Omnizone™ Constant Volume Water-Cooled Cooling Unit 50BVZ: General Maintenance

Cleaning Unit Exterior

Unit exterior panels should be wiped down using a damp soft cloth or sponge with a mixture of warm water and a mild detergent.

Fan Sheaves

Factory-supplied drives are pre-aligned and tensioned; however, it is recommended that the belt tension and alignment be checked before starting the unit. Always check the drive alignment after adjusting belt tension.

To install sheaves on the fan or motor shaft:

Isolate power to the unit.
Remove side unit access panel(s).
Remove any rust-preventive coating on the fan shaft.
Make sure the shaft is clean and free of burrs. Add grease or lubricant to bore of sheave before installing.
Mount sheave on the shaft; to prevent bearing damage, do not use excessive force.

Each factory-assembled fan, shaft, and drive sheave assembly is precision aligned and balanced. If excessive unit vibration occurs after field replacement of sheaves, the unit should be rebalanced. To change the drive ratio, follow the steps in the Evaporator Fan Performance Adjustment section (page 55).

https://www.shareddocs.com/hvac/docs/1005/Public/0B/50BV-5SI.pdf

After 1 to 3 minutes of operation, check the belt tension. Also check tension frequently during the first 24 hours of operation and adjust if necessary. Periodically check belt tension throughout the run-in period, which is normally the initial 72 hours of operation.

ALIGNMENT

Make sure that fan shafts and motor shafts are parallel and level. The most common causes of misalignment are nonparallel shafts and improperly located sheaves. Where shafts are not parallel, belts on one side are drawn tighter and pull more than their share of the load. As a result, these belts wear out faster, requiring the entire set to be replaced before it has given maximum service. If misalignment is in the sheave, belts enter and leave the grooves at an angle, causing excessive belt and sheave wear.

Shaft Alignment

Check shaft alignment by measuring the distance between the shafts at 3 or more locations. If the distances are equal, then the shafts are parallel.

Sheave Alignment

To check the location of the fixed sheaves on the shafts, use a straightedge or a piece of string. If the sheaves are properly aligned, the string will touch them at the points indicated by the arrows in Fig. 28. Rotate each sheave a half revolution to determine whether the sheave is wobbly or the drive shaft is bent. Correct any misalignment.

With sheaves aligned, tighten cap screws evenly and progressively.

NOTE: There should be a 1/8-in. to 1/4-in. gap between the mating part hub and the bushing flange. If the gap is closed, the bushing is probably the wrong size.

With taper-lock bushed hubs, be sure the bushing bolts are tightened evenly to prevent side-to-side pulley wobble. Check by rotating sheaves and rechecking sheave alignment. When substituting field-supplied sheaves for factory-supplied sheaves, only the motor sheave should be changed.

Evaporator Fan Performance Adjustment

To change fan speeds from factory settings:

https://www.shareddocs.com/hvac/docs/1005/Public/0B/50BV-5SI.pdf

Shut off unit power supply.
Loosen nuts on the 4 carriage bolts in the mounting base. Using adjusting bolts and plate, slide the motor and remove the belt.
Loosen movable-pulley flange setscrew.
Screw the movable flange toward the fixed flange to increase speed, and away from the fixed flange to decrease speed. Increasing the fan speed increases the load on the motor. Do not exceed the maximum speed specified in Tables 2 and 3.
Set the movable flange at nearest keyway of the pulley hub and tighten the setscrew. (See Tables 2 and 3 for speed change for each full turn of pulley flange.)
Replace and tighten the belts (see Belt Tension Adjustment section).
Restore power to the unit.

To align fan and motor pulleys:

Loosen fan pulley setscrews.
Slide fan pulley along fan shaft.
Make angular alignment by loosening motor from mounting plate.
Restore power to unit.

BELT TENSION ADJUSTMENT

Using a gage, apply 4 lb of force to the center of the belt and adjust the tension until a deflection of 1/64-in. is achieved for every inch of shaft center distance. See Fig. 29.

Ideal belt tension is the lowest value under which belt slip will not occur at peak load conditions.

Compressor Oil

All units are factory charged with oil. It is not necessary to add oil unless compressor(s) is removed from the unit.

If necessary, oil can be removed/charged via Schrader fitting.

Operate the system at high evaporator temperature prior to oil recharge to assist oil return to the compressor(s) from other system components.

If necessary, recharge the system as shown in Table 32.

Cleaning Unit Exterior

Unit exterior panels should be wiped down using a damp soft cloth or sponge with a mixture of warm water and a mild detergent.

Fan Sheaves

Factory-supplied drives are pre-aligned and tensioned; however, it is recommended that the belt tension and alignment be checked before starting the unit. Always check the drive alignment after adjusting belt tension.

To install sheaves on the fan or motor shaft:

Isolate power to the unit.

Remove side unit access panel(s).

Remove any rust-preventive coating on the fan shaft.

Make sure the shaft is clean and free of burrs. Add grease or lubricant to bore of sheave before installing.

Mount sheave on the shaft; to prevent bearing damage, do not use excessive force.

After 1 to 3 minutes of operation, check the belt tension. Also check tension frequently during the first 24 hours of operation and adjust if necessary. Periodically check belt tension throughout the run-in period, which is normally the initial 72 hours of operation.

ALIGNMENT

Shaft Alignment

Check shaft alignment by measuring the distance between the shafts at 3 or more locations. If the distances are equal, then the shafts are parallel.

Sheave Alignment

With sheaves aligned, tighten cap screws evenly and progressively.

NOTE: There should be a 1/8-in. to 1/4-in. gap between the mating part hub and the bushing flange. If the gap is closed, the bushing is probably the wrong size.

With taper-lock bushed hubs, be sure the bushing bolts are tightened evenly to prevent side-to-side pulley wobble. Check by rotating sheaves and rechecking sheave alignment. When substituting field-supplied sheaves for factory-supplied sheaves, only the motor sheave should be changed.

Evaporator Fan Performance Adjustment

To change fan speeds from factory settings:

Shut off unit power supply.

Loosen nuts on the 4 carriage bolts in the mounting base. Using adjusting bolts and plate, slide the motor and remove the belt.

Loosen movable-pulley flange setscrew.

Screw the movable flange toward the fixed flange to increase speed, and away from the fixed flange to decrease speed. Increasing the fan speed increases the load on the motor. Do not exceed the maximum speed specified in Tables 2 and 3.

Set the movable flange at nearest keyway of the pulley hub and tighten the setscrew. (See Tables 2 and 3 for speed change for each full turn of pulley flange.)

Replace and tighten the belts (see Belt Tension Adjustment section).

Restore power to the unit.

To align fan and motor pulleys:

Loosen fan pulley setscrews.

Slide fan pulley along fan shaft.

Make angular alignment by loosening motor from mounting plate.

Restore power to unit.

BELT TENSION ADJUSTMENT

Using a gage, apply 4 lb of force to the center of the belt and adjust the tension until a deflection of 1/64-in. is achieved for every inch of shaft center distance. See Fig. 29.

Ideal belt tension is the lowest value under which belt slip will not occur at peak load conditions.

Compressor Oil

All units are factory charged with oil. It is not necessary to add oil unless compressor(s) is removed from the unit.

If necessary, oil can be removed/charged via Schrader fitting.

Operate the system at high evaporator temperature prior to oil recharge to assist oil return to the compressor(s) from other system components.

If necessary, recharge the system as shown in Table 32.