Safety Features - Rheem GPT series Installation Instructions Manual

SAFETY FEATURES

LIMIT CONTROL
The high limit cut-off temperature is set
at the factory and cannot be adjusted.
The temperature setting prevents the
air temperature leaving the furnace
from exceeding the maximum outlet air
temperature, which, if exceeded, will
shut the furnace down.
There are several reasons for a limit
switch to open and almost always
involve low airflow through the furnace.
1. A dirty or restricted air filter.
2. A dirty or restricted cooling coil.
3. Undersized or restricted return air
system.
4. Undersized or restricted supply air
system.
5. A problem affecting the main
blower:
A. A wrong speed tap selection.
B. Failing motor bearings.
C. Low voltage to the motor.
D. Dirty blower wheel.
E. Wrong motor rotation.
F. Blower wheel slipping on the
F. motor shaft.
6. Overfiring the furnace with too much
gas pressure.
7. Ventilation problems.
34
FLAME ROLL-OUT
SAFETY SWITCHES
Furnaces are equipped with safety
switches to protect against flame roll-
out conditions in the burner
compartment, which, if tripped, will
terminate the heating cycle. In the
event of a flame roll-out condition, the
switch will shut the furnace down.
Switches for the (-)GPT furnaces are
located on either side of the burner
cover plate and just above the burners
on the blower divider panel. The (-)GLT
requires only one switch on the left
side of burner cover plate. If a switch is
tripped, it must be manually reset. DO
NOT jumper or reset this switch. If this
switch should trip, a qualified installer,
service agency or the gas supplier
should be called to diagnose and/or
correct the source of tripping. If this
unit is mounted in a closet, the door
must be closed when making this
check.
PRESSURE SWITCH
This furnace is equipped with a
normally-open pressure switch that
monitors pressure conditions within the
furnace vent system during the heating
cycle.
There are several reasons for the
pressure switch not to close.
1. An inoperative induced draft blower.
2. A loose or leaky pressure switch
hose.
3. A blockage in the vent.
4. Severe downdrafts canceling the
draft from the inducer fan.
5. A leaky gasket at the induced draft
blower.
6. Improperly sized or installed vent.
The pressure switch contacts must
open before the unit can go through
another heating cycle.
See troubleshooting chart in this book
for troubleshooting recommendations.