Reznor YDSA Unit Installation Manual - Manual (Page 28)

Form I-Y, P/N 273646R6, Page 28
7.5.2 Sensor Wiring
24V Field Control
Wiring Length and
Size Requirements
Total Wire Length Minimum Recommended Wire Size
150 ft (45M) #18 gauge shielded wire
250 ft (76M) #18 gauge shielded wire
350 ft (106M) #14 gauge shielded wire
Discharge Air
Temperature Sensor,
P/N 222753 - applies to
all installations
The manufacturer recommends for optimum temperature control performance that the
analog and digital inputs (CO
2
and air quality sensors) that are connected to the main
controller have a <3% wattage drop and be routed to the unit in one of the following
manners:
1) In separate conduits, isolated from 24 VAC controls and line voltage power to the
unit, OR
2) If the digital sensor wires are to be run in the same conduit as the 24 VAC control
wiring, the wiring MUST be shielded cable and bundled separately from the 24
VAC control wiring. The shield MUST be drained at the unit and taped on the
opposite end.
Comply with the digital control sensor wire gauge and length requirements in the table
below.
Maximum Sensor
Wire Length for
less than 1°F
Signal Error
Wire Gauge Maximum Sensor Wire Length (Digital Control)
14 AWG 800 ft (244M)
16 AWG 500 ft (152M)
18 AWG 310 ft (94M)
7.5.3 Field Wiring by
Control Option
Depending on which field-installed control option was ordered, the unit will operate in
response to a signal from the control. Dotted wires (lines) on the diagrams designate
field wiring. Factory wiring is shown as a solid line.
The discharge air temperature sensor is shipped with every unit and must be field
installed in the duct work. Placement of the discharge air sensor in the duct work is
critical to the correct operation of the system in both the cooling and heating modes.
Location is especially important when installing a unit with dual heat sections; refer to
the information in FIGURE 15 on page 22.
1. Determine the appropriate distance from the unit. Be sure there is sufficient
distance from the outlet to have a good mixture of discharge air temperature.
According to the latest edition of AMCA Standard 201, in straight ducts, the air
is typically well mixed a minimum of five equivalent duct diameters from the
discharge of the unit with equivalent duct diameter defined as equal to the square
root of 4AB/3.14. “A” and “B” are the duct cross-sectional dimensions.
Example: Supply duct work cross-sectional dimension is 24" x 12"
(610mm x 305mm).
5 x
4 x 12 x 24
3.14
= 96 inches 5 x
4 x 305 x 610
3.14
= 2435mm
Locate the sensor a minimum of 96" (2435mm) from the outlet of the unit.
NOTE: If the length of the discharge duct is less than 8 ft (2.4M), a mixing vane is
recommended for mixing the discharge air.
Do not mount the sensor in the duct work after a split in the supply as that will
cause loss of control in the duct that does not house the sensor.
2. Determine the location and orientation of the sensor. The position of the
sensor in the duct is also important. In horizontal duct work, locate the sensor
assembly in the top, middle of the duct with the sensor probe extending vertically
down into the center of the airstream.
In vertical duct work, locate the sensor assembly in the middle of the side of the
duct that corresponds with the top middle of the discharge outlet.
3. Attach the sensor. Mark the selected location and drill a 7/16" hole. Insert
the probe into the hole. Be sure that the blue plastic fitting holding the probe
is centered in the hole. Attach with two No. 8 sheet metal screws (do not
overtighten). Check to be certain that the hole is sealed.
Control Wiring or Tubing
Entrances Below the
Supply Wiring Entrance
on the Outer Panel
Control Wiring or
Tubing Entrances
through the
Bottom Panel
FIGURE 19 - Control
Wiring or Tubing
Entrance Locations
•
Shipped with the unit for
installation in the Supply
Air Duct
7.5 Control Wiring (cont’d)
7.0 Electrical and Wiring (cont'd)