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| | See the bottom part of this page for a general overview, or the articles below for specific topics. |
| ==AFRC Documents and Guides== | | ==AFRC Documents and Guides== |
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| [[Installation Guide]] | | [[AFRC Installation Guide]] |
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| [[Home Screen]] | | [[AFRC Home Screen]] |
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| [[Setup]] | | [[AFRC Setup]] |
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| [[Auto Control Range Alarm]] | | [[AFRC Controlling the Engine]] |
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| == Overview ==
| | [[AFRC Map Setup]] |
| The EMIT air/fuel ratio controller (AFRC) is available in two offerings: the AFRC Advanced and AFRC Lite. Both controllers are designed to control turbocharged or naturally aspirated carbureted stationary natural gas or propane engines for either rich-burn or lean-burn applications. The AFRC Advanced is equipped to control a dual or single-bank engine with multiple options available for sensory monitoring, multi-setpoint control, and an optional control algorithm, Auto Control. The AFRC Lite offers the same setpoint and multi-setpoint control as the AFRC Advanced but has been optimized for single-bank engines. Unless otherwise noted, both controllers will be referred to simply as “AFRC” through the remainder of the manual.
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| Use of the AFRC controller with an appropriate catalytic converter can result in dramatic reductions in exhaust gas pollutants, particularly Oxides of Nitrogen (NOx), Carbon Monoxide (CO), and Hydrocarbons (HC). Rich-burn NSCR catalytic converters require a constant oxygen content of less than 0.5% from the engine in order to work effectively – the AFRC provides the control needed to maintain that constant oxygen concentration. In lean burn applications, the use of the AFRC with an oxidation catalyst can result in dramatic reductions in exhaust gas pollutants of Carbon Monoxide (CO), Hydrocarbons (HC) and Volatile Organic Compounds (VOC).
| | [[Spare_Parts_Reference#AFRC|AFRC Parts]] |
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| The air fuel ratio of the engine is maintained by setting the appropriate oxygen sensor target setpoint that corresponds with the desired emissions reduction. The controller automatically targets and maintains the setpoint by adjusting the valve position which allows or restricts the amount gas streamed into the mixer which then richens or leans the engine. The valve is moved and stabilized using a finely-tuned Proportional Integral Derivative (PID) control loop that automatically adjusts the correct valve position quickly with little overshoot or error. If desired, multiple setpoints can be used to automatically change the target setpoint based on sensor readings through the AFRC’s mapping feature. In addition to this “Setpoint” control type, the AFRC Advanced offers optional “Auto Control” configuration for single bank or dual bank rich burn engines that can efficiently find and maintain the optimum target setpoint automatically for maximum emissions reduction. No setpoint adjustment or multi-setpoint mapping is required.
| | [[AFRC to EIM Wiring Diagrams]] |
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| == AutoControl Range Alarm == | | === Minor Topics === |
| If AutoControl is used on the AFRC Advanced, the final alarm in the Alarms Setup screen (Pg. 206) is the “AutoControl Range” alarm. This alarm can be used to fall back from “AutoControl” to “Setpoint” mode in the event the Post Catalyst O2 sensor milliVolt reading is pushed outside the set range, which can indicate the sensor is failing.
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| On a trigger of the alarm condition, the AFRC will go into “Setpoint” mode with a target setpoint valve defined by the alarm. The default is “777”. To change the fallback setpoint value, select the “Setpoint: 777” button within the alarm row.
| | [[20360 O2 Heater Pin Issue]] |
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| This event will trigger an alarm, AFR062 (min trigger) or AFR063 (max trigger), on the Alarms screen (Pg. 40). This alarm must be reset in order to switch back from “Setpoint” mode to “AutoControl” mode. A security access level of Setup or Engineering is required to reset the alarm.
| | == Overview == |
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| === Controlling The Engine ===
| | [[File:20230-AFRCA assembly ISO.jpg|500px]] |
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| ==== Detecting the Run Signal ====
| | The EMIT air/fuel ratio controller (AFRC) is available in several offerings: |
| With the engine running, the AFRC will detect the engine operation through the sensor trigger defined within the Run Signal Trigger screen (Pg. 10). If a valid run signal is recognized, the black text in the header next to the “Home” button will display “Eng: Run”.
