Daikin RDT-135c Installation And Maintenance Manual

Contents

Daikin RDT-135c Installation And Maintenance Manual Manual pdf 98 page image

96 IM 738-2Unit Options: Propeller Exhaust Fan OptionPropeller Exhaust Fan OptionEconomizer units may include propeller exhaust or centrifugalreturn fan options. This section covers maintenance andoperating instructions for the propeller exhaust option.Centrifugal return fan construction, maintenance and operationis similar to that for supply fans and covered in other sectionsof this manual.Figure 99. Two fans with back return shownPrestarting ChecksCheck all fasteners and set screws for tightness. This isespecially important for bearing set screws.The propeller should rotate freely and not rub on the fan panelventuri. Rotation direction of the propeller should be checkedby momentarily turning the unit on. Rotation should be in thesame direction as the rotation decal affixed to the unit or asshown in Figure 100 on page 96. For three-phase installations,fan rotation can be reversed by simply interchanging any twoof the three electrical leads. For single phase installationsfollow the wiring diagram located on the motor.The adjustable motor pulley is preset at the factory for thespecified fan RPM. Fan speed can be increased by closing ordecreased by opening the adjustable pulley. Two or threegroove variable pitch pulleys must be adjusted an equalnumber of turns open. Any increase in fan speed represents asubstantial increase in horsepower required from the motor.Always check motor load amperage and compare to nameplate rating when changing fan speed.Figure 100. Fan rotationOnce the fan is put into operation, set up a periodicmaintenance program to preserve the reliability andperformance of the fan. Items to include in this program are:• Belts• Bearings• Fasteners• Setscrews• Lubrication• Removal of Dust/DirtBeltsPremature belt failures are frequently caused by improper belttension (either too tight or too loose) or misaligned pulleys.The proper tension for operating a V-belt is the lowest tensionat which the belts will not slip peak load conditions. For initialtensioning, the proper belt deflection half way between pulleycenters is 1/64" for each inch of belt span. For example, if thebelt span is 64 inches, the belt deflection should be one inchusing moderate thumb pressure at midpoint of the drive,See Figure 101.Check belt tension two times during the first 24 hours ofoperation and periodically thereafter. To adjust belt tension,simply loosen four fasteners (two on each side of the motorplate) and slide the motor plate away from the fan shaft untilproper belt tension is attained. On some fans, fastenersattaching the motor to the motor plate must be loosened inorder to adjust the belt.It is very important that the drive pulleys remain in properalignment after adjustments are made. Misalignment of pulleysresults in premature belt wear noise, vibration, and power loss.See Figure 102.Fans and motorsVFDStartersWARNINGRotating parts can cause severe personal injury or death.Replace all belt/fan guards that are removed temporarily forservice.AirflowAirflowRotationRotation