11
will prevent heating and mechanical cooling from coming on. Place
a jumper wire across terminals R and G at TB1 terminal block. Close
disconnect switch; evaporator fan motor will operate so RPM can
be checked.
E
VAPORATOR
F
AN
R
OTATION
C
HECK
(T
HREE
P
HASE
M
ODELS
O
NLY
)
Check that fan rotates clockwise when viewed from the drive side
of unit and in accordance with rotation arrow shown on blower
housing. If it does not, reverse the two incoming power cables at
Single Point Power Block. In this case, repeat bearing check.
Do not attempt to change load side wiring. Internal wiring assures
all motors and compressors will rotate in correct direction once
evaporator fan motor rotation check has been made.
E
LECTRICAL
I
NPUT
C
HECK
Make preliminary check of evaporator fan ampere draw and verify
that motor nameplate amps are not exceeded. A final check of
amp draw should be made upon completion of air balancing of
the duct system (see Appendix C).
BELT DRIVE MODELS ONLY
B
EARING
C
HECK
Prior to energizing any fans, check and make sure that all setscrews
are tight so that bearings are properly secured to shafts.
T
ENSION
AND
A
LIGNMENT
A
DJUSTMENT
Correct belt tension is very important to the life of your belt. Too
loose a belt will shorten its life; too tight, premature motor and
bearing failure will occur. Check you belt drive for adequate “run-
in” belt tension by measuring the force required to deflect the
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
DRIVE BELT TENSION ADJUSTMENT
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
B, BA
Standard
4.3 to 5.5 5.5 + .5 8.2 + .5
1/4 ± 1/16
MODEL
DEFLECTION
(in)
DEFLECTION
FORCE (lbs)
SHEAVE
DIAMETER
(in)
TYPE
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.
