M906 - BUILDING 1 PRESSURIZATION CONTROL SEQUENCES - AHU-17.pdf

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Approved: Project Manager

Cincinnati V.A Medical Center

U.S. Department of Veterans Affairs

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CONSTRUCTION

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FULLY SPRINKLEREDKEVIN HENDERSONPROJECT NO. STATE COA FIRM NO.

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BUILDING 1 PRESSURIZATION

CONTROL SEQUENCES - AHU-17

10/23/25 GSE WJS

REMEDIATE TEMPERATURE

CONTROLS

M906

539-21-108

CINCINNATI, OHIO

2020-05099 01528

SCALE: NONE

AHU-17 CONTROLS - EXISTING CONTROL DIAGRAM

EXISTING SEQUENCES

AHU-17 SEQUENCE OF OPERATIONS

1. SAFETY CONTROLS

A. GENERAL WIRING INSTRUCTIONS

1) THE LOW/HIGH PRESSURE CUT-OUTS AND FREEZESTAT SAFETY CIRCUITS WILL BE

HARDWIRED IN SERIES WITH THE SUPPLY AIR FAN MOTOR STARTER CONTROL

CIRCUIT.

2) HARDWIRE INTERLOCK RETURN AIR FAN STARTER CIRCUIT TO SUPPLY AIR FAN

STARTER CIRCUIT VIA NO AUXILIARY CONTACTS ON SUPPLY AIR FAN MOTOR

STARTER.

B. FIRE ALARM RELAY

1) THE BMCS WILL STOP THE SUPPLY/RETURN FAN(S) AND DRIVE ALL CONTROL

DAMPERS TO THEIR FAILED POSITIONS WHENEVER THE EXISTING FIRE ALARM RELAYS

ARE ACTIVATED BY THE FIRE ALARM PANEL.

C. FREEZESTATS

1) ALL UNITS ARE EQUIPPED WITH LOW LIMIT THERMOSTAT(S) WITH MANUAL RESET

DOWNSTREAM OF THE HEATING COIL.

2) WHEN THE LOW LIMIT THERMOSTAT SENSES A TEMPERATURE LESS THAN 38 DEGF

(ADJ.), THE SUPPLY AND RETURN FANS WILL STOP.

D. SAF DISCHARGE PRESSURE SWITCH

1) THE UNIT IS EQUIPPED WITH SAF DISCHARGE PRESSURE SWITCH WITH MANUAL

RESET TO SHUT DOWN SUPPLY AND RETURN FANS IF SUPPLY FAN DISCHARGE STATIC

PRESSURE EXCEEDS SWITCH SETPOINT.

E. RAF DISCHARGE HIGH PRESSURE SWITCH

1) PROVIDE RETURN AIR FAN HIGH DISCHARGE PRESSURE LIMIT SWITCH WITH

MANUAL RESET TO SHUT DOWN SUPPLY AND RETURN FANS IF RETURN FAN

DISCHARGE STATIC PRESSURE EXCEEDS SWITCH SETPOINT.

2. SUPPLY FAN CONTROL

A. SAF VARIABLE AIR VOLUME UNITS

1) IF SAFETY CONTROLS ARE NORMAL, THE VFD(S) FOR THE SUPPLY FAN(S) WILL BE

ENABLED BY THE BMCS AND WILL RUN CONTINUOUSLY.

2) THE VFD(S) WILL VARY THE SPEED OF THE FAN MOTOR(S) AS REQUIRED TO

MAINTAIN THE SUPPLY DUCT STATIC PRESSURE SENSOR SETTING (ADJ.).

3) FOR DUAL SUPPLY FANS, THE FANS WILL OPERATE IN UNISON AT THE SAME SPEED.

4) PROVIDE SUPPLY FAN(S) WITH CURRENT SWITCH FOR FAN STATUS.

3. SAF STATIC LOAD REDUCTION

A. THE BCMS WILL PROVIDE AUTOMATIC REMOTE STATIC RESET FUNCTIONALITY TO

RESETS THE AIR HANDLER STATIC PRESSURE SETPOINT BASED ON TIME OF DAY,

OUTSIDE AIR TEMPERATURE OR NIGHT SETBACK ROUTINE.

