LCM-OAVS Room Pressurization with Slowacting Damper Actuation (One Exhaust, One Supply) and Hot Water Reheat, Application 2923 Application Note 140-1347 2015-07-07 Building Technologies
Table of Contents Overview ............................................................................................................................. 5 Hardware Inputs .................................................................................................................. 6 Hardware Outputs ................................................................................................................ 7 Ordering Notes .............................................................................
Fail Mode Operation .......................................................................................................... 27 Application Notes ............................................................................................................... 28 Wiring Diagrams ................................................................................................................ 29 Point Database Application 2923 ...................................................................................
Overview Hardware Inputs Overview Application 2923 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.
Overview Hardware Inputs Ventilation and Pressurization Control Drawing. Hardware Inputs Analog Air velocity sensor (s) – (one or two depending on setup) Fume hood controller input or FFM Room temperature sensor Digital Occupancy button (option on room temperature sensor) (Optional) Occupancy switch (Optional) Alarm switch 6 Siemens Industry, Inc.
Overview Hardware Outputs Hardware Outputs Analog Reheat valve Digital Autozero Solenoid in Offboard Air Module (DO 8) (Optional) Alarm Supply damper (two DOs) General exhaust damper (two DOs) Ordering Notes 550-767FN LCM-OAVS Room Pressurization with Slow-acting Damper Actuation (One Supply, One Exhaust) and Hot Water Reheat Requires Offboard Air Module(s) – order and ship separately 550-819B Offboard Air Module (OAM) – order and ship separately 7 Siemens Industry, Inc.
Sequence of Operation Pressurization Control Sequence of Operation The following paragraphs present the sequence of operation for LCM-OAVS Application 2623: Variable Air Volume Room Pressurization with HW Reheat and Slow Damper Actuation — One Exhaust, One Supply. 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 Optional Rate Limiting of Actuators 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 Room Airflow Balance Room Airflow Balance The difference between total supply flow and total exhaust flow is the room airflow balance as shown in these calculations: VOL DIFFRNC = TOTL EXHAUST – TOTL SUPPLY -orVOL DIFFRNC = (HOOD VOL + GEX AIR VOL + OTHER EXH) – (SUP AIR VOL + OTHER SUP) The controller uses these calculations to maintain VOL DIFFRNC at the VOL DIF STPT.
Sequence of Operation Active Flow Minimums and Maximums NOTE: The displayed OCC/UNOCC status of the LCTLR point does not always match the occupancy status of the controller. To get an actual indication of occupancy status, OCC.UNOCC must be used. If network commands are not required and occupancy will be set by sources in the room, set NET OCC CMD to UNOCC. If set to OCC, the controller will stay in occupied mode.
Sequence of Operation VAV versus CV Control When OCC.UNOCC equals UNOCC: The active supply airflow minimum equals UOC SUP MIN. The active supply airflow maximum equals UOC SUP MAX. The active general exhaust airflow minimum equals UOC GEX MIN. The active general exhaust airflow maximum equals UOC GEN MAX. VAV versus CV Control In Application 2923, VAV means that the supply airflow can be varied to provide cooling. CV means the supply airflow is not a source of cooling.
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 AVS Calibration AVS Calibration Calibration of the air velocity transducer(s) is periodically required to maintain accurate air velocity readings. Depending on the value of CAL SETUP, calibration takes place either at fixed time intervals or whenever the application goes into unoccupied mode. 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.
Sequence of Operation Floating Control Actuation Auto-correct Floating Control Actuation Auto-correct Floating Control Actuation Auto-correct In addition to the existing options for floating control actuator full stroke actions, all floating control actuators are provided with additional logic to fully drive open or closed when commanded to 100% or 0%.
Sequence of Operation Room Temperature and Setpoint level of 50 fpm more than MODHTG FLO. Between MODHTG FLO and MODHTG FLO + 50, the internal point “ok_to_mod” will not change value. Room Temperature and Setpoint The application uses the CTL STPT as the setpoint for the Room Temperature PID Loop.
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 [➙ 27]. It also provides the ability to enable the optional RH and CO2 sensors and indicates which thermistor type is connected.
Sequence of Operation Temperature Control Loop 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 Alarms The range of TEMP LOOPOUT is 0 to 100%. Higher values indicate a need for more cooling (or less heat). The Figure Temperature Control Sequence shows that as the value of TEMP LOOPOUT moves from START to 0%, and the reheat VALVE CMD is modulated from 0 to 100%. VALVE CMD is converted to a voltage and put out on REHEAT A01. The setup points, VALVE CLOSED and VALVE OPEN, tell the controller the voltage range the valve needs to reach at each end of its stroke.
Sequence of Operation Alarms The ventilation alarm, VENT ALM, indicates that there is something wrong with the ventilation to the room. VENT ALM has an adjustable alarm level that can vary with the occupancy status of the room. An adjustable delay timer, VENT ALM DEL, prevents nuisance alarms. VENT ALM is turned on when at least one of the following conditions is true: The supply flow to the room, TOTL SUPPLY, stays below the alarm level, for a time at least equal to VENT ALM DEL.
Sequence of Operation Alarms WARNING To ensure that VOL DIF ALM turns on before the pressure in the room changes sign, DIF ALM DBD must be less than the absolute value of VOL DIF STPT. For example, if negative pressure is desired and VOL DIF STPT equals 70 cfm and DIF ALM DBD is 200 cfm, then the room could go positive by almost 130 cfm without the pressure alarm turning on. In this case, if you want the alarm to turn on before the room changes sign, then you must set DIF ALM DBD to be less than 70 cfm.
