PREHEAT-X Module
Technical Guide
Page 1: ...PREHEAT X Module Technical Guide ...
Page 2: ...AON P N G086640 Rev E April 2021 AAON Inc All rights reserved throughout the world AAON is a registered trademark of AAON Inc Tulsa OK AAON assumes no responsibility for errors or omissions in this document This document is subject to change without notice www aaon com PREHEAT X PARTS REFERENCE PART DESCRIPTION PART NUMBER PREHEAT X Module ASM01688 VCCX2 Controller ASM01698 VCB X Controller ASM018...
Page 3: ...ys 9 SEQUENCE OF OPERATIONS 10 Operation Modes 10 LCD SCREENS 12 Navigation Keys 12 Main Screens Map 13 Main Screens 14 Status Screens 15 Setpoints Screens 17 Alarms Screen 18 Configuration Screens 19 Communication Configuration Screens 20 TROUBLESHOOTING 21 LED Diagnostics 21 Alarms 22 APPENDIX A LAT SENSOR 23 Installation 23 Troubleshooting 24 APPENDIX B BACNET 25 Connection to MS TP Network 25 ...
Page 4: ...r Voltage Resistance for Type III Sensors 24 Table 6 PREHEAT X BACnet Points 26 FIGURES Figure 1 PREHEAT X Dimensions 5 Figure 2 PREHEAT X Inputs Wiring Diagram 7 Figure 3 PREHEAT X Outputs Wiring Diagram 8 Figure 4 LCD Display and Navigation Keys 12 Figure 5 PREHEAT X Main Screens Map 13 Figure 6 PREHEAT X LED Locations and Descriptions 21 Figure 7 Leaving Air Temperature Sensor Installation 23 F...
Page 5: ...mm unicating with the VCCX2 or other AAON unit controllers Monitors the Preheater Leaving Air Temperature and Leaving Air Reset Signal and controls to maintain the setpoint Contains a 2 x 8 LCD character display and four buttons that allow for status display and setpoint changes Figure 1 PREHEAT X Dimensions 5 73 5 24 2 62 5 63 5 04 0 21 2 04 0 57 4 09 Note Depth is 1 50 inches Note All dimensions...
Page 6: ...blocks Do not allow wire strands to stick out and touch adjoining terminals which could potentially cause a short circuit 7 When communication wiring is to be used to interconnect AAON unit controllers together or to connect to other communication devices all wiring must be plenum rated minimum 18 gauge two conductor twisted pair with shield AAON can supply communication wire that meets this speci...
Page 7: ... Air 2 Temperature Sensor Mount inside PREHEAT X box wall Entering Air Temperature Sensor Make splice connections inside sensor enclosure as shown Seal all conduit fittings with silicone sealant Mount sensor outdoors in shaded protected area and in upright position as shown 0 10 VDC Reset In GND Heat Enable Signal 24 VAC W1 Note Reset In and Heat Enable inputs are used in Stand Alone Mode only Eme...
Page 8: ...d Note All relay outputs are normally open and rated for 24 VAC power only PREHEAT X 11VA Size transformer for correct total load EBC E BUS cable connects to VCCX2 or other AAON unit controller s expansion port HSSC E BUS cable connects to the VCM X Controller s expansion port ALARM HEAT 1 RELAY HEAT 2 RELAY HEAT 3 RELAY HEAT 4 RELAY HEAT 5 RELAY HEAT 6 RELAY Relay Contact Modulating SCR 0 10 VDC ...
Page 9: ...ated by a 24 VAC signal supplied from a building automation system to enable the PREHEAT X The module will not operate without 24 VAC being applied to this input terminal when used as a stand alone module When the Heat Enable signal is lost or turned off all stages deactivate immediately Emergency Shutdown Input This wet contact 24 VAC input is used to initiate shutdown of the HVAC unit when a N C...
