Carrier WeatherMaker 50KCQ A04 Series Service And Maintenance Instructions page 41

Occupancy Control
The factory default configuration for the EconoMi$er IV con-
trol is occupied mode. Occupied status is provided by the black
jumper from terminal TR to terminal N. When unoccupied
mode is desired, install a field-supplied timeclock function in
place of the jumper between TR and N. When the timeclock
contacts are closed, the EconoMi$er IV control will be in occu-
pied 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 ventila-
tion, there are some equipment selection criteria which should
be considered. When selecting the heat capacity and cool ca-
pacity of the equipment, the maximum ventilation rate must be
evaluated for design conditions. The maximum damper posi-
tion 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 fol-
lowing 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 oc-
cupancy. A proportional-anticipatory strategy will cause the
fresh air supplied to increase as the room CO
even though the CO set point has not been reached. By the time
2
the CO level reaches the set point, the damper will be at maxi-
2
mum ventilation and should maintain the set point.
In order to have the CO sensor control the economizer damper
2
in this manner, first determine the damper voltage output for
minimum or base ventilation. Base ventilation is the ventila-
tion required to remove contaminants during unoccupied peri-
ods. The following equation may be used to determine the per-
cent of outside air entering the building for a given damper po-
sition. For best results, there should be at least a 10 degree
difference in outside and return-air temperatures.
OA
(T x ) + (T
O
100
T = Outdoor-Air Temperature
O
OA = Percent of Outdoor Air
T = Return-Air Temperature
R
RA = Percent of Return Air
T = Mixed-Air Temperature
M
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 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. 65
to determine the maximum setting of the CO
ample, an 1100 ppm set point relates to a 15 cfm per person de-
sign. Use the 1100 ppm curve on Fig. 65 to find the point when
the CO sensor output will be 6.7 volts. Line up the point on
2
thegraph with the left side of the chart to determine that the
range configuration for the CO
The EconoMi$er IV controller will output the 6.7 volts from
the CO sensor to the actuator when the CO
2
the space is at 1100 ppm. The DCV set point may be left at 2
volts since the CO sensor voltage will be ignored by the
2
EconoMi$er IV controller until it rises above the 3.6 volt set-
ting of the minimum position potentiometer.
level increases
2
RA
x ) = T
R M
100
sensor. For ex-
2
sensor should be 1800 ppm.
2
concentration in
2
Once the fully occupied damper position has been determined,
set the maximum damper demand control ventilation potenti-
ometer 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.
CO Sensor Configuration
2
The CO sensor has preset standard voltage settings that can be
2
selected anytime after the sensor is powered up. (See
Table 15.)
Use setting 1 or 2 for Carrier equipment. (See Table 15.)
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 15 — EconoMi$er IV Sensor Usage
APPLICATION
Outdoor Air Dry
Bulb
Differential Dry
Bulb
Single Enthalpy
Differential
Enthalpy
CO for DCV
2
Control using a
wall-mounted
CO sensor
2
CO for DCV
2
33ZCSENCO2†
Control using a
duct-mounted
33ZCASPCO2**
CO sensor
2
* CRENTDIF004A00 and CRTEMPSN002A00 accessories are used on
many different base units. As such, these kits may contain parts that will
not be needed for installation.
† 33ZCSENCO2 is an accessory CO
** 33ZCASPCO2 is an accessory aspirator box required for duct-
mounted applications.
†† CRCBDIOX005A00 is an accessory that contains both 33ZCSEN-
CO2 and 33ZCASPCO2 accessories.
3. Use the Up/Down button to select the preset number. (See
Table 15.)
4. Press Enter to lock in the selection.
5. Press Mode to exit and resume normal operation.
The custom settings of the CO
after the sensor is energized. Follow the steps below to change
the non-standard settings:
1. Press Clear and Mode buttons. Hold at least 5 seconds
until the sensor enters the Edit mode.
2. Press Mode twice. The STDSET Menu will appear.
3. Use the Up/Down button to toggle to the NONSTD menu
and press Enter.
4. Use the Up/Down button to toggle through each of the
nine variables, starting with Altitude, until the desired set-
ting is reached.
5. Press Mode to move through the variables.
6. Press Enter to lock in the selection, then press Mode to
continue to the next variable.
Dehumidification of Fresh Air with DCV (Demand Con-
trolled Ventilation) Control
If normal rooftop heating and cooling operation is not adequate
for the outdoor humidity level, an energy recovery unit and/or
a dehumidification option should be considered.
ECONOMI$ER IV PREPARATION
This procedure is used to prepare the EconoMi$er IV for trou-
bleshooting. No troubleshooting or testing is done by perform-
ing the following procedure.
41
ECONOMI$ER WITH OUTDOOR AIR
DRY BULB SENSOR
Accessories Required
None. The outdoor-air dry bulb sensor
is factory-installed.
CRTEMPSN002A00*
HH57AC078
HH57AC078 and CRENTDIF004A00*
33ZCSENCO2
O
and CRCBDIOX005A00††
R
sensor.
2
sensor can be changed anytime
2