Motor Sheave Adjustments - Daikin DBC Series Installation Instructions Manual

NOTE: Airflow setting below 300 CFM/ton is not recommended,
as evaporator freezing or poor unit performance is possible. For
2-speed models, airflow adjustments must be made with the
evaporator fan motor operating at high speed (in 2nd stage cooling
or in heat mode).
S E F RPM
ET VAPORATOR AN
Actual RPM's must be set and verified with a tachometer or strobe
light. Refer to Appendices A and B for basic unit fan RPM. Refer
also to "Airflow" section of this manual. With disconnect switch
open, disconnect thermostat wires from terminals Y and W. This
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 F R C
VAPORATOR AN OTATION
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 I C
LECTRICAL NPUT 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 B).
B C
EARING HECK
Prior to energizing any fans, check and make sure that all setscrews
are tight so that bearings are properly secured to shafts.
T A A
ENSION AND LIGNMENT 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.
(T P M O
HECK HREE HASE ODELS
*Apply force to the center of the span.
t = Span length, inches
C = Center distance, inches
D = Larger sheave diameter, inches
)
NLY
d = Smaller sheave diameter, inches
h = Deflection height, inches
MODEL
BELT
15 Ton B, BX
20 Ton
B, BA
25 Ton
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, measure
the distance from sheave to sheave using a straightedge or a cord.
This is your reference line. On multiple belt drives, an adjacent
undeflected belt can be used as a reference.

MOTOR SHEAVE ADJUSTMENTS

V , V & 2
L M VP
The driving and driven motor sheaves should be in alignment with
each other and the shafts parallel.
V & V S
L M HEAVES
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.
12
D
C
DEFLECTION
SHEAVE
TYPE
FORCE (lbs)
DIAMETER
(in)
DRIVE Used
Standard 4.3 to 5.5 5.5 ± .5
Standard 4.3 to 5.5 5.5 ± .5
DRIVE BELT TENSION ADJUSTMENT
V P K T M
ARIABLE ITCH EY YPE OTOR
A
DJUSTMENT
DEFLECTION
(in)
New
8.2 ± .5 1/4 ± 1/16
8.2 ± .5 1/4 ± 1/16
S
HEAVES