Carrier 50TCA04-A07 appendix Demand Control Ventilation DCV, CO2 Sensor Configuration

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timeclock function in place of the jumper between TR and N. (See Fig. 52.) When the timeclock contacts are closed, the EconoMi$er IV control will be in occupied mode. When the timeclock contacts are open (removing the 24-v signal from terminal N), the EconoMi$er IV will be in unoccupied mode.

Demand Control Ventilation (DCV)

When using the EconoMi$er IV for demand controlled ventilation, there are some equipment selection criteria which should be considered. When selecting the heat capacity and cool capacity of the equipment, the maximum ventilation rate must be evaluated for design conditions. The maximum damper position must be calculated to provide the desired fresh air.

Typically the maximum ventilation rate will be about 5 to 10% more than the typical cfm required per person, using normal outside air design criteria.

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 setpoint has not been reached. By the time the CO2 level reaches the setpoint, the damper will be at maximum ventilation and should maintain the setpoint.

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 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. 64 to determine the maximum setting of the CO2 sensor. For example, an 1100 ppm setpoint relates to a 15 cfm per person design. Use the 1100 ppm curve on Fig. 64 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$er IV controller will output the 6.7 volts from the CO2 sensor to the actuator when the CO2 concentration in the space is at 1100 ppm. The DCV setpoint may be left at 2 volts since the CO2 sensor voltage will be ignored by the EconoMi$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 12.)

Use setting 1 or 2 for Carrier equipment. (See Table 12.)

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.

Table 12 – EconoMi$er IV Sensor Usage

	ECONOMI$ER IV WITH OUTDOOR AIR
APPLICATION		DRY BULB SENSOR
		Accessories Required
Outdoor Air	None. The outdoor air dry bulb sensor
Dry Bulb		is factory installed.
Differential		CRTEMPSN002A00*
Dry Bulb
Single Enthalpy			HH57AC078
Differential			HH57AC078
					and
Enthalpy
		CRENTDIF004A00*
CO2 for DCV
Control using a			33ZCSENCO2
Wall-Mounted
CO2 Sensor
CO2 for DCV	33ZCSENCO2†			O
Control using a	and					CRCBDIOX005A00††
Duct-Mounted				R
	33ZCASPCO2**
CO2 Sensor

*CRENTDIF004A00 and CRTEMPSN002A00 accessories are used on many different base units. As such, these kits may contain parts that will not be needed for installation.

† 33ZCSENCO2 is an accessory CO2 sensor.

**33ZCASPCO2 is an accessory aspirator box required for duct- mounted applications.

†† CRCBDIOX005A00 is an accessory that contains both 33ZCSENCO2 and 33ZCASPCO2 accessories.

3.Use the Up/Down button to select the preset number. (See Table 12.)

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.

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