Carrier 48HC 04-28 Controls, Start-up, Operation And Troubleshooting

Also see for /50HC 04-28: Manual

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Carrier 48HC 04-28 Controls, Start-up, Operation And Troubleshooting Manual pdf 35 page image

35normal running mode, these limits will prevent stages from be-ing added, or stages to be removed, as applicable. In test mode,these limits are ignored, and the user may continue to operate allstages. The point MODEDMDL (Run StatusMODED.LMT) is used to show if any Demand Limiting is ineffect that prevents the unit from operating either cooling orheating at full-capacity.NOTE: MODEDMDL may reflect that staging is NOT limitedeven though Loadshed is active, or the network points are beingforced, if the stage limits in effect are not less than the stages pres-ent in the unit.If a more drastic mode of Demand Limiting is required, thenetwork point HVACDOWN (Run StatusMODEHV.DN)can be used to prohibit the unit from selecting any HVACmode, thus preventing the operation of the supply fan, com-pressors, condenser fans, and heat stages. This point must alsobe forced, and is reset automatically when not forced, and atPOR.NOTE: HVACDOWN can be used as an immediate shutdown ofthe unit before limiting capacity (ex. Generator switching).LinkageComfortLink controls do not require any configuration settingsto establish linkage with a Linkage Coordinator. This is doneautomatically when the unit’s bus and element address are con-figured in the Linkage Coordinator’s LINKAGE configurationtable. The linkage information that is supplied to the Com-fortLink unit by the Linkage Coordinator is as follows:• Reference zone temperature• Reference zone occupied biased heating and cooling setpoints• Reference zone unoccupied heating and cooling set points• Composite occupancy modeThe unit will control the equipment based on this informationand in return will provide the Linkage Coordinator with thefollowing data:• Operating mode - Cooling, Heating, Free Cooling, FireShutdown Evacuation, or Off• Supply-air temperature• Optimal Start Bias time (Based on worst case zone)This synchronization of data optimizes the efficiency of theunit and the zones to operate at peak system performance at alltimes. This information can be seen in linkage maintenance ta-bles of the Linkage Coordinator and the RTU; it is updated atapproximately 1-minute intervals.Cooling and heating operation is slightly modified duringLinkage control. A PID loop is run to calculate required stages.This is necessary because in stand alone operation, the unittries to anticipate the space. With Linkage, the unit must try tosatisfy the demand as soon as possible. The PID configurationsare in ConfigurationPID. These values have been field test-ed and the default values should NOT BE CHANGED.For information on set up and configuration, see the SpaceTemperature Control-CCN Linkage text in the Controls QuickStart section of this book.For additional information on the Linkage Coordinator or ZoneControllers, please refer to their appropriate manuals.Alarm HandlingThere are a variety of different alerts and alarms in the system.Alerts are indicated by TXXX (where XXX is the alert num-ber) on the display and generally signify that the improperlyfunctioning circuit can restart without human interaction. If analarm occurs, indicated by AXXX (where XXX is the alarmnumber), the damaged circuit will generally not restart withoutan alarm reset via the scrolling marquee display or CCN.The response of the control system to various alerts and alarmsdepends on the seriousness of the particular alert or alarm. Inthe mildest case, an alert does not affect the operation of theunit in any manner. An alert can also cause a “strike.” A “strik-ing” alert will cause the circuit to shut down for 15 minutes.This feature reduces the likelihood of false alarms causing aproperly 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 strike out, causing theshutdown alarm for that particular circuit. Once activated, theshutdown alarm can only be cleared via an alarm reset.However, circuits with strikes will be given an opportunity toreset their strike counter to zero. As discussed above, a striketypically causes the circuit to shut down. Fifteen minutes later,that circuit will once again be allowed to run. If the circuit isable to run for 1 minute, its replacement circuit will be allowedto shut down (if not required to run to satisfy requested stages).However, the “troubled” circuit must run continuously for auser defined time (ConfigurationCOOLRST.C) with nodetectable problems before the strike counter will be reset tozero. Default value is 5 minutes.CCN ALARM BROADCASTOperators of CCN networks might not want to be notified of“striking” alerts for refrigerant circuits until the circuit hasbeen shut down due to 3 strikes. Set the cooling configurationof Alert Each Strike (ConfigurationCOOLALM.N on dis-play, ALM_NOW on CCN) to YES to broadcast each circuitstrike alert. Set Alert Each Strike to NO to broadcast only cir-cuit shut down. Alert Each Strike configuration is ignoredduring Service Test and all alerts are broadcast.ALARM RELAY OUTPUTThe alarm relay output is a normally open 24 vac output be-tween field connection terminal board terminals C and X. Se-lection of which alerts and alarms will result in closing of thealarm relay may be set in the Alarm Relay Configuration (Con-figurationALM.O). Setting a configuration to YES will re-sult in the alarm output relay, ALRM, status of ON and 24 vacbetween C and X on the field connection terminal board whenthat particular condition is in an alarm state. Setting a configu-ration to NO will result in no action by the alarm output relayfor that particular 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 for more information on view-ing, diagnosing, and clearing alerts and alarms.EnergyX® UnitsGENERALAn EnergyX unit is a 48/50HC rooftop unit and energy recov-ery ventilator (ERV). It operates the ERV module in an inte-grated manner with the base rooftop unit. The base rooftop unitfunctions per the base unit sequence of operation, for informa-tion regarding ComfortLink controller operation see the Com-fortLink Controls, Start-Up, Operations, and TroubleshootingInstructions. The ERV will operate based on communicationfrom the ComfortLink controller. The following section dis-cusses the ERV operation in detail. In summary, the ERV oper-ates to provide pre-conditioned outside air for ventilation re-quirements. If equipped with an optional economizer the ERVcan provide free cooling when the outside air conditions aresatisfactory.In general the ERV monitors occupancy and indoor fan state ofthe base unit to determine when to activate. The outside airfan(s) bring in the outside air pass it through the enthalpywheel and into the rooftop mixing box. The building return airis pulled through the enthalpy wheel by the exhaust fan(s) andreleased outside. During operation the enthalpy wheel is rotat-ing to use the building air to pre-condition the outside air.