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Carrier 50HCQA User Manual

Page 29

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29

Field Connections

Field connections for accessory sensors and input devices

are made the RTU--MP, at plugs J1, J2, J4, J5, J11 and J20.

All field control wiring that connects to the RTU--MP

must be routed through the raceway built into the corner

post as shown in Fig. 22. The raceway provides the UL

required clearance between high-- and low--voltage wiring.

Pass the control wires through the hole provided in the

corner post, then feed the wires thorough the raceway to

the RTU--MP. Connect to the wires to the removable

Phoenix connectors and then reconnect the connectors to

the board.

Space Temperature (SPT) Sensors —

A field--supplied Carrier space temperature sensor is

required with the RTU--MP to monitor space temperature.

There are 3 sensors available for this application:

S

33ZCT55SPT, space temperature sensor with override
button

S

33ZCT56SPT, space temperature sensor with override
button and setpoint adjustment

S

33ZCT59SPT, space temperature sensor with LCD
(liquid crystal display) screen, override button, and
setpoint adjustment

Use 20 gauge wire to connect the sensor to the controller.

The wire is suitable for distances of up to 500 ft. Use a

three--conductor shielded cable for the sensor and setpoint

adjustment connections. If the setpoint adjustment

(slidebar) is not required, then an unshielded, 18 or 20

gauge, two--conductor, twisted pair cable may be used.

Connect T--55: See Fig. 31 for typical T--55 internal

connections. Connect the T--55 SEN terminals to

RTU--MP J20--1 and J20--2. See Fig. 50.

SEN

SEN

J20-1

J20-2

C08460

Fig. 50 -- RTU--MP T--55 Sensor Connections

Connect T--56: See Fig. 33 for T--56 internal connections.

Install a jumper between SEN and SET terminals as

illustrated. Connect T--56 terminals to RTU--MP J20--1,

J20--2 and J20--3 per Fig. 51.

SEN

J20-1

J20-2

SEN

SET

Jumper

J20-3

SET

C08461

Fig. 51 -- RTU--MP T--56 Sensor Connections

Connect T--59: The T--59 space sensor requires a

separate, isolated power supply of 24 VAC. See Fig. 51

for internal connections at the T--59. Connect the SEN

terminal (BLU) to RTU--MP J20--1. Connect the COM

terminal (BRN) to J20--2. Connect the SET terminal (STO

or BLK) to J20--3.

OR

SET

SEN

OPB

COM- PWR+

BLU (SPT)

BLK (STO)

24 VAC

SENSOR

WIRING

POWER
WIRING

BRN (COM)

NOTE: Must use a separate isolated transformer.

C07132

Fig. 52 -- Space Temperature Sensor Typical Wiring

(33ZCT59SPT)

Economizer Controls

Outdoor Air Enthalpy Control

(PNO 33CSENTHSW) —

The enthalpy control (33CSENTHSW) is available as a

field--installed accessory to be used with the EconoMi$er2

damper system. The outdoor air enthalpy sensor is part of

the enthalpy control. (The separate field--installed

accessory return air enthalpy sensor (33CSENTSEN) is

required for differential enthalpy control. See Fig. 36.)

Locate the enthalpy control in the economizer next to the

Actuator Motor. Locate two GRA leads in the factory

harness and connect the gray lead labeled “ESL” to the

terminal labeled “LOW”. See Fig. 36. Connect the

enthalpy control power input terminals to economizer

actuator power leads RED (connect to 24V) and BLK

(connect to GND).

The outdoor enthalpy changeover setpoint is set at the

enthalpy controller.

Differential Enthalpy Control —

Differential enthalpy control is provided by sensing and

comparing the outside air and return air enthalpy

conditions. Install the outdoor air enthalpy control as

described above. Add and install a return air enthalpy

sensor.

Return Air Enthalpy Sensor —

Mount the return--air enthalpy sensor (33CSENTSEN) in

the return--air section of the economizer. The return air

sensor

is

wired

to

the

enthalpy

controller

(33CSENTHSW). See Fig. 37.

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