Middleby Marshall PS220 Bearing lubrication, Blower belt tension, Repositioning the blower motor

2.Blower balancing and direction of rotation

Proper blower rotation is extremely important. From the rear of the oven, the blower shaft pulley should turn in a clockwise direction. See Figures 25 and 26.

All blower fans are balanced at the factory. Any fan found to be out of balance should be replaced. Vibra- tion from an out-of-balance fan 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 mo- tor mounting bolts, or an incorrectly tensioned fan belt.

3.Lubricating the blower fan shaft bearings

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 PS200 ov- ens, be sure to use ONLY the standard Middleby grease.

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 28. 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.

4.Blower belt tension

NOTE: Middleby recommends checking the blower belt condition and tension every three months.

Check the blower belt for at least 1" (25mm) deflection at the center, and for cracking or excessive wear. Overtightening the belt will cause premature bearing failure and possible vibrations. See Figure 29.

If necessary, adjust the tension of the belt by loosening the two motor mounting bolts as shown in Figure 30. Reposition the motor as neccessary until the correct deflection is reached, then tighten the bolts.

SECTION 3 - SERVICING COMPONENTS

Figure 28

Bearing lubrication

Grease fittings (1 per bearing, 2 total)

Figure 29

Blower belt tension

1” (25mm)

vertical

deflection

Figure 30

Repositioning the blower motor

Loosen bolts to reposition motor and adjust belt tension

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