Level 3 Priority; Indoor Fan Operation - Carrier 48HC 04-28 Controls, Start-Up, Operation And Troubleshooting

TYPE OF SWITCH
CONFIGURATION
Occupied when
Closed or Unoccupied Normal Open (1)
when Open
Occupied when Open
or Unoccupied when Normal Closed (2)
Closed
NOTE: To perform remote occupancy, an Economizer Control
Board must be installed in the unit.

LEVEL 3 PRIORITY

The following occupancy options are determined by the state
of Occupancy Schedule
  
tion CCN SCH.O SCH.N) and the Global Schedule

Broadcast (Configuration

1. (Configuration CCN
The unit is always considered occupied and the pro-
grammed schedule is ignored. This is the factory default.

2. (Configuration CCN
Follow the local programmed schedule. Schedules 1 to 64
are local within the controller. The unit can only store one
local schedule and therefore changing this number only
changes the title of the schedule table.

3. (Configuration CCN
Follow the global programmed schedule. If the unit is con-
figured as a Global Schedule Broadcaster (Configura-
  
tion CCN BROD
the unit's programmed schedule and broadcast the sched-
ule so that other devices programmed to follow this sched-
ule number can receive the schedule. If the unit is not
programmed as a Global Schedule Broadcaster (Configu-
 
ration CCN BROD
receive broadcasted schedules from a unit programmed to
broadcast this schedule number. While using the pro-
grammed schedule, occupancy can be temporarily
switched from unoccupied to occupied by pressing the
override button for approximately 3 seconds on the T-55,
T-56, T-58 or T-59 space temperature sensor. Override will
only occur if SPT Override Enabled (Configura-
  
tion CCN SCH.O
of the override period when pressing the override button is
determined by the Override Time Limit (Configura-
  
tion CCN SCH.O
override is displayed as Timed Override Hours (Configu-
 
ration CCN SCH.O
changed from the local display or network to set or change
the override period length.

INDOOR FAN OPERATION

The indoor fan is required for every function of the unit and has
several configurations that effect its operation. The Indoor Fan
Type configuration (Configuration
type of fan and how it is controlled. These 48/50HC units can uti-
lize the 1-Speed (FTYP = 0) or the LEN VFD (FTYP = 1) fan
types. The Number of Speeds configuration (Configura-
 
tion I.FAN NSPD) is not used with fan types 1-Speed or
LEN VFD. The fan operation for these two fan types is explained
in detail below. For gas heating units, the IGC fan request output
 
(Inputs GEN.I IGC.F) is also monitored by the MBB con-
trol. This can result in additional modification of fan delays or
other operation due to safety functions of the IGC control. See the
Gas Heating operation section for more details. If configured for
IAQ fan operation, the fan may be turned on to satisfy air quality
demands. See the Indoor Air Quality section if using IAQ (indoor
air quality) accessory sensors. The fan can only run under ther-
mostat or space sensor control if the System Mode (SYS) status is
STATE OF SWITCH
SWITCH
AND STATE OF
OCCUPANCY
Open and Unoccupied
Closed and Occupied
Open and Occupied
Closed and Unoccupied
Number (Configura-
 
CCN BROD B.GS).
 
SCH.O CH.N = 0)
 
SCH.O SCH.N = 1-64)
 
SCH.O SCH.N = 65-99)
B.GS = YES), the unit will follow

B.GS = NO), the unit will
OV.SP) is set to YES. The length
OV.TL). The hours remaining in

OV.EX). This point can also be
 
I.FAN FTYP) sets the
enabled. The fan will remain on if compressors or heat relays are
ever stuck on. If configured for fan status switch (FN.SW) and
Shut Down on IDF Failure is enabled (Configuration
 
UNIT IDF.F = Yes), the fan and unit will be shutdown with-
out delay on alarm. Fan off delays are honored when exiting spe-
cific HVAC modes. The Fan-off Delay delays are as follows:
Mech Cool (Configuration

(Configuration HEAT
 
tion HEAT FOD.G).
Staged Air Volume (SAV) Units (FTYP = LEN VFD)
The SAV option is a new method of controlling the supply fan
in a typical constant volume rooftop unit. This control method
employs a Variable Frequency Drive (VFD) to operate the sup-
ply fan at different speeds in order to achieve energy savings
through reduced fan power. This method is specifically not
concerned with controlling static pressure in the supply duct,
but rather with setting different fan speeds for different operat-
ing conditions, such as ventilation mode or part-load mechani-
cal cooling. This option should not be confused with a linearly
variable VFD concept. The different speeds are programmed
per condition; there is no linear-modulation of fan speed.
The SAV function is NOT a Variable Air Volume (VAV) func-
tion. The fan adapts its speed to one of seven based on mode
and current state to satisfy a demand. The seven speeds consist
of off (0%) and six configurable values. The six configurable
fan speeds are: Maximum Speed (FS.MX), Ventilation
(FS.VN), IAQ Override (FS.AQ), Free Cool Lo (FS.E1),
Mech Cooling (FS.CL), and Reheat2 (FS.RH).
The VFD is powered direct from the distribution block or cir-
cuit breaker (CB) and is always on with power applied unless
the CB is tripped. When the thermostat or space sensor control
conditions require the fan on, the VFD will then ramp to de-
sired speed. Fan speed is always calculated by evaluating the
current applicable conditions. Each fan speed "mode" is evalu-
ated independently, and the highest fan speed is used. For ex-
ample, if an IAQ Override event occurs during Ventilation
mode, the fan speed is set to the higher of the two (FE.VN or
FS.AQ). Refer to the speed configurations below for when the
fan will run at them. When first turning on the fan from 0%, it
will run at max speed (FS.MX) for 1 minute.
Supply Fan Maximum Speed (FS.MX)
Max speed is the highest fan speed allowed. This is typically
100% when pulleys are set to deliver design CFM to the space
per job requirement. Most safety conditions for the unit will
override the fan speed to this to help protect the unit. When in
heat mode this is the only speed available. In free cooling after
the damper has been at max for 5 minutes, the fan will be set to
max before mechanical cooling can be used and locked at max
while damper is 100% and mechanical cooling is on. When
running both cooling stages the fan will be set to max.
Fan Speed - Ventilation (FS.VN)
This configuration defines the fan speed used in Ventilation
(fan-only) mode. Ventilation mode is when the supply fan is
running, but there is no demand for heating or cooling. In ther-
mostat mode, this is with just a G call. In space sensor control,
this is when the unit is Occupied mode and the indoor fan is
configured to always run while occupied (Configura-
 
tion I.FAN OC.FN = YES). If the indoor fan is configured
for intermittent fan (OC.FN = No), the fan will be off instead
of this speed during ventilation. The economizer damper will
adjust its position based on how far away this speed is from
max speed.
IMPORTANT: It is important that the ventilation rate is
checked after setting this speed to verify that the unit can
properly ventilate the space per requirements. Adjusting
this configuration or the economizer minimum setting curve
should be performed to meet job requirements.
19
 
COOL FOD.C), Elect Heat

FOD.E), and Gas Heat (Configura-