BACnet LCM-OAVS Room Pressurization with Slowacting Damper Actuation (One Exhaust, One Supply), Hot Water Reheat and BTU Compensation, Application 6759 Application Note 140-1335 2015-07-07 Building Technologies
Table of Contents Overview ............................................................................................................................. 5 BACnet .............................................................................................................................. 6 Auto Discovery ..................................................................................................................... 7 Auto Addressing ......................................................................
Alarms ............................................................................................................................ 24 Ventilation Alarm ................................................................................................ 24 Pressurization Alarm .......................................................................................... 25 Local Annunciation ............................................................................................. 26 Network Annunciation.......
Sequence of Operation BACnet Overview Application 6759 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 BTU Comp, HW Reheat and Slow Damper Actuation. 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 6759 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 6759, 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 6759 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 Operating Without a Supply or Exhaust Operating Without a Supply or Exhaust It is possible to run this application without the supply or exhaust if the corresponding flow coefficient is set to zero. When the flow coefficient is zero and the offboard air module is not connected the air velocity sensor will not display a FAIL status and the flow loop will be allowed to run with a flow value of zero. See the Application Notes section for more information.
Sequence of Operation Room Temperature and Setpoint Room Temperature and Setpoint The application uses the CTL STPT as the setpoint for the Room Temperature PID Loop. When CTL STPT is not overridden and not being controlled by a field panel, then ROOM STPT and CTL STPT are related to each other as follows: If ROOM STPT is greater than RM STPT MAX, then CTL STPT is set equal to RM STPT MAX. If ROOM STPT is less than RM STPT MIN, then CTL STPT is set equal to RM STPT MIN.
Sequence of Operation Room Unit Operation Room Unit Operation Sensor Select SENSOR SEL is a configurable, enumerated point (values are additive). This point tells the controller what type of room unit is being used and how to handle loss of communication, for more information see Fail Mode Operation [➙ 28]. It also provides the ability to enable the optional RH and CO2 sensors and indicates which thermistor type is connected.
Sequence of Operation PPCL STATUS Room CO2 RM CO2 displays the CO2 value in units of parts-per-million (PPM). RM CO2 (from the digital 2200/2300 room units) can be used with PPCL in the PTEC/ATEC controller or unbundled for control or monitoring purposes. 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.
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 [➙ 23] shows how this value is used to sequence the cooling flow and the supply air temperature setpoint.
Sequence of Operation BTU Calculations Temperature Control Sequence. BTU Calculations – Constant Volume Mode During the Constant Volume Mode, the BTU Compensator operates as follows: During Constant Volume operation, the controller adjusts the supply air temperature set point as necessary to maintain CTL TEMP at CTL STPT. The room temperature PID loop calculates the value of TEMP LOOPOUT. This value is used to adjust the value of the supply air temperature set point.
Sequence of Operation Alarms CTL STPT = 70°F: OCC.UNOCC = UNOCC 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 UOC SUP MAX 80°F 70° + (10° x 100% ÷ 100%) 10°F 0.5 ´ UOC SUP MAX 90°F 70° + (10° x 100% ÷ 50%) –5°F 0.
Sequence of Operation Alarms GEX AIR VOL stays below the currently active general exhaust box minimum, for a time at least equal to VENT ALM DEL. It is turned off only when all of the following conditions are true: The TOTL SUPPLY stays above the alarm level, for a time at least equal to the alarm delay. SUP AIR VOL stays above the currently active supply minimum, for a time at least equal to VENT ALM DEL.
Sequence of Operation Alarms Local Annunciation ALARM ENA is an analog point whose value determines whether or not a particular alarm activates ALARM DO7. For ALARM ENA, the terms enabled and not enabled do not mean that a particular alarm is enabled or not. It means whether or not a particular alarm will or will not activate ALARM DO7. For example, if ALARM ENA is set to 1 (Vent Alarm Enabled) and a ventilation alarm occurs, then both VENT ALM and ALARM DO7 will turn on.
Sequence of Operation Damper Position on Return from Power Failure Network Annunciation If the LCM is connected to a field panel, alarms can be reported using the workstation software, or by using a printer that is set up in a building manager’s office to receive alarms. Points in the controller must be entered in the field panel’s point database (referred to as unbundling) and defined as alarmable.
Sequence of Operation Fail Mode Operation AVS Failure and AVS FAILMODE Table Values. AVS FAILMODE 4 Close Supply, Hold General Exhaust 5 Close Supply, Open General Exhaust 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 Damper if an AVS fails.
Sequence of Operation Fail Mode Operation * 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 Discharge Temperature Sensor – Temperature control is lost and BTU calculations cease if the discharge temperature analog input point, DISCH TEMP fails. This is because the temperature loop stops updating and the discharge loop stops operating. Application Notes Supply Only - Operating Without a General Exhaust Box This application can operate without a general exhaust box.
Sequence of Operation Wiring Diagrams CAUTION The LCM-OAVS has two terminal blocks with terminations numbered identically (terminations 1 through 16). DO NOT mix these up with each other. If the LCM-OAVS is not connected as shown, it is not resistant to electrical surges. It is also susceptible to interference from other equipment. CAUTION A separate power supply is required if a 4-20 mA sensor is used. Failure to follow wiring precautions will result in equipment damage.
Sequence of Operation Wiring Diagrams NOTE: The controller’s DOs control 24 Vac loads only. The maximum rating is 12 VA for each DO. An external interposing relay is required for any of the following: • VA requirements higher than the maximum • 110 or 220 Vac requirements • DC power requirements • Separate transformers used to power the load (for example, part number 540-147, Terminal Equipment Controller Relay Module) NOTE: Thermistor inputs are 10K (default) or 100K software selectable (AI X).
Sequence of Operation Wiring Diagrams BACnet LCM-OAVS Slow Actuation Damper Supply/Damper Exhaust with BTU Compensation – Application 6759 Wiring Diagram. 33 Siemens Industry, Inc.
Point Database Application 6759 Point Database Application 6759 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 6759 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 6759 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 6759 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 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 140-1335 Edition 2015-07-07 © Siemens Industry, Inc., 2015 Technical specifications and availability subject to change without notice.
