Maintenance; Fan Belt Adjustment-Belt Drive Units - Trane TH 150-300 Series Installation, Operation And Maintenance Manual

Maintenance

Make sure all personnel are standing clear of the unit
before proceeding. The system components will start
when the power is applied.
Fan Belt Adjustment—Belt Drive
Units
WARNING
Rotating Components!
The following procedure involves working with rotating
components. Disconnect all electric power, including
remote disconnects before servicing. Follow proper
lockout/tagout procedures to ensure the power can not
be inadvertently energized. Failure to disconnect power
before servicing could result in rotating components
cutting and slashing technician which could result in
death or serious injury.
The fan belts must be inspected periodically to assure
proper unit operation.
Replacement is necessary if the belts appear frayed or
worn. Units with dual belts require a matched set of belts
to ensure equal belt length.
When removing or installing the new belts, do not stretch
them over the sheaves. Loosen the belts using the belt
tension adjustment bolts on the motor mounting base.
Once the new belts are installed, using a Browning or
Gates tension gauge (or equivalent) illustrated in
Figure 29; adjust the belt tension as follows;
1. To determine the appropriate belt deflection;
a. Measure the center-to-center shaft distance (in
inches) between the fan and motor sheaves.
b. Divide the distance measured in
resulting value represents the amount of belt
deflection that corresponds to the proper belt
tension.
2. Set the large O-ring on the belt tension gauge at the
deflection value determined in
3. Set the small O-ring at zero on the force scale of the
gauge plunger.
4. Place the large end of the gauge at the center of the belt
span; then depress the gauge plunger until the large
O-ring is even with the top of the next belt or even with
a straightedge placed across the fan and motor
sheaves.
Refer to Table 13, p. 39.
5. Remove the belt tension gauge. The small O-ring now
indicates a number other than zero on the plunger's
force scale. This number represents the force (in
pounds) required to give the needed deflection.
RT-SVX25J-EN
Step 1a by 64; the
Step 1b.
6. Compare the "force" scale reading
appropriate "force" value listed in
"force" reading is outside the range, readjust the belt
tension.
Note: Actual belt deflection "force" must not exceed the
maximum "force" value shown in
7. Recheck the belt tension at least twice during the first
2 to 3 days of operation. Belt tension may decrease
until the new belts are "run in" .
Figure 29. Belt tension gauge
Table 13. Belt tension measurement and deflection
ranges
Super
Belts Small
Gripbelts
Cross P.D
(in.)
Section Range
(in.) Min. Max.
3.0–3.6 3 4 1/2
A 3.8–4.8 3 1/2
5.0–7.0 4
3.4–4.2 4
4.4–5.6 5 1/8 7 1/8
B
5.8–8.8 6 3/8 8 3/4
Super
Gripbelts
Belts Small P.D
(mm)
Cross Range
Section (mm) Min. Max.
13.3–16.0 13.3
16.9–21.4 15.6
A
22.0–31.1 17.8
15.1–18.7 17.8
19.6–24.9 22.8
B
25.8–39.1 28.4
(Step 5) with the
Table 13, p. 39. If the
Table 13, p.
Deflection Force (lb)
Steel Cable
Gripnotch Gripbelts
(in.) (in.)
Min. Max Min.
3 7/8 5 1/2 3 1/4
5 4 1/2 6 1/4 3 3/4
5 1/2 5 6 7/8 4 1/4
5 1/2 5 3/4 8 4 1/2
6 1/2 9 1/8 5 3/4
7 3/8 10 1/8 7
Deflection Force (kg)
Steel Cable
Gripnotch Gripbelts
(mm) (mm)
Min. Max. Min.
20.0 17.2 24.5 14.5
22.2 20.0 27.8 16.7
24.5 22.2 30.6 18.9
24.5 25.6 35.6 20.0
31.7 28.9 40.6 25.6
38.9 32.8 45.0 31.1
39.
Max.
4
4 3/4
5 1/4
5 1/2
7 1/4
8 3/4
Max
17.8
21.1
23.4
24.5
32.3
38.9
39