BACnet LCM-OAVS Room Pressurization with Slowacting Supply Damper Actuation and Exhaust Venturi Air Valve, Hot Water Reheat and BTU Compensation, Application 6760 Application Note 140-1326 2015-07-07 Building Technologies
Table of Contents Overview ............................................................................................................................. 5 BACnet .............................................................................................................................. 6 Auto Discovery ..................................................................................................................... 7 Auto Addressing ......................................................................
PPCL STATUS .................................................................................................................. 31 Temperature Control Loops ............................................................................................... 31 BTU Calculations ............................................................................................................... 31 BTU Calculations – VAV Mode ..........................................................................
Sequence of Operation BACnet Overview Application 6760 controls pressurization, ventilation, and room temperature in a laboratory room served by one single-duct supply terminal with a reheat coil, one general exhaust terminal, and up to six fume hoods (multiple fume hood flow signals must be averaged using an averaging and scaling module. Pressurization is controlled by maintaining a selected difference between supply and exhaust airflows.
Sequence of Operation BACnet Ventilation and Pressurization Control Drawing. BACnet The controller communicates using BACnet MS/TP protocol for open communications on BACnet MS/TP networks.
Sequence of Operation Auto Discovery Auto Discovery Auto Discovery allows you to automatically discover and identify PTEC/ATEC controllers on the BACnet MS/TP Network. There are two basic configurations: Devices not configured with an address. (Devices are discovered by their unique serial number.) Devices configured with an address and available for modification. Auto Addressing Auto Addressing allows you to automatically assign device addresses to a PTEC/ATEC controller on the BACnet MS/TP Network.
Sequence of Operation Pressurization Control Sequence of Operation The following paragraphs present the sequence of operation for BACnet LCM-OAVS VAV Room Pressurization with HW Reheat, BTU Compensation, Slow Supply Damper Actuation and Slow Exhaust Venturi Air Valve . Pressurization Control The goal of pressurization control is to maintain a fixed difference between the volumes of total supply air and total exhaust air (see the following figure).
Sequence of Operation Room Airflow Balance To deal with the possibility of unequal flow rate changes, the application includes two new points which allow field adjustment to slow down actuators. SUP MAX RATE effectively limits the speed of the supply actuator; GEX MAX RATE effectively limits the speed of the exhaust actuator. SUP MAX RATE and GEX MAX RATE should be changed to values other than 0 only after a thorough analysis has been made of the job specific scenarios.
Sequence of Operation Occupancy NOTE: VOL DIFFRNC and VOL DIF STPT are positive numbers in a room that is negatively pressurized and negative in a positively pressurized room. Application 6760 has the ability to maintain a different volume differential setpoint during occupied mode than during unoccupied mode. When OCC.UNOCC = OCC, VOL DIF STPT = OCC DIF STPT. When OCC.UNOCC = UNOCC, VOL DIF STPT = UOC DIF STPT.
Sequence of Operation Active Flow Minimums and Maximums The following table shows what is enabled when OCC ENA is at a particular value. OCC ENA Values. OCC ENA (value) 0 (default) Description Both OCC BUTN DI1 and OCC SWIT DI2 are disabled. 1 Only OCC BUTN DI1 is enabled. 2 Only OCC SWIT DI2 is enabled. NOTE: OCC ENA does not allow both OCC BUTN DI1 and OCC SWIT DI2 to be enabled at the same time. If OCC ENA is set greater than 2, it will default to 0.
Sequence of Operation VAV versus CV Control VAV versus CV Control In Application 6760, VAV means that the supply airflow can be varied to provide cooling. CV means the supply airflow is not a source of cooling. However, the supply and general exhaust can still change in CV mode to keep the volume differential setpoint constant. This may be necessary if HOOD VOL is varying. Application 6760 can do either Variable Air Volume control (VAV) or Constant Air Volume Control (CV).
Sequence of Operation Flow Tracking – Supply Tracks Exhaust vs. Exhaust Tracks Supply NOTE: If desired, the LCM can be used without any fume hoods attached. In this case, MAX HOOD VOL should be set to 0 cfm to disable the alarming that would occur if the fume hood flow input drops below 1 Vdc. Flow Tracking – Supply Tracks Exhaust vs.
