Operation; Unit Control Type (U.ctl); Occupancy Determination; Indoor Fan - Carrier 48HG014 Controls Operation And Troubleshooting

OPERATION

Unit Control Type (U.CTL) —
determined by Unit Control Type, which can be found in
UNIT, a submode of Configuration. There are three available
options that can be set from the Scrolling Marquee.
1. Auto (U.CTL = 1) — This mode selects the active mode
by evaluating the devices connected to the unit. If a valid
space temperature probe is connected to the unit, the unit
will operate in Space Sensor mode. If not, the unit will
operate in Thermostat mode.
2. Thermostat (U.CTL = 2) — The unit determines cooling
and heating demand by the state of G, Y1, Y2, W1 and
W2.
3. Space Sensor (U.CTL = 3) — The unit determines cool-
ing or heating demand based on the space temperature
and the appropriate set point.
The available set points are Occupied Cool Set Point
(OCSP), Unoccupied Cool Set Point (UCSP), Occupied Heat
Set Point (OHSP), and Unoccupied Heat Set Point (UHSP).
The occupied or unoccupied heating set point should always be
a minimum of 5 F below the corresponding cooling set point.
This ensures that the unit does not switch from cooling to heat-
ing unnecessarily. The cooling and heating set point deadband
can be changed (HC.SG).
Occupancy Determination —
mine whether the unit considers the building occupied or unoc-
cupied. If the unit is operating with a space temperature probe
(T55, T56 or T58), occupancy affects the unit set points and the
operation of the economizer. If the unit is operating under ther-
mostat control, occupancy only affects the operation of the
economizer. The factors affecting occupancy are listed below
from highest to lowest priority.
1. The CCN point OCCUPIED is forced via an external de-
vice such as a ComfortID™ controller — When OCCU-
PIED is forced to YES, the unit is considered occupied.
When OCCUPIED is forced to NO, the unit is considered
unoccupied. If OCCUPIED is not being forced, proceed
to the level 2.
2. Remote Occupancy Switch is configured as Normally
Open or Normally Closed — This switch should be con-
figured to either Normally Open or Normally Closed
when the user would like to control the occupancy with an
external switch. There are three possible configurations
for the remote occupancy switch: No Switch (0), Normal-
ly Open (1) or Normally Closed (2). This configuration is
accessible on the display at Configuration/Unit/RM.SW.
If the switch is configured to No Switch (0), the switch in-
put value will be ignored and software will proceed to the
level 3 priority. For each type of switch, the appropriate
configuration and states are listed in the table below.
SWITCH
TYPE OF SWITCH
CONFIGURATION
Occupied when
closed or Unoccupied Normal Open (1)
when open
Occupied when
open or Unoccupied Normal Close (2)
when closed
3. The following occupancy options are determined by the
state of Occupancy Schedule Number (SCH.N) and the
Global Schedule Broadcast (B.GS). The Schedule Num-
ber is a submode of Time Clock on the Scrolling Marquee
The control method is
Many factors deter-
STATE OF
SWITCH AND STATE
OF OCCUPANCY
Open and Unoccupied
Closed and Occupied
Open and Occupied
Closed and Unoccupied
26
and Global Schedule Broadcast can be found on the
Scrolling Marquee under Configuration/CCN.
a. SCH.N = 0: The unit is always considered occu-
pied and the programmed schedule is ignored. This
is the factory default.
b. SCN.N = 1-64: Follow the local programmed
schedule. Schedules 1 to 64 are local within the
controller. The Centurion unit can only store one
local schedule and therefore changing this number
only changes the title of the schedule table.
c. SCH.N = 65-99: Follow the global programmed
schedule. If the Centurion unit is configured as a
Global Schedule broadcaster (B.GS = YES), the
unit will follow the unit's programmed schedule
and broadcast the schedule so that other devices
programmed to follow this schedule number can
receive the schedule. If the Centurion unit is not
programmed as a Global Schedule broadcaster
(B.GS = NO), the unit will receive its information
from the unit programmed to broadcast this sched-
ule number.

Indoor Fan

48HG UNITS — The indoor fan is controlled by three inde-
pendent relays on a 48HG unit. The MBB fan relay is located
on the MBB and signals the IGC to turn on the indoor fan. The
IGC fan relay is located on the IGC and can operate indepen-
dently of the MBB relay. When the IGC receives a request
from the MBB relay, the IGC will turn on its relay. The IGC
will also turn on its relay when it determines that the indoor fan
should be on for gas heating. The IGC fan relay supplies
24 volts to the final relay known as indoor fan power relay
(IDFP), located on the MBB. This final relay supplies 24V to
the indoor fan contactor and to the indoor fan feedback input.
Unless there is a problem, this relay will be closed. When the
unit needs to shut down immediately because of a smoke prob-
lem, this relay will open. This allows the Centurion unit to turn
off the indoor fan immediately even when the IGC is control-
ling the indoor fan. The fan feedback input allows the MBB to
determine when the IGC has turned on the indoor fan. For in-
door fan operation, see Indoor Fan Control section below.
50HG UNITS — Because a 50HG unit does not have an IGC,
the indoor fan is controlled by the indoor fan relay (IDF) and
the indoor fan power relay (IDFP) on the MBB. The IGC fan
relay is replaced by a jumper wire on the 50HG unit. The in-
door fan will operate whenever the IDF and the IDFP are
closed. For indoor fan operation, see the Indoor Fan Control
section below. Unless there is a problem, the IDFP relay will be
closed. When the unit needs to shut down immediately because
of a smoke problem, this relay will open.
INDOOR-FAN CONTROL
UNITS) — In Space Temperature mode, the IDF relay will be
on in the following situations. If the unit is in Occupied mode
and the indoor fan is configured to always run while occupied
(OC.FN = YES), the indoor fan will be ON. If OC.FN equals
NO or the unit is unoccupied, the indoor fan will operate only
when heating or cooling is necessary.
In Thermostat mode, the IDF relay will be on in the follow-
ing situations. If G is On, then the IDF will be On. If the unit is
in the Cool mode, the IDF will be on. If the unit is in the Heat
mode for a 50HG unit, the IDF will be On. The unit will not
turn on the IDF on a 48HG unit while in Heat mode (unless G
is On) because the IGC is capable of controlling the indoor fan
in this situation.
(48HG AND 50HG