Reznor RXH (Outdoor PreevA) Unit Installation Manual - Manual (Page 51)

Form I-RDH/REH/RHH/RXH (12-14), P/N 215210 R14, Page 51
8.2.3 Two-Stage
Operation - Makeup
Air Heating Only
Application (Option
AG3, AG15, or AG16)
Two-stage makeup air units are equipped with a two-stage gas valve, but instead of
control from a two-stage room thermostat, the outlet air temperature is monitored and
controlled by a two-stage ductstat. When the discharge air temperature drops to the
setpoint, factory-set low fire is energized. If low fire (70%) cannot satisfy the ductstat
setting, high fire (100%) is energized.
A makeup air application is usually adjusted to discharge an outlet air temperature
between 65°F and 75°F. In all applications, the allowable temperature rise of the fur-
nace in the installation dictates the limits of the ductstat temperature setting.
Depending on the option selected, the factory-installed sensor is either field-connected
by capillary tubing to the unit-mounted ductstat ( FIGURE 44A) or electrically connected
to a remote electronic temperature selector ( FIGURE 44B). The remote temperature
selector with stage adder is available with or without a display module.
Optional Unit-Mounted Ductstat with Capillary Tubing (Option AG3) - The control
illustrated in FIGURE 44A has an adjustable range from 50° to 120°F with a fixed dif-
ferential of 2-1/2°F. Due to different CFM settings and outside air temperatures, the
average downstream outlet temperature may not match the ductstat setting exactly.
After the installation is complete, adjust the setpoint of the ductstat to achieve the
desired average outlet air temperature.
Optional Ductstat with Electronic Remote Setpoint Module (Options AG15 and
AG16) - The factory-installed sensing probe must be field-wired to a remote tempera-
ture selector. The temperature selector has an operating range to 120°F. Follow the
wiring diagram with the unit and the manufacturer’s instructions for wiring and installa-
tion. CAUTION: Be sure heat/cool selector switch is set at “Heat” position. There will
be one module for selecting temperature and one-stage adder module. The optional
digital display module is only in Option AG16. See FIGURE 44B.
FIGURE 44A - Unit-
mounted Ductstat,
P/N 211481, in Options
AG3 and AG60
Factory
set at
70°F
FIGURE 44B - Remote Temperature
Selector, Stage-Adder Module,
and Optional Display Module for
Ductstat Control in Two-Stage
Makeup Air Control Options (Option
AG15, AG16, AG61, and AG62)
(A) Temperature Selector, P/N 115848;
(B) Stage Adder, P/N 115849;
(C) Display Module, P/N 115852
(A) (B) (C)
8.2.4 Constant
Discharge Air
Temperature with
Maintained Thermal
Efficiency - Makeup
Air Heating Only
Application (Options
AG60, AG61, AG62)
Two-Speed Venter System in Options AG60, AG61,
and AG62 - A proprietary electronically controlled
venter system provides the correct quantity of
combustion air to maintain an overall average of 81%
thermal efficiency through a range of gas inputs from
100 to 33 percent for natural gas and through a gas
input range of 100 to 40 percent for propane gas.
The venter’s low speed operation is controlled by an
electronic board ( FIGURE 45) and a two-stage ductstat
(either FIGURE 44A or 44B).
The proprietary electronically controlled venter system
always operates at high speed during pre-purge and
post-purge periods. Speed selection occurs after there
is a call for burner ignition.
Optional Unit-Mounted Ductstat with Capillary Tub-
ing (Option AG60) - Uses the unit-mounted control illus-
trated in FIGURE 44A with an adjustable range from 0°
to 120°F. Due to different CFM settings and outside air
temperatures, the average downstream outlet tempera-
ture will be constant but may not match the ductstat set-
ting exactly. After the installation is complete, adjust the
setpoint of the ductstat to achieve the desired outlet air
temperature.
FIGURE 45 - Venter
Speed Control
Board in Control
Options AG8, AG9,
AG9H, AG40, AG58,
AG60, AG61, AG62,
DG1, DG2, DG5,
DG6, D12B, D12C