Carrier 50PG20-28 Controls, Start-up, Operation, Service And Troubleshooting Instructions

Also see for 48PG20---28: User's information manual User's information manual Installation and service instructions

Carrier 50PG20-28 Controls, Start-up, Operation, Service And Troubleshooting Instructions Manual pdf 52 page image

Timed Override Hours (SCH.O_OV.EX) This displaysthe current number of hours left in an override. It is possible tocancel an override in pr%mess by writing "0" to this variable,thereby relnoving the override time left.SPY Override Enabled? (SCH.O_OV.SP) Ifa space sen-sor is present, then it is possible to ovm_ide an unoccupiedperiod by pushing the override button on the T55 or T56sensor. This option allows the user to disable tNs function bysetting this configuration to NO.Alarm Handling -- There are a variety of difl'erent alertsand alarms in the system. Alerts are indicated by Tnnn (wherennn is the alert number) on the display and generally simnifythat the improperly functioning circuit can restart without hu-man interaction. If an alarm occurs, indicated by Annn (wherennn is the alarm number), the dumaged circuit will generallynot restart without an alarm reset via the Serolling Marqueedisplay or CCN.The response of the control system to various alerts andalarms depends on the seriousness of the particular alert oratann. In the mildest case, an alert does not affect the operationof the unit in any manner. An alert can also cause a "strike." A"striking" alert will cause the circuit to shut do,a_ for 15 min-utes. This feature reduces the likelihood of False atanns causinga properly working system to be shut down incorrectly. If threestrikes occur before the circuit has an opportunity to show thatit can function properly, the circuit will be deactivated, causingthe shutdown alarm for that particular circuit. Once activated,the shutdown alarm can only be cleared via an alarm reset.Howevei; circuits with strikes wilt be given an opportunityto reset their strike counter to zero. As discussed above, a striketypically causes the circuit to shut do,a_. Fifteen minutes later,that circuit will once again be allowed to ran. If the circuit isable to run for 1 minute, its replacmnent circuit will be allowedto shut down (if not required to mn to satisfy requested stages).However, the "troubled, circuit must mn continuously fora user defined time ((bnfiguration _'OOL--+RST.. 0 with nodetectable problems before the strike counter will be reset tozero. DeFault value is 5 lninutes.CCN ALARM BROADCAST Operators of CCN net-works might not want to be notified of "striking" alerts forrefiigerant circuits until the circuit has been shut do,a_ due to3 strikes. Set the cooling configuration of Alert Each Strike((bnfiguration4DOL--_ALM.N on display, ALM NOWon CCN) to YES to broadcast each circuit strike alert. Set AlertEach Strike to NO to broadcast only circuit shut down. AlertEach Strike configuration is ignored during Sel_TiceTest and allalerts are broadcast. The default is YES.ALARM RELAY OUTPUT The alarm relay output is anonnalty open 24 vac output between field connection terminalboard terminals C and X. Selection of which alerts and alarmswill result in dosing of the alarm relay may be set in the AlarmRelay Configuration ((bnfiguration -+ALM.O). Setting a con-figuration to YES will result in the alarm output relay, ALRM,status of ON and 24 vac between C and X when that particularcondition is in an atann state. Setting a configuration to NOwill result in no action by the alarm output relay for that partic-ular condition.NOTE: An accessory filter switch can be used along with thealarm relay output function to indicate dirty filter service need.See the Troubleshooting section tbr more information onviewing, diamaosing, and clearing alerts and alarms.TROUBLESHOOTINGThe Scrolling Marquee display shows the actual operatingcoMitions of the unit while it is running. If there are alarms orthere have been atanns, they will be displayed in either thecurrent alarm list or the history alarm list. See Table 43. TheSela_iceTest mode allows proper operation of the compressors,tans, and other components to be checked while the unit is notoperating. See Sea:ice Test on page 36.Complete Unit Stoppage -- There are several coMi-tions that can cause the unit not to provide heating or cooling:• If an alarm is active which causes the unit to shut do,a_,diagnose the problem using the information provided inAlarms and Alerts section below.• Cooling and heating loads are satisfied.• Programmed occupancy schedule.• General power t;aihire.• Tripped CB1, CB2, or CB3 (24-volt transformer circuitbreakers).• Blown fuse (FU1 or FU2)• Unit is turned offthrough the CCN network.• If supply-air temperature is less than the Minimmn SATLower Level (SAT.L) configuration value, unit cannotcool.• If outdoor-air temperature is less than the CompressorLockout Temperature (CA.LO, CB.LO, (_'.LO) configu-ration value, unit cannot cool.• If outdoor-air temperature is greater than the HeatingLockout Temperature (HT..LO) configuration value, unitcannot heat.52