Carrier 48HC 04-28 Manual

Also see for /50HC 04-28: Controls, Start-Up, Operation and Troubleshooting

Carrier 48HC 04-28 Manual Manual pdf 29 page image

29Reheat ControlThe cooling staging and compressor control routines areresponsible for controlling each circuit in one of the threesub--modes (Cool, Reheat1, or Reheat2). When there is only acooling demand, one or more circuits will operate in normalcooling mode. When there is only dehumidification demand, allcircuits will operate in Reheat2 mode. When there is both coolingdemand and dehumidification demand, all circuits will operate ineither Reheat1 or Reheat2 mode, with the portion of Reheat1circuits determined from the cooling demand. The RequestedReheat2 Stages (Operating Modes→COOL→HMZR→REQ.R)shows the control’s request for reheat circuits if cooling is notalready requesting all stages. Available Reheat2 Stages (OperatingModes→COOL→HMZR→AVL.R) displays circuits that areavailable for reheat use. Actual Reheat2 Stages (OperatingModes→COOL→HMZR→ACT.R) displays the current numberof circuits running in Reheat2 mode. These three status pointsshould only be monitored when there is only a dehumidificationdemand, because their values can be forfeited to cooling stageswhen cooling demand is present. Reheat2 Stage Incr. Time(Configuration→HMZR →R.INC) and Reheat2 Stage Decr. Time(Configuration→HMZR→R.DEC) set the time delay whenadding or subtracting a compressor for a reheat function. Theseonly apply when using adaptive thermostat or space sensor control.There are three relay outputs that show reheat status. Cool -- >Reheat1 Control (Outputs→COOL→CRC) show when the unithas switch from pure cooling to reheat ready (based on adehumidification demand). Reheat2 Valve A (Outputs→COOL→RH2.A) and Reheat2 Valve B (Outputs→COOL→RH2.B) display when the respective circuit’s Reheat2valve is energized.A circuit can be restricted from Reheat2 operation by the outsidetemperature and saturated suction temperature. Reheat2 OAT LimitA (Configuration→HMZR→RA.LO) and Reheat2 OAT Limit B(Configuration→HMZR→RB.LO) set the lowest outsidetemperature the respected circuit is allowed to run in reheat2 mode.The lockout on/off status is shown as Reheat2 OAT Lockout A(Operating Modes→COOL→HMZR→R.LO.A) and Reheat2OAT Lockout B (Operating Modes→COOL→HMZR →R.LO.B)for their respective circuit. If a circuit’s saturated suction pressurefalls below the low limit configuration during Reheat2 operation,the circuit will switch to reheat1 (the circuits Reheat2 valve will beturned off) for at least 2 minutes and until its suction rises backabove the high limit. Reheat2 SSP Lo Limit A(Configuration→HMZR→RA.LP) and Reheat2 SSP Lo Limit B(Configuration→HMZR→RB.LP) set the low pressure limit forReheat2 mode for individual circuits. Reheat2 SSP Hi Limit A(Configuration→HMZR→RA.HP) and Reheat2 SSP Hi Limit B(Configuration→HMZR→RB.HP) set the high pressure limit forReheat2 mode for each circuit.Reheat Mode Diagnostic HelpThe status of reheat mode sensor inputs may be viewed within thedisplay Inputs menu. The status of reheat mode outputs may beviewed within the display Outputs or Run Status→COOL menus.Additional diagnostic help, including status of circuit reheattemperature limit lockouts may be viewed within theHumidi-MiZer™ sub-menu of the cooling mode diagnostic table atOperating Modes→COOL→HMZR.The Service Test mode may be used to force the system to operatein various stages of Reheat1 or Reheat2 mode, or to independentlyoperate the reheat valve control outputs.The following forced operating states are changed or added to theavailable service test operation for a Humidi-MiZer equipped unit:Service Test→COOL→CMP.A (Cool A Test)A value of On will turn on circuit A in Normal Cooling mode.Service Test→COOL→CMP.B (Cool B Test)A value of On will turn on circuits A and B in Normal Cooling mode.Service Test→HMZR→RH1.A (Reheat1 A Test)A value of On will turn on circuit A in Reheat1 mode.Service Test→HMZR→RH1.B (Reheat1 B Test)A value of On will turn on circuits A and B in Reheat1 mode.Service Test→HMZR→RH2.A (Reheat2 A Test)A value of On will turn on circuit A in Reheat2 mode.Service Test→HMZR→RH2.B (Reheat2 B Test)A value of On will turn on circuits A and B in Reheat2 mode.Service Test→HMZR→CRC (Cool-Reheat1 Valve Test)For 48/50HC04--12 units, a value of On will turn on the CRCrelay. This will turn on CLV.x valves and turn off RLV.x valves.For 48/50HC14--28 units, a value of On will turn on the CRCrelay. This will energize the LDV.x valves.Service Test→HMZR→RHV.A (Reheat2 Valve A Test)A value of On will turn on the RDV.A valve.Service Test→HMZR→RHV.B (Reheat2 Valve B Test)A value of On will turn on the RDV.B valve.EnergyXFor units equipped with the EnergyX factory installed option, therewill be an EnergyX Supplement Installation Instructions in theunit’s information packet. Refer to this supplement for details onhow the ERV operates relative to the base unit.Temperature Compensated StartThis logic is used when the unit is in the unoccupied state. Thecontrol will calculate early Start Bias time based on SpaceTemperature deviation from the occupied cooling and heating setpoints. This will allow the control to start the unit so that the spaceis at conditioned levels when the occupied period starts. This isrequired for ASHRAE 90.1 compliance. A space sensor is requiredfor non-linkage applications.Setting Up the SystemThe settings for temperature compensated start can be found in thelocal display under Configuration→UNIT.ITEM EXPANSION RANGE UNITS CCN POINTTCS.C Temp.Cmp.Strt.Cool Factr 0 - 60 min TCSTCOOLTCS.H Temp.Cmp.Strt.Heat Factr 0 - 60 min TCSTHEATTemp Comp Strt Cool Factr (TCS.C)This is the factor for the start time bias equation for cooling.Temp Comp Strt Heat Factr (TCS.H)This is the factor for the start time bias equation for heating.NOTE: Temperature compensated start is disabled when thesefactors are set to 0.Temperature Compensated Start LogicThe following conditions must be met for the algorithm to run:S Unit is in unoccupied state.S Next occupied time is valid.S Current time of day is valid.S Valid space temperature reading is available (sensor or CCNnetwork).The algorithm will calculate a Start Bias time in minutes using thefollowing equations:If (space temperature > occupied cooling set point)Start Bias Time = (space temperature – occupied cooling setpoint)* TCS.CIf (space temperature < occupied heating set point)Start Bias Time = (occupied heating set point – spacetemperature)*TCS.HComfortLINK v1.X