Microwave Oven User Manual

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2. Blower balancing and direction of rotation
Proper blower rotation is extremely important. Proper
blower rotation is shown in Figure 45.
Early PS570 blower wheels were positioned so that
the open end of the wheel faced into the baking cham-
ber. This was changed on the PS570S (and all later
models) to improve airflow. Note that this also means
that on early PS570 ovens the counterclockwise wheel
is moved to the left side of the oven, and the clockwise
wheel moved to the right side, so that the wheel blades
point in the same direction. This is reflected in the
Part Number Reference information on Page 77.
All blower wheels are balanced at the factory. Any
blower wheel found to be out of balance should be re-
placed. Vibration from an out-of-balance wheel can
cause poor baking and premature bearing failure. Note
that vibrations can also be caused by other sources,
including defective motor or blower shaft bearings, loose
bearings or motor mounting bolts, or an incorrectly
tensioned fan belt.
Figure 45
PS500-series blower wheel orientation
Clockwise:
Right end
Counter-
clockwise:
Left end
PS570:
Open end of wheel faces IN
Counter-
clockwise:
Right end
Clockwise:
Left end
PS570S, PS570G, PS555:
Open end of wheel faces OUT
Note slant of blades
3. Lubricating the blower shaft bearings
NOTE: Middleby recommends lubricating the blower
fan shaft bearings every three months.
Use a grease gun to lubricate the main blower fan shaft
bearings. See Figure 46. When lubricating the bear-
ings:
 Use a high-quality NLGI #2, lithium soap grease with
petroleum oil, such as Middleby P/N 17110-0015.
 Add the grease slowly until a small bead of grease
is present at the seals. AVOID OVERGREASING.
Excessive greasing may cause harm to the bearing.
Manually turn the blower shaft by pulling on the belt to
purge the grease. Wipe off any excess grease. The
oven cannot be operated until the rear shroud is replaced.
IMPORTANT: Middleby uses two different types
of grease in blower shaft bearings:
 DuPont Krytox® grease is used in some
PS536 ovens. Refer to Service Bulletin MM-
192 (included in the Appendices section of
this chapter) for details on identifying
Krytox® bearings.
 All other ovens use the standard Middleby
high-temperature grease, P/N 17110-0015.
Mixing grease types within the bearing will
cause the bearing to seize. For all PS555/570-
series ovens, be sure to use ONLY the stan-
dard Middleby grease.
Figure 46
Bearing lubrication
Grease fittings
(1 per bearing,
4 total)
PS570,
PS570S
Grease fittings
(1 per bearing,
4 total)
PS570G,
PS555
SECTION 3 - SERVICING COMPONENTS