
4. The EMCS automatically rotates each pump as lead, 1st lag, and 2nd lag operation.
The operator can also manually select the lead/1st lag/2nd lag pump sequence. The
adjustable time delays between pump start/stop is approximately 20 minutes.
5. The secondary loop differential pressure setpoint is reset based on remote DP sensors.
6. A pump failure alarm is sent to the operator work station if a pump is commanded ON
but a positive status signal is not received to verity pump operation. Pump failure is
detected via a current switch mounted on the electrical power leads to the motor.
7. Variable speed drives: An alarm is sent to the operator work station upon drive failure.
Drives report speed (RPM) to the EMCS.
8. During a fire/smoke event, all cooling coil valves will be commanded 100% open if the
outdoor air temperature is below 40F. The secondary pumps will run under normal
control to circulate water through the coils to prevent them from freezing.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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CONDENSING WATER AND COOLING TOWER CONTROL
Cooling Tower Operation
Three cooling towers operate in lead/1st lag/2nd lag configuration, in conjunction with seven
condenser water pumps (CDP1 through CDP7). Each tower is equipped with a two-speed fan
motor, which cycles between OFF/LOW/HIGH speed as necessary in order to maintain
condenser water temperature setpoint. The selection of lead, 1st lag, and 2nd lag tower is rotated
automatically by the EMCS, but the operator can also manually select both lead and lag towers.
Each tower has an automatic isolation valve that will open when the respective tower is
commanded to be operational. Tower and fan staging is outlined below.
1. The lead cooling tower is enabled 24 hours per day to serve the water-cooled Liebert
units that provide cooling to dedicated computer rooms.
2. The 1st lag cooling tower is enabled when either CDP1 or CDP3 is commanded ON. The
respective automatic isolation valve is commanded open and condenser water is allowed
to flow through the tower.
3. The 2nd lag cooling tower is enabled when both CDP1 and CDP3 is commanded ON.
Both automatic isolation valves are commanded open and condenser water is allowed to
flow through both towers.
4. Each cooling tower fan is staged from OFF to low speed to high speed to maintain a
minimum of 70F and maximum of 80F condenser water supply temperature by
sequencing fans on a rise of temperature. There is an 8 minute minimum time delay for
the fans once staged either up, down, or off.
a. Below 70F, all fans are off
b. Low-speed is enabled when condenser water temperature rises above 75F and is
disabled when condenser water temperature falls below 70F.
c. High-speed is enabled when condenser water temperature rises above 80F and is
disabled when condenser water temperature falls below 75F.
5. The normally open by-pass valve and the normally closed lead tower isolation valve are
modulated in sequence to maintain 70F minimum condenser water supply temperature.
6. A current switch for each tower fan motor is used to alarm on motor failure.
7. Vibration sensor will alarm on excessive vibration.
8. There is a level sensor in the common water basin in the cooling towers that monitors the
water level and performs the following:
a. High water alarm
b. Low water alarm
c. Open Make-up water valve
d. Close Make-up water valve
e. System shutdown.
On a drop in the water level, the make-up valve is opened to allow water into the basin.
9. Two stage electric sump heaters are staged to maintain a minimum sump temperature of
45F. A current switch is used to monitor the heaters, and an alarm is sent upon failure.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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Condenser Water Pumps for Chillers
The condenser water pumps are constant volume. Operation and staging of the condenser water
pumps is executed as described below.
1. On a Chilled Water System Enable command calling for stage 1 mechanical cooling and
a positive status signal to verify operation of the primary chilled water pump, condenser
water pump CDP4 or CDP5 is commanded ON. CDP4 and CDP5 are dedicated to CH3
(stage 1 chiller) and are configured in lead/stand-by operation. Selection of CDP4 and
CDP5 for lead/stand-by operation is rotated automatically by the EMCS. The stand-by
pump is automatically commanded ON if a positive status signal is not received to verify
operation of the lead pump. A positive pump status signal is necessary before the chiller
will be allowed to start.
2. Upon calls for stage 2, 3, 4, and 5 mechanical cooling, the condenser water pump
associated with the respective chiller is commanded ON as required per the chiller
staging sequences described above. CDP1 and CDP3 are dedicated to CH1 and CH2,
respectively, and both pumps are configured in lead/stand-by operation with CDP2. If
the lead pump fails to start, an alarm is generated at the operator work station. In this
case, the isolation valve(s) in the distribution piping associated with CDP2 must be
opened manually and the stand-by pump must be commanded ON by the facility
operator. A positive pump status signal is needed before the chiller will be allowed to
start.