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| ==== Sensor Warm Up ==== | | {| class="wikitable" style="margin:auto" |
| Upon detecting the system run signal, the bank status within the control box will display “Heater Warmup” indicating the sensors have been started. After the sensor heaters are warmed, the AFRC will be ready to control. When the AFRC is ready, and in “Manual” control mode, the bank status will display “Ready” and will wait until the control mode is transitioned from “Manual” to “Auto”. A security level of ''Setup'' or ''Engineering'' is required to toggle the control mode.
| | |+ AFRC Item Numbers |
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| | ! Item Number !! Description !! Richburn (Narrowband) Banks !! Leanburn (Wideband) Banks |
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| | | 20360 || AFRC-Single Richburn || 1 || 0 |
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| | | 20235 || AFRC-Dual Richburn || 1 or 2 || 0 |
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| | | 20230 || AFRC-Dual Rich or Leanburn || 1 or 2 || 1 or 2 |
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| If the AFRC is already in “Auto” mode, it will start the process for initializing control.
| | All controllers are designed to control turbocharged or naturally aspirated carbureted stationary natural gas or propane engines for either rich-burn or lean-burn applications. The AFRC Advanced Dual is equipped to control a dual or single-bank engine with multiple options available for sensory monitoring, multi-setpoint control, and an optional control algorithm, Auto Control. The AFRC Advanced Single bank offers the same setpoint, multi-setpoint, and Auto control as the AFRC Advanced Dual but only covers single bank and narrowband applications. Unless otherwise noted, the controllers will be referred to simply as “AFRC” through the remainder of the manual. |
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| ==== Load Delay ====
| | Use of the AFR controller with an appropriate catalytic converter can result in dramatic reductions in exhaust gas pollutants, particularly Oxides of Nitrogen (NOx), Carbon Monoxide (CO), and Hydrocarbons (HC). Rich-burn NSCR catalytic converters require a constant oxygen content of less than 0.5% from the engine in order to work effectively – the AFRC provides the control needed to maintain that constant oxygen concentration. In lean burn applications, the use of the AFRC with an oxidation catalyst can result in dramatic reductions in exhaust gas pollutants of Carbon Monoxide (CO), Hydrocarbons (HC) and Volatile Organic Compounds (VOC). |
| Once the sensor is warm and in “Auto” mode, the AFRC will go into a load delay. By default, the load delay waits 30 seconds before the controller starts to move the valve.
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| If an AFRC Advanced is used and “Auto Control” is enabled, the controller not transition to delay mode until the pre-catalyst or post-catalyst thermocouple read a light off temperature of 550 degrees F.
| | The air fuel ratio of the engine is maintained by setting the appropriate oxygen sensor target setpoint that corresponds with the desired emissions reduction. The controller automatically targets and maintains the setpoint by adjusting the valve position which allows or restricts the amount gas streamed into the mixer which then richens or leans the engine. The valve is moved and stabilized using a finely-tuned Proportional Integral Derivative (PID) control loop that automatically adjusts the correct valve position quickly with little overshoot or error. If desired, multiple setpoints can be used to automatically change the target setpoint based on sensor readings through the AFRC’s mapping feature. In addition to this “Setpoint” control type, the AFRC Advanced offers optional “Auto Control” configuration for single bank or dual bank rich burn engines that can efficiently find and maintain the optimum target setpoint automatically for maximum emissions reduction. No setpoint adjustment or multi-setpoint mapping is required. |
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| ==== Starting Control ====
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| When starting control, the bank status will update to “Attempting To Control”. The valve will automatically adjust to try and match the actual O2 reading with the desired target setpoint. As the valve finds the position that’s meets the target and is stable, the status will update to “Controlling”.
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| ==== Optimizing The Target Setpoint ====
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| The oxygen target setpoint “Target” should be set to optimize catalyst performance. This should be conducted while the engine is at a normal operating temperature and under normal loading. An exhaust gas analyzer should be used to reach optimum performance.
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| If an AFRC Advanced is used and “Auto Control” is enabled, no target setpoint adjustment is necessary.
