CAUTION
When operating conditions of the fan are to be
changed (speed, pressure, temperature, etc.),
consult manufacturer to determine if the unit can
operate safely at the new conditions.
Supply Fan (Plenum Type)
The unit contains one plenum supply fan located on
the end of the unit opposite
the outdoor air intake (see
beginning of Unit Start-Up
section for diagram of unit
layout). Be sure to check
the belt drives per the start-
up recommendations in the
following section. Efficient fan
performance can be maintained by having the correct
offset. These items should be checked before start-up
and after the fan has been in operation for 24 hours.
Plenum Supply Fan
Refer to Plenum and Plug Fan IOM for additional start-
up and maintenance information regarding the QEM
Plenum Supply Fan.
Unit Start-Up
Refer to Component section for component locations.
Fan
The fan should be checked for free rotation. If any
binding occurs, check for concealed damage and
foreign objects in the fan housing.
Fan Performance Modifications
Due to job specification revisions, it may be necessary
to adjust or change the sheave or pulley to obtain
the desired airflow at the time of installation. Start-up
technician must check blower amperage to ensure
that the amperage listed on the motor nameplate is
not exceeded. Amperage to be tested with access
doors closed and ductwork installed.
Fan Belt Drives
The fan belt drive components, when supplied by
manufacturer, have been carefully selected for the
unit's specific operating condition. Utilizing different
components than those supplied could result in
unsafe operating conditions which may cause
personal injury or failure of the following components:
• Fan Shaft
• Bearings
• Motor
• Fan Wheel
• Belt
Tighten all fasteners and set screws securely and
realign drive pulleys after adjustment. Check pulleys
and belts for proper alignment to avoid unnecessary
belt wear, noise, vibration and power loss. Motor and
drive shafts must be parallel and pulleys in line (see
diagrams in this section).
Belt Drive Installation
1. Remove the protective coating from the end of
the fan shaft and assure that it is free of nicks and
burrs.
2. Check fan and motor shafts for parallel and
angular alignment.
3. Slide sheaves on shafts. Do not drive sheaves on
as this may result in bearing damage.
4. Align fan and motor sheaves with
a straight-edge or string and
tighten.
5. Place belts over sheaves.
Do not pry or force belts,
as this could result in
damage to the cords in
the belts.
6. With the fan off, adjust the belt tension by moving
the motor base. (See belt tensioning procedures
in the Routine Maintenance section of this
manual). When in operation, the tight side of the
belts should be in a straight line from sheave to
sheave with a slight bow on the slack side.
Model QEM
Inlet
Cone
Wheel
Offset
Offset:
Proper offset, or overlap, is
adjusted by loosening the wheel hub
from the shaft and moving the wheel
to the desired position along the shaft.
The transition between the inlet cone
and the wheel should
be as shown; there is
a smooth feel to the
profile when moving
one component to the
other.
QEM
Model
Size
Wheel Cone to Inlet Cone
Offset
± Tolerance
(inches)
Offset
± Tolerance
(millimeters)
12
7/16
± 1/16
11
± 1.5
15
7/16
± 1/16
11
± 1.5
16
7/16
± 1/16
11
± 1.5
18
7/16
± 1/16
11
± 1.5
20
7/16
± 1/16
11
± 1.5
22
7/16
± 1/16
11
± 1.5
24
7/16
± 1/16
11
± 1.5
WRONG
WRONG
WRONG
CORRECT
25
Model MPX Make-Up Air Unit
Model XMPX Make-Up Air Unit
