LCM-OAVS Room Pressurization with Slowacting Supply Damper Actuation and Exhaust Venturi Air Valve and Hot Water Reheat, Application 2924 Application Note 140-1304 2015-07-07 Building Technologies
Table of Contents Overview ............................................................................................................................. 5 Hardware Inputs .................................................................................................................. 6 Hardware Outputs ................................................................................................................ 7 Ordering Notes .............................................................................
Pressurization Alarm .......................................................................................... 33 Local Annunciation ............................................................................................. 34 Network Annunciation......................................................................................... 35 Alarms in Open Loop Mode ................................................................................ 35 Actuator Position on Return from Power Failure ............
Overview Hardware Inputs Overview Application 2924 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 General exhaust Venturi Air Valve Digital Autozero Solenoid in Offboard Air Module (DO 8) (Optional) Alarm Supply damper (two DOs) Ordering Notes 550-767GN LCM-OAVS Room Pressurization with Slow-acting Supply Damper, Venturi Exhaust Actuation 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 VAV Room Pressurization with HW Reheat, 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 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 2924, 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 Airflow Control Damper Status When an Autozero solenoid from an Offboard Air Module is wired to D08, the physical damper position may vary from what the application’s position point is indicating.
Sequence of Operation Airflow Control NOTES: 1. VOL DIF STPT must be set to 0 while the flow loops are being tuned. 2. The Venturi Air Valve command point, GEX DMPR AO3, indicates Venturi Air Valve position. The Venturi Air Valve may be set up for normally open or normally closed operation. 3. Adjusting P gain to a value greater than 0.1 may cause system instability.
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%. {Commented by Geszvain, Mimi, 08/02/2013 20:51:30: This applies to any P1 or BACnet controller/application with actuation on the DOs (Valve or Damper).
Sequence of Operation Table Access Feature (Mode 1, 3) Venturi Table Statement Example (active values). Exhaust Venturi Air Valve a) cfm volts 0 a) 10 a) 180 5.48 216 5.08 244 4.68 340 3.88 368 3.48 452 2.98 476 2.73 504 2.48 572 1.98 604 1.73 618 1.48 712 0.98 760 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.
Sequence of Operation Table Access Feature (Mode 1, 3) Venturi Airflow @ 350 fpm. Valve Size in Inches cfm 5 48 6 69 8 122 10 191 12 275 Dual 10 380 Dual 12 550 Triple 12 825 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) Venturi Table Evaluation and Editing (Mode 1, 3) A Venturi Air Valve table statement consists of two sets of voltage/flow values—one set is active and the other inactive. When you run the calibration, the first thing that happens is that the inactive table values are filled in with new values generated by the calibration. Then the application checks these new values to make sure they are good.
Sequence of Operation Venturi Table Evaluation and Editing (Mode 1, 3) ⇨ However, if either point is set to NOTCAL, you must gather and view the voltage/flow values to see where the problem lies. NOTES: 1. If SUP FLO COEF is 0, the table edit feature uses a supply flow coefficient of 1. 2. If SUPDUCT AREA is 0, the table edit feature uses a supply duct area of 1 square foot. 3. If GEX FLO COEF is 0, the table edit feature uses a general exhaust flow coefficient of 1. 4.
Sequence of Operation PID Only (Mode 2) Venturi Air Valve Table Statement V TABLE PT Exhaust Swap 121 Description Setting V TABLE PT to 121 instructs the controller to evaluate the values in the inactive exhaust portion of the table using standard calibration pass/fail logic. If they pass, they are exchanged with those in the active exhaust portion of the table.
Sequence of Operation Open Loop (Mode 3) Set G OPEN LOOP to YES to indicate that the general exhaust actuator is to operate open loop. Setting this enable point to YES will suppress the AVS failure indication that otherwise would occur when no airflow sensor is connected. When operating open loop, there is no flow sensor for use in the calibration sequence. Instead, the Venturi table values are directly input by the user.
Sequence of Operation Open Loop (Mode 3) Example 3 - Table with Voltage End Limits and Low Flow Value – direct acting Point Flow Volt 1 300 7.0 2 0 10.0 3 0 10.0 15 0 10.0 16 1200 0.0 Example 4 - Table with Voltage End Limits and Low Flow Value – reverse acting 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.
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 Offset If ROOM STPT is less than RM STPT MIN, then CTL STPT is set equal to RM STPT MIN. If ROOM STPT is less than or equal to RM STPT MAX and greater than or equal to RM STPT MIN, then CTL STPT is set equal to ROOM STPT. If CTL STPT is overridden or being controlled by a field panel, then RM STPT MIN and/or RM STPT MAX have no effect on CTL STPT. The application also uses CTL TEMP as the temperature input 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 [➙ 37]. 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 Actuator 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 GEX Valve On a return from power failure, the AOs remain OFF for 5 seconds prior to resuming control. Because of this it is recommended that the General Exhaust Valve be set to Normally Opened for rooms where negative or neutral pressurization is required and Normally Closed for positively pressurized rooms. Setting of the Venturi direction is via VENTURI ACT.
Sequence of Operation Fail Mode Operation If AVS FAILMODE equals 7, the supply Damper will hold. The general exhaust Venturi Air Valve will also hold if a fume hood is present (that is, if MAX HOOD VOL > 0). If a fume hood is absent, then the general exhaust Venturi Air Valve will close if the room is being positively pressurized and open if the room is neutral or negatively pressurized (that is if VOL DIF STPT is equal to or greater than 0).
Sequence of Operation Fail Mode Operation Fume Hood Flow – If MINHOODVOLTS is 1 Volt or higher, HOOD VOL will fail when the LCM receives an invalid (less than .4 Vdc) fume hood flow signal or when the fume hood controller (FHC) loses power or when it loses its flow sensor. If HOOD VOL fails and if VOL DIF STPT is greater than or equal to 0 (negative or neutral pressurization required), the supply and exhaust loops assume a hood exhaust value of 0 cfm and continue to maintain user-defined pressurization.
Sequence of Operation Application Notes Application Notes Supply Only - Operating Without a General Exhaust Box This application can operate without a general exhaust box. If a general exhaust box is not being controlled, set TRACK METHOD to FLOW and set the following points: TRACK MODE to 3. – Without a fume hood attached, use a value of 3 = ETS (exhaust tracks supply) Flow Tracking, should be used for both the occupied and unoccupied modes.
Sequence of Operation Wiring Diagrams Wiring Diagrams Offboard Air Module Wiring. 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.
Sequence of Operation Wiring Diagrams 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 – Application 2924 Wiring Diagram. 42 Siemens Industry, Inc.
Point Database Application 2924 Point Database Application 2924 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 2924 Point Number Descriptor Factory Default (SI Units) Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text (1604.46) {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.
Point Database Application 2924 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 2924 Point Number Descriptor Factory Default (SI Units) Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text 107 DO DIR.REV 0 -- 1 0 -- -- {108} RM RH 50 PCT 0.4 0 -- -- 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 -- -- 117 MINHOODVOLTS 1 VOLTS 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 140-1304 Edition 2015-07-07 © Siemens Industry, Inc., 2015 Technical specifications and availability subject to change without notice.
