20
Do not run sensor or relay wires in the same conduit or race-
way with Class 1 AC or DC service wiring. Do not abrade, cut,
or nick the outer jacket of the cable. Do not pull or draw cable
with a force that may harm the physical or electrical properties.
Avoid splices in any control wiring.
Perform the following steps to connect the SAT sensor to
the zone controller:
1. Locate the opening in the control box. Pass the sensor
probe through the hole.
2. Drill or punch a
1
/
4
-in. hole in the duct
downstream
of the
unit, at a location that conforms to the requirements
shown in Fig. 23.
3. Use two field-supplied, self-drilling screws to secure the
sensor probe to the duct. Use field-supplied bushings as
spacers when installing the sensor probe in a duct 6 in. or
less in diameter.
Perform the following steps if state or local code requires
the use of conduit, or if your installation requires a cable length
of more than 8 ft:
1. Remove the center knockout from a field-supplied 4 x
2-in. junction box and secure the junction box to the duct
at the location selected for the sensor probe.
2. Drill a
1
/
2
-in. hole in the duct through the opening in the
junction box.
3. Connect a
1
/
2
-in. nominal field-supplied conduit between
the zone controller enclosure and the junction box.
4. Pass the sensor probe wires through the conduit and insert
the probe in the duct. Use field-supplied bushings as
spacers when installing the sensor probe in a duct 6 in. or
less in diameter.
5. Secure the probe to the duct with two field-supplied self-
drilling screws.
6. If extending cable length beyond 8 ft, use plenum rated,
20 AWG (American Wire Gage), twisted pair wire.
7. Connect the sensor leads to the zone controller’s wiring
harness terminal board at the terminals labeled SAT and
GND.
8. Neatly bundle and secure excess wire.
INDOOR AIR QUALITY SENSOR INSTALLATION —
The indoor air quality (IAQ) sensor accessory monitors carbon
dioxide levels. This information is used to modify the position
of the outdoor air dampers to admit more outdoor air as
required to provide the desired ventilation rate. Two types of
sensors are supplied. The wall sensor can be used to monitor
the conditioned air space; the duct sensor monitors the return
air duct. Both wall and duct sensors use infrared technology to
measure the levels of CO
2
present in the air. The wall sensor is
available with or without an LCD (liquid crystal display) read-
out to display the CO
2
level in ppm. See Fig. 24.
The sensor part number is 33ZCSENCO2. To mount the
sensor, refer to the installation instructions shipped with the
accessory kit.
The CO
2
sensors (33ZCSENCO2) factory set for a range of 0
to 2000 ppm and a linear voltage output of 0 to 10 vdc. Figure 25
shows ventilation rates for various CO
2
set points when outside
air with a typical CO
2
level of 350 ppm is used. Refer to the
instructions supplied with the CO
2
sensor for electrical require-
ments and terminal locations. The zone controller requires a
24 vac, 25 va transformer to provide power to the sensor.
To convert the CO
2
sensor into a duct-mounted CO
2
sensor,
the duct-mounted aspirator (33ZCASPCO2) will need to be
purchased.
To accurately monitor the quality of the air in the condi-
tioned air space, locate the sensor near the return air grille so it
senses the concentration of CO
2
leaving the space. The sensor
should be mounted in a location to avoid direct breath contact.
Do not mount the space sensor in drafty areas such as near
supply ducts, open windows, fans, or over heat sources. Allow
at least 3 ft between the sensor and any corner. Avoid mounting
the sensor where it is influenced by the supply air; the sensor
gives inaccurate readings if the supply air is blown directly onto
the sensor or if the supply air does not have a chance to mix with
the room air before it is drawn into the return air stream.
To accurately monitor the quality of the air in the return air
duct, locate the sensor at least 6 in. upstream or 15 in.
downstream of a 90-degree turn in the duct. The downstream
location is preferred. Mount the sensor in the center of the duct.
IMPORTANT: If the sensor is mounted in the return-air
duct, readjust the mixed-air dampers to allow a small
amount of air to flow past the return-air damper when-
ever the mixing box is fully open to the outside air. If the
damper is not properly adjusted to provide this mini-
mum airflow, the sensor may not detect the indoor-air
quality during the economizer cycle.
ZC
AIR
TERMINAL
UNIT
OCTOPUS
HEAT
SAT
2 FT. MIN.
PRIMARY
AIR INLET
ZC
AIR
TERMINAL
UNIT
HEAT
SAT
2 FT. MIN.
PRIMARY
AIR INLET
ZC —
Zone Controller
Fig. 23 — Supply Air Temperature Probe
(Part No. 33ZCSENSAT) Locations
UNIT WITH ELECTRIC REHEAT
UNIT WITH OCTOPUS
DRILL 1/4" HOLE
IN TOP OF DUCT
AND LET SENSOR
HANG DOWN
ALTERNATE INSTALLATION
LOCATION INSIDE OF DUCT
SUPPLY DUCT
Fig. 22 — DAT Installation Location
Содержание 3V VVT 33ZCVVTZC-01
Страница 59: ......
