Carrier 48TM016-028

DIFFERENTIAL ENTHALPY CONTROL (Fig. 30) —

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

relay 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

altitude 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 3/4-in. TEK screws. Insert the screws

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

Mount the enthalpy sensor in a location where the indoor air

can be sampled (such as the return air duct). The enthalpy

sensor is not a NEMA 4 enclosure 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 3/4-in. TEK screws. Insert

the screws through the holes in the sides of the enthalpy sensor.

Wiring — Carrier recommends the use of 18 to 22 AWG

twisted pair or shielded cable for all wiring. All connections

must be made with 1/4-in. female spade connectors.

The PremierLink™ board provides 24-vac to power the

enthalpy switch/receiver. 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 econ-

omizer harness, connect power of the enthalpy switch/receiver

to the red and brown wires (1 and 4) on the economizer

harness.

Connect the LOW Enthalpy terminal on the enthalpy

switch/receiver to J4 — pin 2 of the PremierLink control on the

HVAC unit. The switch can be powered through the Premier-

Link control board if desired. Wire the 24VAC terminal on the

enthalpy switch/receiver to J4 — pin 1 on the PremierLink

control. Wire the GND terminal on the enthalpy switch/

receiver to J1 — pin 2 on the PremierLink control. The HI

Enthalpy terminal is not used. See Fig. 29.

Connect the 4-20 mA IN terminal on the enthalpy switch/

receiver to the 4-20 mA OUT terminal on the return air

enthalpy sensor. Connect the 24-36 VDC OUT terminal on the

enthalpy switch/receiver to the 24-36 VDC IN terminal on the

return air enthalpy sensor. See Fig. 30.

Enthalpy Switch/Receiver Jumper Settings —Therearetwo

jumpers. One jumper determines the mode of the enthalpy

switch/receiver. The other jumper is not used. To access the

jumpers, remove the 4 screws holding the cover on the

enthalpy switch/receiver and then remove the cover. The

factory settings for the jumpers are M1 and OFF.

The mode jumper should be set to M2 for differential

enthalpy control. The factory test jumper should remain on

OFF or the enthalpy switch/receiver will not calculate enthalpy.

Enthalpy Sensor Jumper Settings — There are two jumpers.

One jumper determines the mode of the enthalpy sensor. The

other jumper is not used. To access the jumpers, remove the

4 screws holding the cover on the enthalpy sensor and then

remove the cover. The factory settings for the jumpers are M3

and OFF.

Fig. 30 — Differential Enthalpy Control Wiring

24 VAC OUTPUT FROM N/C CONTACT WHEN THE

OUTDOOR ENTHALPY IS LESS THAN THE

INDOOR ENTHALPY

(ENABLE ECONOMIZER)

24 VAC OUTPUT FROM N/O CONTACT WHEN THE

INDOOR ENTHALPY IS GREATER THAN THE

OUTDOOR ENTHALPY

24 VAC

SECONDARY

HI LOW GND 24

VAC

ENTHALPY 4-20

24-36

VDC

OUT

JUMPER SETTINGS FOR 33CSENTHSW

50%

100%

OFF

33CSENTHSW

JUMPER SETTINGS FOR 33CSENTSEN

50%

100%

OFF

33CSENTSEN

24-36

VDC

ORN

120 VAC

LINE VOLTAGE

4-20

OUT

LEGEND

N/C — Normally Closed

N/O — Normally Open