Sequence of Operation Damper Position on Return from Power Failure ALARM DO7 is used to operate a local alarm annunciation device such as a light or horn in or near the room. Inputs can be set up to annunciate alarms from any combination of the following sources: Pressurization alarm point, VOL DIF ALM (To connect VOL DIF ALM to DO 7, set ALM ENA to a value that enables the pressure alarm (4, 5, 6 or 7)).
Sequence of Operation Operation of AVS FAILMODE Operation of AVS FAILMODE AVS FAILMODE is an enumerated point that describes how the supply Damper and the general exhaust Damper will respond if one or both Air Velocity Sensors (AVS) fail. It can handle both positively pressurized rooms and negatively pressurized rooms. The default value of AVS FAILMODE is 0. This default causes both the supply and general exhaust to hold their current position 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 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. Electronic Actuator – If the actuator fails, typically, flow control is lost and alarms are triggered. Upon loss of power or control signal to the actuator, it will move to its fail-safe position.
Sequence of Operation Wiring Diagrams The application varies the supply airflow as the fume hood flow changes, in order to maintain the proper room pressurization. The supply airflow is not varied for cooling purposes; all temperature control is done by the reheat valve. Because of this, START should be set to 100 to allow the reheat valve to be controlled by the full range of TEMP LOOPOUT and to prevent the room temperature PID Loop from winding up.
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 – Application 2923 Wiring Diagram. 32 Siemens Industry, Inc.
Point Database Application 2923 Point Database Application 2923 Point Number Descriptor Factory Default (SI Units) Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text 1 CTLR ADDRESS 99 -- 1 0 -- -- 2 APPLICATION 2997 -- 1 0 -- -- 3 TEMP OFFSET 0.0 (0.0) DEG F (DEG C) 0.25 (0.14) -31.75 (-17.78) -- -- {04} ROOM TEMP 74.0 (23.44888) DEG F (DEG C) 0.25 (0.14) 48.0 (8.88888) -- -- 5 OCC DIF STPT 400 (188.7599) CFM (LPS) 4 (1.
Point Database Application 2923 Point Number Descriptor Factory Default (SI Units) Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text {32} OCC SUP MIN 340 (160.446) CFM (LPS) 4 (1.8876) 0 -- -- {33} OCC GEX MAX 1100 (519.09) CFM (LPS) 4 (1.8876) 0 -- -- {34} OCC GEX MIN 600 (283.14) CFM (LPS) 4 (1.8876) 0 -- -- {35} SUP AIR VOL 0 (0.0) CFM (LPS) 4 (1.8876) 0 -- -- 36 SUP FLO COEF 0.73 -- 0.01 0 -- -- {37} REHEAT AO1 0 VOLTS 0.
Point Database Application 2923 Point Number Descriptor Factory Default (SI Units) Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text {68} UOC GEX MIN 500 (235.95) CFM (LPS) 4 (1.8876) 0 -- -- {69} TOTL SUPPLY 0 (0.0) CFM (LPS) 4 (1.8876) 0 -- -- 70 SUP P GAIN 0.015 -- 0.001 0 -- -- {71} UOC SUP MAX 2200 (1038.18) CFM (LPS) 4 (1.8876) 0 -- -- {72} UOC SUP MIN 220 (103.818) CFM (LPS) 4 (1.8876) 0 -- -- {73} CTL STPT 74.0 (23.
Point Database Application 2923 Point Number Descriptor Factory Default (SI Units) Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text 109 FAIL TIME 60 SEC 2 0 -- -- 110 MTR SETUP 0 -- 1 0 -- -- {111} SUP DMP POS 0 PCT 0.4 0 -- -- 112 MTR1 TIMING 95 SEC 1 0 -- -- 113 MTR1 ROT ANG 90 -- 1 0 -- -- {114} GEX DMP POS 0 PCT 0.
Point Database (Slave Mode) Application 2997 Point Database (Slave Mode) Application 2997 Point Number Descriptor Factory Default (SI Units) Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text 1 CTLR ADDRESS 99 -- 1 0 -- -- 2 APPLICATION 2997 -- 1 0 -- -- 3 TEMP OFFSET 0.0 (0.0) DEG F (DEG C) 0.25 (0.14) -31.75(-17.78) -- -- {04} ROOM TEMP 74.0 (23.44888) DEG F (DEG C) 0.25 (0.14) 48.0 (8.88888) -- -- {13} ROOM STPT 74.0 (23.
Point Database (Slave Mode) Application 2997 Point Number Descriptor Factory Default (SI Units) Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text {84} AI 5 74.0 (23.496) DEG F (DEG C) 0.5 (0.28) 37.5(3.056) -- -- {94} CAL AIR NO -- -- -- YES NO 95 CAL SETUP 4 -- 1 0 -- -- 96 CAL TIMER 12 HRS 1 0 -- -- 97 DUCT AREA 1 1.0 (0.09292) SQ. FT (SQ 0.025 M) (0.
Issued by Siemens Industry, Inc. Building Technologies Division 1000 Deerfield Pkwy Buffalo Grove IL 60089 Tel. +1 847-215-1000 Document ID 140-1347 Edition 2015-07-07 © Siemens Industry, Inc., 2015 Technical specifications and availability subject to change without notice.