3. A pump failure alarm is sent to the operator work station if a pump is commanded ON
but a positive status signal is not received to verity pump operation. Pump failure is
detected via a current switch mounted on the electrical power leads to the motor.
Condenser Water Pumps for the Heat Exchanger (cooling tower side)
A plate-and-frame heat exchanger is used to transfer heat from the water-cooled Liebert units to
the cooling towers. Condenser water pumps CDP6 and CDP7 are constant volume and circulate
water from the cooling tower through the heat exchanger and back to the cooling tower 24 hours
per day. CDP6 and CDP7 are configured in lead/stand-by operation, and selection for
lead/stand-by operation is rotated automatically by the EMCS. The stand-by pump is
automatically commanded ON if a positive status signal is not received to verify operation of the
lead pump. A pump failure alarm is sent to the operator work station if a pump is commanded
ON but a positive status signal is not received to verity pump operation. Pump failure is detected
via a current switch mounted on the electrical power leads to the motor.
Distribution Water Pumps for the Heat Exchanger (Liebert side)
A plate-and-frame heat exchanger is used to transfer heat from the water-cooled Liebert units to
the cooling towers. Distribution water pumps CDP8 and CDP9 are constant volume and
circulate water from the heat exchanger through the Liebert units and back to the heat exchanger
24 hours per day. CDP8 and CDP9 are configured in lead/stand-by operation, and selection for
lead/stand-by operation is rotated automatically by the EMCS. The stand-by pump is
automatically commanded ON if a positive status signal is not received to verify operation of the
lead pump. A pump failure alarm is sent to the operator work station if a pump is commanded
ON but a positive status signal is not received to verity pump operation. Pump failure is detected
via a current switch mounted on the electrical power leads to the motor.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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HEATING WATER SYSTEM DESCRIPTION AND CONTROL
Heating for the building is provided by a central hot water plant, consisting of the following
equipment:
 Two (2) condensing hot water boilers with fully modulating burners
 Three (3) non-condensing hot water boilers with two-stage modulating burners
(low/high fire)
 Five (5) constant volume primary pumps dedicated to individual boilers
 Three (3) variable volume secondary pumps connected to a common distribution
header, each controlled by an individual VFD
 Combustion air fan system (SF-3)
Detailed sequence of operations for the heating water plant is provided below.
GENERAL SYSTEM CONTROL
System start-up
The system is enabled to operate based on the following:
1. The system is in the Occupied mode and the outside air temperature is less than 65F.
2. The system is in the Unoccupied mode and either the “Night Low Limit” or “Warm-up”
control cycles are enabled for AHU5, AHU6, AHU11, or AHU12.
3. Upon an enable signal, the secondary pump(s) and SF-3 are commanded ON
4. Upon a positive run status via a current switch from the pumps and SF-3, the boiler plant
will be enabled.
Note: The system cannot start if the generator is running.
System Shutdown
The system is disabled when any of the following occur:
1. When the outside air temperature is greater that 5.0F above start-up setpoint.
2. When the boiler system is in an unoccupied mode with no heating fans operating (AHU5, 6, 11 or 12)
3. Generator run status (Note: Fans shutdown when generator run)
4. On loss of SF-3 fan status, the boilers are disabled but the secondary loop still runs.
5. Power loss to the EMCS system panel in the boiler room.
With the system disabled, the boilers and SF-3 are disabled but the pumps will continue to run
for 20 minutes before stopping to dissipate the heat from the boilers.
CONDENSING BOILER CONTROL
The first boilers in the loop are the Aerco condensing boilers and they are intended to raise return
water temperature to a minimum of 140F before the water enters the non-condensing boilers.
The reason being that if the water temperature entering the non-condensing boilers is less than
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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140F, the flue gases can condense on the heat transfer surfaces causing severe corrosion. The
Aerco boilers are controlled by both the EMCS and a manufacturer-specific controller as
described below.
1. Upon completion of the start-up procedure described above, HWP-1 and HWP-2 are
commanded ON by the EMCS.
2. Upon a positive run status via a current switch from the pumps, an enable signal is sent
from the EMCS to the Aerco boiler control panel.
