APC AFX Series Specifications download pdf (Page 14)

13

Control/Safety Adjustments

After the installation and start-up of the AFX

Series unit has been completed, "fine tuning"

of the system's controls and safety systems is

necessary, as described below.

Belt Tension

The blower motor is mounted on an adjustable

base. Belt tension can be increased or

decreased by raising or lowering the base.

A deflection of about 3/4 - 1" per foot of span

between the blower and motor pulleys should be

obtained by pressing the belt firmly. The

adjusting belt should be locked in position after

adjustment is made.

WARNING

Too much tension will shorten bearing,

shaft and belt life.

For quiet operation, the belt should be as loose

as possible without slippage. Slippage may

result in belt squeal or insufficient airflow, or

both. A simple test for the belt slippage is to

check the temperature of the smaller pulley in

relation to the larger pulley. If the small pulley is

noticeably warmer, this is an indication of belt

slippage and the belt should be tightened

slightly. Do not test temperature while pulleys

are turning.

Belt tension should be readjusted if the variable

speed pulley setting is changed or if the belt is

replaced.

Motor Pulley

The pulley on the blower motor has a variable

pitch diameter to allow the blowers to be sped

up or slowed down to compensate for higher or

lower external static pressure, or in some cases,

high altitude compensation.

The motor pulley has been factory sized and the

unit has been factory tested with the pitch in the

middle of its adjustment range.

To increase blower speed, remove the belt from

the pulley by taking it off the larger non-

adjustable blower pulley first. Loosen the set

screw on both movable sheaves. Turn them

inward toward the center stationary sheave to

increase the effective pitch diameter. To

decrease the blower speed, spread the sheaves

further apart.

Turn both sheaves the same number of times.

This is necessary to maintain uniform tension on

both belts.

Tighten the set screws again, making sure that

they are not on the threaded portion of the

sheave, and put the belts back on.

Check for proper alignment between the driving

and driven sheaves (pulleys). Improper

alignment will cause premature wear on the

blower belts.

Air Pressure Differential (optional)

The CM unit uses an APD switch to sense

airflow loss through the unit. The APD is factory

set to make the switch close at 0.2" W.G. across

the internal APD bellows. The pressure setting

is adjustable by turning the adjustment screw

clockwise to increase the setting.

Clogged Filter Switch (optional)

The clogged filter switch senses the air pressure

drop across the filters. When the pressure drop

is too high due to dirty filters, the switch closes

and causes an alarm. While the clogged filter

switch has been set at the factory for

approximately 1.0 of pressure drop across the

filters, the setting should be checked at unit

start-up. Cover one-third of the filter area and

increase or decrease the clogged filter switch

sensitivity so that the switch closes when one-

third of the filter area is blocked. This procedure

can only be used with new, clean filters.

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