Table 23 — Field Wiring for Incoming Conductors
Sized for 125% of Heater Load
WIRE SIZE
(AWG or kcmil)
LOAD AMPS*
WIRE SIZE
(AWG or kcmil)
LOAD AMPS*
Copper
Copper
14
12
1/0
120
12
16
2/0
140
10
24
3/0
160
8
40
4/0
184
6
52
250
204
4
68
300
228
3
80
350
248
2
92
400
268
1
104
500
304
LEGEND
AWG — American Wire Gage
kcmil — Thousand Circular Mils
NEC
— National Electrical Code
*Values are based on Table 310-16 of the NEC for 75 C insulated
copper wire. Not more than 3 conductors in a raceway.
NOTES:
1. Be sure to consider length of wiring run and possible voltage drops
when sizing wires.
2. Field power wiring — Heaters are furnished with a terminal block
sized for incoming copper conductors with 75 C insulation rated to
carry at least 125% of the heater load. However, conductors can
be sized to carry 100% of the heater load if the heater is rated at
50 kW or more, and the heater is controlled by a cycling device
such as a multi-stage thermostat, step controller, or SCR (silicon
control rectifier) power controller. Terminal blocks and knockouts
are sized to handle either 100% or 125% conductors.
START-UP
Checklist —
Make a walkway inside unit components to
protect insulation. Remove all construction debris from unit
interior. Remove walkway before starting unit.
FILTERS — Install unit filters in all filter sections.
AIRFOIL AND FORWARD-CURVED FANS
1. Remove holddown plate that fastens the fan sled to the
section frame.
2. Check lubrication of fan, motor bearings, and linkages.
a. Note that bearings are shipped completely full of grease
for corrosion protection and may run warm tempo-
rarily on start-up until excess grease has discharged.
b. Hand operate all linkages, such as damper and guide
vanes, to check for freedom of movement.
3. Check tightness of bearing setscrews or locking collars
(Fig. 60). Also, check tightness of setscrews on fan wheels
and sheaves.
4. Check tightness of fan-shaft bearing mounting.
5. Recheck sheave alignment and belt tension. (Refer to
Fig. 26 and 28.)
6. Hand turn fan to make certain fan wheel does not rub in
housing.
7. Check fan speed with a strobe-type tachometer or use the
following formula:
Obtain the motor rpm from the fan motor nameplate and
read sheave pitch diameters marked on the fan and motor
pulleys, or approximate the pitch diameters by using the
pulley ODs.
Then:
Motor Rpm x Motor Sheave
Pitch Diameter (in.)
Fan Rpm =
Fan Sheave Pitch Diameter (in.)
Example:
Actual
Approximate
Nameplate
=
1760
1760
Motor Rpm
Motor Sheave
=
8.9 in.
9.0 (OD)
Pitch Diameter
Fan Sheave
=
12.4 in.
12.5 (OD)
Pitch Diameter
1760 x 8.9
1760 x 9
Fan Rpm
=
12.4
12.5
=
1263 Rpm
1267 Rpm
Refer to Tables 9-12 for maximum allowable fan speeds
for fan wheels. Excessive fan speed may result in con-
densate carryover from cooling coil or fan motor over-
load and wheel failure.
8. Check direction of rotation (see Fig. 61). Arrow on drive
side of fan housing indicates correct direction of
rotation.
9. Check vibration. If excessive vibration occurs, check for
the following:
a. Variable sheave (if air balance of system has been ac-
complished; replace sheave with fixed sheave for con-
tinuous application).
b. Drive misalignment.
c. Mismatched, worn, or loose belts.
d. Wheel or sheaves loose on shaft.
e. Loose bearings.
f. Loose mounting bolts.
g. Motor out of balance.
h. Sheaves eccentric or out of balance.
i. Vibration isolators improperly adjusted.
j. Out-of-balance or corroded wheel (rebalance or re-
place if necessary).
k. Accumulation of material on wheel (remove excess
material).
PLENUM FANS — Start-up procedures for plenum fans are
similar to those for airfoil or forward-curved fans described
in the preceding section. Also refer to the fan manufactur-
er’s Installation, Operation, and Maintenance instructions
shipped with the plenum fan section for further details.
72
Summary of Contents for 39T
Page 43: ...Fig 34 Discharge Fabrication Draw Thru Plenum Fans 43 ...
Page 49: ...Fig 41 Coil Connections and Lifting Points Fig 42 Steam Coil PIping 49 ...
Page 78: ...Fig 64 Blow Thru Unit Coil Removal Fig 65 Plan View Typical Coil 78 ...
Page 81: ...Fig 68 Filter Arrangement 2 in and 4 in Flat 81 ...
Page 82: ...Fig 68 Filter Arrangement 2 in and 4 in Flat cont 82 ...
Page 83: ...Fig 69 Filter Arrangement Angle Filters 2 in Only 83 ...
Page 84: ...Fig 69 Filter Arrangement Angle Filters 2 in Only cont 84 ...
Page 85: ...Fig 70 Filter Arrangement BCF1 Bag or Cartridge Draw Thru 85 ...
Page 86: ...Fig 70 Filter Arrangement BCF1 Bag or Cartridge Draw Thru cont 86 ...
Page 87: ...Fig 71 Filter Arrangement BCF3 Bag or Cartridge Blow Thru 87 ...
Page 88: ...Fig 71 Filter Arrangement BCF3 Bag or Cartridge Blow Thru cont 88 ...
Page 92: ...NOTE A frame shown shaded Fig 74 Fan Discharge Positions 92 ...
Page 102: ......
Page 103: ......
