Bryant 604D--A Economizer Controller, Enthalpy Changeover Setpoints, 604D-- --A

12

CONTROL

CURVE

A

B

C

D

18 16 14

CONTROL POINT
APPROX ˚F (˚C)
AT 50% RH
73 (23)
70 (21)
67 (19)
63 (17)									DRY
						POUND
									34
					PER
						32
				BTU
			–		30
				28
26
	ENTHALPY
24
22
20
									55
								(13)
						50
						(10)				C
				45
							D
				(7)
		40
		(4)
	35
	(2)

40

AIR	38
36

65

(18)

60

(16)

A

B

		46
	44
42			80
			(27)
		75
		(24)
70
(21)
100	90	80
			70
			60

D C B

85	90	95	100	105	110
(29)	(32)	(25)	(38)	(41)	(43)

HUMIDITY	(%)
RELATIVE

50 40

30

20

10

A

N1		EXH	TR
N		Set
	2V	10V
P1	EXH		24
			Vac
P		Min	HOT
T1		Pos
T		Open
		DCV	1
		Max
	2V	10V
AQ+	DCV
AQ		DCV
SO+		Set	3
SO	2V	10V
SR+	Free		EF
	Cool
SR	B	C
	A	D

Fig. 43 - Economizer Controller

TR1

24Vac

COM

2

5

4

EF1

A09712

604D-- -- A

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) (36) (38) (41) (43)

APPROXIMATE DRY BULB TEMPERATURE — ˚F (˚C)

A09711

Fig. 41 - Enthalpy Changeover Setpoints

6000
5000
4000						800 ppm
3000						900 ppm
						1000 ppm
2000						1100 ppm
1000
0
2	3	4	5	6	7	8
						A09713

Fig. 42 - CO2 Sensor Maximum Range Setting

OUTDOOR ENTHALPY CHANGEOVER—For enthalpy control, accessory enthalpy sensor (part number HH57AC078) is required. Replace the standard outdoor dry bulb temperature sensor with the accessory enthalpy sensor in the same mounting location.

When the outdoor air enthalpy rises above the outdoor enthalpy changeover set point, the outdoor-air damper moves to its minimum position. The outdoor enthalpy changeover set point is set with the outdoor enthalpy set point potentiometer on the Economizer controller. The set points are A, B, C, and D. See Fig.

41.The factory-installed 620-ohm jumper must be in place across terminals SR and SR+ on the Economizer controller. See Fig. 43 and Fig. 44.

DIFFERENTIAL ENTHALPY CONTROL — For differential enthalpy control, the Economizer controller uses two enthalpy sensors (HH57AC078 and CRENTDIF004A00), one in the outside air and one in the return airstream. The Economizer controller compares the outdoor air enthalpy to the return air enthalpy to determine Economizer use. The controller selects the lower enthalpy air (return or outdoor) for cooling. For example, when the outdoor air has a lower enthalpy than the return air and is below the set point, the Economizer opens to bring in outdoor air for free cooling. Replace the standard outside air dry bulb temperature sensor with the accessory enthalpy sensor in the same mounting location. Mount the return air enthalpy sensor in the return air duct. See Fig. 40. When using this mode of changeover control, turn the enthalpy set point poten- tiometer fully clockwise to the D setting.

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 potentiometers to correspond to the DCV voltage output of the indoor air quality sensor at the user determined set point. See Fig. 42. If a separate field-supplied transformer is used to power the IAQ sensor, the sensor must not be grounded or the Economizer 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 power exhaust is installed). The set point is modified with the Exhaust Fan Set Point (EXH SET) potentiometer. See Fig. 44 for Wiring Diagram. The set point represents the damper position above which the exhaust fans will be turned on. When there is a call for exhaust, the Economizer controller provides a 45 ±15 second delay before exhaust fan activation to allow the dampers to open. This delay allows the damper to reach the appropriate position to avoid unnecessary fan overload.

MINIMUM POSITION CONTROL — There is a minimum damper position potentiometer on the Economizer controller. See Fig. 38 and 44. The minimum damper position maintains the minimum airflow into the building during the occupied period. When using demand ventilation, the minimum damper position represents the minimum ventilation position for VOC (volatile organic compound) ventilation requirements. The DCV Max potentiometer must be fully closed (CCW) to allow the Minimum Position potentiometer to function correctly.

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