3. The Aerco boiler control panel then will select a boiler to start (B-1 or B-2) based on
lead/lag cycle. The Aerco boiler control panel will modulate the lead and/or the lag
boiler as necessary to maintain the return water temperature at 140F. This water
temperature is measured in the return loop downstream of the Aerco boilers.
4. When the Aerco panel cannot achieve setpoint or a boiler failure occurs, a contact closure
from the panel from the panel is used to notify the EMCS and an alarm is generated.
NON-CONDENSING BOILER CONTROL
The distribution supply water temperature is reset linearly between 120F and 180F based on
outdoor air temperature, per the following schedule:
 120F water temperature @ 62F outdoor air temperature
 180F water temperature @ 35F outdoor air temperature
Distribution supply water temperature setpoint is held constant:
 at 120F when OAT is greater than 62F
 at 180F when OAT is less than 35F
 at 180F when the night low limit or warm-up cycles associated with AHU5 and AHU6
are enabled
The three (3) large non-condensing boilers are staged as necessary to maintain distribution
supply water temperature setpoint.
1. Boilers 3, 4 or 5 will be selected to run as lead, 1st lag and 2nd lag in any order.
2. Before the lead boiler is commanded ON, its respective primary hot water pump is
started.
3. Upon proof of run status via a current switch, the lead boiler is commanded ON at low
fire. The lead boiler will run at high fire if distribution supply water temperature setpoint
is not met and the 20 minute stage-up timer has expired.
4. The 1st lag boiler is enabled if the distribution supply water temperature setpoint is still
not met. The respective primary hot water pump is commanded ON.
5. Upon proof of run status via a current switch, the 1st lag boiler is commanded ON at low
fire. The boiler will run at high fire if distribution supply water temperature setpoint is
not met and the 20 minute stage-up timer has expired.
6. The 2nd lag boiler is enabled if the distribution supply water temperature setpoint is still
not met. The respective primary hot water pump is commanded ON.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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7. Upon proof of run status via a current switch, the 2nd lag boiler is commanded ON at low
fire. The boiler will run at high fire if distribution supply water temperature setpoint is
not met and the 20 minute stage-up timer has expired.
8. The system will incrementally stage-down once the distribution supply water temperature
setpoint is met. The primary pumps will continue to run for approximately 20 minutes to
remove any residual heat from the respective boiler once it is commanded OFF.
DISTRIBUTION WATER LOOP CONTROL
Heating water is distributed throughout the building via three (3) variable volume pumps. HWP6, HWP-7, and HWP-8 will be selected by the EMCS to run as lead, 1st lag and 2nd lag in any
order. Each pump is controlled by an individual VFD to maintain differential pressure setpoint.
If the differential pressure falls as heating valves open, the speed of the lead pump increases to
maintain pressure. When the flow rate exceeds the pump design conditions, the 1st lag pump is
started and the speed of both pumps is modulated in unison to maintain differential pressure
setpoint. If differential pressure continues to fall, the 2nd lag pump is started and the speed of all
three pumps is modulated in unison to maintain differential pressure setpoint.
As load within the building decreases and heating coil valves begin to close, the differential
pressure in the secondary distribution loop increases. In response, the VFD decreases the speed
of the pumps to maintain DP setpoint until the secondary flow equals near-design flow of two
pumps. At this point the 2nd lag pump will stop. The speed of the remaining two pumps are
modulated in unison to maintain DP setpoint. If the DP continues to increase as heating valves
close further, the VFD decreases the speed of the pumps until the secondary flow equals neardesign flow of one pump. Then the 1st lag pump stops. Then the VFD modulates the speed of
the lead pump as necessary to maintain DP setpoint. The lead pump is shut off when the Boiler
Enable command is OFF.
GENERAL CONTROL FEATURES


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


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Pump Failure: A current switch is used to monitor the HWPS 1-5. If pump status does
not match the command condition, an alarm is sent.
Boiler Failure: An alarm is sent out on failure of any boilers.
Variable Speed Drives: Alarm is sent on drive failure. Units report RPM to the
EMCS.
Calculated Load: The EMCS calculates load based on flow rate and temperature
differential.
Graphics: System graphic included.
General Notes: After a power failure, the Aerco system will need to be manually reset.
This requires that:
1. Both boilers are clear of alarms and are in the run position
2. You must then cycle the power to the Aerco control panel.
If the system is enabled to run and the hot water temperature is below setpoint, the lead
boiler should start-up.
