MORNING WARM-UP (VAV Only) (Stand-Alone Opera- tion) Ð When the unit operates in stand-alone mode, morn- ing warm-up occurs when the unit is energized in Occupied mode and return-air temperature (RAT) is below 68 F. Warm-up will not terminate until the RAT reaches 68 F. The heat in- terlock relay output is energized during morning warm-up. (A ®eld-installed 24-vdc heat interlock relay is required.) The output will be energized until the morning warm-up cycle is complete. Refer to Fig. 42 for heat interlock relay wiring.

SPACE TEMPERATURE RESET SENSOR (VAV Only) Ð An accessory space temperature sensor wired to terminals T1 and T2 on the control module is required. Space tem- perature reset is used to reset the supply-air temperature set point of a VAV system higher, as the space temperature falls below the Occupied Cool set point. As the space tempera- ture falls below the Occupied Cool set point, the supply-air temperature will be reset upward as a function of the reset ratio. (Default is 3.) Reset ratio is expressed in degrees change

in supply-air temperature per degree of space temperature change. A reset limit will exist which will limit the maxi- mum number of degrees the supply-air temperature may be raised. (Default is 10 F.) Both the reset ratio and the reset limit are user de®nable. The sequence of operation is as follows:

1.The on/off status of the unit supply fan is determined.

2.If the fan is ``on,'' the sequence will check if the system is occupied.

3.If the system is occupied, the sequence will determine if the reset option is enabled.

4.If the reset option is enabled, the sequence will read the space temperature and compare it to the Occupied Cool set point. If the temperature is below the Occupied Cool set point, the algorithm will compute the reset value and compare this value against the reset limit. If it is greater than the reset limit, the sequence will use the reset limit as the reset value.

CB4

3.2 AMPS

BASE MODULE

CONTROL BOARD

INDOOR FAN RELAY COM

T

30

T29

T

28

TRAN2

B COM

SECONDARY

24 VOLT

 

LEGEND

CB

Ð Circuit Breaker

COM

Ð Common

HIR

Ð

Heat Interlock Relay

T

Ð

Terminal

TRAN Ð Transformer

HIR

FIELD

INSTALLED

(HN61KK040)

(24V, 9.5VA)

Fig. 42 Ð Heat Interlock Relay Wiring

BASE MODULE

CONTROL BOARD

(+) T11

(–) T12

LEGEND

T Ð Terminal

4-20 mA

INPUT

FIELD

SUPPLIED

INPUT DEVICE

mA INPUT

DEG. F RESET

4

0.00

5

1.25

6

2.50

7

3.75

8

5.00

9

6.25

10

7.50

11

8.75

12

10.00

13

11.25

14

12.50

15

13.75

16

15.00

17

16.25

18

17.50

19

18.75

20

20.00

NOTE: The 4 to 20 mA input is a ®eld-supplied non-

Carrier EMS (Energy Management System) device.

Fig. 43 Ð Space Temperature Reset Wiring

42

Page 41 Page 43
Page 42
Image 42
Carrier EK, 48EJ, EW, EY024-048 installation instructions Com, Hir, DEG. F Reset
Page 41 Page 43

EW, EY024-048, EK, 48EJ specifications

The Carrier 48EJ, 48AW, 48EK, 48AJ, and 48EY024-068 are cutting-edge rooftop air conditioning units designed for commercial applications. These models are renowned for their reliability, energy efficiency, and innovative technologies aimed at providing optimal indoor comfort.

One of the standout features of these units is their advanced cooling and heating capabilities. They employ a multi-stage compressor system that allows for precise temperature control, accommodating various load requirements. This flexibility is particularly beneficial in commercial settings where the cooling load can fluctuate throughout the day.

Energy efficiency is paramount in today’s environmental landscape, and Carrier has ensured that these models meet stringent efficiency standards. They incorporate high-efficiency scroll compressors, which significantly reduce energy consumption while delivering powerful performance. The units are also equipped with variable speed fans that adjust airflow based on demand, further optimizing energy use.

In terms of construction, these rooftop units feature a robust design that enhances durability and longevity. The cabinet is constructed to withstand harsh weather conditions, ensuring reliable performance year-round. Additionally, the units are equipped with corrosion-resistant coatings, particularly useful in coastal environments where salt exposure can be a concern.

The Carrier 48EJ, 48AW, 48EK, 48AJ, and 48EY models utilize advanced controls and connectivity features, allowing for easy integration into building management systems. This connectivity enables remote monitoring and control, facilitating quick response to changing conditions and simplifying maintenance tasks.

Noise reduction is another key characteristic of these models. They are designed with sound-absorbing insulation and low-noise fan blades to ensure quiet operation, making them suitable for noise-sensitive environments such as schools and hospitals.

These units are also available with various options for air filtration and dehumidification. The use of high-efficiency air filters enhances indoor air quality by trapping dust, pollen, and other airborne particles. Enhanced dehumidification capabilities ensure that spaces remain comfortable even in humid conditions.

In conclusion, the Carrier 48EJ, 48AW, 48EK, 48AJ, and 48EY024-068 rooftop units are engineered to offer exceptional performance, energy efficiency, and durability. With their advanced technologies and user-friendly features, they stand out as reliable solutions for meeting diverse commercial cooling and heating needs, making them a popular choice for many businesses.
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