39
On upflow units, guide dimples locate the side return cutout locations. Use a straight edge to scribe lines connecting the
dimples. Cut out the opening on these lines.
NOTE:
An undersized opening will cause reduced airflow.
Refer to the Filter Sizing Chart to determine filter area requirements.
Change filters before occupants take ownership of a new home!
U
PRIGHT
I
NSTALLATIONS
Depending on the installation and/or customer preference, differing filter arrangements can be applied. Filters can be installed in the
central return register or a side panel external filter rack kit (upflows). As an alternative a media air filter or electronic air cleaner can
be used as the requested filter.
H
ORIZONTAL
I
NSTALLATIONS
Filters must be installed in either the central return register or in the return air duct work.
S
TARTUP
P
ROCEDURE
& A
DJUSTMENT
Furnace must have a 115 VAC power supply properly connected and
grounded. Proper polarity must be maintained for correct opera-
tion. In addition to the following start-up and adjustment items,
refer to further information in
Operational Checks
section.
• The furnace control board adjusts to the low firing rate.
• After 2 minutes, the furnace control board accepts the
specific heat requested demand.
• If the differential is equal to or less than 2 degrees,
the furnace control board will follow the conventional
2-Stage algorithm, equivalent to a W1 request and be
reflected in the heat current demand status %.
• If the heat differential is greater than 2 degrees, the
furnace control board will follow the conventional 2-
Stage algorithm, equivalent to a W2 request and be
reflected in the heat current demand status %.
• The circulator will operate per the heat airflow profile.
Call for heat, thermostat energizes W1 on the furnace control board (W2 input is ignored).
After a successful Light Off Sequence and expiration of the Ignition Stabilization Period:
• The furnace control board adjusts the firing rate to 35% (low fire rate).
• After 2 minutes, the furnace control board increases the firing rate to 57% at a rate of 1% per second.
• After 10 total minutes, the furnace control board increases the firing rate to 78% at a rate of 1% per second.
• After 20 total minutes, the furnace control board increases to 100% at a rate of 1% per second for the remainder
of the call for heat.
• The circulator fan is adjusted to the appropriate CFM,
corresponding to the current firing rate.
Call for 1st-Stage Heat - Thermostat contacts close R to W1.
After a successful Light Off Sequence and expiration of the
Ignition Stabilization Period:
• The furnace control board adjusts to the low firing rate.
• After 2 minutes, the furnace control board increases the
firing rate to 50% for the next 8 minutes.
• Thereafter, the furnace control board will increase the
firing rate 10%, at a rate of 1% per second, every 10
minutes for the remainder of the call for heat (See above
figure).
MIN.
50%
60%
(80%)
70%
IGNITION
10 MINS.
8 MINS.
2 MINS.
Operation with Conventional 2-Stage Thermostat
(DIP switch selects 2-stage heat)
Figure 45
MIN.
57%
78%
(80%)
100%
IGNITION
UNIT CALL FOR HEAT ENDS
10 MINS.
8 MINS.
2 MINS.
Operation with Conventional 1-Stage Thermostat
(DIP switch selects 1-Stage heat)
Figure 44