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Installation (continued)
4. Install and Wire the Discharge Air Temperature Sensor
CAUTION
As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
CAUTION
Before attempting to perform any service or
maintenance, turn the electrical power to unit OFF
at disconnect switch.
The tip of the sensor must be located in a region of fully
mixed supply of air before the take-offs (not in a dead
air space) in order for the system to work correctly.
a. Wire discharge air temperature probe to control
center using thermostat wire. Note that the
temperature sensor is not polarity sensitive.
b. Be sure that the tip of the sensor is located at least
15 inches from the top of the indoor coil if using a
furnace, or at least 15 inches from the top of the
electric heat section if using a coil blower. Mount
the sensor in the discharge plenum, 1/3 of the
depth (D/3) of the plenum (D) from the front (the
front is the side with the furnace or CB access
doors), and centered side to side. Move the
adjustable bracket along the length of the
discharge air sensor to achieve proper sensor tip
location (tip of sensor to be located at W ÷ 2).
The sensor can be mounted from any side of the
plenum, as long as the tip of the sensor is in the
correct position. See Figure 3.
IMPORTANT: The discharge air sensor is required.
If a short or open circuit is detected between the
Discharge Air Sensor terminals, the control panel
will only respond to Zone 1 and the dampers will
stay in their normal position.
5. Install the system transformer – DO NOT USE the
HVAC equipment transformer to power the control
panel. Refer to the instructions provided with the
transformer.
18 AWG thermostat wire minimum recommended.
FIGURE 3 – DISCHARGE AIR SENSOR LOCATION
Sizing the Transformer:
The system requires approximately 10 VA for the
control panel and thermostats and 10 VA for each
damper. The size of the transformer will depend on the
greatest number of dampers that could be energized
at any given time (at least one zone's dampers will not
be energized during a heating or cooling call when
using power close, spring open dampers). The size of
the transformer must not exceed 75VA. If the value is
greater than 75VA, some dampers will need to be
powered by a separate transformer – refer to Field
Wiring Damper Diagram 2 on page 10.
For instance, if you have 3 dampers, then you would
require 10VA for the system, 20VA (10VA X 2) for the
dampers for a total of 30VA, so catalog number 10P17
would be an adequate transformer size at 40VA.
TABLE 1 – TRANSFORMERS
Part Number
10P17
10P87
12P61
83P74
The transformers listed in this chart include a plate
mount for a 4" square electrical box.
Page 4
15"
D/3
W
D
FRONT
Size
Voltage Description
40VA
120/208/240V-24V
50VA
120/208/240V-24V
75VA
120/208/240V-24V
4" Square Electrical Box
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