Single Point Boxes And Supplementary Fuses; Safety Devices; Completing Heater Installation - Carrier 50FCQ 04-07 Series Service And Maintenance Instructions

Single Point Boxes and Supplementary Fuses

When the unit MOCP device value exceeds 60A, 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. 39.
Control Wiring
Foam Power
Wiring
Fig. 39 — Typical Single Point Installation
On 50FCQ units, all fuses are 60A. Single point boxes containing
fuses for 208/230-v applications use UL Class RK5 250-v fuses
(Bussmann FRNR 60 or Ferraz Shawmut TR 60R). Single
™1
point boxes for 460-v and 575-v applications use UL Class T 600-
v fuses (Bussmann JJS 60 or Ferraz Shawmut A6T 60). (Note
™1
that all heaters are qualified for use with a 60A fuse, regardless of
actual heater ampacity, so only 60A fuses are necessary.)

Safety Devices

CRHEATERS323A00-341A00 electric heater applications use a
combination of 24-v control side break/auto-reset, line-break/non-
resettable "one shot" limit switches and a fan stator/manual reset
limit switch to protect the unit against over-temperature situations.
Line-break/auto-reset limit switches, 24-v control side break/auto-
reset and line-break/non-resettable "one shot" limit switches are
mounted on the base plate of each heater module. See Fig. 40.
These are accessed through the indoor access panel. Remove the
switch by removing 2 screws into the base plate and extracting the
existing switch.
Fan stator/manual reset limit switch is located in the side plate of
the indoor (supply) fan housing. See Fig. 40.
1. Third-party trademarks and logos are the property of their respective
owners.
Heater Heater
Relay Mounting Screws
Control Side
Automatic Reset
Limit Switches
Fig. 40 — Typical Location of Heater Limit Switches
(3-phase heater shown)

Completing Heater Installation

FIELD POWER CONNECTIONS
Tap conductors must be installed between the base unit's field
power connection lugs and the single point box (with or without
fuses). See Fig. 41. Refer to unit wiring schematic. Use copper
wire only. For connection using the single point box without fuses,
connect the field power supply conductors to the heater power
leads and the field-supplied tap conductors inside the single point
box. Use UL-approved pressure connectors (field-supplied) for
these splice joints.
LOW-VOLTAGE CONTROL CONNECTIONS
Pull the low-voltage control leads from the heater module(s) —
ORN, VIO and BRN — to the 4-pole terminal board TB4 located
on the heater bulkhead to the left of heater 1. Connect the ORN
lead to terminal TB4-1. Connect the VIO lead to terminal TB4-2.
Connect the BRN lead to terminal TB4-3. See Fig. 41.
T
UCB
2 PNK
3 ORN
TRAN 1
C
ORN
TB4
VIO
Field
Connections
Fig. 41 — Accessory Electric Heater Control
25
Stator Manual
Reset Limit
Switch
Line Break
"One Shot"
Limit Switches
PNK BRN
1 2 3
VIO BRN BRN
Elec Htr
VIO HR2 BRN
VIO HR1 BRN
HR1: Heater Circuit 1
HR2: Heater Circuit 2
(if two-circuit module installed)
Connections