Bryant 580F operation manual Enthalpy Changeover Set Points

for cooling. For example, when the outdoor air has a lower enthalpy than the return air and is below the set point, the EconoMi$erIV opens to bring in outdoor air for free cooling.

Replace the standard outside air dry bulb temperature sen- sor with the accessory enthalpy sensor in the same mounting location. See Fig. 25. Mount the return air enthalpy sensor in the return airstream. See Fig. 30. The outdoor enthalpy changeover set point is set with the outdoor enthalpy set point potentiometer on the EconoMi$erIV controller. When using this mode of changeover control, turn the enthalpy set point potentiometer fully clockwise to the D setting.

NOTE: Remove 620-ohm resistor if differential enthalpy sen- sor is installed.

Indoor Air Quality (IAQ) Sensor Input

The IAQ input can be used for demand control ventilation control based on the level of CO2 measured in the space or return air duct.

Mount the accessory IAQ sensor according to manufacturer specifications. The IAQ sensor should be wired to the AQ and AQ1 terminals of the controller. Adjust the DCV potentiome- ters to correspond to the DCV voltage output of the indoor air quality sensor at the user-determined set point. See Fig. 33.

If a separate field-supplied transformer is used to power the IAQ sensor, the sensor must not be grounded or the EconoMi$erIV control board will be damaged.

Exhaust Set Point Adjustment

The exhaust set point will determine when the exhaust fan runs based on damper position (if accessory power exhaust is

installed). The set point is modified with the Exhaust Fan Set Point (EXH SET) potentiometer. See Fig. 28. The set point represents the damper position above which the exhaust fan will be turned on. When there is a call for exhaust, the EconoMi$erIV controller provides a 45 ± 15 sec- ond delay before exhaust fan activation to allow the dampers to open. This delay allows the damper to reach the appropri- ate position to avoid unnecessary fan overload.

Minimum Position Control

There is a minimum damper position potentiometer on the EconoMi$erIV controller. See Fig. 28. The minimum damper position maintains the minimum airflow into the building during the occupied period.

When using demand ventilation, the minimum damper posi- tion represents the minimum ventilation position for VOC (volatile organic compound) ventilation requirements. The maximum demand ventilation position is used for fully occu- pied ventilation.

When demand ventilation control is not being used, the min- imum position potentiometer should be used to set the occu- pied ventilation position. The maximum demand ventilation position should be turned fully clockwise.

Adjust the minimum position potentiometer to allow the minimum amount of outdoor air, as required by local codes, to enter the building. Make minimum position adjustments with at least 10° F temperature difference between the out- door and return-air temperatures.

85	90	95	100	105	110
(29)	(32)	(35)	(38)	(41)	(43)

CONTROL

CURVE

A

B

C

D

1 8

1 6

1 4

1 2

CONTROL POINT

APPROX. °F (°C)

AT 50% RH

73(23)

70(21)

67(19)

63(17)

												PO	U	N
											R
									P	E		32
								TU
						—	B			30
				LP	Y			28
			HA
		NT		26
	E		4
		2
2	2

2 0

50

(10)

45 D

(7)

40

(4)

35

(2)

						IR		40
			Y	A			3	8
		DR
D				3	6
	3	4

65

(18)

60

(16)

A

55

(13)B

C

4 4

42

70

(21)

1	0	0		0
			9

46

80

(27)

75

(24)

80 70

6 0

50

D C B A

4 0

REL A TIVE

3 0

				%	)
		Y	(
	IDIT
HUM

20

0 1

HIGH LIMIT

CURVE

35	40	45	50	55	60	65	70	75	80	85	90	95	100	105	110
(2)	(4)	(7)	(10)	(13)	(16)	(18)	(21)	(24)	(27)	(29)	(32)	(35)	(38)	(41)	(43)

APPROXIMATE DRY BULB TEMPERATURE— °F (°C)

Fig. 31 — Enthalpy Changeover Set Points

—21—