Page 10: ...nput Communications Mode When the PREHEAT X is connected and communicating with an AAON unit controller via a modular cable the necessary information will be passed between the PREHEAT X and the AAON unit controller to properly operate in the Heating Mode If the communication is interrupted between the PREHEAT X and the AAON unit controller both boards will show an alarm and the PREHEAT X outputs ...
Page 11: ... as needed to maintain the Leaving Air Setpoint Controlled by an Internal PID Loop Heat Staging Up The following conditions must be met before the first next stage of heat can be energized Preheat Enable Signal Command must be active The LAT must be below the LAT Setpoint by any amount If Mod Heat is configured it must be at 100 for the Stage Up Delay The Minimum Off Time must be met The Stage Up ...
Page 12: ...navigate through the Main Menu Screen categories Editing Key Key Function UP or DOWN Use the UP or DOWN key to enter editing mode on a user adjustable screen Edit Mode is indicat ed by the underscore appearing on the screen NOTE Entering Edit Mode will also adjust the value up one UP key or down one DOWN key so you may have to readjust the value ENTER Use the ENTER key to move through the digits i...
Page 13: ... COMM CONFIG COM MODE S ALONE MAC ADDR 0 BAC ID 15000 BAC BAUD 38 400 EBUS CFG VCB VCCX STATUS SOFTWARE VER X XX PREHEAT ENABLED CONT TMP XX X LA SPT XX X STGS ON 2 MOD HEAT XX LA1 TEMP XX X LA2 TEMP XX X AVG TEMP XX X ENT AIR XX X CommPKTs XX ALARMS E SHUTDN ALARM LA1 SENS BAD LA2 SENS BAD LOW LAT ALARM HI LAT ALARM EA SENS ALARM COM STAT ALARM ACTIVE ALARMS Figure 5 PREHEAT X Main Screens Map LC...
Page 14: ... to go to ALARMS Screens ALARMS Press to scroll through ALARMS Screens Press to go to CONFIG Screens CONFIG Press to scroll through CONFIG Screens Press to go to COMM CONFIG Screens Main Screens Refer to the following map when navigating through the LCD Main Screens The first screen is an initialization screen To scroll through the rest of the screens press the MENU button COMM CONFIG Press to scr...
Page 15: ...Leaving Air Sensor 2 or 3 the average of both LA SPT XX X LEAVING AIR TEMPERATURE SETPOINT Displays the current Leaving Air Setpoint the module is trying to maintain This value can come from the following based on configuration 1 Internal Setpoints Setpoint Reset Input 2 E BUS Input from VCCX2 or other AAON unit controllers or 3 BACnet point STGS ON 2 CURRENT NUMBER OF ACTIVE STAGES Displays the n...
Page 16: ...XX X ENTERING AIR TEMPERATURE Displays the current Entering Air Temperature Sensor reading CommPKTs XX COMMUNICATION PACKETS Communication Packets are used to show the EBUS packets re ceived from main controller LCD SCREENS Status Screens ...
Page 17: ...alue to raise the sensor s temperature or a negative value to lower the sensor s temperature Minimum Default Maximum 100ºF 0 0ºF 100ºF 55 5ºC 21ºC 55 5ºC LA2 CAL XX X LEAVING AIR SENSOR 2 CALIBRATION OFFSET If the sensor is reading incorrectly you can use this screen to enter an offset temperature to adjust the sensor s temperature Enter a positive value to raise the sensor s temperature or a nega...
Page 18: ... shorted open or missing for more than 60 seconds This alarm will be disabled when the sensor is working again LOW LAT This indicates a Leaving Air Temperature Cutoff alarm condition which is activated if the Controlling LeavingAir Temperature has dropped below 35ºF for more than 2 minutes The alarm will be disabled if after a fixed delay period the Leaving Air Temperature has risen above 35ºF HI ...
