Minimum Position Control — There is a minimum damper position potentiometer on the EconoMi$er IV controller. See Fig. 28. The minimum damper position maintains the mini- mum airflow into the building during the occupied period.
When using demand ventilation, the minimum damper position represents the minimum ventilation position for VOC (volatile organic compounds) ventilation requirements. The maximum demand ventilation position is used for fully occu- pied ventilation.
When demand ventilation control is not being used, the minimum position potentimeter should be used to set the occu- pied ventilation position. The maximum demand ventilation position should be turned fully clockwise.
Adjust the minimum position potentiometer to allow the minimum amount of outdoor air, as required by local codes, to enter the building. Make minimum position adjustments with at least 10° F temperature difference between the outdoor and
1.Calculate the appropriate mixed air temperature using the following formula:
(TO x OA) + (TR x RA) = TM
TO =
As an example, if local codes require 10% outdoor air during occupied conditions,
(60 x .10) + (75 x .90) = 73.5 F
2.Disconnect the mixed air sensor from terminals T and T1.
3.Ensure that the
4.Connect 24 vac across terminals TR and TR1.
5.Carefully adjust the minimum position potentiometer until the measured mixed air temperature matches the calculated value.
6.Reconnect the mixed air sensor to terminals T and T1.
Remote control of the EconoMi$er IV damper is desirable when requiring additional temporary ventilation. If a
To control the minimum damper position remotely, remove the
Damper Movement — When the EconoMi$er IV board re- ceives initial power, it can take the damper up to 21/2 minutes before it begins to position itself. After the initial positioning, subsequent changes to damper position will take up to 30 sec- onds to initiate. Damper movement from full open to full closed (or vice versa) takes 21/2 minutes.
Thermostats — The EconoMi$er IV control works with con- ventional thermostats that have a Y1 (cool stage 1), Y2 (cool stage 2), W1 (heat stage 1), W2 (heat stage 2), and G (fan). The EconoMi$er IV control does not support space temperature sensors like the T55 or T56. Connections are made at the ther- mostat terminal connection board located in the main control box.
Demand Control Ventilation — When using the Econo- Mi$er IV for demand control ventilation, there are some equip- ment 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 nor- mal 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 set point has not been reached. By the time the CO2 level reaches the set point, the damper will be at maximum ventila- tion 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 unoccu- pied periods. The following equation may be used to determine the percent of
(TO x OA) + (TR x RA) = TM
TO =
OA = Percent of Outdoor Air
TR =
RA = Percent of Return Air
TM =
Once base ventilation has been determined, set the mini- mum 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. 29 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. 29 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$er IV controller will output the 6.7 volts from the CO2 sensor to the actuator when the CO2 concentra- tion in the space is at 1100 ppm. The DCV set point may be left at 2 volts since the CO2 sensor voltage will be ignored by the EconoMi$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 deter- mined, set the maximum damper demand control ventilation potentiometer to this position. Do not set to the maximum position as this can result in
CO2 Sensor Configuration — The CO2 sensor has preset standard voltage settings that can be selected anytime after the sensor is powered up. See Table 29.
Use setting 1 or 2 for Carrier equipment. See Table 29.
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.
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