If the Aerco panel locks up, the EMCS will continue to stage-up the larger boilers. The
control will be “choppy” due to the capacity of the large boilers.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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
On any boiler system failures (pumps or boiler) the system will stage-up to the next
stage.
 On any secondary pump failure, the next pump will start.
GARAGE EXHAUST FAN (EF-1) CONTROL
The garage exhaust fans are to control carbon monoxide (CO) within the garage area. EF-1 is
scheduled to operate for approximately 1.5 hours each morning and afternoon when peak
vehicular traffic is expected. Outside of the scheduled operating period, EF-1 is enabled when
any one of the CO sensors located throughout the garage exceed 40 ppm, and the fans are
disabled when the CO level drops below 30 ppm. An alarm is generated in the EMCS when any
two CO sensors exceed 50 ppm measurements.
GENERAL EXHAUST FAN CONTROL
All general exhaust fans serving the building are interlocked with the supply fans. The fans start
or shutdown upon signal from the EMCS. Basic system operating schedule is from 5:30 AM to
5:30 PM, Tuesday through Friday, with Monday (or the first day after a holiday shutdown) startup at 3:30 AM. The system is shut down on weekends and holidays.
LIGHTING CONTROL
The building is configured as described below:
 B-1 and B-2 levels are primarily parking
 1st and 2nd floors are primarily office space
 3rd though 7th floors are primarily office space
 8th and penthouse floors are primarily mechanical rooms (partial office on 8th floor)
 9th through 16th floors are conference rooms and office space
Lighting control for each zone-type is outlined below.
Parking Area
The lights in this area are controlled manually, but typically operate 24 hours per day.
General Public and Jury Assembly Areas
The lights in these areas are controlled manually. Typical operating schedule for these lights is
approximately 6:00 AM to 6:00 PM Monday through Friday.
Office Spaces
The lights in these areas are controlled by a combination of manual wall switches connected to a
lighting sweep control system. The sweep control system is intended to enable the lighting
circuits between approximately 6:00 AM and 6:00 PM, during which time occupants use the
manual wall switches to turn individual lights ON/OFF. Past 6:00 PM, the sweep is intended to
disable the lighting circuits. Occupants could re-enable individual lighting circuits via the
manual wall switches until the next sweep command disables the lights again. Several individual
offices were also equipped with occupancy sensors as an additional level of lighting control.
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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Due to inadequate programming of the lighting sweep control system during initial start-up, as
well as too few lighting control relays and the inaccessibility of several override switches,
occupants were unable to control the lights satisfactorily during unoccupied hours. As a result,
the lighting sweep control system was disabled and the lights effectively run 24 hours per day.
In addition, many of the occupancy sensors have also been disabled because their current
locations do not control the lights effectively when the zone is occupied.
GSA and facility operating staff are currently in the process of re-enabling all lighting controls
by:
 Mapping out each lighting circuit and labeling them with an appropriate point name in
the lighting sweep control system.
 Determining the appropriate schedule for each lighting zone and program the control
system accordingly.
 Adding new control relays in zones that need additional separation of the lights.
 Making all override switches accessible to the occupants.
 Relocating the occupancy sensors as necessary to achieve the desired control.
Once automatic control is re-established, it is recommended that all occupants be fully trained on
how the system in intended to work. At a minimum, this would include:
 Outlining the programmed operating schedule for each lighting zone.
 Demonstrating how to re-enable individual lighting zones for after-hours operation.
 Developing procedures for temporary schedule modification requests by the occupants.
Mechanical Rooms
The lights in these areas are controlled manually and only used when the space is occupied.
Conference Rooms
The conference room lights are controlled by a combination of manual switches and occupancy
sensors. Basic lighting schedule is 7:00 AM to 5:00 PM Monday through Friday.
FIRE/LIFE SAFETY SYSTEM CONTROL
During a fire/life safety event, the following occurs:
 All air handling and exhaust fan systems are commanded OFF.
 Individual floor return plenum dampers are commanded closed.
 Individual supply and return fans, outdoor and exhaust dampers, and return plenum
dampers can be controlled manually by fire/life safety personnel via the fire control
panel to execute the desired smoke control strategy.
 All elevators are commanded to the bottom floors and can only be accessed via fire/life
safety personnel
Ongoing Commissioning Plan Appendix B – Sequence of Operation Sample
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