Sequence of Operation Calculating Exhaust Flow Setpoint TRACK METHOD TRACK METHOD is a point associated with TRACK MODE. TRACK MODE determines which airflow (supply or general exhaust) gets tracked and which airflow does the tracking. TRACK METHOD determines how tracking is accomplished. If TRACK MODE is set to ETS and TRACK METHOD is set for FLOW tracking, the general exhaust flow setpoint is calculated according to the measured value, SUP AIR VOL.
Sequence of Operation Calculating Supply Flow Setpoint When Exhaust Tracks Supply (ETS) flow tracking is used, the general exhaust airflow setpoint is calculated the same during both VAV and CV operation, as follows: To calculate GEX FLO STPT, the controller determines the general exhaust airflow value that pressurizes the room based on the values of VOL DIF STPT, OTHER EXH, OTHER SUP and either SUP FLO STPT or SUP AIR VOL depending on the value of TRACK METHOD.
Sequence of Operation Ventilation – VAV Mode Ventilation – VAV Mode During VAV operation, the ventilation works as follows: OCC SUP MIN, the occupied supply minimum, is used to ensure that the room receives enough supply air for proper ventilation during the occupied mode. UOC SUP MIN is used to ensure that the room receives enough supply air for proper ventilation during the unoccupied mode.
Sequence of Operation Airflow Control When calibration is in progress, CAL AIR equals YES. After calibration, CAL AIR returns to NO. The application uses Autozero Modules connected to AUTOZERO DO8. This means that the supply and general exhaust flow control devices do not close during calibration of the transducers. NOTE: The LCM does not monitor Fume Hood flow changes for 3 seconds during AVS calibration.
Sequence of Operation Airflow Control When initiated, the firmware module sets DMPR STATUS from CAL to RECAL and decrements/increments the damper position (in a reiterative sequence up to four cycles in length) until sensed airflow matches setpoint. NOTE: It is important to realize that while the Damper Status module runs, the damper position point (SUP DMP POS will change in value but the flow point (SUP VOL) might not.
Sequence of Operation Floating Control Actuation Auto-correct Table Statement and Feedback Loop Interaction General exhaust Air Velocity Control – A table statement and the general exhaust air velocity feedback control loop work together to control the general exhaust air velocity. (The table statement values are generated automatically during calibration of the general exhaust Venturi Air Valve.
Sequence of Operation Venturi Air Valve Calibration (Mode 1, 3) Venturi Air Valve Calibration (Mode 1, 3) Prerequisites for calibrating Venturi Air Valves: Fully operational supply and general exhaust airflow systems. Supply and general exhaust Air Velocity Sensors are calibrated and working normally (SUP AIR VOL and GEX AIR VOL cannot be Failed).
Sequence of Operation Table Access Feature (Mode 1, 3) Venturi Table Statement Example (active values). Exhaust Venturi Air Valve a) cfm volts 760 0.73 800 0.48 904 0 These voltage/flow values constitute the “low flow” element (or “point”) for the Exhaust Venturi Air Valves. They are shown here with factory default values. They are not altered during calibration—they must be set manually.
Sequence of Operation Venturi Table Evaluation and Editing (Mode 1, 3) During calibration, voltage/flow values are automatically generated. Typically there are 8 or 9 pairs. The first pair of voltage/flow values—the low flow point—is not generated; it must be set manually. The Venturi Valve actuator is then fed the voltages and the application reads the resulting airflows.
Sequence of Operation Venturi Table Evaluation and Editing (Mode 1, 3) You can change the active values using the following steps: 1. Set V TABLE PT to a “swap” value that tells the application to exchange active table values with inactive table values (see the Table Venturi Air Valve Table Statement for swap value). This step is necessary because the application does not allow active values to be manually overridden. NOTE: An exception to this rule is when active values cannot be manually overridden.
Sequence of Operation Venturi Table Evaluation and Editing (Mode 1, 3) The following table lists all values for V TABLE PT and describes their use. Any range of points not specifically mentioned (such as 47 through 60) is unused. Venturi Air Valve Table Statement V TABLE PT Description 0 Default value for V TABLE PT. When V TABLE PT equals 0, changes to TABLE FLOW or TABLE VOLTS are ignored. Setting V TABLE PT to 0 cancels an edit session.
