Space Sensor Control
Space sensor staging control is an adaptive anticipation control that weighs the actual space demand against the trend of that demand and the trend of the supply air. It also honors stage time guards and supply air limits. The demand for cooling in the space is displayed as the Cooling Demand (Run Status→COOL →DMD.C). The control tries to anticipate the change in the space because of its current stage status. This anticipation is based on the Supply−Air Trend (Operating Modes→COOL→SA.TR) and the Cool Demand Trend (Operating Modes→COOL→TRD.C). These trends will show the control how the space is reacting to the current running conditions and help it decide when to add or remove one stage from the requested stages. The Cool Stage Increase Time (Configuration→COOL→C.INC) or the Cool Stage Decrease Time (Configuration→COOL→C.DEC) has to expire before another stage can be added or a stage can be subtracted. If at any time the Supply−Air Temperature (SAT) falls below the Minimum Supply Air Temperature Upper Level (Configuration→COOL→SAT→SAT.U), the requested stages will not be allowed to increase. If at any time the SAT falls below the Minimum Supply Air Temperature Lower Level (Configuration→COOL→SAT→SAT.L), the requested stages will be reduced by one without honoring C.DEC. If SAT.L and SAT.U are configured so that they are close together, the last stage of compressor might cycle rapidly, slowed only by its minimum on and off−time requirements.
Compressor Control
The compressor control works hand and hand with the staging control. As the staging control requests stages, the compressor control determines what actual compressors are available or running and tries to provide stages for what is requested. The availability of a compressor depends on time guards, circuit diagnostics, outdoor temperature, and the unit size.
The Number of Circuits (Configuration→COOL→N.CIR) configuration tells the control how many compressors are installed
on the unit. The Circuit A Lockout Temp (Configuration→COOL→CIR.A →CA.LO), Circuit B Lockout Temp (Configuration→COOL →CIR.B→CB.LO), and Circuit C Lockout Temp (Configuration →COOL→CIR.C→CC.LO) configurations set the outdoor temperature in which the respective compressor is allowed to run down to. Timeguard A (Run
Status→COOL→CIR.A→TG.A), Timeguard B (Run Status→COOL→CIR.B→TG.B), and Timeguard C (Run Status→COOL→CIR.C→TG.C) display the time a respective compressor has before it is available for use. Individual circuit diagnostic tests are performed during operation which may or may not allow a compressor to be used. The configuration point Compressors On Circuit A (Configuration →COOL→N.A) informs the control to run diagnostics on one or two compressors for circuit A. The available stages at any given time are displayed as Available Compressors (Run Status→COOL →AVL.C). The actual compressors running at any given time are displayed as Actual Cooling Stages (Operating Modes→COOL →ACT.C). Compressor A (Run Status→COOL→CIR.A →CMP.A), Compressor B (Run Status→COOL→CIR.B →CMP.B), and Compressor C (Run Status→COOL→CIR.C →CMP.C) are displayed on when the respective compressor is running.
There are time guards to protect the compressors. Compressor Min On Time (Configuration→COOL→MRT.C) and Compressor Min Off Time (Configuration→COOL→MOT.C) apply before a compressor can be turned back on or turned off.
Outdoor Fan Control
Each unit has a means for variable outdoor airflow to control condenser pressure control within an acceptable range by responding to varied operating modes and ambient temperatures. This is implemented differently on different units using multi−speed motors, multiple outdoor fans, or variable−speed motor controllers.
NOTE: Factory default configurations account for these model differences and should not be changed. The default configurations have been qualified over a large range of conditions and are provided in case a field replacement of a control board occurs and the settings need to be checked or manually configured. Outdoor fan operation is further described below to assist in troubleshooting.
The outdoor fans are controlled by levels. There are 4 levels of operation (0−3) and the current operating level is shown as Outdoor Fan Level (Operating Modes→COOL→F.LEV). The fan level selected during operation is based on factory configurations of outdoor temperature limits and condenser pressure limits. These are in the Outdoor Fan Control submenu (Configuration→COOL→OFC) and shown in Table 5. The starting level is picked after a compressor is turned on and is based on the Outdoor Air Temperature (Temperatures→AIR.T→OAT). A circuit’s Saturated Condensing Temperature (Temperatures →REF.T→SCT.x) can override the fan level at any time if the specific Fan Level Max Pressure (Configuration→COOL→OFC →x.MXP) is exceeded. This override will end if the circuit’s saturated condensing temperature (SCT) drops below the specific Fan Level Min Pressure (Configuration→COOL→OFC →x.MNP). The number of fans and contactors on at a given fan level depends on the specific unit options and size. See Tables 6 and 7 and below text for specific fan and contactor status at any given fan level.
Units Without Humidi−MiZert System
Outdoor Fan Motors (OFM) are controlled by Outdoor Fan Contactors (OFC) which are controlled by the main base board (MBB).
For 48/50PG03−07 units, a duel speed motor is used. The Compressor Contactor (C.A1) turns the OFM on in high speed and the OFC1 is used to change to low speed.
For 48/50PG08−14 units, OFM1 is controlled by OFC1 and OFM2 is controlled by OFC2.
For 48/50PG16 units, OFM1 is controlled by OFC1 and OFM1 and 2 are controlled by OFC2.
For 48/50PG20−28 and 48/50PM16−28 units, OFM1 is controlled by OFC1, OFM4 is controlled by OFC3, and OFC2 controls the remaining two fans (16 and 20 size) or remaining 4 fans (24 and 28 sizes).
Units With Humidi−MiZer System
Outdoor fan control for Humidi−MiZer units includes a MotormasterR variable−speed control of some or all outdoor fans, depending on unit size. The Motormaster control automatically adjusts the outdoor fan speed to maintain approximately 80_ to 100_F condenser temperature for circuit A at all outdoor ambient temperatures. Some unit sizes have additional on/off staging of some outdoor fans. The fan level operation is determined by some or all Outdoor Fan Control configurations described above, plus additional Humidi−MiZer Configuration (Configuration →HZMR). Refer to the Humidi−MiZer operation section for details on the Reheat function fan control.
48/50PG and PM
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