Reznor RXH (Outdoor PreevA) Unit Installation Manual - Manual (Page 52)

Form I-RDH/REH/RHH/RXH (12-14), Page 52
FIGURE 46 - Maxitrol
Signal Conditioner, P/N
134170, used in Options
AG40, DG2, and DG6
Optional Modulation Gas Control with Field-Supplied Controller (Option AG40) -
With this control, the modulation gas heating system is identical to digital Options DG2
and DG6 in Paragraph 8.3. The programmable digital controller is not supplied. The unit
is equipped with a Maxitrol signal conditioner ( FIGURE 46) that accepts an input signal
of either 4-20 milliamps or 0-10 volts from a field-supplied controller and converts it to
the 0-20 volt DC current required to control the modulating valve.Temperature selection
or building management is controlled by customer-supplied software.
8.0 Controls and
Operation (cont’d)
8.2.4 Constant Discharge Air Temperature with Maintained Thermal
Efficiency (cont’d)
8.3.1 Optional Digital Heating/Cooling/Makeup Air Controls, Options
DG1, DG2, DG5, DG6 - Model RDH only
Application NOTES: Options DG 1, 2, 5, and 6 do not apply to units with reheat pump
(dehumidification) Option AU7L or AU7R. Model RDH with Option AU7 requires D12B,
D12C, or D12G; see Paragraph 8.3.2.
8.3 Digital Controls
for Heating/
Cooling,
Makeup Air, and
Dehumidification -
Models RDH, REH,
RHH, and RXH
Digital control systems (Options DG1, DG2, DG5, and DG6) have a unit-mounted, factory-
wired, 24 volt, DDC programmable controller ( FIGURE 47); a venter speed control board
( FIGURE 45); and a room command module (either FIGURE 48A or 48B). Options DG2
and DG6 with modulating gas heat have a Maxitrol conditioner ( FIGURE 46).
The four DG control sequences include a wall-mounted Fan/Heat/Cool/Auto Switch.
Option DG1 -
Room control with 2-stage gas heating and 3-stage cooling control. The
wall mount interface allows the user to adjust the space setpoint from 45°F to 95°F and
select the unit mode. Unit modes are Cool Only, Heat Only, Fan Only, Auto Mode, and Off.
Option DG2 - Room control with 4:1 modulated gas heat and 3-stage cooling control.
The wall mount interface allows the user to adjust the space setpoint from 45°F to 95°F and
select the unit mode. Unit modes are Cool Only, Heat Only, Fan Only, Auto Mode, and Off.
Option DG5 - Room control with 2-stage gas heating and 3-stage cooling control. The
wall mount interface allows the user to adjust the discharge air temperature ± 6°F from the
factory-mounted controller setpoint and select unit mode. Unit modes are Cool Only, Heat
Only, Fan Only, Auto Mode, and Off.
Option DG6 - Room control with 4:1 modulated gas heat and 3-stage cooling control. The
wall mount interface allows the user to adjust the discharge air temperature ± 6°F from the
factory-mounted controller setpoint and select unit mode. Unit modes are Cool Only, Heat
Only, Fan Only, Auto Mode, and Off.
FIGURE 47 -
Programmable Digital
Controller, Johnson
Controls FX05 used in all
DG Options
For explanation on the
settings and functions of
the FX05 programmable
control, see Form CP-
PREEVA-DG with FX05.
The heating and cooling equipment will cycle to maintain the active heating discharge
or space temperature setpoint, based upon the unit mode and time of day schedule.
Optional Ductstat with Electronic Remote Setpoint Module (Options AG61 and
AG62) - The factory-installed sensing probe must be field-wired to the 0-120°F remote
temperature selector illustrated in FIGURE 44B.
The remote modules are shipped separately for field installation. Follow the wiring
diagram with the unit and the manufacturer’s instructions for wiring and installation.
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 used only in Option AG62. See FIGURE 44B.
Electronic Modulation between 50% and 100% Firing Rate (Options AG8, AG9 & AG9H)
Depending on the heat requirements as established by the thermistor sensor, the burner
modulates between 100% and 50% firing. The thermistor is a resistor that is temperature
sensitive in that as the surrounding temperature changes, the Ohms resistance changes
through the thermistor. This change is monitored by the solid state control center (ampli-
fier) which furnishes varying DC current to the modulating valve to adjust the gas input.
Each modulating valve is basically a regulator with electrical means of raising and lower-
ing the discharge pressure. When no DC current is fed to this device, it functions as a gas
pressure regulator, supplying 3.5" w.c. pressure to the main operating valve.
Refer to the wiring diagram supplied with the furnace for proper wiring connections.
Electronic modulation control systems for makeup air applications controlled by a field-
installed duct sensor (See Paragraph 6.7.3) and temperature selector (55-90°F) are
identified as either Option AG8 or Option AG9 & AG9H. The temperature selector set-
ting for Option AG8 is on the amplifier; Option AG9 & AG9H has a remote temperature
selector. Both systems are available with an override thermostat.
FIGURE 46B -
Amplifier in Options
AG8 (P/N 260864); AG9
and AG9H (P/N 260863
for both)
8.2.6 Optional Electronic Modulation
8.2 Analog Controls
for Heating or
Heating/Makeup
Air (cont’d)
8.2.5 Modulation Gas Control with Field Supplied Digital Control