SECTION I
GENERAL INFORMATION
© Midmark Corporation 2002 SF-1803 Printed in U.S.A.
Page 1 - 3
B. Theory of Normal Operation (115 or 230 VAC
Units) (See Section 2 for Normal Operation Table 2-1
and Main Printed Circuit Board (PCB) and Compo-
nent Layout, Figure 2-2).
Power Up Mode:
(Display: INITIALIZING SYSTEM)
• When the Power Cord is plugged into an outlet, line volt-
age is supplied to the Sterilizer’s Main PCB to J5 connec-
tor.
• F1 and F2 fuses on the Main PCB protect the board’s
circuitry from excessive current draw. A transformer
along with the voltage regulators on the PCB reduces line
voltage to 5 & 12 VDC. The DC voltage provides power
to operate the circuitry on the PCB, touchpads, and
printer circuitry.
• Line voltage is also supplied from N / L2 of the plug out-
let to one side of the Axial Flow Fan and from J5 (4) on
the Main PCB to the Fan Thermostat.
The Fan Thermostat closes at 130°F(+/- 8°F) and opens
at 101°F (+/- 6°F). If closed, power would be supplied to
the other side of the Axial Fan Motor energizing it.
• During the Power Up Mode, the sterilizer executes an
intialization upon all subsystems. In addition certain error
conditions are also tested for, and the beginning mes-
sages are displayed (see Normal Operation
Table 2-1).
• Power Up Mode ends when all systems have been ini-
tialized, or when an error condition is encountered.
Select Cycle Mode:
(Display: SELECT CYCLE)
• When SELECT CYCLE is being displayed, before the
user presses one of the cycle keys, the software opens
the Air Valve for a maximum of 10 minutes or until the a
Cycle is initiated by pressing the START key. This makes
it easier to open the door.
Power is supplied thru J5 connector and the Normally
Closed Hi Limit switches. The software has energized K5
relay, closing its contacts. Current is provided to termi-
nals J6 and J7 and the Air Valve solenoid, opening the
valve.
• During Select Cycle Mode, the user enters which sort of
sterilization cycle that he would like to perform on the
load (UNWRAPPED, POUCHES, PACKS, HAND-
PIECES, or programmable buttons 1 or 2).
• Select Cycle Mode ends when the user chooses a
cycle-type, and presses the START button, or when an
error condition occurs.
• “Additional Heat”
feature will be activated if the START
button is pressed before a cycle-type is selected.
K1 (Heater) contacts close. Current is supplied thru J5
connector, terminals 5 & 6, thru the two normally closed
High Limit Switches and the closed contacts of K1 relay
to terminals J3 & J4 on the PC board and to the Heating
Element. The software will cycle the heating element on
and off for five (5) seconds, once each minute for a period
of 10 minutes.
• “Additional Heat” will not activate
if one of the following
occurred:
1. The Additional Heat feature has already been started
once during the Select Cycle Mode.
2. The STOP button has been pressed prior to depress-
ing the START button during Select Cycle.
3. Any of the cycle buttons have been pressed prior to
pressing the START button during the Select Cycle.
• “Additional Heat”, if enabled, will end and be disabled
for the rest of this Select Cycle Mode for the following rea-
sons:
1. Any of the cycle buttons have been pressed while in
“Additional Heat”.
2. The STOP button has been pressed prior to pressing
the START button during Select Cycle.
3. Ten (10) minutes elapses, starting from the time that
“Additional Heat” was enabled.
Fill Mode:
(Display: FILLING CHAMBER)
• During Fill Mode water is allowed to run from the reser-
voir into the pressure vessel (chamber) by operation of a
Fill Valve.
• After the software checks the system for errors it starts
a 5 minute timer. The Main PCB supplies line voltage to
the Fill Solenoid thru K2 (Fill Valve) contacts thru J5 con-
nector, terminals 5 & 6, thru two normally closed High
Limit Switches and the Door Interlock Switch (closed
when door is closed) terminals J1 & J2 to terminals W3 &
W4 on the Main PC board and to the Fill Valve, energiz-
ing it. The Heater is off. The Vent Valve is energized
closed.
• Fill Mode ends
when:
1. There is enough water in the chamber to activate the
level sensor (J8 connector) sending a signal back to the
Main PC board. (Display: CHAMBER IS FULL). K2 relay
opens, closing the Fill Valve.
The Vent Valve remains closed (energized), the Air Valve
remains open (energized), Heater is off.
2. An error condition occurs.
3. The user presses the STOP button.
Heat Up Mode:
(Display: HEATING - UNWRAPPED)
• During the Heat Up Mode, steam temperature and pres-
sure within the chamber are brought up to their set points
chosen by the program button that was selected
(UNWRAPPED in this example). This is done by energiz-
ing the Heating Element and manipulating the Air Valve
to open and close, expelling air from the chamber.
• The Vent Valve (normally open) is energized to the
closed position
. Power is supplied thru K4 (Vent Valve)
contacts thru J5 connector, terminals 5 & 6 thru the two
normally closed High Limit Switches and to terminals W5
& W6 on the Main PC board to the Vent Valve energizing
it (Closes).
• K1 (Heater) contacts are closed supplying line voltage
thru J5 connector, terminals 5 & 6 thru the two normall
NOTE
To simplify explanation, the cycle chosen is
UNWRAPPED. Basically, all cycles function the
same. Time, temperature, and vent settings (slow or
fast) could be different.
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