SECTION 20: S
TART
-
UP
P
ROCEDURES
63
20.2.2 Belt Tension
• Belt tension sho
u
ld be checked
w
ith a belt-tension
ga
u
ge
w
hen one is a
v
ailable. Follo
w
the belt
tension ga
u
ge instr
u
ctions.
• When a tension ga
u
ge is not a
v
ailable, meas
u
re
the belt span of the belts (
).
• Allo
w
for 1/64" (0.40 cm) of deflection for each
inch of center distance length for the charted
po
u
nds of force. Check
for
proper deflection force.
• EXAMPLE: A 40" (101.6 cm) shaft center
distance
w
o
u
ld dictate 40"/64" or 5/8" (1.59
cm) of deflection. With a standard B-belt and
a motor shea
v
e meas
u
ring bet
w
een 5.8"
(14.7 cm) and 8.6" (21.84 cm), the belt
w
ill
ha
v
e proper tension if a 5/8" deflection can be
achie
v
ed
w
ith a minim
u
m of 6-3/8 lbs. and a
maxim
u
m of 8-3/4 lbs. of press
u
re as
meas
u
red
w
ith a belt tensioning ga
u
ge.
FIGURE 33: Belt Tension
Table 14: Deflection Force B and BX Belts (in lbs)
NOTE: If drive belts squeal during start-up, increase belt tension
to the highest allowed value. Re-check tension during each
inspection. See Page 69, Section 21 for additional information.
20.2.3 Air Temperature Sensin
g
The sensing probe is factory mo
u
nted in the blo
w
er
ho
u
sing (Not incl
u
ded if c
u
stomer orders BMS-
ready).
20.3 Electrical
1. Check motor starter for proper o
v
erload set-
tings. The o
v
erload setting sho
u
ld meet f
u
ll
load amps (FLA) of motor.
2.
Meas
u
re the s
u
pply
v
oltage
w
ith the air handler
off and then on. For a system that is po
w
ered
w
ith three phase po
w
er, meas
u
re the
v
oltage of
each phase.
3.
Verify correct blo
w
er rotation.
4.
While the blo
w
er is r
u
nning and the b
u
rner is
off, meas
u
re the total system c
u
rrent dra
w
w
ith
an ammeter. Meas
u
re the system c
u
rrent dra
w
again after the b
u
rner adj
u
stments are made
and
w
ith the b
u
rner and blo
w
er both on.
5.
If applicable, compare all
v
ariable freq
u
ency
dri
v
e (VFD) programming parameters
w
ith
specifications pro
v
ided on electrical dra
w
ing.
20.4 Airflow
The air flo
w
s
w
itches are factory calibrated safety
de
v
ices for b
u
rner air flo
w
. If an air flo
w
s
w
itch does
not close, the problem may not be the air flo
w
s
w
itch.
It co
u
ld be an indication of an air flo
w
problem
(incorrect blo
w
er rotation, d
u
ct restrictions, etc.).
20.4.1 Differential Pressure
In order to
v
erify proper airflo
w
across the b
u
rner, the
differential press
u
re across the profile plate needs to
be meas
u
red. Attach a manometer to the press
u
re
test ports
w
here the press
u
re s
w
itch is attached and
meas
u
re the differential press
u
re
w
ith a manometer.
This reading m
u
st be 0.9 in
w
c +/- 0.1 in
w
c.
(2.24 mbar +/- 0.25 mbar)
To adj
u
st the differential press
u
re that
w
as meas
u
red
in the step abo
v
e,
u
se the adj
u
stable shea
v
e. To
decrease the speed of the blo
w
er and the differential
press
u
re, t
u
rn the adj
u
stable half of the shea
v
e
o
u
t
w
ard (decrease diameter). To increase the speed
of the blo
w
er and the differential press
u
re meas
u
red
at the b
u
rner, rotate the adj
u
stable half of the shea
v
e
in
w
ard (increase diameter). Both sides of the shea
v
e
m
u
st be t
u
rned eq
u
al, m
u
ltiple groo
v
es m
u
st be
adj
u
sted eq
u
al.
After any adj
u
stment, it is necessary to re-check the
alignment, belt tensions and
v
erify that all shea
v
e set
scre
w
s are tightened to the specified torq
u
e
v
al
u
e
before engaging the blo
w
er.
and
. Typically, all shea
v
es ha
v
e t
w
o set
scre
w
s to sec
u
re the shea
v
e to the motor shaft.
Some shea
v
es may be press fit onto the motor shaft.
On the t
w
o belt shea
v
es, there are fo
u
r setscre
w
s
that hold the size adj
u
stment. On the single belt
shea
v
es, there are t
w
o set scre
w
s to hold the size
Belt
Cross-
Section
Motor Sheave
Dimension Ran
g
e
in - cm
TYPE B
TYPE B-X
(Hi
g
h HP)
Min.
Max.
Min.
Max.
B
3.4-4.2
4
5 1/2
5 3/4
8
4.4-5.6
5 1/8
7 1/8
6 1/2
9 1/8
5.8-8.6
6 3/8
8 3/4
7 3/8
10 1/8
Span Length
Deflection 1/64” per inch of span
T
Summary of Contents for XT112
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