Sequence of Operation PID Only (Mode 2) NOTE: The calibration table initially contains all zeros by default, that is, it contains no calibration information. When the application detects all zeros, the application operates, but runs with only PID control. If PID only control is satisfactory for a given job, there is no need to populate the table. Should it be necessary, a populated table can later be edited back to all zeroes to force PID only control.
Sequence of Operation Open Loop (Mode 3) 15 0 0.0 16 1200 10.0 Example 1 - Table with CFM End Limit – direct acting It may not be necessary to enter 0 values since 0 values are initially in the table by default when direct acting is selected. Point Flow Volt 1 0 10.0 2 0 10.0 15 0 10.0 16 1200 0.0 Example 2 - Table with CFM End Limits – reverse acting It may not be necessary to enter 10.0 values since 10.0 values are initially in the table by default when reverse acting is selected.
Sequence of Operation Operating Without a Supply or Exhaust You can also manually populate the table with additional values as shown in Example 5 below. In this case, the table becomes indistinguishable from a table generated using the calibration process. Point Flow Volt 1 300 3.0 2 0 0 7 0 0 8 340 3.2 9 390 3.5 10 521 3.8 11 531 4.1 12 598 4.9 13 691 5.8 14 798 7.0 15 0 0 16 1200 10 Example 5 - Multi-point Table The point values above are for the exhaust table.
Sequence of Operation Heating Safety Heating Safety NOTE: As a safety feature, these applications include MODHTG FLO to ensure that adequate airflow is present before heating coils are energized. When the supply airflow (in fpm as derived from the supply air velocity sensor) is greater than MODHTG FLO, then the internal point “ok_to_mod” is set to Yes and the modulating heating device is allowed to modulate.
Sequence of Operation Room Temperature Offset The application also uses CTL TEMP as the temperature input for the Room Temperature PID Loop. When CTL TEMP is not overridden, then: CTL TEMP = ROOM TEMP + TEMP OFFSET. Room Temperature Offset NOTE: The Room Temperature Offset feature is optional. TEMP OFFSET is a user-adjustable offset that will compensate for deviations between the value of ROOM TEMP and the actual room temperature. This corrected value is displayed in CTL TEMP.
Sequence of Operation Room Unit Operation Room Temperature, Setpoint, RH and CO2 When the digital room unit (Series 2200/2300) is used, SENSOR SEL selects the source for temperature and setpoint and enables a loss of communications indication: – 1 = enables supervision (from the room unit) for fail communications for temperature and setpoint. – 2 = enables supervision (from the room unit) for fail communications for relative humidity.
Sequence of Operation PPCL STATUS Room RH RM RH displays the relative humidity value in percent. RM RH can be used for PPCL in the PTEC or unbundled for control or monitoring purposes. RM RH displays the relative humidity value in percent. PPCL STATUS PPCL STATUS displays LOADED or EMPTY. LOADED = PPCL - programming is present in the controller. A new application number must be assigned (12000 through 12999). EMPTY = NO PPCL - programming is present. The maximum number of PPCL dynamic points is 15.
Sequence of Operation BTU Calculations BTU Calculations – VAV Mode During VAV operation, the controller adjusts the supply airflow and the supply air temperature setpoint as necessary to maintain CTL TEMP at CTL STPT. The room temperature PID loop calculates the value of TEMP LOOPOUT. The Figure Temperature Control Sequence [➙ 33] shows how this value is used to sequence the cooling flow and the supply air temperature setpoint.
Sequence of Operation BTU Calculations As the demand for heating decreases (TEMP LOOPOUT drops), DISCH STPT eventually reaches DISCH MIN. If TEMP LOOPOUT drops further, then the value of TEMP CTL VOL begins to rise from the currently active supply airflow minimum to the currently active supply airflow maximum to provide more cool air to the space. If this value is compatible with correct room pressurization, then it is used as the supply flow setpoint, SUP FLOW STPT.
Sequence of Operation Alarms Example CTL STPT = 70°F: OCC.UNOCC = OCC If TEMP LOOPOUT = and SUP AIR VOL = then DISCH STPT = Formula for DISCH STPT: CTL STPT + (TEMP LOOPOUT x 100% ÷ SUP AIR VOL) 10°F OCC SUP MAX 80°F 70° + (10° x 100% ÷ 100%) 10°F 0.5 ´ OCC SUP MAX 90°F 70° + (10° x 100% ÷ 50%) –5°F 0.
