Model 1280 Series ____________________________________________________________________Routine Maintenance
Section 9 - Routine Maintenance
Before any maintenance work is performed in
the biological safety cabinet, the unit must first
be decontaminated.
9.1 Checking the Static Pressure Gauge “Zero”
Note:
In order to provide an accurate reading, the indicating
needle of the static pressure gauge should be precisely at zero
when the cabinet is shut off. If the cabinet is connected to a
central exhaust system, the exhaust system must also be shut
off.
Following HEPA filter replacement, the static pressure
gauge should be checked for zero when the cabinet is shut off.
(refer to Section 9.2). When the cabinet is started up and proper
airflow balance has been reached, the reading on the gauge
should be recorded. This initial reading will serve as a baseline
indication of subsequent filter loading. When the reading
increases by approximately 50%, the airflow balance should
again be checked. Replacement of the filters may be required.
9.2 Zeroing the Static Pressure Gauge
1. Turn the cabinet off.
2. Remove the front cover from the static pressure gauge
by grasping the front cover and turning it counterclock-
wise.
3. Locate the Allen-type adjustment screw beside the gauge
needle.
4. Turn the adjustment screw counterclockwise to lower
the reading; clockwise to raise it.
9.3 Adjusting the Damper
Since the HEPA filter resistance may vary from filter to fil-
ter (even filters of the same size), a damper has been installed
in the cabinet exhaust system for maintaining proper airflow
balance. The purpose of the damper is to regulate the amount of
exhaust air, intake velocity and supply velocity. The damper has
been preset at the factory and should not be readjusted unless
the proper velocities cannot be obtained.
Adjustments must be made by qualified personnel
only!
1. Layout test grids (refer to Section 9.4).
2. Start-up the cabinet and allow it to run for at least twen-
ty minutes.
3. Take airflow measurements. If airflow specifications are
not sufficient, open the control panel and check the volt-
age on the power switch.
Note:
Airflow measurements and voltages are recorded at the
factory with the cabinet connected to the appropriate AC power
supply.
4. Open the hinged control panel by removing the screw on
the top and bottom of the control panel and swinging the
panel door open. Locate the blower motor circuit board.
(Figure 9-1 & 9-2) Using a true RMS voltmeter, meas-
ure and record the voltage drop across the white and
black wires leading to the terminal strip. (Figure 9-1)
The blower speed control adjustment pot is located on
the upper left side of the board. Clockwise adjustment of
this pot increases voltage supply to the blower motor,
counterclockwise adjustment lowers the voltage supply.
Adjust it 2-3 volts, up or down, depending upon the air-
flow required. Retake the airflow measurements.
Figure 9-1
9 - 1