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| ==== External Dynamic and “600” Series Manual Valve Adjustment ====
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| If an external dynamic or 600 series valve is in use and the desired oxygen sensor target setpoint cannot be reached, then the valve will need manual adjustments. These valves contain an external “load” screw, which must be rotated to make adjustments (for more information, refer to “APPENDIX D. EXTERNAL DYNAMIC AND 600 SERIES VALVES”).
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| ==== STOPPING THE ENGINE ====
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| The engine may be stopped at any time. The AFRC will detect the engine has stopped based on the trigger selected on the Run Signal Trigger screen (Pg. 10). When using thermocouples as the run indicator (“AFRC Pre-Cat TC” or “EMD Pre-Cat TC”), the controller will detect the engine has stopped after the pre-catalyst thermocouple drops below the trigger point (450°F by default). When using an oil pressure switch (“AFRC Oil Pressure” or “EMD Oil Pressure”), AFRC RPM, or Ignition State, the controller will immediately detect the engine has been shut down.
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| After the controller detects a shutdown, the digital power valve will fully open and then move to the startup position. This digital power valve cycle is repeated once after each engine shutdown to maintain calibration of the digital power valve position.
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| == Engineering Adjustments ==
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| While in ''Engineering'' security mode, the Engineering Setup screen (Lite Pg. 304, Adv. Pg. 207) is available through the Setup screen (Lite Pg. 301, Adv. Pg. 201). This screen provides access to gain adjustment and other engine configuration settings.
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| <nowiki>*</nowiki>Insert Image*
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| AFRC Engineering Setup Screen
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| === GAIN ADJUSTMENT ===
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| The AFRC operates on a PID control loop to automatically adjust the valve to match the actual sensor reading to the target setpoint. By default, the control loop has been pre-tuned to find the target setpoint quickly while maintaining stability. If the condition exists where the valve needs to be either more or less responsive, the PID control loop can be adjusted by selecting the “Faster” or “Slower” buttons around the “Response Time” label. Slowing the valve response will decrease the sensitivity of the control loop, and increasing the valve response will increase the sensitivity of the control loop. The individual PID values are automatically adjusted based on the single “Response Time” value. The default “Response Time” value is 50 and is adjustable between 0 and 100.
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| === CONTROL TYPE ===
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| The AFRC Advanced has the ability to switch between control types “Setpoint” and “Auto Control”. The AFRC Lite is fixed for “Setpoint” type control.
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| ==== Auto Control ====
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| “Auto Control” is a patented control algorithm that uses both a pre-catalyst and post-catalyst O2 sensor to find the most appropriate target setpoint and maintains that setpoint through a variety of conditions. The target setpoint is not user adjustable and is managed by the AFRC Advanced without the need for any user input. “Auto Control” is only available for single bank and dual bank rich burn engine configurations. Multi-setpoint mapping is disabled while in this mode.
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| If “Auto Control” is selected as the control type, options will be made available to adjust the software to target either for a richer or leaner setting using the “Lean” and “Rich” buttons on the Engineering Setup screen (Pg. 207). By default, this setting is configured for equal CO and NOx reduction with a rich/lean setting value of 50. Due to varying site conditions, including fuel gas and ignition timing, this value may require an initial adjustment after installation. If lower CO emissions are desired at the expense of higher NOx, the rich/lean setting can be reduced by selecting the “Lean” button to adjust rich/lean value less than 50. Similarly, if lower NOx emissions are desired at the expense of higher CO, the rich/lean setting can be increased by selecting the “Rich” button to adjust rich/lean value greater than 50. The rich/lean value’s range is 0 to 100, where 0 is the maximum lean value and 100 is the maximum rich value.
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| When “Auto Control” is selected, an alarm is automatically generated on the Alarm Setup screen (Pg. 206) to switch to “Setpoint” control if the “Auto Control” setpoint drifts below 600 or above 800. If the alarm is triggered, it must be reset on the Alarms screen (Pg. 40) before “Auto Control” can be re-enabled. Typical cause of the drift outside of this range is an expired or ineffective Post-Cat O2 sensor.
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| ==== Setpoint Control ====
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| “Setpoint” control mode controls off of a user, or mapping table, defined setpoint that corresponds with the desired emissions reduction. If desired, multiple setpoints can be used to automatically change the target setpoint based on sensor readings through the AFRC’s mapping feature.
