Thermostats; Non-Communicating Thermostats; Sequence Of Operation - Rheem RGPE series Installation Instructions Manual

THERMOSTATS

NON-COMMUNICATING
THERMOSTATS
THERMOSTAT WIRING
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
48 and 49.
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.

SEQUENCE OF OPERATION

See the section of this book titled
"Electrical Wiring - Thermostat" for a
wiring diagram showing how to connect
a thermostat.
SINGLE-STAGE HEAT THERMOSTAT
NOTE: Single-stage heat operation is
determined by the position of dipswitch-
es SW1-3 options are: 7 minutes
st nd
between 1 and 2 stage, or OFF.
For single-stage operation, "W" from the
thermostat must be connected to "W"
on the furnace control.
a. Connect the "W" terminal on the ther-
mostat to the "W" terminal on the
control board.
b. When there is a call for heat, the "R"
and "W" contacts close and the IFC
runs a self check routine to verify that
the pressure switch contacts are
open. The limit switch contacts are
constantly monitored.
c. The induced draft motor starts on
high until the low pressure switch
contacts close (a maximum of 60
seconds), and then changes to low
speed. After a 30 second pre-purge,
the spark ignitor energizes and the
low fire gas valve opens, lighting the
burners.
d. After the gas valve opens, the
remote flame sensor must prove igni-
tion for one second using the
process of flame rectification. If the
burners do not light, the system goes
through another ignition sequence. It
does this up to 4 times. (2 tries on
low fire and 2 tries on high fire.)
80
FIGURE 47
24-VOLT TERMINALS
­ e. The main blower starts on low heat
speed 30 seconds after the flame is
sensed. The furnace operates on low
fire for 5 or 12 minutes and then, if the
thermostat is not satisfied, shifts to
high fire, causing the draft inducer to
go to high speed, the gas valve to
shift to 100% and the main blower
goes to high heat speed.
f. When the thermostat cycle ends, the
gas valve closes, and the burners go
out.
g. The draft inducer will continue running
for a 10 second (low speed) or 5 sec-
ond (high speed) post purge.
­ h. The main blower runs for 50-140
seconds on high heat speed or 80-
170 seconds on low heat speed (this
timing is field adjustable). See Figure
22 for switch settings.
Sequence if the system doesn't light
or doesn't sense flame
a. If flame is not sensed within 8 sec-
onds after the gas valve opens, the
valve closes and the ignitor is de-
energized. The induced draft motor
will run for 60 seconds on low, and
then begins another heat cycle.
b. The ignition process goes through
one more try on low fire. If this fails,
there are two attempts on high fire
with a 30 second interpurge between
trials. During high fire ignition
attempts, the inducer steps to high
speed, the high pressure switch
closes (both pressure switches are
now closed), and the gas valve
steps to high fire.
c. If there is no ignition after the 2nd
trial on high fire, the furnace goes
into soft lockout for one hour.
d. The sequence repeats after a one
hour delay and continues repeat-
ing until ignition is successful or
the call for heat is terminated.
e. To reset the lockout, break power
either at the thermostat or at the
unit disconnect switch for 5 to 10
seconds. The furnace then goes
through another set of trials for
ignition (provided call for heat is
still present).
f. If flame is established and main-
tained during the trial for ignition
period and flame is lost, the gas
valve is de-energized, the draft
inducer continues to run, and con-
trol begins timing the inter-purge
delay. The indoor blower motor will
be energized and/or remain ener-
gized on low speed for low fire and
heat speed for high fire for the
selected delay off time.
When the inter-purge delay is over,
the control initiates another igni-
tion trial period. The control will
recycle up to 5 flame losses (4 re-
cycles) within a single call for heat
before going into lockout.
TWO STAGE HEAT THERMOSTAT
Connect "W1" and "W2" terminals on
the thermostat to "W" and "W2" termi-
nals on the control board.
See the section of this book titled
"Electrical Wiring - Thermostat" for a
wiring diagram showing how to con-
nect a thermostat.
Call for 1st stage heat
a. The "R" and "W" thermostat con-
tacts close and the control module
runs a self-check routine. After the
control module verifies that both
sets of pressure switch contacts
are open, the induced draft motor
starts on high until the low pres-
sure switch contacts close (a maxi-
mum of 60 seconds), then
changes to low speed.
b. After a 30 second pre-purge the
spark igniter energizes and the low
fire gas valve opens, lighting the
burners.