Reset MAT Table Entries? (MAT.R) — This configuration allows the user to reset the internally stored MAT learned con- figuration data back to the default values. The defaults are set to a linear relationship between the economizer damper posi- tion and OAT and RAT in the calculation of MAT.
MAT Outside Air Position Default (MAT.D) — This config- uration is used to calculate MAT when the economizer option is disabled. The configuration is adjustable from 0 to 100% outside air. This defines the fixed ventilation position that will be used to correctly calculate MAT.
Altitude……..In Feet: (ALTI) — The control does not in-
clude a barometric pressure sensor to determine altitude. The altitude must be defined the calculation of enthalpy and cfm. The altitude parameter is used to set up a default barometric pressure for use with calculations. The effect of barometric pressure in these calculations is not great, but could have an ef- fect depending on the installed elevation of the unit. If the unit is installed at a particularly high altitude and enthalpy or cfm are being calculated, set this configuration to the current elevation.
Start Up Delay Time (DLAY) — This option delays the unit from operating after a power reset. The configuration may be adjusted from 0 to 900 seconds of delay.
TSTAT — Both Heat and Cool (STAT) — This option, if en- abled, allows both heating and cooling requests to be made at the same time. If the unit is configured for staged gas heat, and if a cooling request is initiated (Y1 or Y2), then W1 initiates re- heat and W2 initiates dehumidification.
Auxiliary Relay Configuration (AUX.R) — This option con- figures the auxiliary relay on the MBB (RLY11). The function of this relay is configurable in the following ways:
•AUX.R = 0 (Alarm Output) — The relay is used for remote annunciation of an alarm state.
•AUX.R = 1
•AUX.R = 2 (Occup. State) — The relay is used to reflect occupancy. When the control is in occupied mode, the relay will be ON. When the control is in unoccupied mode, the relay will be OFF.
•AUX.R = 3 (S. Fan State) — The relay is used to reflect the supply fan commanded state. When the supply fan is on, the relay will be ON. When the supply fan is off, the relay will be OFF.
Space Temp Sensor (SPT.S) — If a space temperature sensor is installed, this configuration should be enabled.
Space Temp Offset Sensor (SP.O.S) — If a space tempera- ture sensor with a space temperature offset slider is installed (T56), this configuration should be enabled.
Space Temp Offset Range (SP.O.R) — If a space tempera- ture offset sensor is installed, it is possible to configure the range of the slider by adjusting this range configuration.
Return RH Sensor (RRH.S) — If a return air relative humidi- ty sensor is installed, this configuration should be enabled.
Filter Status Switch Enabled? (FLT.S) — If a filter status switch is installed, enable this configuration to begin the moni- toring of the filter status input (Inputs→GEN.I→FLT.S). See the Dirty Filter Switch section for more details on installation and operation.
Cooling Control — When mechanical cooling is required, the A Series ComfortLink™ control system has the capability to control the staging of the compressors in several different ways. Three scroll compressors are used on sizes 020 to 027 and four on sizes 030 to 060. In addition, the ComfortLink control system supports the use of an optional minimum load hot gas bypass valve (MLV) that is directly controlled by the ComfortLink control system. This provides an additional stage of capacity as well as low load coil freeze protection. The con- trol also integrates the use of an economizer with the use of
mechanical cooling to allow for the greatest use of free cool- ing. When both mechanical cooling and the economizer are being used, the control will use the economizer to provide bet- ter temperature control and limit the cycling of the compres- sors. The control also checks on various other operation parameters in the unit to make sure that safeties are not exceeded and the compressors are reliably operated.
The A Series ComfortLink™ control system offers two ba- sic control approaches to mechanical cooling. Constant volume operation for 2 stages of cooling or VAV operation for multiple stages of cooling. In addition to these methods of control, the A Series ComfortLink control offers the ability to run multiple stages of cooling for either a space temperature sensor or ther- mostat by controlling the unit to either a low or high cool supply air set point. The control type Configuration →UNIT→C.TYP) determines the selection of the type of cool- ing control as well as the method for selecting a cooling mode.
There are either three or four compressors divided among two refrigeration circuits in the unit. Circuit A always contains two compressors (A1,A2). Circuit B has either one or two compressors (B1,B2). There may be a minimum load valve (MLV), which, if present, is only associated with circuit A. The decision as to which compressor should be turned on or off is decided by the compressor’s availability followed by a pre- ferred staging order.
NOTE: Configuration of the machine control type (C.TYP) has no effect on whether a unit has a VFD or just a supply fan installed for static pressure control. No matter what the control type is, it is possible to run the unit in either CV or VAV mode provided there are enough stages to accommodate lower air volumes for VAV operation. Refer to the section on static pres- sure control for information on how to set up the unit for the type of supply fan control desired.
SETTING UP THE SYSTEM
Machine Control Type (Configuration→UNIT→C.TYP) — The most important cooling control configuration is located
under Configuration→UNIT.
This configuration defines the method and control source responsible for selecting a cooling mode. The configuration also determines the method by which compressors are staged. Control types are:
•C.TYP = 1
Both of these configurations refer to standard VAV opera- tion. If the control is occupied, the supply fan is run continu- ously and
•C.TYP = 3
This configuration will force the control to monitor the ther- mostat inputs to make a determination of mode. Unlike tra- ditional
•C.TYP = 4
This configuration will force the control to monitor the ther- mostat inputs to make a determination of mode.
•C.TYP = 5
This configuration will force the control to monitor a space temperature sensor to make a determination of mode. Un- like traditional
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