JULY 19, 2017
6
STM-E, STM-EL, STM-EX & STM-ELX STERILIZERS
PRESSURE ACTUATED TEMPERATURE CONTROL
STM-E AND STM-EL
The pressure actuated temperature control, located be-
hind the control panel assembly, governs the manufac-
ture of steam by controlling the input of electric current to
the heating elements.
HOW IT WORKS
When the Timer is set, rear and front contactors will be-
come energized allowing input of current to the tempera-
ture control, thus closing the contacts completing the
current to the heating elements. Steam will then be gen-
erated within the sterilizing chamber.
The steam pressure within the sterilizing chamber is
transmitted by means of a tube to the bellows of the tem-
perature control; as the steam pressure increases, its
compression action on the bellows is set to cause the
Switch #1 on the control to cut out on rising pressure at
13.5 PSI and to cut in on falling pressure at 13 PSI (con-
trolling the two outer banks of heating elements). Switch
#2 is set to cut out on rising pressure at 15.5 PSI and cut
in on falling pressure at approximately 15 PSI (controlling
center heater element only).
Thus, a balancing effect of steam pressure build-up and
heater element current is constantly maintained during
the sterilizing cycle. When the Timer signifies the end of
the cycle, the electric current to the contactors will auto-
matically be broken; the temperature control contacts will
be broken; and steam generation will stop.
ADJUSTING THE RANGE OF OPERATION, STM-E
NOTE: These instructions should be performed by
qualified service personnel only.
The operational range of the temperature control is fac-
tory set as follows: Outer bank of elements OFF at 13.0-
13.5 PSI; Center bank of elements OFF at 15.5- 15.0 PSI;
minor compensating adjustments can be made by turning
the adjusting screws counter-clockwise to increase pres-
sure and clockwise to decrease pressure. Both screws
should be turned the same amount when making an ad-
justment.
NOTE:
When resetting this control for elevations above
sea level a correction of 6/10 Ib. per thousand
feet is necessary.
1. Before making adjustments, shut all electrical current
to the sterilizer OFF to eliminate shock hazard.
2. Remove the Flue Cover.
3. Make sure that all exposed wires are not in a hazard-
ous position, and then turn on electrical power.
4. Run unit through cycle, observing pressure and tem-
perature gauges, turn adjusting screws as required.
Figure 5
CHECKING THE 230° SETTING, STM-EL
The Unit should be completely evacuated then tempera-
ture selector dial should be turned on 230° Fahrenheit.
Observe the current until it takes a sharp drop to ap-
proximately one-third of the full load; at this instant, there
should be a corresponding chamber pressure of 2 PSI
Observing the current further will show another sharp
drop to approximately 2 Amps; at this instant, there should
be a corresponding chamber pressure of 6.1 PSI and a
temperature reading of 228° to 232° Fahrenheit, on the
temperature gauge.
ADJUSTING THE RANGE OF OPERATION
STM-EL
The range of operation of Model STM-EL is adjusted by
simply turning the adjusting knob on the outside of the
Control Panel. A counter-clockwise turn decreases the
pressure while a clockwise turn increases the pressure.
Observe pressure and temperature gauges and adjust
knob as required.
NOTE: When resetting this control for elevations above
sea level, a correction of 6/10 Ibs. per thousand
feet is necessary.