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| === LOAD DELAY ===
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| The load delay setting adjusts the amount of time to delay the AFRC from taking control of the valve after it has detected a valid run signal and the sensors are warm. The intention of this configuration is to allow the engine to fully warm up and load before taking control.
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| The default value is set to 30 seconds, but the delay can optionally be configured to 1 minute, 5 minutes, 10 minutes, or 20 minutes.
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| === COMBUSTION TYPE ===
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| The AFRC can be configured to control either a rich-burn or lean-burn engine. Adjusting this parameter sets various displays elements within the user interface.
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| === O2 TYPE ===
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| The AFRC allows the O2 sensor type to be selected while the combustion type is configured as “Rich Burn”. The two O2 sensor types supported are narrowband and wideband. The narrowband sensor is a 4-wire heated sensor that can only read within a very narrow window around stoichiometric combustion and is suitable for rich burn combustion. The wideband sensor is a 6-wire that can read a much wider range and is suitable for both rich and lean burn combustion types.
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| === NUMBER OF BANKS ===
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| The AFRC Advanced allows for the number of banks to be selected as one (1) or two (2). The AFRC Lite does not include this configuration as it is intended for single bank configurations only.
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| === “ERROR” DISPLAY ===
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| When making ‘Control Type’, ‘O2 Type’, or ‘Banks’ adjustments on the Engineering Setup screen (Lite Pg. 304, Adv. Pg. 207), it is normal for text in red to present itself next to the ‘Engine Configuration’ label for a short period of time. The purpose of this text is to declare that the EIM and the AFRC configuration are out of synchronization. Once the synchronization is successfully completed (typically 2 seconds), the error message will be removed indicating the requested change was made.
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| == Mapping Setup ==
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| The AFRC features the ability for the target setpoint to automatically adjust based on changes to environmental conditions or sensor readings. This is accomplished by building a table, or map, that associates multiple target setpoints to a set of sensor conditions. As the sensor readings change, an offset can be applied to the target setpoint so that it changes autonomously. This feature can be used to account for environmental factors or load swings that may affect the engine’s performance or emissions.
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| A map can contain as little as two, or as many as five, points. Each point includes an offset to the target setpoint and a sensor reading associated with that offset. The offset is a value that is applied to the original, or base, target setpoint displayed on the AFRC Home screen (Lite Pg. 300, Adv. Pg. 200). The sensor value can come from any of the available sensors that are mappable, but all points in the table must be associated with a single sensor.
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| The generated target setpoint is calculated based on the two to five points entered within the table. If the sensor reading is between any two of the configured points within the table, the offset will be interpolated. If the sensor reading is less than the lowest value in the table, the corresponding lowest offset will be used. If the sensor reading is greater than the highest value in the table, the corresponding highest offset will be used.
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| <nowiki>*</nowiki>Insert Image*
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| Multi-Setpoint Graph Example
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| === MAPPING SENSORS ===
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| While in “Setpoint” control mode, the AFRC Advanced provides the following sensor options for mapping while, if properly equipped:
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| * Manifold Pressure
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| * Ambient Temperature
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| * Manifold Temperature
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| * RPM
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| * Post-Catalyst O2
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| The AFRC Lite provides the following option for mapping, if properly equipped:
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| * Manifold Pressure
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| === ADDING MAPPING POINTS ===
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| While in ''Engineering'' security mode, the Mapping Setup screen (Lite Pg. 330, Adv. Pg. 230) is available through the Setup screen (Lite Pg. 301, Adv. Pg. 201). This screen provides access to generating mapping points and enabling the mapping feature.
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| Before adding points to the mapping table, a sensor must be selected from the “Sensor” drop down box in the top center of the screen. The drop down box is populated based on sensors that are connected and enabled through any of the sensor setup screens. For the AFRC Lite, no drop down box is available as the only supported sensor is the manifold pressure sensor.
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| Upon selecting a sensor from the drop down box, the current sensor reading will be displayed within the “Create New Point” box on the mapping screen along with an offset of zero. If the engine emissions are currently satisfactory at current conditions, this condition can be added to the table by selecting any of the “Add” buttons within the “Mapping Table” box. The sensor value and associated offset of 0 will be added to the table.