B. THE CONTRACTOR WILL PROVIDE A RESET TABLE GRAPHIC THAT PROVIDES THE

FOLLOWING POINTS FOR EACH AIR HANDLER:

1) AHU REMOTE STATIC PRESSURE

2) REMOTE STATIC SETPOINT

3) TIME OF DAY MULTIPLIER SETPOINT

4) TEMPERATURE MULTIPLIER SETPOINT

5) NIGHT SETBACK MULTIPLIER SETPOINT

6) PERCENT REMOTE STATIC RESET

7) CURRENT REMOTE STATIC RESET VALUE

C. THE BCMS WILL MULTIPLY THE AHU REMOTE STATIC PRESSURE SET POINT BY THE TIME

OF DAY MULTIPLIER SETPOINT, TEMPERATURE MULTIPLIER SETPOINT, AND THE NIGHT

SETBACK MULTIPLIER SETPOINT TO GENERATE A MODIFIED AHU REMOTE STATIC

SETPOINT FOR THE AIR HANDLER.

1) THE CONTRACTOR IS RESPONSIBLE FOR ALL PROGRAMMING NECESSARY TO

IMPLEMENT THE CONTROL LOGIC IN THE BCMS. THE OWNER WILL BE RESPONSIBLE

FOR FINE ADJUSTMENT OF ALL PARAMETER SETTINGS ONCE THE CONTROL LOGIC

HAS BEEN COMMISSIONED AND FOUND SATISFACTORY BY THE BO ENGINEER.

4. RETURN FAN CONTROL

A. RAF TRACKING, OBC

1) IF SAFETY CONTROLS ARE NORMAL, THE VFD(S) FOR THE RETURN FAN(S) WILL BE

ENABLED BY THE BMCS AND WILL RUN CONTINUOUSLY.

2) THE VFD(S) WILL VARY THE SPEED OF THE FAN MOTOR(S) AS REQUIRED TO

MAINTAIN A RETURN FAN DISCHARGE STATIC PRESSURE SETPOINT PER THE

SPECIFIED STATIC PRESSURE RESET SCHEDULE. FOR DUAL RETURN FANS, THE FANS

WILL OPERATE IN UNISON AT THE SAME SPEED.

3) THE RETURN AIR PLENUM PRESSURE SETPOINT WILL BE RESET BASE ON RS-4

OUTDOOR AIR ENTHALPY RESET SCHEDULE AS FOLLOWS:

4) AT OR BELOW 17.5 BTU’S PER LB, THE RETURN AIR PLENUM PRESSURE WILL

INITIALLY BE SET AT 0.0 IN WC BY THE BMS CONTRACTOR. FINAL STATIC SETTING WILL

BE DETERMINED BY BO ENGINEER AFTER FIELD ANALYSIS.

5) THE RETURN AIR PLENUM PRESSURE WILL BE LINEARLY RESET UPWARDS AS THE

OUTDOOR AIR ENTHALPY INCREASES FROM 17.5 TO 25.0 BTU’S PER LB. THE INITIAL

BMS CONTRACTOR SETTING OF THIS RESET WILL BE 0.0 IN WC AT 17.5 BTU’S PER LB

AND BE 0.40 IN WC AT 25.0 BTU’S PER LB. FINAL RESET SCHEDULE STATIC SETTING

WILL BE DETERMINED BY BO ENGINEER AFTER FIELD ANALYSIS.

6) THE RETURN AIR PLENUM PRESSURE WILL BE +/- 2.5 IN WC WHEN IN THE

ECONOMIZER IS IN THE OUTSIDE AIR LOCK-OUT MODE AND THE AIR HANDLERS

EXHAUST AIR DAMPERS WILL BE 100% CLOSED. FINAL STATIC PRESSURE RESET

SETTINGS WILL BE DETERMINE BY BO ENGINEER AFTER FIELD ANALYSIS.

