Carrier 48TM016-028 - Manual (Page 30)

30
In order to have the CO
2
sensor 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.
T
O
= Outdoor-Air Temperature
OA = Percent of Outdoor Air
T
R
= Return-Air Temperature
RA = Percent of Return Air
T
M
= 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 CO
2
sensor. 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 CO
2
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 CO
2
sensor should be 1800 ppm. The
EconoMi$erIV controller will output the 6.7 volts from the
CO
2
sensor to the actuator when the CO
2
concentration in the
space is at 1100 ppm. The DCV set point may be left at 2 volts
since the CO
2
sensor voltage will be ignored by the
EconoMi$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.
CO
2
Sensor Configuration — The CO
2
sensor 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 CO
2
sensor 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 — CO
2
Sensor Standard Settings
LEGEND
ppm — Parts Per Million
(T
O
x
OA
) + (TR x
RA
) = T
M
100 100
SETTING EQUIPMENT OUTPUT
VENTILATION
RATE
(cfm/Person)
ANALOG
OUTPUT
CO
2
CONTROL RANGE
(ppm)
OPTIONAL
RELAY SETPOINT
(ppm)
RELAY
HYSTERESIS
(ppm)
1
Interface with Standard
Building Control System
Proportional Any
0-10V
4-20 mA
0-2000 1000 50
2 Proportional Any
2-10V
7-20 mA
0-2000 1000 50
3 Exponential Any
0-10V
4-20 mA
0-2000 1100 50
4
Economizer
Proportional 15
0-10V
4-20 mA
0-1100 1100 50
5 Proportional 20
0-10V
4-20 mA
0- 900 900 50
6 Exponential 15
0-10V
4-20 mA
0-1100 1100 50
7 Exponential 20
0-10V
4-20 mA
0- 900 900 50
8 Health & Safety Proportional —
0-10V
4-20 mA
0-9999 5000 500
9
Parking/Air Intakes/
Loading Docks
Proportional —
0-10V
4-20 mA
0-2000 700 50