14
cool and heat setpoints (EFF COOL SETPOINT and EFF HEAT
SETPOINT). However, to minimize unnecessary cool to heat and
heat to cool changes, there is a 10 minute delay after the last stage
turns off before the control will switch modes. Linkage operation
overrides the mode changeover delay to 15 seconds. The cooling
and heating Mode Select Time guards (COOL MODE T.GUARD
and HEAT MODE T.GUARD) show the remaining time before
allowing the respective mode to be entered.
Demand Determination
Based on the unit control type (UNIT CONTROL TYPE),alarm
conditions, and user interaction, the control will determine an
overall demand of the unit. Table 8 shows the possible system
demands with their priority level and summary description.
Thermostat Demand
When the unit control type is configured for thermostat (UNIT
CONTROL TYPE = TSTAT) the level 5 demand in Table 8 will be
determined by thermostat inputs and the Thermostat Type
configuration (THERMOSTAT TYPE) as shown in the tables
below. Table 9 shows the cooling thermostat inputs and how they
map to the system demand. Table 10 shows the heating thermostat
inputs and how they map to the system demand.
SUB-
MODE
IDLE - NO DEMAND
SUPPLY FAN ON UNOCC. FREE COOL
MODE TIMEGUARD MECH. COOLING
UNIT DISABLED ECON/MECH COOLING
URGENT SHUTDOWN DEHUMIDIFICATION
SAFETY CONTROL DEHUM/MECH COOL
MODE OFF VENT COOL HEAT TEST
STARTING UP MODE TIMEGUARD ECON FREE COOLING HEATING MANUAL TEST
OUTSIDE AIR TEMPERING
HEATING PREVENTED
AUTO TEST
SHUTTING HEAT OFF
SHUTTING TEST OFF
DEHUM PREVENTED
COOLING PREVENTED
SHUTTING COOL OFF
a48---9374
Fig. 10 -- Modes and Sub-- Modes
Table 8 – Demand List and Priority
DEMAND Priority Description
EMERGENCY 1 An emergency condition occurs which requires a unit shutdown
SAFETY FAULT 2 A safety diagnostic requires the unit to run in safety mode.
SERVICE TEST 3 User request test mode
SHUTDOWN 4 A minor or user condition requires the unit to shutdown
NO DEMAND
5
There is no comfort demand from the building
FAN ONL Y Only circulation or ventilation is requested form the building
DEHUM A dehumidification load is present in the building
LOW COOL A low cooling load is present in the building
MED COOL A medium cooling load is present in the building
HIGH COOL A high cooling load is present in the building
LOW COOL & DEHUM A low cooling and dehumidification load is present in the building
MED COOL & DEHUM A medium cooling and dehumidification load is present in the building
HIGH COOL & DEHUM A high cooling and dehumidification load is present in the building
UFC LOW COOL A low cooling load is present in the building due to the unoccupied free cooling algorithm
UFC MED COOL A medium cooling load is present in the building due to the unoccupied free cooling algorithm
UFC HIGH COOL A high cooling load is present in the building due to the unoccupied free cooling algorithm
LOW HEAT A low heating load is present in the building
HIGH HEAT A high heating load is present in the building
SUPPL Y AIR TEMPERING Due to outside air, supply air is uncomfortably cool during ventilation
Table 9 – Thermostat Cooling System Demands
Thermostat Inputs THERMOSTA T TYPE
Y1 Y2 Y3 CONV 2C2H** CONV 3C2H DIGI 2C2H* DIGI 3C2H
0 0 0 No Cool No Cool No Cool No Cool
0 0 1 No Cool Alert & Low Cool No Cool High Cool
0 1 0 Alert & Low Cool Alert & Low Cool Medium Cool Medium Cool
0 1 1 Alert & Low Cool Alert & Med Cool Medium Cool High Cool
1 0 0 Low Cool Low Cool Low Cool Low Cool
1 0 1 Low Cool Alert & Med Cool Low Cool High Cool
1 1 0 High Cool Medium Cool High C o ol Medium Cool
1 1 1 High Cool High Co ol High Co ol High Cool
*Y3isignored
** Set the LOW COOL COMP as needed, and Y3 is ignored
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