Reznor SHH (Indoor PreevA) Unit Installation Manual - Manual (Page 38)

Form I-PDH/SDH/PEH/SHH/PXH, Page 38
All gas or electric control options for makeup air (except AG40) include a discharge
air sensor that requires field installation in the discharge duct. (Sensor is field-supplied
with Option AG 40.)
Options AG3, AG15, AG16, AG58, AG60, AG61 and AG62 are analog controls. Options
AG3 and AG60 have a unit mounted ductstat with a capillary sensor that will fit in the
holder in FIGURE 32. Options AG16, AG58, AG60, AG61 and AG62 include sensors
that require duct mounting using the holder in FIGURE 32 and field wiring. Follow the
instructions below to attach the holder and the sensor.
Sensors in Options DG5, DG6, D12B, D12C, D12D, D12E, D12F, and D12G are digital
and require duct mounting using the holder in FIGURE 32 and field wiring. Digital con-
trol inputs are low-current, resistance-based signals. For optimum temperature control
performance, the analog and digital inputs (zone sensors, discharge air sensors, etc.)
that are connected to the main digital controller should be routed to the unit in one of
the following manners:
•
In separate conduits, isolated from 24 VAC controls and line voltage power to the
unit, OR
• If the main controller sensor wires are to be run in the same conduit as the 24
VAC control wiring, the sensor wiring must be completed using 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.
See TABLE 23 for wire gauge and length requirements of digital control signal wiring.
( NOTE: Sensor wire supplied with the FX05 digital controller is 22AWG. There is no
sensor wire supplied with the FX06 controller; it must be field supplied.)
6.7.3 Discharge Air
Sensor for Makeup
Air Application
FIGURE 32 - Discharge
Air Sensor Holder,
P/N 115850, used in
Makeup Air Installations
Secure sensor in clip.
Position holder so that it
shields sensor from direct
airflow.
TABLE 23 - Digital
Control Signal Wire
Gauge and Length
Maximum
Sensor
Wire
Length for
less than
1°F Signal
Error
Wire Gauge Maximum Sensor Wire Length (Digital Control)
AWG Feet Meters
14 800 244
16 500 152
18 310 94
20 200 61
22 124 38
Instructions for
Installing Discharge Air
Sensor in the Ductwork
1. Installation requires the discharge air sensor holder including the box cover.
2. Determine a location in the ductwork to install the sensor. If installing Options AG3
or AG60 with a capillary sensor, determine the location based on the length of the
capillary tubing.
If installing wiring to the sensor, select a location a sufficient distance from the
outlet to provide 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 ductwork cross-sectional dimension is
24" x 12" (610mm x 305mm).
5 x
4 x 12 x 24
3.14
= 96" 5 x
4 x 305 x 610
3.14 = 2435mm
Solution: 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.
6.7 Unit Discharge
(cont’d)
6.0 Mechanical
(cont’d)
6.7.2 Discharge Duct (cont’d)
• Discharge Air Horizontal Connection (See FIGURE 31.) - The seal between the
heater and the duct must be mechanical. Duct connection should be made with
“U” type flanges on the top and bottom of the connecting duct. Slide the duct over
the flanges of the heater giving an airtight fit. Provide “U” type channels for the
side flanges to ensure tight joints. Fasten “U” channels with sheetmetal screws.