Operating Limits; Fan Vibration Levels - Daikin Destiny VFD Series Installation And Maintenance Manual

Operating Limits

Do not exceed the operating limits in
A fan wheel that is operated beyond the rpm and temperature
limits shown may suffer permanent distortion or fracture. The
resulting unbalance may cause severe unit vibration.
Table 33: Forward Curved Fan Operating Limits
Forward curved—housed
Dia.,
7–7 9–9 10–10
(in)
Max.
2680 2650 2100
rpm
Table 34: Backward Inclined Plenum Fan Operating Limits
Backward inclined —plenum
Dia., (in) 9 10
Max. rpm 2680 2650
Dia., (in) 18 20
Max. rpm 1500 2675
For units with direct drive plenum fans employing variable
frequency drives, use the formula below to calculate the
maximum allowable frequency associated with the maximum
allowable fan speed.
F = 60 Hz × (W / W
max max motor
F
– maximum frequency allowable for particular application
max
(Hz)
W – maximum fan speed (rpm); refer to fan curves
max
33 through Figure 41)
W – nominal motor speed (1800/3600 rpm); refer to motor
motor
nameplate
www.DaikinApplied.com
Table 33 and Table
Twin Twin
12–12
10" 12"
1700 2100 1700
11 12.5 14
2100 1700 2100
22 25 28
2310 2060 1840
)
(Figure

Fan Vibration Levels

34. Each unit as shipped is trim balanced to operate smoothly. To
provide satisfactory operation after shipping and installation,
use the accepted industry guidelines for field balancing fans.
Vibration ≤ 0.20 in/sec.
NOTE: Excessive vibration from any cause contributes to
premature fan and motor bearing failure. Monitor
overall vibration levels every six months of operation.
An increase in levels is an indication of potential
Twin trouble.
15"
Vibration Causes
1500
1. Wheel imbalance
a. Dirt or debris on wheel blades
b. Loose setscrews in wheel hub or bearing-to-shaft
16
c. Wheel distorted from overspeed
1700
2. Bent shaft
3. Drive faulty
a. Variable pitch sheaves—Axial and radial runout of
flanges, uneven groove spacing, out of balance.
Also similar faults in driven sheave.
b. Bad V-belts, lumpy or mismatched, belt tension too
tight or too loose
4. Bad bearings, loose bearing hold-down bolts
5. Motor imbalance
6. Fan section not supported evenly on foundation
45
Operation Guidelines
IM 782-12 • DESTINY AIR HANDLERS