B. ALL RETURN AIR FANS:

1) THE BMCS WILL MONITOR RETURN FAN(S) STATUS WITH CURRENT SWITCH(S) AND

ISSUE ALARMS TO THE OPERATOR ON FAN FAILURE.

5. OUTSIDE AIR AND RETURN AIR DAMPER CONTROL

A. ECONOMIZER, OBC (RA AND SINGLE OSA DAMPER)

1) PROVIDE VARYING SUPPLY AIR TEMPERATURE PID CONTROL LOOP SPEEDS FOR

SUMMER AND WINTER COOLING PERIODS. THE SUPPLY AIR CONTROL LOOP WILL

REACT VERY SLOWLY IN THE COLDEST MONTHS, AND THEN GRADUALLY INCREASE IN

SPEED AS THE OUTDOOR AIR TEMPERATURES INCREASE. THE CONTROL LOOPS MUST

BE FAST ENOUGH TO MAINTAIN SUPPLY TEMPERATURE SETPOINT AT ALL TIMES BUT

SLOW ENOUGH TO PREVENT RESENT FREEZESTAT TRIPS IN THE WINTER.

2) WHEN THE ECONOMIZER CONTROL IS INACTIVE, MODULATE THE OUTSIDE AIR

DAMPER AS REQUIRED TO MAINTAIN THE SCHEDULED MINIMUM OUTSIDE AIR

QUANTITY AS MEASURED BY THE OUTSIDE AIRFLOW STATION.

3) DURING NORMAL OCCUPIED MODES OF OPERATION, THE RETURN AIR DAMPER

CONTROL SIGNAL WILL BE RESET WHEN REQUIRED TO ASSIST IN MAINTAINING

MINIMUM OUTSIDE AIRFLOW. THE BMCS WILL COMPARE THE NORMAL RETURN AIR

DAMPER POSITION COMMAND SIGNAL TO THE MINIMUM OUTSIDE AIR RESET

SCHEDULE RS-1 (SEE RESET SCHEDULE TABLE) AND MAINTAIN THE RETURN AIR

DAMPER IN THE MOST CLOSED POSITION REQUEST BY THE BMCS.

4) WHEN THE ECONOMIZER CONTROL IS ACTIVE, THE OSA DAMPER AND RETURN AIR

DAMPER WILL BE SEQUENCE TO CONTROL THE AIR HANDLERS SUPPLY AIR

TEMPERATURE WHILE MAINTAINING MINIMUM OSA FLOW REQUIREMENTS AT ALL TIME

AS FOLLOWS:

A) THE OUTSIDE AIR DAMPER WILL REFERENCE A MAXIMUM SIGNAL SELECTOR

OUTPUT TO DETERMINE ITS DAMPER POSITION. THIS MAXIMUM SIGNAL SELECTOR

WILL COMPARE THE MINIMUM OSA REQUIREMENTS CONTROL LOOP SIGNAL

STRENGTH TO THE COOLING CONTROL LOOP SIGNAL STRENGTH AND SELECT THE

MAXIMUM CONTROL SIGNAL TO CONTROL THE OSA DAMPER POSITION.

B) IF THE COOLING DEMAND IS GREATER THAN THE MINIMUM OSA REQUIREMENT

DEMAND, THE BMCS WILL IGNORE THE MINIMUM OSA CONTROL SIGNAL AND

MODULATE THE OSA DAMPER AS THE FIRST STAGE OF COOLING.

C) IF THE MINIMUM OSA REQUIREMENT DEMAND IS GREATER THAN THE COOLING

DEMAND, THE BMCS WILL IGNORE THE COOLING DEMAND CONTROL SIGNAL AND

MODULATE THE OSA DAMPER TO MAINTAIN MINIMUM OSA FLOW.

5) THE ECONOMIZER CONTROL WILL BE ACTIVATED WHEN THE OUTSIDE AIR

ENTHALPY IS LESS THAN 25 BTU'S.

6) WHEN THE SUPPLY AND RETURN FANS ARE OFF, THE NORMALLY CLOSED

OUTSIDE AIR DAMPER WILL BE CLOSED, AND THE NORMALLY OPEN RETURN AIR

DAMPER WILL BE OPEN.

