Lennox 80UHG Series, Service Literature

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Page 12
TABLE 6
BLOWER CONTROL A15 TERMINAL DESIGNATIONS
Terminal
Designation
(See fig. 10)
Type Function
R Screw Strip 24VAC to Thermostat (Red)
G Screw Strip
Manual Fan Input from Thermostat
(Green)
W Screw Strip
Heat Demand Input from Thermostat
(White)
Y Screw Strip
Cool Demand Input from Thermostat
(Yellow)
C Screw Strip Common Ground to Thermostat
1 1/4" Spade 24VAC Hot from Transformer
2 1/4" Spade 24VAC Return to Transformer
3 1/4" Spade 24VAC Ground
4, 5, 6 1/4" Spade 120VAC Return - 120VAC Common
7 1/4" Spade
120VAC Return - 120VAC Common
Input
8 1/4" Spade Combustion Blower (Line Voltage)
9 1/4" Spade Heat Only Accessory (Line Voltage)
10 1/4" Spade 120VAC Hot to Transformer
11 1/4" Spade 120VAC Hot Input
12, 13 1/4" Spade Accessories (Line Voltage)
14 1/4" Spade ACB Cool Speed (Line Voltage)
15 1/4" Spade ACB Heat Speed (Line Voltage)
TABLE 7
EGCĆ2 CONTROL JACK/PLUG 20 TERMINAL DESIGNATIONS
Pin # Function
1 Rollout Switch Out
2 Spare
3 Gas Valve Common
4 Pressure Switch Return
5 Hi Limit Return / Pressure Switch Out
6 Flame Sensor
7 Gas Valve Out
8 High Limit Out
9 Rollout Switch Return
6-Blower Motors and Capacitors
All 80UHG units use direct drive blower motors. All motors
used are 120V permanent split capacitor motors to ensure
maximum efficiency. See table 8 for ratings.
TABLE 8
80UHG BLOWER RATINGS 120V 1PH
BLOWER MOTOR
HP
80UHG2
80UHG3
80UHG3/4
CAP
1/2
1/3
1/4 5MFD 370V
5MFD 370V
7.5MFD 370V
80UHG5/6
80UHG4
80UHG4/5
1/2 7.5MFD 370V
3/4 40MFD 370V
3/4 40MFD 370V
FIGURE 11
SUPPLY AIR BLOWER
AND SECONDARY LIMITS
Front
Bottom
Right
Left
Top Back
BLOWER
MOTOR
To Remove Blower From Unit: Remove Bolts and
Wiring Jackplugs. Then Slide Out Front of Unit.
MOTOR
CAPACITOR
SECONDARY
LIMITS (S21)
7-Combustion Air Inducer (B6)
All 80UHG units use a combustion air inducer to move air
through the burners and heat exchanger during heating
operation. The blower uses a 120VAC motor. The motor
operates during all heating operation and is controlled by
furnace control A3. The blower also operates for 15 seĆ
conds before burner ignition (preĆpurge) and for 5 seconds
after the gas valve closes (postĆpurge)
A proving switch connected to the combustion air inducer
housing is used to prove combustion air inducer operation.
The switch monitors air pressure in the blower housing. DurĆ
ing normal operation, the pressure in the housing is negaĆ
tive. If pressure becomes less negative (signifying an obĆ
struction) the prove switch opens. When the prove switch
opens, the furnace control (A3) immediately closes the gas
valve to prevent burner operation.
8-Flame Rollout Switches (S47)
Flame rollout switch is a high temperature limit located on
top of the burner box. Each furnace is equipped with two
identical switches. One switch is located over the leftmost
burner and the other switch is located over the rightmost
burner. The limit is a N.C. SPST manualĆreset limit conĆ
nected in series with the ignition control A3. When S47