Carrier 50TCA04-A07 appendix Completing Heater Installation, Typical Single Point Installation

50TC

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 distribution and fuse blocks. The single point box will be installed directly under the unit control box, just to the left of the partition separating the indoor section (with electric heaters) from the outdoor section. The Single Point Box has a hinged access cover. See Fig 30.

CONTROL

BOX

BUSHING

SINGLE
POINT BOX
MOUNTING
SCREWS
DRIP BOOT
BRACKET
MOUNTING
SCREWS
POWER
WIRES
FOAM
BUSHING
	22.2
23	1
	3

HEATER

RELAYS

HEATER

MOUNTING

SCREWS

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Fig. 30 - Typical Single Point Installation

On 50TC 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 ampacity, so only 60-A fuses are necessary.)

Unit heater applications not requiring supplemental fuses do not require a Single Point Box. Connect power supply conductors to heater conductors and field-supplied base unit power tap leads (see text below re: “Completing Heater Installation”) below the unit’s main control box using UL-approved connectors.

Safety Devices — Electric heater applications use a combination of line-break/auto-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. 31. 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. 28.

Completing Heater Installation

Field Power Connections — Field-supplied tap conductors must be installed between the base unit’s field power connection lugs and the splice connection between field power supply conductors and the conductors to the electric heater(s). Refer to unit wiring schematic. Use

copper wire only. Size these conductors based on the MCA (Minimum Circuit Ampacity) value marked on the 50TC unit’s info plate for the base unit less electric heater load. Use UL-approved pressure connectors (field-supplied) for these splice joints.

Line-Break

Limit Switches

	23		21
	13		11
ALLIED PA
MODEL	OD
NO.
ERIAL NO.
ISTED AIR		1
NDITIONING	23
UIP ACCESS		3
346N.	2-
P / N		5610-4	REV

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Fig. 31 - Typical Location of Heater Limit Switches

(3-phase heater shown)

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. 32.

LCTB

CONTL

BOARD

2VIO

3ORN

12 BRN

	ORN	VIO	BRN
TB4	1	2	3
Field	VIO	VIO	BRN BRN
Connections

Elec Htr

VIO HR2 BRN

VIO HR1 BRN

HR1: On Heater 1 in Position #1

HR2: On Heater 2 in Position #2 (if installed)

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Fig. 32 - Accessory Electric Heater Control

Connections

22