WHAT THE SPECIFICATIONS ASK WHEN TESTING CONTROL SYSTEM

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WHAT THE SPECIFICATIONS ASK WHEN TESTING CONTROL
SYSTEM

• Gaylon Richardson
• Engineered Air Balance Co., Inc.

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SPECIFICATIONS

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

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SPECIFICATIONS

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

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SPECIFICATIONS

• BOTTOM LINE THE AIR FLOWS CAN BE SET, THE WATER
  FLOWS CAN BE SET, BUT IF THE CONTROL SYSTEM IS
  NOT VERIFIED TO BE CALIBRATED AND ALL SEQUENCES
  OPERATING IT ISNT WORKING.

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What Should Be In The Specification?

• Verify all control devices are properly connected
  and operated by the intended controller.
• Observe all valves are properly installed in the
  piping system in relation to direction of flow.
• Verify the proper application of all normally
  opened and normally closed valves and dampers.

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What Should Be In The Specification?

• Observe the location of all sensors to determine
  whether their position will allow them to sense
  only the intended temperatures or pressures. If
  the sensor is in the wrong location the Control
  Contractor must be required to relocate the
  sensor.
• Observe the calibration of all controllers.

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What Should Be In The Specification?

• Verify the sequence of operation for all control
  modes, that each is in accordance with the
  specifications and that the approved shop
  drawings are correct.
• Verify the operation of all interlock systems.
• Verify all safeties and alarms.

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What Should Be In The Specification?

• Verify on single zone systems there is a dead
  band between cooling and heating.
• Verify the pressure set points in variable flow
  systems track from a full flow condition to a
  minimum flow condition.
• Document all the above observations and
  verifications.

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How Can Everything Be Documented?

• Start with the terminal box controls.
• The flows must be established which involves
  testing all flows at maximum and minimum values
  and adjusting the terminal box software to
  provide the correct airflows.

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How Can Everything Be Documented?

• The terminal box verification should list a
  controller number which identifies the
  application, the room number, DDC address, type
  of terminal, terminal size, cooling and heating
  primary maximum settings,

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How Can Everything Be Documented?

• show the calibration of each control sensor (note
  some devices can not be calibrated and the
  control contractor will replace any device not
  within the specified tolerances).
• Show control sequence verification.

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How Can Everything Be Documented?

• Show trend logs for room sensors.
• If specified verify all points back to the
  central data acquisition system by causing a
  change in value and seeing the correct point name
  have a change in value at the remote monitoring
  point.

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Terminal Box Verification
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Terminal Box Verification
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Sensor Calibration
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Control Sequence Verification

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

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Control Sequence Verification

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

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Control Sequence Verification

• Des Max Cooling CFM 36920 Act Max CFM 38455
• Des Max Heating CFM 14660 Act Max CFM15625
• Heating Max CFM 20920 Act Cool CFM 21570
• Sub Max Cool CFM 42000 Act Cool Max 40210
• Des RA CFM 28655 Act RA CFM 30545
• Des OSA CFM 8255 Act OSA CFM 8255
• Minimum Speed Set point 20HZ

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Control Sequence Verification

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

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Control Sequence Verification

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

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Control Sequence Verification

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

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Control Sequence Verification

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

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Control Sequence Verification

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

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Control Sequence Verification

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

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Control Sequence Verification

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

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Control Sequence Verification

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

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Control Sequence Verification

• Cooling Valve Control Verification
• Cooling Coil Discharge Air gt Set point Chilled
  Water Valve Modulate. Open
• Cooling Coil Discharge Air. lt Set point Chilled
  Water Valve Will Modulate Closed
• Cooling Coil Valve will close when the AHU is
  disabled from the BAS
• Set point 52?F

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Control Sequence Verification

• Re-heat Valve Control Verification
• Re-heat Coil Discharge Air gt Set point Hot Water
  Valve Will Modulate Closed
• Re-heat Coil Discharge Air lt Set point Hot Water
  Valve Will Modulate Open
• Re-heat Coil Valve will close when the AHU is
  disabled from the BAS
• Set point 54?F

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Control Sequence Verification

• Dehumidification Control The BAS will
  monitor the relative humidity in the return air
  duct. If the return air relative humidity exceeds
  60 the cold deck discharge air temperature will
  be lowered 1?F per 5 humidity above 50. The
  cold deck will be proportionally lowered
  from 52?F to 50?F. When 50 relative humidity is
  obtained the cold deck temperature set point will
  return to 52. Return relative humidity gt 60
  cold deck temperature 50?F. Return relative
  humidity lt 50 cold deck temperature 52?F.
• Set point 60
• Set point 50?F

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Control Sequence Verification

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

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Control Sequence Verification

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

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Control Sequence Verification

• Alarm when cold deck lt 45 F for 5 minutes
• Alarm when cold deck gt 65F for 5 minutes
• Alarm when CDl filter ?P gt 1.2 WG for 10min
• Alarm when HDl filter ?Pgt 1.2 WG for 10 min
• Alarm when pre- filter ?Pgt 0.5 WG for 10 min
• Alarm when VFD not in auto position
• Alarm when fan commanded value does not match the
  status proof condition

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Control Sequence Verification

• STOP BMS DISABLED (VFD IN AUTO)
• Unit Disabled
• Fan Stop - AHU status off
• OA terminal disabled
• Controls disabled

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Control Sequence Verification

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

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Control Sequence Verification

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

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Point to Point
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Point to Point
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Conclusion

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

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Conclusion

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