Carrier 33ZCVAVTRM Specifications download pdf (Page 144)

Enthalpy Switch/Receiver — The accessory en-

thalpy switch/receiver (33CSENTHSW) senses temperature

and humidity of the air surrounding the device and calculates

the enthalpy when used without an enthalpy sensor. The relay is

energized when enthalpy is high and deenergized when en-

thalpy is low (based on ASHRAE [American Society of Heat-

ing, Refrigeration, and Air Conditioning Engineers] 90.1 crite-

ria). If an accessory enthalpy sensor (33CSENTSEN) is at-

tached to the return air sensor input, then differential enthalpy is

calculated. The relay is energized when the enthalpy detected by

the return air enthalpy sensor is less than the enthalpy at the en-

thalpy switch/receiver. The relay is deenergized when the en-

thalpy detected by the return air enthalpy sensor is greater than

the enthalpy at the enthalpy switch/receiver (differential en-

thalpy control). See Fig. 22 and 23.

OUTDOOR ENTHALPY CONTROL (Fig. 24) — Outdoor

enthalpy control requires only an enthalpy switch/receiver

(33CSENTHSW). The enthalpy switch/receiver is mounted in

the outdoor air inlet and calculates outdoor air enthalpy. The

enthalpy switch/receiver energizes the relay output when the

outdoor enthalpy is above 28 BTU/lb OR dry bulb tempera-

ture is above 75 F and is deenergized when the outdoor

enthalpy is below 27 BTU/lb AND dry bulb temperature is

below 74.5 F. The relay output is wired to the unit economizer

which will open or close depending on the output of the

switch.

NOTE: The enthalpy calculation is done using an average alti-

tude of 1000 ft above sea level.

Mounting

— Mount the enthalpy switch/receiver in a location

where the outdoor air can be sampled (such as the outdoor air

intake). The enthalpy switch/receiver is not a NEMA 4 enclo-

sure and should be mounted in a location that is not exposed to

outdoor elements such as rain or snow. Use two field-supplied

no. 8 x

-in. TEK screws. Insert the screws through the holes

in the sides of the enthalpy switch/receiver.

Wiring

— Carrier recommends the use of 18 to 22 AWG

twisted pair or shielded cable for all wiring. All connections

must be made with

-in. female spade connectors.

A 24-vac transformer is required to power the enthalpy

switch/receiver; as shown in Fig. 24, the PremierLink™ board

provides 24 vac. Connect the GND and 24-vac terminals on the

enthalpy switch/receiver to the terminals on the transformer.

On some applications, the power from the economizer harness

can be used to power the enthalpy switch/receiver. To power

the enthalpy switch/receiver from the economizer harness, con-

nect power of the enthalpy switch/receiver to the red and

brown wires (1 and 4) on the economizer harness.

For connection to rooftop units with PremierLink™ control,

connect the LOW Enthalpy terminal on the enthalpy switch/re-

ceiver to J4 — pin 2 of the PremierLink control on the HVAC

(Heating, Ventilation, and Air Conditioning) unit. The switch

can be powered through the PremierLink control board if de-

sired. Wire the 24-vac terminal on the enthalpy switch/receiver

to J4 — pin 1 on the PremierLink control. Wire the GND ter-

minal on the enthalpy switch/receiver to J1 — pin 2 on the Pre-

mierLink control. The HI Enthalpy terminal is not used. See

Fig. 24.

DIFFERENTIAL ENTHALPY CONTROL (Fig. 25) —

Differential enthalpy control requires both an enthalpy switch/

receiver (33CSENTHSW) and an enthalpy sensor

(33CSENTSEN). The enthalpy switch/receiver is mounted in

the outdoor air inlet and calculates outdoor air enthalpy. The

enthalpy sensor is mounted in the return airstream and calcu-

lates the enthalpy of the indoor air.

The enthalpy switch/receiver energizes the HI Enthalpy re-

lay output when the outdoor enthalpy is greater than the indoor

enthalpy. The LOW Enthalpy terminal is energized when the

outdoor enthalpy is lower than the indoor enthalpy. The relay

output is wired to the unit economizer which will open or close

depending on the output of the switch.

NOTE: The enthalpy calculation is done using an average alti-

tude of 1000 ft above sea level.

Mounting

— Mount the enthalpy switch/receiver in a location

where the outdoor air can be sampled (such as the outdoor air

intake). The enthalpy switch/receiver is not a NEMA 4 enclo-

sure and should be mounted in a location that is not exposed to

outdoor elements such as rain, snow, or direct sunlight. Use

two field-supplied no. 8 x

-in. TEK screws. Insert the screws

through the holes in the sides of the enthalpy switch/receiver.

Fig. 22 — Enthalpy Switch/Receiver Dimensions

Fig. 23 — Enthalpy Sensor Dimensions

(33CSENTSEN)

1 2 ... 139 140 141 142 143 144 145 146 147 148 149 ... 315 316

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Carrier 33ZCVAVTRM Specifications Page 144

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