Motor Sheave Adjustments - Daikin DCC Series Installation Instructions Manual

Upon completion of the air flow balancing, we recommend replac-
ing the variable pitched motor sheave with a properly-sized fixed
sheave. A matching fixed sheave will provide longer belt and bear-
ing life and vibration free operation. Initially, it is best to have a
variable pitched motor sheave for the purpose of airflow balanc-
ing, but once the balance has been achieved, fixed sheaves main-
tain alignment and minimize vibration more effectively. For direct
drive units, move fan speed wire.
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.
For heat pump units, the airflow must be adjusted so that the air
temperature rise falls within the ranges given stated on Data Plate
(see Appendix A - Blower Performance).
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 mea-
sured using a belt tension gauge, available through most belt drive
manufacturers.
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
C
TYPE
MODEL
BELT DRIVE
7.5 Ton
8.5 Ton
A, AX Standard
10 Ton
12.5 Ton
RECOMMENDED POUNDS OF FORCE PER BELT
When new V-belts are installed on a drive, the initial tension will
drop rapidly during the first few hours of use. Check tension fre-
quently during the first 24 hours of operation. Subsequent
retentioning should fall between the minimum and maximum force.
To determine the deflection distance from a normal position, use
a straightedge or stretch a cord from sheave to sheave to use as a
reference line. On multiple belt drives, an adjacent undeflected
belt can be used as a reference.

MOTOR SHEAVE ADJUSTMENTS

V , V & 2 V P
L M VP ARIABLE
The driving and driven motor sheaves should be in alignment with
each other and the shafts parallel.
V & V S A
L M HEAVES 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 FIVE 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.
12
DEFLECTION
SHEAVE
FORCE (lbs)
DIAMETE
R (in)
Used New
2.6 to 3.6 3.75 +/- 0.5 4.0 +/- 0.5 9/32 +/- 1/16
2.6 to 3.6 3.75 +/- 0.5 4.0 +/- 0.5 9/32 +/- 1/16
3.0 to 4.0 3.75 +/- 0.5 4.0 +/- 0.5 9/32 +/- 1/16
2.6 to 3.6 3.75 +/- 0.5 4.0 +/- 0.5 9/32 +/- 1/16
K T M S
ITCH EY YPE OTOR HEAVES
DEFLECTION
(in)