maintain diagnostics, although the end user will see a Dehumidification mode at the display. In addition, for
•Reheat When Cooling Demand is Present — For reheat control during dehumidification: If reheat follows an offset subtracted from
•The heating control point will be whatever the actual cooling set point would have been (without any supply air reset applied).
•Reheat During Vent Mode — If configured (Configura- tion→DEHU→D.V.CF = 0), the heating control point will be equal to RAT – D.V.RA. If configured (Configu- ration→DEHU→D.V.CF=1), the heating control point will be equal to the D.V.HT set point.
Ending Dehumidification and Reheat Control — When ei- ther the humidity sensor fall 5% below the set point (Configu- ration→DEHU→D.RH.S) or the discrete input reads “LOW”, the Dehumidification mode will end.
Temperature Compensated Start — This logic is
used when the unit is in the unoccupied state. The control will calculate early Start Bias time based on Space Temperature deviation from the occupied cooling and heating set points. This will allow the control to start the unit so that the space is at conditioned levels when the occupied period starts. This is required for ASHRAE 90.1 compliance. A space sensor is re- quired for
SETTING UP THE SYSTEM — The settings for tempera- ture compensated start can be found in the local display under Configuration→UNIT.
ITEM | EXPANSION | RANGE | UNITS | CCN POINT |
TCS.C | Temp.Cmp.Strt.Cool Factr | 0 - 60 | min | TCSTCOOL |
TCS.H | Temp.Cmp.Strt.Heat Factr | 0 - 60 | min | TCSTHEAT |
NOTE: Temperature compensated start is disabled when these factors are set to 0.
TEMPERATURE COMPENSATED START LOGIC — The following conditions must be met:
•Unit is in unoccupied state.
•Next occupied time is valid.
•Current time of day is valid.
•Valid space temperature reading is available (sensor or
The algorithm will calculate a Start Bias time in minutes us- ing the following equations:
If (space temperature > occupied cooling set point)
Start Bias Time = (space temperature – occupied cooling set point)* TCS.C
If (space temperature < occupied heating set point)
Start Bias Time = (occupied heating set point – space temperature)*TCS.H
When the Start Bias Time is greater than zero the algorithm will subtract it from the next occupied time to calculate the new start time. When the new start time is reached, the Temperature Compensated Start mode is set (Operating Modes→MODE→ T.C.ST), the fan is started and the unit controlled as in an
occupied state. Once set, Temperature Compensated mode will stay on until the unit goes into the Occupied mode. The Start Bias Time will be written into the CCN Linkage Equipment Table if the unit is controlled in DAV mode. If the Unoccupied Economizer Free Cool mode is active (Operating Modes→ HVAC = “UNOCC FREE COOL”) when temperature com- pensated start begins, the Unoccupied Free Cool mode will be stopped.
Carrier Comfort Network® (CCN) System — It
is possible to configure the ComfortLink™ control to partici- pate as an element of the Carrier Comfort Network (CCN) sys- tem directly from the local display. This section will deal with explaining the various programmable options which are found under the CCN
The major configurations for CCN programming are locat- ed in the local displays at Configuration→CCN. See Table 86.
CCN Address (CCNA) — This configuration is the CCN ad- dress the rooftop is assigned.
CCN Bus Number (CCNB) — This configuration is the CCN bus the rooftop is assigned.
CCN Baud Rate (BAUD) — This configuration is the CCN baud rate. For units equipped with the optional UPC, the CCN Baud Rate must be set to 9600.
CCN Time/Date Broadcast (TM.DT) — If this configuration is set to ON, the control will periodically send the time and date out onto the CCN bus once a minute. If this device is on a CCN network then it will be important to make sure that only one device on the bus has this configuration set to ON. If more than one time broadcaster is present, problems with the time will occur.
NOTE: Only the time and date broadcaster can perform daylight savings time adjustments. Even if the rooftop is stand alone, the user may want to set this to ON to accomplish the daylight/savings function.
CCN OAT Broadcast (OAT.B) — If this configuration is set to ON, the control will periodically broadcast its
CCN OARH Broadcast (ORH.B) — If this configuration is set to ON, the control will periodically broadcast its outside air relative humidity at a rate of once every 30 minutes.
CCN OAQ Broadcast (OAQ.B) — If this configuration is set to ON, the control will periodically broadcast its outside air quality reading at a rate of once every 30 minutes.
Global Schedule Broadcast (G.S.B) — If this configuration is set to ON and the schedule number (SCH.N) is between 65 and 99, then the control will broadcast the internal time schedule once every 2 minutes.
CCN Broadcast Acknowledger (B.ACK) — If this configu- ration is set to ON, then when any broadcasting is done on the bus, this device will respond to and acknowledge. Only one de- vice per bus can be configured for this option.
Schedule Number (SCH.N) — This configuration determines what schedule the control may follow.
SCH.N = 0 The control is always occupied.
SCH.N = 1 The control follows its internal time sched- ules. The user may enter any number between 1 and 64 but it will be overwritten to “1” by the control as it only has one internal schedule.
SCH.N =
71
