analog to digital converter . . . . . . . . . . . . . . . 4 - UPGNet

351579-YTS-B-0608(optional) are disabled, so cooling is disabled and theoptional economizer outside air dampers are closed.3. When the return air temperature climbs above the MWUPsetpoint, heating is disabled, VAV and the economizer areenabled.4. A call for first stage cooling initiates the cooling sequence.The optional economizer is enabled, and drives thedamper to the minimum open position. If free cooling isavailable, dampers open to satisfy setpoints. If there is noeconomizer, the control powers terminal C1 to energizecompressor 1.The control provides a minimum of 30 seconds betweeneach cooling stage call [see Lead-Lag], a 4 minute minimumON time for each cooling stage and a 5 minute minimumOFF time for each cooling stage.5. A call for Compressor 1 powers the high pressure safetyswitch (HPS1), the low pressure switch (LPS1), the coil ofcontactor 6M (condenser fan 1), and the coil of contactor7M (contactor, condenser fan 2) through condenser fancycling switch PS5 (PS5 disables condenser fan 2 operationbased upon the discharge pressure of the Compressor1). If the system pressures are within HPS1 (high refrigerantpressure) and LPS1 (low refrigerant pressure) switchsettings is not tripped, contactor 1M is engaged to startscroll Compressor 1.6. A call for Compressor 2 powers contactor 2M (contactor,compressor 2) if HPS2 and LPS2 (high and low refrigerantpressure) contacts are closed.7. 30 and 40 ton only (all R410a): A call for Compressor 3powers the coils of contactors 8M (contactor, condenserfan 3) and 9M (contactor, condenser fan 4 - 40 ton only). IfHPS3 and LPS3 (high and low refrigerant pressure) contactsare closed, power is applied to the coil of Contactor3M, which starts compressor 3.8. 40 Ton Only (all R410a): A call for Compressor 4 powersthe coils of contactor 4M if HPS4 and LPS4 (high and lowrefrigerant pressure) contacts are closed.9. When the internal time clock matches the setting in the holidayand daily schedules, the unit enters Unoccupiedmode. The control disables the supply fan, the optionalpower exhaust, cooling, heating, and the economizer. Theoptional outside air dampers are closed with the optionalinlet guide vanes.10. When the space temperature falls below the heating setpoint,the control powers contactor 5M from terminal FANto engage the supply fan motor. If the supply fan operatescorrectly (proper rotation) the pressure difference betweenthe heating section and the supply fan section increasesand APS closes to enable heating operation. If heat safetiesare satisfied, the VAV speed signal (VFD or Inlet GuideVanes) goes to maximum flow [the customer-installed connectionwill drive the VAV boxes to full open]. The controlengages unit heat (optional) at full capacity. Until heat isenergized, duct pressure control is activated. The optionalpower exhaust system is activated.In heat mode, cooling is disabled and the optional economizeroutside air dampers are closed. This operation ismaintained until the space temperature rises above theheating setpoint or Occupied mode is engaged.11. Gas Heat Single Stage Module: Each module installedhas it own ignition control and its own set of safeties. Whenthere is a call for heat from the unit control board (UCB) foreach module, the ignition control board (ICB) for that modulechecks the state of the flame sense, the roll out switch,the pressure switch and the primary temperature limitswitch circuits for that module. If they are in the expectedstate, then the ICB energizes the draft motor and verifiesthat the pressure switch closes. After the pressure switchcloses, a 30 second heat exchanger purging period is completed.After this purging period, the ICB will energize thegas valve and the ignition coil for 10 seconds. Once theflame sensor senses a flame is present, the ignition coil isde-energized. The ICB monitors flame stability for 10 seconds.The ICB will retry 3 times to obtain a stable flame. Ifthe furnace fails to light 3 times during the same call forheat, then the ICB will lock out operation of that moduleuntil the next call for heat exists. The ICB monitors themodule's safety devices during that module's operation.When the UCB de-energizes the call for heat for a givenmodule, the ICB closes the gas valve for that module andperforms a 30 second purging of the heat exchanger bycontinuing the operation of the draft motor.Gas Heat Operation Errors - During furnace operation,the ICB monitors the flame sense circuit, the pressureswitch, the primary limit switch and the roll out switch. Ifa signal from any of the inputs moves to a fault state,then the ICB immediately closes the main gas valve.The ICB will determine the device that is signaling a faultand flash a code for that device (Table 7). A primary limittrip, pressure switch trip or flame sense fault triggers atemporary lock out. A roll out switch trip requires manualreset. Some UCB's installed on Millennium also monitorthe primary limit and/or gas valve for fault conditions toset warning flags.Temperature Limits - The primary limit is located suchthat a temperature sensitive switch can sense the temperatureof the heat exchanger tubes. The limit ismounted just above the inlet of the heat exchangertubes on the left side. If a primary limit fault occurs (theprimary limit opens due to excessive heat exchangertemperature), then the ICB will flash the appropriatecode (Table 7) and monitor the primary limit. The ICB willenergize the draft motor during the time the primary limitis open. When the primary limit closes and the call forheat still exists, the ICB will start the ignition sequenceover.Gas Valve - The gas valve is of the redundant type suchthat if either one of two valves inside the gas valve failsto shut off the gas flow then the other valve will shut offthe flow.22 Johnson Controls Unitary Products