Single Point Boxes And Supplementary Fuses; Safety Devices; Low-Voltage Control Connections - Carrier WeatherExpert 50LC 07 Series Service And Maintenance Instructions

Fig. 30 — Typical Module Installation

Single Point Boxes and Supplementary Fuses

When the unit MOCP device value exceeds 60-A, unit-mounted
supplementary fuses are required for each heater circuit. These
fuses are included in accessory single point boxes, with power dis-
tribution and fuse blocks. The single point box will be installed di-
rectly under the unit control box, just to the left of the partition
separating the indoor section (with electric heaters) from the out-
door section. The single point box has a hinged access cover. (See
Fig. 31.) The single point box also includes a set of power taps to
complete the wiring between the single point box and the unit's
main control box terminals. Refer to accessory heater and single
point box installation instructions for details on tap connections.
CONTROL
BOX
BUSHING
SINGLE
POINT BOX
MOUNTING
SCREWS
DRIP BOOT
BRACKET
MOUNTING
SCREWS
POWER
WIRES
FOAM
BUSHING
HEATER
RELAYS
HEATER
MOUNTING
SCREWS
Fig. 31 — Typical Single Point Installation
On 50LC units, all fuses are 60-A. Single point boxes containing
fuses for 208/230-v applications use UL Class RK5 250-v fuses
(Bussman FRNR 60 or Shawmut TR 60R). Single point boxes for
460-v and 575-v applications use UL Class T 600-v fuses
(Bussman JJS 60 or Shawmut A6T 60). (Note that all heaters are
qualified for use with a 60-A fuse, regardless of actual heater am-
pacity, so only 60-A fuses are necessary.)
Unit heater applications not requiring supplemental fuses require a
special single point boxes without fuses. The accessory single
point boxes contain a terminal block and a set of power taps to
complete the wiring between the single point box and the unit's
main control box terminals. Refer to accessory heater and single
TRACK
point box installation instructions for details on tap connections.

Safety Devices

Electric heater applications use a combination of line-break/auto-
FLANGE
reset limit switches and a pilot-circuit/manual reset limit switch to
protect the unit against over-temperature situations.
Line-break/auto-reset limit switches are mounted on the base plate
of each heater module. (See Fig. 32.) These are accessed through
the indoor access panel. Remove the switch by removing two
screws into the base plate and extracting the existing switch.
Pilot-circuit/manual reset limit switch is located in the side plate of
the indoor (supply) fan housing. (See Fig. 29.)
Fig. 32 — Typical Location of Heater Limit Switches

Low-Voltage Control Connections

Pull the low-voltage control leads from the heater module(s) -
VIO and BRN (two of each if two modules are installed; identify
for Module #1) - to the 4-pole terminal board TB4 located on the
heater bulkhead to the left of Heater #1. Connect the VIO lead
from Heater #1 to terminal TB4-1. Connect the VIO lead from
Heater #2 to terminal TB4-2. Connect both BRN leads to terminal
TB4-3. (See Fig. 33.)
21
(3-phase heater shown)
Line-Break
Limit Switches