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Carrier 50HCQA User Manual

Page 30

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To wire the return air enthalpy sensor, perform the

following:

1. Use a 2--conductor, 18 or 20 AWG, twisted pair cable

to connect the return air enthalpy sensor to the enthal-

py controller.

2. Connect the field--supplied RED wire to (+) spade

connector on the return air enthalpy sensor and the

(+) terminal on the enthalpy controller. Connect the

BLK wire to (--) spade connector on the return air en-

thalpy sensor and the (--) terminal on the enthalpy

controller.

Indoor Air Quality (CO

2

sensor) —

The indoor air quality sensor accessory monitors space

carbon dioxide (CO

2

) levels. This information is used to

monitor IAQ levels. Several types of sensors are available,

for wall mounting in the space or in return duct, with and

without LCD display, and in combination with space

temperature sensors. Sensors use infrared technology to

measure the levels of CO

2

present in the space air.

The CO

2

sensors are all factory set for a range of 0 to

2000 ppm and a linear mA output of 4 to 20. Refer to the

instructions supplied with the CO

2

sensor for electrical

requirements and terminal locations. See Fig. 38 for

typical CO

2

sensor wiring schematic.

To accurately monitor the quality of the air in the

conditioned air space, locate the sensor near a return--air

grille (if present) so it senses the concentration of CO

2

leaving the space. The sensor should be mounted in a

location to avoid direct breath contact.

Do not mount the IAQ sensor in drafty areas such as near

supply ducts, open windows, fans, or over heat sources.

Allow at least 3 ft (0.9 m) between the sensor and any

corner. Avoid mounting the sensor where it is influenced

by the supply air; the sensor gives inaccurate readings if

the supply air is blown directly onto the sensor or if the

supply air does not have a chance to mix with the room air

before it is drawn into the return airstream.

Wiring the Indoor Air Quality Sensor: For each sensor,

use two 2--conductor 18 AWG (American Wire Gage)

twisted--pair cables (unshielded) to connect the separate

isolated 24 vac power source to the sensor and to connect

the sensor to the control board terminals.

To connect the sensor to the control, identify the positive

(4 to 20 mA) and ground (SIG COM) terminals on the

sensor. See Fig. 38. Connect the 4--20 mA terminal to

RTU--MP J4--2 and connect the SIG COM terminal to

RTU--MP J4--3. See Fig. 53.

SEN

COM

J4-2

J4-3

IAQ Sensor

24 VAC

C08462

Fig. 53 -- RTU--MP / Indoor CO

2

Sensor

(33ZCSENCO2) Connections

Outdoor Air Quality Sensor

(PNO 33ZCSENCO2 plus weatherproof enclosure) —

The outdoor air CO

2

sensor is designed to monitor carbon

dioxide (CO

2

) levels in the outside ventilation air and

interface with the ventilation damper in an HVAC system.

The OAQ sensor is packaged with an outdoor cover. See

Fig. 40. The outdoor air CO

2

sensor must be located in the

economizer outside air hood.

Wiring the Outdoor Air CO

2

Sensor — A dedicated power

supply is required for this sensor. A two--wire cable is

required to wire the dedicated power supply for the sensor.

The two wires should be connected to the power supply

and terminals 1 and 2.

To connect the sensor to the control, identify the positive

(4 to 20 mA) and ground (SIG COM) terminals on the

OAQ sensor. See Fig. 38. Connect the 4 to 20 mA

terminal to RTU--MP J4--5. Connect the SIG COM

terminal to RTU--MP J4--6.

SEN

COM

J4-5

J4-6

OAQ Sensor/RH Sensor

24 VAC

C08463

Fig. 54 -- RTU--MP / Outdoor CO

2

Sensor

(33ZCSENCO2) Connections

On 50HCQ units equipped with factory--installed Smoke

Detector(s), the smoke detector controller implements the

unit shutdown through its NC contact set connected to the

unit’s CTB input. The FSD function is initiated via the

smoke detector’s Alarm NO contact set. The RTU--MP

controller communicates the smoke detector’s tripped

status to the BAS building control. See Fig. 49, the

RTU--MP system control wiring schematic.

The

Fire

Shutdown

Switch

configuration,

MENU

Config

Inputs

input

5,

identifies

the

normally open status of this input when there is no fire

alarm.

Connecting Discrete Inputs —

Filter Status: The filter status accessory is a

field--installed accessory. This accessory detects plugged

filters. When installing this accessory, the unit must be

configured

for

filter

status

by

setting

MENU

Config

Inputs

input 3, 5, 8, or 9 to Filter

Status and normally open (N/O) or normally closed (N/C).

Input 8 or 9 is recommended for easy of installation. Refer

to Fig. 47 and Fig. 49 for wire terminations at J5.

Fan Status: The fan status accessory is a field--installed

accessory. This accessory detects when the indoor fan is

blowing air. When installing this accessory, the unit must

be

configured

for

fan

status

by

setting

MENU

Config

Inputs

input 3, 5, 8, or 9 to Fan

Status and normally open (N/O) or normally closed (N/C).

50H

C

Q

A