52
1. DEFAULT A/C AIRFLOW WHEN A/C SWITCHES ARE IN OFF POSITION
2. DEFAULT CONT. FAN AIRFLOW WHEN CF SWITCHES ARE IN OFF POSITION
3. SWITCH POSITIONS ARE ALSO SHOWN ON FURNACE WIRING DIAGRAM
525
2
700
700
875
2
1050
875
1050
1
1225
1225
1400
1225
1750
1
1225
2100
DEF.
DEF.
070
110, 135
BASED ON 350 CFM/TON (SETUP SWITCH SW1-5 OFF, SW4-3 OFF)
SETUP SWITCH SW2 OR SW3 POSITIONS
MODEL
SIZE
525
2
700
875
1050
1225 1400
1
1400
DEF.
090
600
2
800
1000 1200
1
1400 1400 1400
DEF.
BASED ON 400 CFM/TON (SETUP SWITCH SW1-5 ON, SW4-3 OFF)
SETUP SWITCH SW2 OR SW3 POSITIONS
MODEL
SIZE
800
1000
2
1200 1400
1600 2000
1
2200
DEF.
600
2
800
1000 1200
1400 1600
1
1600
DEF.
488
2
651
651
814
2
976
814
976
1
1139
1139
1302
1139
1627
1
1139
1950
DEF.
DEF.
070
110, 135
BASED ON 325 CFM/TON (SETUP SWITCH SW1-5 OFF, SW4-3 ON)
SETUP SWITCH SW2 OR SW3 POSITIONS
MODEL
SIZE
488
2
651
814
976
1139 1302
1
1302
DEF.
090
558
2
744
744
930
2
1116
930
1116
1
1302
1302
1488
1302
1860
1
1302
2200
DEF.
DEF.
070
110, 135
BASED ON 370 CFM/TON (SETUP SWITCH SW1-5 ON, SW4-3 ON)
SETUP SWITCH SW2 OR SW3 POSITIONS
MODEL
SIZE
558
2
744
930
1116
1302 1488
1
1488
DEF.
090
070
110, 135
090
AIR CONDITIONING
AIRFLOW
070 MODEL
090 MODEL
110 and 135
TONS (12,000 BTU/HR)
(CFM)
MODELS
1-1/2
525
X
X
2
700
X
X
X
2-1/2
875
X
X
X
3
1050
X
X
X
3-1/2
1225
X
X
X
4
1400
X
X
5
1750
X
6
2100
X
X-INDICATES AN ALLOWABLE SELECTION.
2
1
1
1
2
COOLING TONNAGE VS. AIRFLOW (CFM)
2
A12091
Fig. 58 -- Cooling (A/C) or Continuous--Fan (CF) Airflow Selection Chart
The furnace will start up in either low-- or high--heat. If the
furnace starts up in low--heat, the control CPU determines the
low--heat on--time (from 0 to 16 minutes) which is permitted
before switching to high--heat.
If the power is interrupted, the stored history is erased and the
control CPU will select low--heat for up to 16 minutes and then
switch to high--heat, as long as the thermostat continues to call for
heat. Subsequent selection is based on stored history of the
thermostat cycle times.
The wall thermostat “calls for heat”, closing the R--to--W circuit.
The furnace control performs a self--check, verifies the low--heat
and high--heat pressure switch contacts LPS and HPS are open,
and starts the inducer motor IDM in high--speed.
a.
Inducer Prepurge Period
(1.) If the furnace control CPU selects low--heat oper-
ation the inducer motor IDM comes up to speed,
the low--heat pressure switch LPS closes, and the
furnace control CPU begins a 15--second prepur-
ge period. If the low--heat pressure switch LPS
fails to remain closed the inducer motor IDM will
remain running at high--speed. After the low--heat
pressure switch re--closes the furnace control CPU
PG
8M
VA
