Lennox 80MGF3/4-100 User Manual

Page 19
FIGURE 18
SPARK ELECTRODE TO BURNER GAP
SPARK ELECTRODE
BURNER
FLAME SENSOR TO BURNER GAP
BURNER
FLAME SENSOR
SPARK
ELECTRODE
5/16 in.
(7 mm)
5/16 in.
(7 mm)
FIGURE 19
WHITE RODGERS 36E SERIES GAS VALVE
GAS VALVE SHOWN IN OFF POSITION
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
MANIFOLD
PRESSURE
OUTLET
ON
OFF
FIGURE 20
HONEYWELL VR8205 SERIES GAS VALVE
GAS VALVE SHOWN IN OFF POSITION
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
MANIFOLD
PRESSURE
OUTLET
I−Combustion Air Blower Prove
(Pressure) Switch (S64)
80MGF series units are equipped with a combustion air
prove switch located on the vestibule panel. The switch is
connected to the combustion air blower housing by means
of a flexible silicone hose. It monitors air pressure in the
combustion air blower housing.
The switch is a single-pole single-throw pressure switch
electrically connected to the furnace control. The purpose
of the switch is to prevent burner operation if the combus-
tion air blower is not operating.
FIGURE 21
PROVE SWITCH
COMBUSTION AIR BLOWER
PROVE SWITCH
Normally Open
Closes on Negative Pressure
PROVE
SWITCH
Sensing Tube
Attaches to Top
Side Of Blower
Top
Bottom
Left
Right
Back
Front
On start-up, the switch senses that the combustion air
blower is operating. It closes a circuit to the furnace control
when pressure inside the combustion air blower increases
above pressure switch set point (In. negative w.c.). The
pressure sensed by the switch is relative to atmospheric
pressure. If the flue becomes obstructed during operation,
the switch senses a loss of negative pressure (pressure
becomes more equal with atmospheric pressure) and
opens the circuit to the furnace control and gas valve. The
switch trip pressure is different depending on unit model
number. The trip pressure is printed on the side of the limit.
The switch is factory set and is not field adjustable. It is a
safety shut-down control in the furnace and must not be
bypassed for any reason.
II−PLACEMENT AND INSTALLATION
Make sure unit is installed in accordance with installation
instructions and applicable does.
III−START-UP
BEFORE LIGHTING smell all around the appliance area
for gas. Be sure to smell next to the floor because some gas
is heavier than air and will settle on the floor.
Use only your hand to turn the gas control knob. Never use
tools. If the knob will not turn by hand, do not try to repair it,
call a qualified service technician. Force or attempted repair
may result in a fire or explosion.

Lennox 80MGF3/4-100 Specifications

General

Brand	Lennox
Model	80MGF3/4-100
Category	Furnace
Language	English