7) THE BMCS WILL USE RAMPING LOGIC TO SLOWLY ENTER OR EXIT THE

ECONOMIZER CYCLE.

8) THE ECONOMIZER CONTROL DAMPERS SHALL BE RAMPED OPEN OR CLOSED

NOT MORE THAN 1% PER 9 SECONDS WHEN ENTERING OR EXITING THE

ECONOMIZER CYCLE (0-100 % = 15-MINUTES RAMP TIME).

9) DURING START-UP PERIODS, THE BMCS SHALL USE THE FOLLOWING RAMPING-

UP LOGIC TO SLOWLY DECREASES THE AIR HANDLERS SUPPLY AIR TEMPERATURE

TO SETPOINT:

A) ABOVE 40 DEGF, THE OSA DAMPER(S) SHALL BE SEQUENCED OPEN USING A

MINIMUM OF 15-MINUTES RAMP PERIOD TO GO FROM 0 TO 100% OPEN.

B) BELOW 40 DEGF, THE OSA DAMPER(S) SHALL BE SEQUENCED OPEN USING A

MINIMUM OF 30-MINUTES RAMP PERIOD TO GO FROM 0 TO 100% OPEN.

GREATER RAMP PERIODS MAY BE REQUIRED TO PREVENT NUISANCE

FREEZESTAT SHUT-DOWNS.

C) THE MINIMUM OSA FLOW SHALL BE SET TO ZERO (0) CFM UNTIL THE UNIT

HAS REACHED SA TEMPERATURE SETPOINT.

D) BELOW 25 DEGF, THE OSA DAMPER(S) SHALL BE SEQUENCED OPEN USING

A MINIMUM OF 45-MINUTES RAMP PERIOD TO GO FROM 0 TO 100% OPEN.

E) GREATER RAMP PERIODS MAY BE REQUIRED TO PREVENT NUISANCE

FREEZESTAT SHUT-DOWNS. ALWAYS USE THE SLOWEST RAMP TIMES

POSSIBLE DURING COLD WEATHER OPERATIONS. IN MOST CASES, EVEN A 1-

HOUR RAMP TIME WILL ALLOW THE AIR HANDLER TO COME TO SETPOINT

WITHIN 15-MINUTES BECAUSE THE DAMPER WILL NEVER DRIVE TO 100%

DURING START-UP.

6. RELIEF AIR DAMPER CONTROL

A. RELIEF AIR DAMPER CONTROL

1) THE RELIEF AIR DAMPER WILL BE MODULATED AS REQUIRED TO MAINTAIN A

BUILDING STATIC PRESSURE OF 0.05 IN WG (ADJ.) RELATIVE TO THE OUTSIDE AIR

PRESSURE.

2) WHEN THE AIR HANDLER IS OFF, THE RELIEF AIR DAMPER WILL BE CLOSED.

7. PREHEAT CONTROL

A. HOT WATER PREHEAT COIL:

1) IF THE MIXED AIR TEMPERATURE IS BELOW 50 DEGF (ADJ.) OR IF THE OUTDOOR AIR

TEMPERATURE IS BELOW 40 DEGF (ADJ.), THE PREHEAT COIL CONTROL SHALL BE

ENABLED AND MODULATE TO MAINTAIN SUPPLY AIR TEMPERATURE SETPOINT OF 55

DEGF (ADJ.).

8. CHILLED WATER COOLING COIL CONTROL

A. CHILLED WATER COOLING COIL CONTROL

1) WHEN OUTSIDE AIR TEMPERATURE IS ABOVE 55 DEGF (ADJ.) AND CHILLED WATER

IS AVAILABLE, THE CHILLED WATER COOLING COIL CONTROL SHALL BE ENABLED AND

MODULATE TO MAINTAIN THE SUPPLY AIR TEMPERATURE AT 55 DEGF (ADJ.).

2) ON ECONOMIZER EQUIPPED UNITS, THE CHILLED WATER CONTROL VALVE SHALL BE

SEQUENCED WITH THE OSA CONTROL DAMPER(S) AS THE FINAL STAGE OF COOLING.