Page 19: ...g Output It sets the voltage level needed for 0 Range is 0 10 Default is 0 AOUT VHI XX X MAXIMUM SCR VOLTAGE This is the High Voltage setting for the Analog Output It sets the voltage level needed for 100 Range is 0 10 Default is 10 STG UP XX STAGE UP DELAY If configured for SCR modulation this is the amount of time in seconds the controller must wait to activate an additional stage of heat if the...
Page 20: ...ENT MAC ADDRESS Valid range is 0 to 128 Default is 0 BAC ID 15000 BACnet CURRENT ID START Range is 0 to 30000 Default is 15000 Communication Configuration Screens Refer to the following map when navigating through the Communication Configuration Screens From the COMM CONFIG Screen press ENTER to scroll through the screens and change setpoints Use the UP and DOWN arrow keys to change your selection...
Page 21: ...the PREHEAT X s cover above the LCD display will light up to indicate an alarm The type of alarm s will be shown on the LCD display Communication LED COMM This yellow LED will light up and blink when communications are detected Relay LEDs RLY 1 6 These green LEDs will light up and stay lit as long as the Heat Relay s is active Binary Input LEDs HEAT EN This green LED will light up when Heat is ena...
Page 22: ...d wiring Refer to chart in back of this guide for readings Leaving Air Temperature Failure Verify that the Leaving Air Temperature sensor s is connected to the AIN1 and or AIN2 and GND on the PREHEAT X Remove AIN1 and AIN2 and GND wiring from the PREHEAT X and ohm out the sensor this may indicate open or failed wiring Refer to chart in back of this guide for readings Communications Loss Check COMM...
Page 23: ... wall over the sensor This will help prevent thermal gradients from affecting the sensor WARNING Make sure your Leaving Air Temperature Sensor s are mounted and wired according to these instructions prior to testing the unit or else the modulating valve will not control properly and may damage your equipment Figure 7 Leaving Air Temperature Sensor Installation Note Leads are non polarized Butt spl...
Page 24: ...eck the thermistor sensor while disconnected from the controllers not powered 2 Use the voltage column to check sensors while connected to powered controllers Read voltage with meter set on DC volts Place the minus lead on GND terminal and the plus lead on the sensor input terminal being investigated APPENDIX A LAT SENSOR Troubleshooting Temp F Temp C Resistance Ohms Voltage Input VDC 10 23 3 9333...
Page 25: ...l wiring to be T to T SHLD G to SHLD G and R to R T SHLD G R 1 All wiring to be in accordance with local and national electrical codes and specifications Wiring Notes 2 All communication wiring to be 18 gauge minimum two conductor twisted pair with shield Use Belden 82760 or equivalent Size transformer for correct total load PREHEAT X 11VA Line Voltage GND 18 30 VAC APPENDIX B BACnet Connection to...
Page 26: ... Off 1 On BI 6 Heat 2 Relay Status The current status of the Heat 2 Relay Read Only 0 Off 1 On BI 7 Heat 3 Relay Status The current status of the Heat 3 Relay Read Only 0 Off 1 On BI 8 Heat 4 Relay Status The current status of the Heat 4 Relay Read Only 0 Off 1 On BI 9 Heat 5 Relay Status The current status of the Heat 5 Relay Read Only 0 Off 1 On BI 10 Heat 6 Relay Status The current status of th...
Page 27: ...roperty Identifier BACNETPropertyIdentifier AllAlarmGroup1Bits BIT STRING Reserved 0 BadLeavingAir1 1 BadLeavingAir2 2 LowLeavingAir 3 HighLeavingAir 4 Reserved 5 BadEnteringAir 6 CommAlarm 7 ShutDownAlarm 8 APPENDIX B BACnet PREHEAT X BACnet Points ...
Page 28: ...erved AAON Factory Technical Support 918 382 6450 techsupport aaon com AAON Controls Support 866 918 1100 Monday through Friday 7 00 AM to 5 00 PM Central Standard Time Controls Support website www aaon com controlstechsupport NOTE Before calling Technical Support please have the model and serial number of the unit available PARTS For replacement parts please contact your local AAON Representative...
