48/50PG and PM
RH2.x
RH1.x
COND COIL |
|
|
| |
|
|
COMP
OUTDOOR AIR
METERING
DEVICE
| EVAP COIL |
CLOSED VALVE |
|
OPEN VALVE |
|
INDOOR ENTERING | |
| |
| AIR |
C07124
Fig. 14 − Hot Gas Reheat Mode (Reheat2) — Humidi−MiZert System
48/50PG20−28 and 48/50PM16−28
Reheat Control
The cooling staging and compressor control routines are responsible for controlling each circuit in one of the three sub−modes (Cool, Reheat1, or Reheat2). When there is only a cooling demand, one or more circuits will operate in normal cooling mode. When there is only dehumidification demand, all circuits will operate in Reheat2 mode. When there is both cooling demand and dehumidification demand, all circuits will operate in either Reheat1 or Reheat2 mode, with the portion of Reheat1 circuits determined from the cooling demand. The Requested Reheat2 Stages (Operating Modes→COOL→HMZR→REQ.R) shows the control’s request for reheat circuits if cooling is not already requesting all stages. Available Reheat2 Stages (Operating Modes→COOL→HMZR→AVL.R) displays circuits that are available for reheat use. Actual Reheat2 Stages (Operating Modes→COOL→HMZR→ACT.R) displays the current number of circuits running in Reheat2 mode. These three status points should only be monitored when there is only a dehumidification demand, because their values can be forfeited to cooling stages when 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 when adding or subtracting a compressor for a reheat function. These only 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 unit has switch from pure cooling to reheat ready (based on a
dehumidification demand). Reheat2 Valve A (Outputs→COOL→RH2.A) and Reheat2 Valve B,C
(Outputs→COOL→RH2.B) display when the respective circuit’s Reheat2 valve is energized.
A circuit can be restricted from Reheat2 operation by the outside temperature and saturated suction temperature. Reheat2 OAT Limit A (Configuration→HMZR→RA.LO) and Reheat2 OAT Limit B,C (Configuration→HMZR→RB.LO) set the lowest outside temperature 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 Reheat2 OAT Lockout B,C (Operating Modes→COOL→HMZR →R.LO.B) for their respective circuit. If a circuit’s saturated suction pressure falls below the low limit configuration during Reheat2 operation, the circuit will switch to reheat1 (the circuits Reheat2 valve will be turned off) for at least 2 minutes and until its suction rises back above the high limit. Reheat2 SSP Lo Limit A (Configuration→HMZR→RA.LP) and Reheat2 SSP Lo Limit B,C (Configuration→HMZR→RB.LP) set the low pressure limit for Reheat2 mode for individual circuits. Reheat2 SSP Hi Limit A (Configuration→HMZR→RA.HP) and Reheat2 SSP Hi Limit B, C (Configuration→HMZR→RB.HP) set the high pressure limit for Reheat2 mode for each circuit.
Reheat Outdoor Fan Control
On specific units, the outdoor fans are controlled differently while in a reheat mode versus just cooling mode. If Reheat Fan Control (Configurations → HMZR → RH.FN) is set to yes, reheat fan control is enabled and anytime the unit is running reheat it will use the following logic to control the outdoor fans.
During reheat fan control, the outdoor fans will start and stay at level 1 until the Reheat ODF Fan On Temp (Configurations → HMZR → RF.ON) is reached. When the outdoor air temperature is above this reheat fan on temperature, the outdoor fans will change to the Reheat ODF Fan On Level (Configurations → HMZR → RF.LV). The fans will stay at this level until the Reheat ODF Fan Off Temp (Configurations → HMZR → RF.OF) is reached. When the outdoor temperature drops below the reheat fan off temperature, the outdoor fans will change back to level 1. Reheat fan control will cease if at any time the unit stops running reheat and shuts off or switches to just cooling. At this time the fans will either stay off or run under normal fan control.
28