THE CHILLED WATER CONTROL VALVE SHALL NOT BEGIN TO MODULATE OPEN UNTIL

ALL ECONOMIZER DAMPERS HAVE BEEN SEQUENCED OPEN TO THE

FULL 100% OPEN POSITION BY THE COOLING PID CONTROL LOOP.

3) THE CHILLED WATER CONTROL VALVE SHALL NOT MODULATE OPEN UNTIL ALL

PREHEAT DEVICES HAVE BEEN DISABLED FOR A CONTINUOUS 30 MINUTES.

9. MISCELLANEOUS

A. POWER MONITORING

1) THE BMCS SHALL MONITOR THE KWH POWER CONSUMPTION OF ALL AIR HANDLER

SUPPLY, RETURN AND EXHAUST AIR FANS OF THE FOLLOWING AIR HANDLER FANS:

A) SUPPLY AIR FANS:

B) RETURN AIR FANS:

C) EXHAUST AIR FANS:

2) CHILLED WATER SUB-METERING: (TBD)

3) HOT WATER SUB-METERING: (TBD)

B. FILTRATION MONITORING:

1) MONITOR PRE-FILTER STATUS (DI):

A) THE BMCS SHALL MONITOR THE PRE-FILTER STATUS (DI) AND ISSUE AN ALARM

TO THE OPERATOR WHEN ACTIVATED.

2) MONITOR FINAL FILTER STATUS (DI):

A) THE BMCS SHALL MONITOR THE FINAL-FILTER STATUS (DI) AND ISSUE AN ALARM

TO THE OPERATOR WHEN ACTIVATED.

RESET SCHEDULES

AHU RETURN DAMPER RESET FOR MINIMUM OSA

MINIMUM OSA DAMPER POSITION RETURN AIR DAMPER POSITION

0 TO 95% 100% OPEN

100% OPEN 80% OPEN

RETURN PLENUM PRESSURE SETPOINT RESET

OSA ENTHALPY RETURN AIR PRESSURE SETPOINT

17.5 BTU'S PER Lb 0.0 In WC

25 BTU'S PER Lb 0.1 In WC

BO ENGINEER TO ADJUST AND SET FINAL PLENUM PRESSURE SETPOINTS IN FIELD. BMS

CONTRACTOR SHALL HARD CODE THESE SETTINGS IN AHU PROGRAM ONCE FINAL

PARAMETERS ARE ESTABLISHED BY BO ENGINEER.

TIME OF DAY REMOTE STATIC RESET

PHOTO CELL BREAK (DUSK) SP MULTIPLIER INWC

DAY TIME AHU REMOTE SP

SETPOINT 1.0

DUSK AHU REMOTE SP

SETPOINT (AFTER SPECIFIED DELAY) 1 (ADJ.)

BO ENGINEER TO ADJUST AND SET FINAL PLENUM PRESSURE SETPOINTS IN FIELD. BMS

CONTRACTOR SHALL HARD CODE THESE SETTINGS IN AHU PROGRAM ONCE FINAL

PARAMETERS ARE ESTABLISHED BY BO ENGINEER.

SCOPE OF WORKGENERAL NOTES

1. DIAGRAM AND SEQUENCE OF OPERATION IS INFORMATION FROM ORIGINAL SHOP

DRAWINGS AND IS FOR REFERENCE ONLY.

A. COMMISSION AHU TO VERIFY IT IS OPERATING PER THE WRITTEN SEQUENCE OF

OPERATIONS. MODIFY AS REQUIRED.

B. RECALIBRATE ALL PRESSURE TRANSDUCERS.

C. PROVIDE PREVENTATIVE MAINTENANCE ON ALL DAMPERS AND ACTUATORS. CLEAN,

LUBRICATE AND ENSURE SMOOTH OPERATION OF DAMPERS AND ACTUATUORS. VERIFY

DAMPER IS CLOSING AND SEALING SHUT. REPORT ANY WORN DAMPER SEALS AND/OR

MALFUNCTIONING ACTUATORS TO THE VA.