Sequence of Operation Alarms Ventilation Alarm The alarm level depends on whether the room is occupied or vacant. When the OCC.UNOCC point indicates occupancy, the OC V ALM LVL is used. When the OCC.UNOCC point indicates vacancy, the UC V ALM LVL is used. NOTE: In the following discussion, the currently active supply flow minimum is OCC SUP MIN during occupancy and UOC SUP MIN during the unoccupied period.
Sequence of Operation Alarms Pressurization Alarm The pressurization alarm, VOL DIF ALM indicates that the difference between supply and exhaust flow is not what it should be, or that the controller can't calculate the flow difference, VOL DIFFRNC, because it has lost a flow signal. The Figure Failure Mode Sequence lists reasons why VOL DIFFRNC may fail. The pressurization alarm point is turned on when at least one of the following conditions occurs: VOL DIFFRNC has a status of Failed.
Sequence of Operation Alarms ALARM ENA Values. ALARM ENA 4 Dif Alarm is enabled. 5 Vent Alarm and Dif Alarm are enabled. 6 Alarm Switch and Dif Alarm are enabled. 7 Vent Alarm, Alarm Switch, and Dif Alarm are all enabled. NOTE: If ALARM ENA is set greater than 7, it will default to 0. ALM ENA is additive. For example, if ALM ENA equals 5, then either a ventilation or a pressurization alarm will activate ALARM DO7, but the alarm switch will not.
Sequence of Operation Actuator Position on Return from Power Failure Actuator Position on Return from Power Failure Supply Damper On a return from power failure, the damper-command DOs (DOs1 through 2) remain OFF for 5 seconds prior to resuming control.
Sequence of Operation Operation of AVS FAILMODE AVS Failure and AVS FAILMODE Table Values. AVS FAILMODE 6 Open Supply, Close General Exhaust 7 VENTILATION 8 PRESSURE AVS FAILMODE values are not additive. For example, if AVS FAILMODE equals 3, this means to open the supply Damper and hold the general exhaust Venturi Air Valve if an AVS fails. The first seven values of AVS FAILMODE (0 through 6) describe specific actions taken when an AVS fails.
Sequence of Operation Fail Mode Operation Fail Mode Operation If one of the controller’s accessories (inputs) fails, a failure mode sequence is initiated that leads to the failure of VOL DIFFRNC. The following figure shows the order in which points will fail. * If MAX HOOD VOL is set to 0, a “Failed” status of HOOD VOL will not initiate a failure in TOTL EXHAUST or VOL DIFFRNC. See Fume Hood Flow Input.
Sequence of Operation Application Notes NOTE: If desired, the LCM can be used without any fume hoods attached. In this case, MAX HOOD VOL should be set to 0 cfm to disable the alarming that would occur if the fume hood flow input drops below 1 Vdc. Laboratory Room Controller – If the LCM power fails, all actuators default to their userdefined fail-safe states. Since there is no power to the controller, no LEDs are available.
Sequence of Operation Wiring Diagrams OCC GEX MIN and UOC GEX MIN to 0. If these two points are not set to 0, GEX AIR VOL— will read 0 since GEX FLO COEF was set to 0—will be less than the general exhaust box minimum, resulting in a false ventilation alarm. OCC GEX MAX and UOC GEX MAX left at default or a higher value.
Sequence of Operation Wiring Diagrams Wiring for AI with a 4 to 20 mA Sensor. CAUTION Each 4-20 mA sensor requires a SEPARATE dedicated power limited 24 Vdc power supply. DO NOT use the same transformer to power both the sensor and the controller. NOTE: If the voltage/current switch is set to current and a 4 to 20 mA sensor is connected to an AI, then special wiring requirements must be followed. NOTE: The controller’s DOs control 24 Vac loads only. The maximum rating is 12 VA for each DO.
Sequence of Operation Wiring Diagrams BACnet LCM-OAVS Slow Actuation Damper Supply/Venturi Exhaust with BTU Compensation - Application 6760 Wiring Diagram. 44 Siemens Industry, Inc.
