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Vibration Isolation

When your VAV fan is energized, it generates a thrust force which

causes the fan to be displaced opposite to the direction of air flow.

This force must be resisted to maintain duct alignment and to

protect the flexible connectors. Some installations, particularly

horizontal units with long hanging rods, may require snubbers to

limit the fan movement.

B-6 Free Inlet

VAV fans with open inlets require the use of an inlet bell or inlet

cone. Published fan performance is based on the use of an inlet

bell. Operation of unit with bare open inlet will result in decreased

performance and increased noise.

B-7 Outlet Cone

The VAV Vaneaxial fan is inherently a high velocity air moving device

so it is quite common to utilize a diverging cone on the fan discharge

to minimize the velocity pressure loss and regain static pressure.

The use of an outlet cone enables more of the fan’s pressure capabil-

ity to be available to overcome system static pressure.


Flexible Connections

All ducts should be closely aligned with the fan and flexible connections

provided between the fan and duct to prevent structure borne noise

from being transmitted through the ductwork.

Axial fans, since they require the air to enter the wheel unobstructed,

require special care in the installation of inlet flexible connections.

Since the inlet side of the fan is under negative pressure, construction

material tends to be sucked inward disrupting the flow of air to the

wheel and reducing fan performance. The thrust of the fan aggravates

this situation in that the fan tends to move forward against the direction

of the air flow when it is operating. Flexible connections made at the

large diameter of inlet belts and/or cones eliminate this problem.

B-9 Fan Mounting Hardware

All hardware used in the field for support or connection of your VAV fan

should be a minimum of Grade 5 quality.

B-10 Electrical

The motor leads terminate in the conduit box mounted on the exterior

of the fan casing. Rigid conduit should be run from the motor starter to

the fan with a short section of flexible conduit at the conduit box to allow

for fan movement.

Wire size and motor overloads should be sized in accordance with the

motor nameplate electrical data. On Arrangement 4 fans, a motor name-

plate is located on the casing adjacent to the Chicago Blower nameplate.

The WR


of your VAV fan is quite low, in comparison with comparable

centrifugal fans, with a start-up time of the magnitude of 3-6 seconds.

The VAV fan and motor is capable of across-the-line starting, however,

reduced voltage starting may be required by local conditions or limitations.

B-11 Start-up Check List

After the equipment has been installed correctly and a check has been

made for tightness of all hardware and mounting bolts, the fan will be

ready to operate after these final safety checks to prevent injury to

personnel or damage to the equipment.

1. Check for correct supply voltage and motor overloads.

2. Remove all tramp material from fan, duct, and in front of fan intake.

3. Check blade pitch setting against nameplate.

4. If belt driven fan, check alignment of belts and sheaves.

5. “Bump” motor to check for fan rotation. Rotation is CCW looking

into the fan.

6. Start fan. Check motor amperage in each phase for balance and

correct motor load.

7. Check for vibration and any unusual noise.

B-12 Mounting Accessories/Ductwork

Chicago Blower requires that all appurtenances, including ductwork or

stacks, which are attached to the fan inlet or outlet, be independently

supported, unless prior approval has been obtained from Chicago

Blower. Excess dead loads or wind loads can distort the fan housing

causing misalignment and possible failure. Flexible connections are

also necessary to prevent duct expansion or movement from adding

loads to the fan.

C. Maintenance

C-1 General

The basic design and precision construction of Chicago Blower VAV

fans are intended to provide long, trouble-free life.Wheels are statically

and dynamically balanced after assembly and the completely assem-

bled fan is given a running balance before final inspection/shipment.

To insure long life and trouble-free service, routine maintenance and

inspection should be observed.Your VAV fan has been lubricated prior

to shipment from the factory and should be relubricated per the proper

schedule after start-up. Motor and bearing manufacturers’ recom-

mended schedules are packed with the fan.

Mixing of lubricants is not recommended.

