Carrier EK, 48EJ, EW, EY024-048 Ð Heat Interlock Relay Wiring, Ð Space Temperature Reset Wiring

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