Point Database Application 6760 Point Database Application 6760 Object Type Object Instance (Point Number) Object Name (Descriptor) Factory Default (SI Units) Eng Units (SI Units) Range Active Text Inactive Text AO 1 CTLR ADDRESS 255 -- 0-255 -- -- AO 2 APPLICATION 6792 -- 0-32767 -- -- AO 3 TEMP OFFSET 0.0 (0.0) DEG F (DEG C) -31.75-32 -- -- AI {04} ROOM TEMP 74.0 (23.44888) DEG F (DEG C) 48-111.75 -- -- AO 5 OCC DIF STPT 400 (188.
Point Database Application 6760 Object Type Object Instance (Point Number) Object Name (Descriptor) Factory Default (SI Units) Eng Units (SI Units) Range Active Text Inactive Text AO {32} OCC SUP MIN 340 (160.446) CFM (LPS) 0-32764 -- -- AO {33} OCC GEX MAX 1100 (519.09) CFM (LPS) 0-32764 -- -- AO {34} OCC GEX MIN 600 (283.14) CFM (LPS) 0-32764 -- -- AI {35} SUP AIR VOL 0 (0.0) CFM (LPS) 0-32764 -- -- AO 36 SUP FLO COEF 0.73 -- 0-2.
Point Database Application 6760 Object Type Object Instance (Point Number) Object Name (Descriptor) Factory Default (SI Units) Eng Units (SI Units) Range Active Text Inactive Text AO 64 ROOM I GAIN 0.001 -- 0-3.2767 -- -- AO {67} UOC GEX MAX 1000 (471.9) CFM (LPS) 0-32764 -- -- AO {68} UOC GEX MIN 500 (235.95) CFM (LPS) 0-32764 -- -- AI {69} TOTL SUPPLY 0 (0.0) CFM (LPS) 0-32764 -- -- AO 70 SUP P GAIN 0.015 -- 0-4.095 -- -- AO {71} UOC SUP MAX 2200 (1038.
Point Database Application 6760 Object Type Object Instance (Point Number) Object Name (Descriptor) Factory Default (SI Units) Eng Units (SI Units) Range Active Text Inactive Text AO 97 SUPDUCT AREA 1.0 (0.09292) SQ. FT (SQ M) 0-6.375 -- -- AO 98 LOOP TIME 5 SEC 0-255 -- -- AO {99} ERROR STATUS 0 -- 0-255 -- -- AO 104 SENSOR SEL 0 -- 0-255 -- -- AO 105 VENTURI ACT 1 -- 0-255 -- -- AO 106 MODHTG FLO 300 (1.524) FPM (MPS) 0-4095 -- -- AO 107 DO DIR.
Point Database (Slave Mode) Application 6792 Point Database (Slave Mode) Application 6792 Object Type Object Instance (Point Number) Object Name (Descriptor) Factory Default (SI Units) Eng Units (SI Units) Range Active Text Inactive Text AO 1 CTLR ADDRESS 255 -- 0-255 -- -- AO 2 APPLICATION 6792 -- 0-32767 -- -- AO 3 TEMP OFFSET 0.0 (0.0) DEG F (DEG C) -31.75-32 -- -- AI {04} ROOM TEMP 74.0 (23.44888) DEG F (DEG C) 48-111.75 -- -- AI {13} ROOM STPT 74.0 (23.
Point Database (Slave Mode) Application 6792 Object Type Object Instance (Point Number) Object Name (Descriptor) Factory Default (SI Units) Eng Units (SI Units) Range Active Text Inactive Text AI {84} AI 5 74.0 (23.496) DEG F (DEG C) 37.5-165 -- -- BO {94} CAL AIR NO -- Binary YES NO AO 95 CAL SETUP 4 -- 0-255 -- -- AO 96 CAL TIMER 12 HRS 0-255 -- -- AO 97 DUCT AREA 1 1.0 (0.09292) SQ. FT (SQ M) 0-6.
Issued by Siemens Industry, Inc. Building Technologies Division 1000 Deerfield Pkwy Buffalo Grove IL 60089 Tel. +1 847-215-1000 Document ID 140-1326 Edition 2015-07-07 © Siemens Industry, Inc., 2015 Technical specifications and availability subject to change without notice.
