Internal Vibration Isolation; Removing Holddown Bolts, Airfoil, Plenum And Forward-Curved Fans; Adjusting Isolator Springs; External Vibration Isolation - Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual

Fig. 17 — Lifting Lug Detail for Pad-Mounted Unit
with or without Isolation

Internal Vibration Isolation

Units equipped with internal vibration isolation must be prepared
as described in this section before they are installed.
For applications that do not require internal fan isolation, leave the
holddown bracket screwed or bolted in place. Otherwise, the com-
bination of internal and external unit isolation could lead to un-
wanted oscillation magnification.
REMOVING HOLDDOWN BOLTS, AIRFOIL, PLENUM
AND FORWARD-CURVED FANS
Remove the holddown bolts (Fig. 18) as follows:
1. Open the fan access door.
2. Remove the bolts that fasten the fan sled to the holddown
bracket (Fig. 18). Remove "S" shaped brackets.
3. Repeat Steps 1 and 2 on the opposite side of the fan section.
Fan sled assembly should float on isolator springs when done.
ADJUSTING STEM
"S" SHAPED
BRACKET
HOLDDOWN
BOLT
SPRING
Fig. 18 — Spring Isolator and Holddown Bracket

ADJUSTING ISOLATOR SPRINGS

Units with factory-supplied motors and drives are preset to
/ -in. clearance between the base frame assembly and the bottom
1
8
panels; field adjustment of the isolator springs is not normally
required.
WARNING
When adjusting fan isolation components, DO NOT enter or
reach into the fan cabinet while fan is running. Serious injury
can result. Be sure to disconnect power and tag controls before
making adjustments.
a39-4329
SLED MEMBER
HOLDDOWN
BOLT
"S" SHAPED BRACKET
/
13
16
When field-supplied motors and drives have been installed, adjust
the isolator springs as shown in Fig. 18 and described as follows:
1. Loosen the locknut on adjusting stem.
2. Turn the adjusting stem until the specified clearance of
/ -in. is obtained. (Turn clockwise to decrease clearance or
1
8
counterclockwise to increase clearance.)
3. Tighten the locknut.
4. Repeat for each of the isolator springs and ensure that the fan
sled is floating on the springs.

External Vibration Isolation

Install external vibration isolators per certified drawings, job spec-
ifications, and the instructions of the isolator manufacturer.
For applications that do not require internal fan isolation, leave the
holddown bracket screwed or bolted in place. Otherwise, the com-
bination of internal and external unit isolation could lead to un-
wanted oscillation magnification.
The coil piping must also be isolated or have flexible connectors
to avoid coil header damage due to motion or vibration. Flexible
connections should also be installed at the fan inlet (if ducted) and
at the discharge.

Roof Curb

Roof curbs can be factory or field supplied for 39MW units and
should be installed according to the manufacturer's instructions.
Before installing roof curb, check overall unit length. Figure 19
shows AHU (air-handling unit) curb pocket dimensions.
1.00
3.00
4.50
2.25
NOTE: All dimensions are shown in inches.
Fig. 19 — Curb Pocket Dimensions
(Sizes 03-110 Typical)
+
Curbs are typically shipped knocked down and require field as-
sembly as follows:
1. Curbs greater than 12 ft in airway length will be split and
joined together by a splice plate. Butt the two sections and
bolt together with the splice plate as shown in Fig. 20.
2. Arrange sides and ends together at right angles and bolt
together using the corner bracket as shown in Fig. 21.
3. Fasten cross supports, when required, per the drawings with
supplied screws as shown in Fig. 22.
85
1.893
1.00
1.221
Ø1.50
1.74
1.00
2X Ø 0.625
1.893
3.00
/ +
13
16
6.00