Thermostats; Non-Communicating Thermostats - Rheem RGFE Installation Instructions Manual

THERMOSTATS

NON-COMMUNICATING
THERMOSTATS
THERMOSTAT WIRING
NOTE: For fully modulating function
with a non-communicating thermostat,
the furnace must be installed with the
(-)HC-TST412MDMS Modulating
Touch-Screen Thermostat.
NOTE: Do not use 24 volt control wire
smaller than No. 18 AWG.
Wire all non-communicating ther-
mostats to the 24V connections on the
integrated furnace control. See Figures
86, 87, 88, 89, and 90.
NOTE: A larger wire gage may be be
required for longer lengths of thermo-
stat wire.
For proper installation of the Variable
Output Thermostat, follow the
"Thermostat Installation, Programming
and Troubleshooting Manual" included
as section II of this manual. For proper
installation of a Single-Stage or Two-
Stage Thermostat, see the Installation
Instructions included with the thermo-
stat.
® FURNACE OPERATION USING
MODULATING, SINGLE-STAGE, AND
TWO-STAGE THERMOSTATS
The modulating furnace with the UT
Electronic Controls IFC is also capable
of operating with a traditional single-
stage or a two-stage non-communicat-
ing thermostat as well as the modulat-
ing (both communicating and non-com-
municating) thermostat. The control will
operate with either single-stage or two-
stage non-communicating thermostats
as a modulating system using an algo-
rithm that utilizes three distinct firing
rates; 40%, 65% and 100% of the fur-
nace heating capacity (See below for
operation of each).
Figures 86, 87, 88, 89 and 90 detail
how to wire the modulating furnace for
operation with non-communicating
modulating thermostat, single-stage
thermostat, or two-stage thermostat.
® FURNACE OPERATION WITH A
MODULATING THERMOSTAT
As described previously in this manual,
operation with a non-communicating
modulating or communicating thermo-
stat when installed as shown in
Figures 90 are 91 is fully modulating
between 40% and 100% of furnace
capacity. The firing rate is first deter-
mined by the thermostat and then sent
to the furnace. This is the optimum
mode of operation and will give the
108
FIGURE 85
24-VOLT TERMINALS
best temperature control with minimal
temperature variation from the desired
set point.
WARNING
WHEN A NON-COMMUNICATING
(24V) MODULATING THERMOSTAT IS
INSTALLED, DO NOT APPLY 24VAC
TO V/W2 AT THE FURNACE CON-
TROL (THIS IS SOMETIMES DONE
DURING SETUP, TROUBLESHOOT-
ING AND/OR WHILE DIAGNOSING
PROBLEMS). DOING SO WILL DAM-
AGE THE THERMOSTAT.
® FURNACE OPERATION WITH A
SINGLE STAGE NON-COMMUNICAT-
ING THERMOSTAT
To operate the furnace with a single-
stage non-communicating thermostat,
set switches 2 & 3 of SW2 (See Figure
66) to the "OFF" position. Note that
these switches should be in the "OFF"
position from the factory. The lack of the
modulating "V" signal will automatically
be sensed as a single-stage thermostat
and the furnace will operate according-
ly.
With a single-stage non-communicat-
ing thermostat (installed as shown in
Figure 89), during a call for heat, the
furnace will operate as follows:
Phase 1: 0 to 5 minutes = 40% of
furnace capacity
Phase 2: 5 to 12 minutes = 65% of
furnace capacity
Phase 3: After 12 minutes = 100 %
of furnace capacity
NOTE: If the call for heat ends dur-
ing any phase, the furnace will termi-
nate immediately at the firing rate of
that phase.
If switches 2 & 3 of SW2 are in the
"ON" position, the furnace will
always operate at 40% with a single-
stage non-communicating thermostat
installed as shown in Figure 89.
THIS CONFIGURATION IS NEI-
THER RECOMMENDED NOR
APPROVED.