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Optional Flue Outlet
(Horizontal Installation)
Top Cap
Flue Outlet Hole
Reattach
(
Cutout Here)
Cut out
FIGURE 17
10. 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 manual-reset limit con-
nected in series with the primary limit S10. When S47
senses rollout, the circuit breaks and the ignition control im-
mediately stops ignition and closes the gas valve.
If unit is running and flame rollout is detected, the gas valve
will close and ignition control will be disabled. Rollout can
be caused by a blocked heat exchanger, flue or lack of
combustion air. The switch is factory set to trip (open) at
210°F and cannot be adjusted. The switch can be manually
reset. To manually reset a tripped switch, push the reset but-
ton located on the control.
Top View of Furnace
Supply Air
Opening
Optional
Flue Outlet
11. Primary Limit Control (S10)
The primary limit (S10) on G60UHV(X) units is located in the
heating vestibule panel. When excess heat is sensed in the
heat exchanger, the limit will open. If the limit is open, the fur-
nace control energizes the supply air blower and closes the
gas valve. The limit automatically resets when unit tempera-
ture returns to normal. The switch must reset within three min-
utes or the SureLight board will go into Watch guard for one
hour. The switch is factory set and cannot be adjusted. The
switch may have a different set point for each unit model
number. If limit switch must be replaced, call Lennox Repair
Parts for correct length and set point.
12. Secondary Limit Controls (S21)
The secondary limit (S21) on G60UHV(X) units is located in
the blower compartment on the back side of the blower hous-
ing. See figure 1. Blower speed chart on the wiring diagram
show secondary limit quantities per unit. When excess heat is
sensed in the blower compartment, the limit will open. If the
limit is open, the furnace control energizes the supply air blow-
er and closes the gas valve. The limit automatically resets
when unit temperature returns to normal. G60UHV−1 and −2
units use a surface type limit factory set to open at 125°F.
G60UHV−3 units and later use an airstream type limit factory
set to open at 135°. The secondary limit cannot be adjusted.
13. Gas Valve
The G60UHV(X) uses a two−stage gas valve manufactured
by White Rodgers or Honeywell (figures 18 and 19). The
valve is internally redundant to assure safety shut−off. If the
gas valve must be replaced, the same type valve must be
used.
24VAC terminals and gas control knob or switch are located
on the valve. All terminals on the gas valve are connected to
wires from the electronic ignition control. 24V applied to the ter-
minals energizes the valve.
Inlet and outlet pressure taps are located on the valve. A regu-
lator adjustment screw is located on the valve.
LPG change over kits (Honeywell valve only) are available
from Lennox. Kits include burner orifices and a gas valve regu-
lator conversion kit.
Page 30
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