Technical data

0803UDSA-2GBEN, Pag. 32/36
23. Limit controls
If a limit control needs replacing,
use only the factory authorized re-
placement part for the size of
heater.
For approximate limit locations,
see figure 11a..
22. Combustion
air pressure
switch
See figure 10, for location. If it is
determined that the pressure
switch needs replacing, use only
the factory-authorized replace-
ment part that is designed for the
model and size of heater being
serviced.
Figure 24
Figure 25 : LC1
Figure 26 : LC3
Figure 27 : Fan control (KFC)
Warning :
Never bypass the limit controls,
hazardous conditions could result.
The combustion air pressure switch ensures that proper combustion airflow is
available. The switch senses the differential pressure between the negative
pressure in the flue gas collector box and the pressure in the control section.
(For switch location, see figure 11b).
On startup when the heater is cold, the sensing pressure is at the most negative
level, and as the heater and flue system warm up, the sensing pressure be-
comes less negative.
If a restriction or excessive flue pipe length causes the sensing pressure to be
below the allowable level, the pressure switch will shut off the main burner.
DANGER : Safe operation of this
unit requires proper venting flow.
Never bypass the combustion air
pressure swtich or attempt to
operate the unit without the
venter operating.
All units are equipped with temperature activated limit controls. The controls
are factory set and non-adjustable. If either setpoint is reached, the correspond-
ing limit control will interrupt the electric power to the gas valve. These safety
devices provide protection in the case of motor failure or lack of airflow due to
restrictions. (For locations, see figure 11a.)