National 3402, Instruction Manual

Page: 13 / 28

Machine Maintenance
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HEPA FILTER REPLACEMENT PROCEDURE
1. Turn the machine on then block the inlet with a fl at and rigid material to place the
machine under vacuum pressure.
2. Remove the motor deck socket truss screws.
3. Turn the machine off and disconnect the power source.
4. Unscrew the cable grip in the HEPA fi lter housing spacer.
5. Push about a foot of the power cord into the HEPA fi lter housing spacer.
6. Separate the motor deck from the HEPA fi lter housing spacer then disconnect the
motor deck ground wire from the HEPA fi lter adapter plate assembly via the push-
on terminal.
7. Disconnect the three power cord wires from the terminal block on the underside of
the motor deck (See Figure K).
8. Remove the motor deck.
9. Remove the four lock nuts retaining the two HEPA fi lter brackets.
10. Remove the ring-to-tab terminal, HEPA fi lter brackets and HEPA fi lter.
11. Center the new fi lter on the HEPA adapter plate, gasket side down.
12. Position the provided lengths of self-adhering fl at gasket material on the HEPA fi lter
frame (if not already done so) to cushion the HEPA fi lter brackets.
13. Replace the HEPA fi lter brackets and ring-to-tab terminal then thread the locking
nuts over the rods and tighten.
14. Set the motor deck on the HEPA fi lter housing spacer.
15. Connect the three power cord wires to the their respective terminals in the terminal
block on the underside of the motor deck.
16. Connect the motor deck ground wire to the HEPA adapter plate assembly via the
push-on terminal then seat the motor deck on the HEPA fi lter housing spacer.
17. Pull any unnecessary slack in the power cord back through the cable grip then
secure the cable.
18. Connect the power source.
19. Turn the machine on then block the inlet with a fl at and rigid material to place the
machine under vacuum pressure.
20. Secure the motor deck then turn the machine off.
FIG. J
FIG. K
NOTE:
THE DIFFERENTIAL PRESSURE GAGE MEASURES THE PRESSURE
ABOVE, AGAINST THE PRESSURE BELOW THE HEPA FILTER, THEREBY
MEASURING THE RESTRICTION OF AIRFLOW THROUGH THE FILTER. FILTERS
SHOULD BE REPLACED WHEN THE GAGE CONSISTENTLY READS 4 INCHES.
CAUTION:
DO NOT OVER TIGHTEN. THE EFFECTIVENESS OF THE FILTER
MAY BE COMPROMISED IF ITS FRAME IS BENT.