Nature Air RGRM-04*MAES Installation Instructions Manual - page 45
45
goes through another ignition
sequence. It does this up to 4 times.
e. The inducer and gas valve
immediately drop to low fire, the main
blower starts on low heat speed 20
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 to high heat speed. (In
some models low and high fire have
identical main blower airflow CFM.)
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 post purge.
h. The main blower runs for 80-180
seconds on high heat speed or 90-180
seconds on low heat speed (this
timing is field adjustable). See Figure
47 for switch settings.
Sequence if the system doesn’t light
or doesn’t sense flame
a. If flame is not sensed within 8 seconds
after the gas valve opens, the valve
closes and the ignitor is de-energized.
The induced draft motor will run for 60
seconds on high, and then begins
another heat cycle.
b. The ignition process goes through 3
more attemps.
c. If there is no ignition after the 4th trial,
the furnace goes into soft lockout for
one hour.
d. The sequence repeats after a one
hour delay and continues repeating
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 maintained
during the trial for ignition period and
flame is lost, the gas valve is de-
energized, the draft inducer completes
the post purge, and control shuts off
the inducer, senses the open pressure
switch and begins the ignition
sequence again from pre-purge. The
indoor blower motor will be energized
and/or remain energized on low speed
for low fire and heat speed for high fire
for the selected delay off time.
The control initiates another ignition
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” terminals on
the control board.
See the section of this book titled
“Electrical Wiring - Thermostat” for a
wiring diagram showing how to connect a
thermostat.
NOTE: When there is a low heat call
present at the time of ignition, this
furnace will light on high fire heat and
immediately drop to low fire as soon as
flame is sensed. This can sometimes
appear to be ignition on low heat stage
but this is not the case. Listen carefully to
hear the inducer and gas valve relays
switch to low fire after ignition when a low
heat call is present. If a high heat call is
present at the time of ignition and steady
state heat will occur at high fire and there
will be no change in operation after
ignition.
Call for 1st stage heat
a. The “R” and “W” thermostat contacts
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 pressure switch contacts close
(a maximum of 60 seconds).
b. After a 30 second pre-purge the spark
igniter energizes and the high fire gas
valve opens, lighting the burners.
c. After the burners light, the remote
flame sensor must prove ignition. If the
burners do not light, the system goes
through another ignition sequence. It
does this up to 4 times.
d. The furnace immediately drops
inducer and gas value to low fire after
sensing flame. The main blower starts
on low-heat speed 20 seconds after
the flame is proven. The furnace
continues to run on low fire until the
call for heat is satisfied or the 2nd
stage contacts close. If the 1st stage
call for heat is satisfied the gas valve
closes and the induced draft motor
continues running for a 10 second post
purge time. the main blower runs for
its blower off delay (this timing is field
adjustable). See Figure 45 for switch
settings.
Call for 2nd stage heat after 1st stage
The “R” and “W2” thermostat contacts
close, calling for 2 stage heat. The
induced draft motor switches to high
speed and the high pressure switch
contacts close. The gas valve switches to
high fire and the main blower switches to
high heat speed.
2nd stage heat satisfied, 1st stage
heat still required
The “R” and “W2” thermostat contacts
open. The induced draft motor
switches to low speed, the main
blower motor switches to low heat
speed and the gas valve changes to
low fire. The furnace continues to run
in this mode until the 1st stage heat
call is satisfied. The system will shut
down as noted in “d,” under 1st stage
call for heat.
NOTE: Under extreme cold
conditions, the 2-stage thermostat
may call for the furnace to cycle
between 1st and 2nd stage operation.
INTEGRATED FURNACE
CONTROL & ECM MOTOR
SETTINGS
These furnaces have ECM blower
motors. These motors deliver a
constant level of air flow over a wide
range of external static pressures (0.1
to 0.8
ⴖ W.C.).
There is a bank of 12 dip switches
(SW1) on the control board which
define the operation of the ECM
motor. (See Table 8.) (See Figure 47.)
Many of these switches (except for
switches 9 and 12) are actually broken
down into dip switch pairs. The
following switches are paired 1 & 2, 3
FIGURE 45
é
FACTORY
SETTING
TABLE 8
DIP SWITCH BANK SW1
SWITCHES
FUNCTION
1 & 2
Heat Rise Adjustment
3 & 4
Not Used
5 & 6
Nominal Cooling/Heat Pump Air Flow
7 & 8+
Latent/Sensible Airflow Adjustment
9
Continuous Fan Airflow
10 & 11*
On Demand
Dehumidification
Settings
12
1 or 2 Stage Cool