Carrier 48TM016-028

In order to have the CO2sensor control the economizer

damper in this manner, first determine the damper voltage out-

put 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 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= 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 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 out-

put of 3.6 volts to the actuator provides a base ventilation rate

of 5% and an output of 6.7 volts provides the maximum venti-

lation rate of 20% (or base plus 15 cfm per person). Use Fig. 43

to determine the maximum setting of the CO2sensor. For ex-

ample, a 1100 ppm set point relates to a 15 cfm per person de-

sign. Use the 1100 ppm curve on Fig. 43 to find the point when

the CO2sensor 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 CO2sensor should be 1800 ppm. The

EconoMi$erIV controller will output the 6.7 volts from the

CO2sensor to the actuator when the CO2concentration in the

space is at 1100 ppm. The DCV set point may be left at 2 volts

since the CO2sensor voltage will be ignored by the

EconoMi$erIV 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 posi-

tion as this can result in over-ventilation to the space and poten-

tial high-humidity levels.

CO2Sensor Configuration —TheCO

2sensor has preset

standard voltage settings that can be selected anytime after the

sensor is powered up. See Table 13.

Use setting 1 or 2 for Carrier equipment. See Table 13.

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 13.

4. Press Enter to lock in the selection.

5. Press Mode to exit and resume normal operation.

The custom settings of the CO2sensor can be changed any-

time 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 set-

ting 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.

Dehumidification of Fresh Air with DCV Control — Infor-

mation from ASHRAE indicates that the largest humidity load

on any zone is the fresh air introduced. For some applications,

a field-installed energy recovery unit can be added to reduce

the moisture content of the fresh air being brought into the

building when the enthalpy is high. In most cases, the normal

heating and cooling processes are more than adequate to re-

move the humidity loads for most commercial applications.

If normal rooftop heating and cooling operation is not ade-

quate for the outdoor humidity level, an energy recovery unit

and/or a dehumidification option should be considered.

Table 13 — CO2Sensor Standard Settings

LEGEND

ppm — Parts Per Million

(TOxOA )+(TRxRA )=T

100 100

SETTING EQUIPMENT OUTPUT

VENTILATION

RATE

(cfm/Person)

ANALOG

OUTPUT

CO2

CONTROL RANGE

(ppm)

OPTIONAL

RELAY SETPOINT

(ppm)

RELAY

HYSTERESIS

(ppm)

Interface with Standard

Building Control System

Proportional Any 0-10V

4-20 mA 0-2000 1000 50

2Proportional Any 2-10V

7-20 mA 0-2000 1000 50

3Exponential Any 0-10V

4-20 mA 0-2000 1100 50

Economizer

Proportional 15 0-10V

4-20 mA 0-1100 1100 50

5Proportional 20 0-10V

4-20 mA 0- 900 900 50

6Exponential 15 0-10V

4-20 mA 0-1100 1100 50

7Exponential 20 0-10V

4-20 mA 0- 900 900 50

8Health &Safety Proportional — 0-10V

4-20 mA 0-9999 5000 500

9Parking/Air Intakes/

Loading Docks Proportional — 0-10V

4-20 mA 0-2000 700 50