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RP-HRPD-IOM (07-22) 132210-B
Optional Ductstat with Capillary Tubing (Options AG3 and AG4)
The unit-mounted ductstat shown in
, DETAIL A has an adjustable range between 0°F and 100°F with a
fixed differential of 3°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 AG17)
•
The field-installed sensing probe is field-wired to the remote temperature selector shown in
which has a temperature operating range to 130°F . The remote modules and sensing probe are shipped separately
for field-installation . Follow the wiring diagram provided with the unit and the manufacturer’s instructions for wiring
and installation .
Depending on the staging provided, there will be one module for selecting temperature and either
one or two stage-adder modules.
⚠ CAUTION ⚠
Ensure that the heat/cool selector switch on the remote temperature selector is positioned to
Heat
.
Optional Electronic Modulation
NOTE: Unit sizes 350 and 400 for RP models and 350–800 for HRPD models with electronic modu-
lation require a minimum natural gas supply pressure of 6 IN WC.
The type and capability of the electronic modulation system depends on the option selected . Electronic modulation
options are identified by a suffix to the serial No . printed on the heater rating plate . AG7 is identified as MV-1, AG8
is identified as MV-3, AG9 is identified as MV-4, AG21 is identified as MV-A, AG39 is identified as MP-1, and AG40
is identified as MP-2 . AG39 and AG40 are available only on model RP . AG41 is identified as MP3 and AG42 is
identified as MP4 . Both AG41 and AG42 apply to model HRPD .
Electronic Modulation Between 50% and 100% Firing Rate (Options AG7, AG8, and AG9)
•
Depending on the heat requirements 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 (amplifier) that furnishes varying DC current to the modulating valve to adjust the gas input .
•
Each modulating valve is basically a regulator with the electrical means of raising and lowering the discharge
pressure . When no DC current is fed to this device, it functions as a gas pressure regulator to supply 3 .5 IN WC
pressure to the combination gas valve .
•
Refer to the wiring diagram provided with the furnace for proper wiring connections .
•
Electronic modulation for heating that is controlled by a specially-designed room thermostat (60–85°F) is identified
as option AG7 .
•
Electronic modulation for makeup air application that is controlled by a duct sensor and temperature selector
(55–90°F) is identified as option AG8 or AG9 . The temperature selector setting for option AG8 is on the amplifier
(see
) . Option AG9 has a remote temperature selector . Both systems are available with an override
thermostat .
AMPLIFIER
SIGNAL CONDITIONER
Figure 15. Maxitrol Amplifier and Signal Conditioner
