47
VOLT / OHM
METER
Testing Primary Limit Control
VOLT / OHM
METER
COLOR
IDENTIFYING
TAB
Testing Primary Limit Control
(90% Furnaces)
4. After completing check and/or replacement of primary
limit control, reinstall burner compartment door.
5. Turn on electrical power and verify proper unit operation.
To aid in identifying these controls, refer to the
Primary Limit
Charts
in furnace Technical Manual for part number, tempera
-
ture setting and color(s) code.
Manual Reset Auxiliary Limit Located in Blower Deck
The
90% single-stage
upflow furnaces use two auxiliary limit
switch for control of high temperatures within the furnace or
duct work. This control is preset, nonadjustable and auto
reset. The control is located in the blower compartment of
the furnace on the blower deck, as shown in the following
illustration.
WARNING
HIGH
VOLTAGE
D
ISCONNECT
ALL
POWER BEFORE SERVICING OR
INSTALLING THIS UNIT.
M
ULTIPLE POWER SOURCES MAY
BE PRESENT.
F
AILURE TO DO SO MAY CAUSE PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.
WARNING
T
O AVOID POSSIBLE FIRE, ONLY RESET THE AUXILIARY LIMIT CONTROL
ONCE.
I
F IT SHOULD OPEN A SECOND TIME, A QUALIFIED SERVICER
MUST DETERMINE WHY THE AUXILIARY LIMIT OPENED BEFORE
RESETTING AGAIN.
To aid in identifying these controls, color coded labels are
attached to the back of the controls. Refer to the
Auxiliary
Limit Charts
in furnace Technical Manual for color codes and
temperature settings.
S-302 CHECKING FLAME ROLLOUT CONTROL
A temperature activated manual reset control is mounted to
the manifold assembly on 90% furnaces, as shown in the
following illustrations.
Should read continuous unless heat exchanger temperature
is above limit control setting. If not as above, replace the
control.
FLAME
ROLLOUT
SWITCHES
Flame Rollout Switch Location
The control is designed to open should a flame roll out oc
control opens, the air circulation blower will run continuously.
On single-stage and 90% models, the ignition control di
-
agnostic light will flash (6) six times indicating a trip of the
rollout switch.
To aid in iderntifying these controls, color-coded labels have
been affixed to the back of these controls. Refer to the Rollout
Limit Charts in furnace Technical Manual for temperature
settings and color codes.
