Carrier 48FK Controls Operation And Troubleshooting

Carrier 48FK Controls Operation And Troubleshooting Manual pdf 21 page image

EXTERNAL ALARM SIGNAL — The unit controls pro-vide an external alarm status signal via a 115-vac output sig-nal at the relay board J5, available at TB2-4 and TB2-5(common). This signal can be forwarded to the BMS by add-ing a signal relay at the alarm output, placing its coil acrossterminals TB2-4 and TB2-5 and using its contacts to controla discrete input to the BMS (see Fig. 31).The alarm signal output is energized when any of the di-agnostic codes is tripped.REMOTE ECONOMIZER CONTROL — Economizer con-trol is tightly integrated into the unit’s capacity control al-gorithms and diagnostic routines. Consequently, controlmodifications that interfere with this standard operating se-quence are not recommended.Economizer position is determined by the unit processorboard based on current outdoor air enthalpy status and cool-ing capacity demand. The economizer damper actuator is afloating point device with an internal brake and spring re-turn. Its position is determined by the sequencing of relaysEOR (Economizer Open Relay) and ECR (Economizer CloseRelay). The economizer’s current position is sensed by theprocessor board through position feedback potentiometer P2.Whenever the economizer position potentiometer signalis not consistent with the processor board’s commanded po-sition, a fault condition is determined by the processor boardand an alarm signal is initiated. The processor board alsoattempts to return the economizer damper to its fully closedposition during this fault condition by energizing the ECRrelay.Any attempt to effect an external control of the econo-mizer actuator will lead to an alarm condition and an auto-matic response by the unit control to attempt to close thedampers.Smoke Control Modes — It is common practice touse rooftop units for aid in building smoke control in theevent of a building fire. The available functions include: FireShutdown, Pressurization, Evacuation, and Smoke Purge. Thesefunctions are enhanced when multiple rooftop units are usedto zone a building.Implementation of the various Smoke Control modes onthese units requires the installer to modify the unit wiring toadd contacts (via either manual switches or relays) that willselectively interrupt and override standard factory control se-quences. See Table 5.FIRE SHUTDOWN MODE — Fire Shutdown mode termi-nates all unit operation (cooling, heating, supply fan and powerexhaust). This mode prevents recirculation of contaminatedair back into the space or the admission into the space ofunsuitable outside air.PRESSURIZATION MODE — Pressurization mode is in-tended to keep smoke out of a zone. Factory-installed op-tional economizer is required for this function. Pressuriza-tion is accomplished by:• opening the economizer (option)• running the supply fan (optional inlet guide vanes open oroptional VFD (variable frequency drive) at normal ductstatic pressure set point)• closing the power exhaust dampers (if installed as optionor accessory)• shutting off the power exhaust fans (if installed as optionor accessory)This allows the space to be overpressurized relative to ad-jacent zones and prevents or slows entry of smoke into thisspace from adjacent zones.EVACUATION MODE — Evacuation mode removes smokeor undesirable air from interior spaces without reintroducingunsuitable air. Factory-installed, optional economizer withoptional or accessory power exhaust are required for this func-tion. Evacuation is accomplished by:• turning supply fan off• opening the economizer (option required for this function)• running the exhaust fans (must be provided via option oraccessory)• opening the exhaust dampersSMOKE PURGE MODE — Smoke Purge mode removessmoke from the interior spaces and replaces it with fresh out-side air. Factory-option economizer with optional or acces-sory power exhaust are required for this function. Smoke purgeis accomplished by:• turning supply fan on• opening the economizer (option required for this function)• running the exhaust fans (must be provided via option oraccessory)• opening the exhaust dampers1215034-048: TB3054-104: TB4 TRANSDUCERR P BMSCONTROL(4 TO 20 MAOR2 TO 10 VDCSIGNAL)LEGENDP — Manual PotentiometerR — Fixed ResistorField WiringFig. 30 — Remote SASP WiringLIGHT4 5TB2 TB2RELAYRSIGNAL TO BMSLEGENDR — Resistor (Factory Installed)Factory WiringField WiringFig. 31 — External Alarm Indication21