12
belt at the midpoint of the span length. Belt tension force can be
measured using a belt tension gauge, available through most belt
drive manufacturers.
SPAN LENGTH t
*DEFLECTION
FORCE
h
C
d
H
D
*Apply force to the center of the span.
t = Span length, inches
C = Center distance, inches
D = Larger sheave diameter, inches
d = Smaller sheave diameter, inches
h = Deflection height, inches
BELT
DRIVE
Used
New
15 Ton
B, BX
Standard
4.3 to 5.5
5.5
±
.5
8.2
±
.5
1/4
±
1/16
20 Ton
25 Ton
B, BA
Standard
4.3 to 5.5
5.5
±
.5
8.2
±
.5
1/4
±
1/16
MODEL
TYPE
DEFLECTION
FORCE (lbs)
SHEAVE
DIAMETER
(in)
DEFLECTION
(in)
DRIVE BELT TENSION ADJUSTMENT
RECOMMENDED POUNDS OF FORCE PER BELT
New V-belts will drop rapidly during the first few hours of use.
Check tension frequently during the first 24 hours of operation.
Tension should fall between the minimum and maximum force. To
determine the deflection distance from a normal position, mea-
sure the distance from sheave to sheave using a straightedge or a
cord. This is your reference line. On multiple belt drives, an adja-
cent undeflected belt can be used as a reference.
MOTOR SHEAVE ADJUSTMENTS
V
L
, V
M
& 2
VP
V
ARIABLE
P
ITCH
K
EY
T
YPE
M
OTOR
S
HEAVES
The driving and driven motor sheaves should be in alignment with
each other and the shafts parallel.
V
L
& V
M
S
HEAVES
A
DJUSTMENT
1. Loosen set screw “B” using a 5/32" Allen key.
2. Making half or full turns from closed position, adjust
sheave pitch diameter for desired speed. DO NOT OPEN
MORE THAN SIX FULL TURNS.
3. Tighten set screw “B” securely over flat.
4. Carefully put on belts and adjust belt tension. DO NOT
FORCE BELTS OVER GROOVES.
5. Ensure all keys are in place and the set screws tight before
starting drive. Recheck set screws and belt tension after
24 hours service.
NOTE:
Future adjustments should be made by loosening the belt
tension and increasing or decreasing the pitch diameter of the
sheave by half or full turns as required. Readjust belt tension before
starting drive.
C
B
VL & VM
NOTE:
Do not operate sheave with flange projecting beyond the
hub end.
R
EFRIGERATION
S
YSTEM
The unit is equipped with a thermal expansion valve as a
metering device.
Ensure the hold-down bolts on the compressor are secure and have
not vibrated loose during shipment. Check that vibration grom-
mets have been installed. Visually check all piping for damage and
leaks; repair if necessary. The entire system has been factory
charged and tested, making it unnecessary to field charge. Factory
charges are shown on the unit’s namelate. To confirm charge lev-
els or, if a leak occurs and charge needs to be added to the system,
it is recommended to evacuate the system and recharge refriger-
ant to unit nameplate specifications. This unit has been rated in
the cooling mode at the AHRI rated conditions of: Indoor (80°db /
67°wb) and outdoor (95°db). While operating at this condition,
the subcooling should range from 12° to 15° F for each refrigera-
tion circuit, for 15 and 20 ton models. Subcooling for 25 ton mod-
els should be from 16° to 19° F for circuit 1, and from 12° to 15° F
for circuit 2.
S
TART
-U
P
P
ROCEDURE
AND
C
HECKLIST
Begin with power turned off at all disconnects.
1. Turn thermostat system switch to “Cool,” and fan switch
to “Auto” and turn temperature setting as high as it will
go.
2. Inspect all registers and set them to the normal open
position.
3. Turn on the electrical supply at the disconnect.
4. Turn the fan switch to the “ON” position. The blower
should operate after a 7-second delay.
5. Turn the fan switch to “Auto” position. The blower should
stop after a 65 second delay.