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| Alternatively, the sensor value can be adjusted by selecting the “Increase” or “Decrease” buttons around the value. The offset associated with the selected sensor value can similarly be adjusted by pressing the “Rich” or “Lean” buttons around the displayed offset. When both the sensor and offset values are configured, select the “Add” button of the slot within the “Mapping Table” where the point is to be added.
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| The table is capable of accepting up to five (5) points but is valid with as few as two (2). Mapping points can be cleared out by selecting the associated “Delete” button next to the entry. The order of the points within the “Mapping Table” does not matter as the system will automatically sort the points based on the sensor value when the map is enabled. Points can only be added or deleted when the mapping feature is disabled.
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| <nowiki>*</nowiki>Insert Image*
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| Mapping Setup Screen with Mapping Enabled
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| === RUNNING THE MAP ===
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| The toggle button in the upper left corner of the mapping screen must be selected to engage the mapping table. Enabling mapping will change the text to the right of the toggle button from “Mapping Off” to “Mapping On” and remove the buttons from the mapping table to make changes.
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| Below the toggle button is the status of the AFRC. Possible status messages include:
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| * “Attempting to Engage Mapping” – Mapping feature is being initialized
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| * “Mapping Active” – Mapping is currently operational
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| * “Mapping Not Enabled” – Mapping is off
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| * “AFRC Not Detected” – No AFRC was found when mapping attempting to initialize
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| * “Error – Check Setup” – An error occurred attempting to initialize mapping
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| * Not enough mapping points available
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| * Duplicate mapping points were present
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| == Run Signal Trigger and System Temperature Units ==
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| The run signal trigger and system temperature units are configured on the Run Signal Trigger screen (Pg. 10) of the EIM, which can be accessed under the AFRC Setup page (Pg. 201).
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| The AFRC uses one of seven possible methods to recognize if an engine is running. The available sensors to trigger the run signal are below.
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| * Auto-Detect (Default)
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| * Scans all other run-signal sources for conditions indicating the engine is running
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| * AFRC Pre-Catalyst Thermocouple
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| * AFRC Advanced terminals 48 and 49
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| * AFRC Lite terminals 21 and 22
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| * AFRC Oil Pressure Switch
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| * AFRC Advanced terminals 15 and 16
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| * Oil Pressure Switch must be enabled on Sensor Setup – AI/DI (Pg. 202) screen of the AFRC Advanced
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| * AFRC RPM
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| * AFRC Advanced terminals 17 and 18
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| * RPM must be enabled and pulses per revolution must be defined on Sensor Setup – RPM (Pg. 205) screen of the AFRC Advanced
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| * EMD Pre-Catalyst Thermocouple
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| * EMD terminals 24 and 25
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| * EMD Oil Pressure Switch
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| * EMD terminals 39 and 40
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| * Oil Pressure Switch must be enabled on Sensor Setup – AI/DI (Pg. 104) screen of the EMD
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| * Ignition State
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| * Uses the current ignition state to determine run signal, if the ignition is in the “Engine Running” or “Engine Running With Warnings” state the run signal is set to running.
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| “Auto-Detect” will scan the other enabled “Trigger Sensor” inputs of the AFRC Advanced, AFRC Lite, EMD, and Ignition and toggle the engine run signal to “Run” if any of them indicate the engine is running.
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| If “Auto-Detect”, “AFRC Pre-Cat TC”, or “EMD Pre-Cat TC” is selected, a trigger temperature must also be configured. The trigger temperature defines the temperature at which the run signal will toggle. Any temperatures above the trigger will indicate the engine is running, and any temperatures below the trigger will indicate the engine is off. The default trigger temperature is 450°F.
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| Regardless of the selection on this screen, the ETS system will use “Auto-Detect” for the “Eng. Run” text on the top of pages, engine runtime hours, and alarm activation. The selection on the Run Signal Trigger page only effects when the AFRC considers the engine running. Note that if the AFRC pre-cat TC is the only sensor available, it will take time for the sensor to warm up enough for the EIM to display “Eng. Run”.
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| <nowiki>*</nowiki>Insert Image*
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