Cleanliness is very important in lubrication. Any grease used should

be fresh and free from contamination. Similarly, care should be

taken to properly clean the area around the grease inlet to prevent


Maintenance personnel should be alert for excessive vibration or

any unusual sounds in the equipment. If the fan is to remain idle for

an extended period, it is recommended that the exposed surfaces

be covered with a protective coating. Bearings should be protected

in line with the manufacturer’s recommendations and the wheel

should be rotated periodically.

C-2 Lubrication – Arrangement 4

In an Arrangement 4 VAV fan, the motor is the heart of the unit and

particular care should be taken in maintenance of the motor to

insure a long and continuous operating life. The unit should be

checked periodically for vibration and any unusual noises.

There are two bearings in the motor, so two grease leads extend

from the motor to the outside of the casing. These leads are

terminated with standard grease fittings.

The following procedure should be followed for proper lubrication:

1. Stop motor and lock out the switch.

2. Locate the grease inlet fittings. Clean the area thoroughly,

remove plastic caps from grease fittings.

3. Add the recommended volume* of the recommended lubri-

cant* using a hand operated grease gun. If possible, rotate the

fan wheel by hand during greasing.

4. Remove excess grease and purged grease from area and

replace plastic grease fitting caps.

5. Run motor for at least one hour.

6. Clean up any purged grease.

7. Return unit to operation.

* The various motor manufacturers have different recommended

volumes and types of grease. Check the motor manufacturer’s

instructions, packed with the fan, before lubricating the motor.

C-3 Lubrication – Arrangement 9

In an Arrangement 9 VAV fan, both the fan bearings and the motor

bearings need to be included in your planned maintenance

schedule. The fan unit should be inspected periodically for any

unusual noises or change in vibration.

The two fan bearings have grease leads extended to the outside of

the fan casing. These leads are fitted with standard grease fittings.

The following procedure should be followed for proper lubrication.

1. Stop motor and lockthe switch.

2. Locate the grease inlets and reliefs on the motor and clean

the area of dirt and contaminated grease. Grease the mo t o r

per the recommendation of the motor manufacturer.

3. Locate the grease inlets in the fan casing and clean the area

of dirt and contaminated grease. Remove plastic cap from

grease fitting.

4. Lubricate the bearings per the manufacturer’s instructions

packed with the fan.

5. Add lubricant slowly and rotate fan wheel during lubrication,

when possible and where good safety practice permits.

6. Replace plastic grease fitting caps and clean excess grease

from area..

7. Return unit to operation. Unit should be watched for several

hours for proper operation.

C-4 Grease Lead Location

On the Arrangement 4 VAV fan, the grease inlet fittings are located

on the outside of the fan casing within 15° of the electrical conduit

box. All two fittings are in the same area. The leads have standard

grease fittings.

On the Arrangement 9 VAV fan, the grease leads are brought to the

outside of the fan through the belt tunnel. The grease fittings are

attached to clips which are welded to the adjustable motor base.

The two fittings are located 180° apart.

D. Disassembly and Assembly

D-1 Adjustable Pitch – Arrangement 4

Warning: Disconnect all power sources from fan to avoid electrical

shock and personal injury from rotating parts.

D-1-a Wheel Removal

1. Remove nose spinning from hub. Spinning is attached to hub

by either six (A Hub) or eight (B, LB & C Hubs) screws located

around the periphery of the hub.

2. Remove hex head bolts securing hub to Q-D bushing.


out the switch.






f dirt and contaminated grease. Grease the mot




























n excess grease



hours for proper operation.


heck for co rect su ply voltage and motor overloads.


e ove all tra p material from fan, duct, and in front o fan intake.

. Check blade pitch se ting against na eplate.

. If belt driven fan, check align ent of belts and sheaves.

5. “Bump” motor to check for fan rotation. Rotation is CCW looking

into the fan.

6. Start fan. Check motor amperage in each phase for balance and

co r ct t r lo .


heck for vibration and any unusual noise.