D. CLEAN AND CALIBRATE ALL AIR FLOW MONITORING STATIONS.

E. REVISE SUPPLY FAN CONTROL AS FOLLOWS:

1. SUPPLY FAN SYSTEM SPEED CONTROL

A. THE VARIABLE SPEED DRIVES SHALL BE MODULATED BY A STATIC PRESSURE

SENSOR LOCATED TWO-THIRDS DOWN THE MAIN SUPPLY DUCT, AND A

PROPORTIONAL PLUS INTEGRAL CONTROL SHALL PROVIDE A SIGNAL TO

MODULATE THE VFD SPEED OF THE SUPPLY FAN SYSTEM TO MAINTAIN THE STATIC

PRESSURE SETPOINT (INITIALLY SET TO 0.75” W.C.).

B. SUPPLY AIR STATIC PRESSURE SETPOINT RESET

i. THE SUPPLY AIR STATIC PRESSURE SETPOINT SHALL BE RESET BY POLLING

ALL VAV BOX DAMPER POSITIONS. IF ALL VAV BOX DAMPERS ARE BELOW 80

PERCENT OF FULL OPEN, RESET THE SUPPLY DUCT STATIC PRESSURE

SETPOINT DOWNWARD 0.05” W.C. EVERY 10 MINUTES UNTIL AT LEAST ONE VAV

BOX DAMPER IS 80 PERCENT OF FULL OPEN. IF ANY BOX DAMPER IS MORE

THAN 90 PERCENT OF FULL OPEN, REVERSE THE SEQUENCE (RESET THE

STATIC SETPOINT UPWARD 0.05” W.C. EVERY 5 MINUTES UNTIL ALL VAV BOX

DAMPERS ARE LESS THAN 90 PERCENT OF FULL OPEN. LOW LIMIT OF THE

SETPOINT SHALL BE 0.25” W.C. AND HIGH LIMIT SETPOINT SHALL BE 1.25” W.C.

AUTOMATICALLY DETECT THOSE ZONES THAT MAY BE EXCESSIVELY DRIVING

THE RESET LOGIC AND GENERATE AN ALARM TO THE SYSTEM OPERATOR.

READILY ALLOW OPERATOR REMOVAL OF ZONE(S) FROM THE RESET

ALGORITHM.

F. REVISE/ADD SUPPLY AIR TEMPERATURE RESET AS FOLLOWS:

1. THE RESET SHALL FOLLOW ASHRAE 36.

2. PROVIDE A REQUEST TABLE GRAPHIC.

A. THE COR WILL PROVIDE AN IMPORTANCE MULTIPLIER FOR EACH ZONE.

B. THE IMPORTANCE MULTIPLIER SHALL BE SHOWN ON THE REQUEST TABLE.

C. A PERCENTAGE OF TIME A ZONE HAS BEEN IN REQUEST FOR THE PAST MONTH

SHALL BE PROVIDED.

D. THIS WILL ASSIST IN IDENTIFYING ROGUE ZONES.

3. ROGUE ZONE ALARMS SHALL BE SENT TO THE ENERGY MANAGER.

A. THE COR WILL PROVIDE THE IGNORE REQUEST SETPOINT (ADJ).

B. THE PROGRAM SHALL ALLOW THE TRIM AND RESPONSE PROGRAM TO DISREGARD

ROGUE ZONES UNTIL THEY ARE FIXED.

4. TEMPERATURE RESET

A. WHEN THE HUMIDITY LEVEL IN THE RETURN, EXHAUST, OR ROOM EXCEEDS 61%,

THE TRIM AND RESPOND COMMAND WILL BE BASED ON THE HUMIDITY LEVEL AND

NOT ON THE ROOM TEMPERATURE IN EACH ZONE. ONCE THE HUMIDITY LEVEL

DROP BELOW 57%, THE TRIM AND RESPOND WILL BE BASED ON ROOM

TEMPERATURE IN EACH ZONE.

G. MODIFY RELIEF AIR DAMPER CONTROL FOR MAX SPACE PRESSURE PER SHEET M900.

# DESCRIPTION DATE

1 ADDENDUM 4 01-12-2026