Bryant 551B, 551C installation instructions CO2 Sensor Configuration, EconoMi$er IV Control

A proportional anticipatory strategy should be taken with the following conditions: a zone with a large area, varied occupancy, and equipment that cannot exceed the required ventilation rate at design conditions. Exceeding the required ventilation rate means the equipment can condition air at a maximum ventilation rate that is greater than the required ventilation rate for maximum occupancy. A proportional-anticipatory strategy will cause the fresh air supplied to increase as the room CO2 level increases even though the CO2 set point has not been reached. By the time the CO2 level reaches the set point, the damper will be at maximum ventilation and should maintain the set point.

In order to have the CO2 sensor control the economizer damper in this manner, first determine the damper voltage output for minimum or base ventilation. Base ventilation is the ventilation required to remove contaminants during unoccupied periods. The following equation may be used to determine the percent of outside-air entering the building for a given damper position. For

N1

N

P1

P

T1

T

AQ1

AQ

SO+

SO

SR+

SR

	EXH	TR	TR1
	Set
2V	10V
EXH		24	24 Vac
		Vac	COM
	Min	HOT	_
	Pos	+
Open
	DCV	1	2
	Max
2V	10V
DCV			5
	DCV		4
	Set	3
2V	10V
Free		EF	EF1
Cool
B	C
A	D

551B,C

best results there should be at least a 10 degree difference in outside and return-air temperatures.

(TO x 100OA ) + (TR x 100RA ) =TM

TO = Outdoor-Air Temperature OA = Percent of Outdoor Air TR = Return-Air Temperature RA = Percent of Return Air TM = Mixed-Air Temperature

Once base ventilation has been determined, set the minimum damper position potentiometer to the correct position.

The same equation can be used to determine the occupied or maximum ventilation rate to the building. For example, an output of 3.6 volts to the actuator provides a base ventilation rate of 5% and an output of 6.7 volts provides the maximum ventilation rate of 20% (or base plus 15 cfm per person). Use Fig. 38 to determine the maximum setting of the CO2 sensor. For example, a 1100 ppm set point relates to a 15 cfm per person design. Use the 1100 ppm curve on Fig. 38 to find the point when the CO2 sensor output will be 6.7 volts. Line up the point on the graph with the left side of the chart to determine that the range configuration for the CO2 sensor should be 1800 ppm. The EconoMi$er IV controller will output the 6.7 volts from the CO2 sensor to the actuator when the CO2 concentration in the space is at 1100 ppm. The DCV set point may be left at 2 volts since the CO2 sensor voltage will be ignored by the EconoMi$er IV controller until it rises above the 3.6 volt setting of the minimum position potentiometer.

Once the fully occupied damper position has been determined, set the maximum damper demand control ventilation potentiometer to this position. Do not set to the maximum position as this can result in over-ventilation to the space and potential high-humidity levels.

CO2 Sensor Configuration

The CO2 sensor has preset standard voltage settings that can be selected anytime after the sensor is powered up. (See Table 7.)

C06038

Fig. 37 ---EconoMi$er IV Control

CO2 SENSOR MAX RANGE SETTING

	6000
(ppm)	5000
CONFIGURATION	4000						800 ppm
	3000						900 ppm
							1000 ppm
	2000						1100 ppm
RANGE	1000
	0
	2	3	4	5	6	7	8
	DAMPER VOLTAGE FOR MAX VENTILATION RATE

C06039

Fig. 38 ---CO2 Sensor Maximum Range Setting

Use setting 1 or 2 for Bryant equipment. (See Table 7.)

1.Press Clear and Mode buttons. Hold at least 5 seconds until the sensor enters the Edit mode.

2.Press Mode twice. The STDSET Menu will appear.

3.Use the Up/Down button to select the preset number. (See Table 7.)

4.Press Enter to lock in the selection.

5.Press Mode to exit and resume normal operation.

The custom settings of the CO2 sensor can be changed anytime after the sensor is energized. Follow the steps below to change the non-standard settings:

1.Press Clear and Mode buttons. Hold at least 5 seconds until the sensor enters the Edit mode.

2.Press Mode twice. The STDSET Menu will appear.

3.Use the Up/Down button to toggle to the NONSTD menu and press Enter.

4.Use the Up/Down button to toggle through each of the nine variables, starting with Altitude, until the desired setting is reached.

5.Press Mode to move through the variables.

6.Press Enter to lock in the selection, then press Mode to continue to the next variable.

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