Maintenance; Fan Belt Adjustment-Belt Drive Units - Trane RRU150F N Series Installation, Operation And Maintenance Manual

Maintenance

WARNING
Hazardous Service Procedures!
Failure to follow all precautions in this manual and on
the tags, stickers, and labels could result in death or
serious injury.
Technicians, in order to protect themselves from
potential electrical, mechanical, and chemical hazards,
MUST follow precautions in this manual and on the
tags, stickers, and labels, as well as the following
instructions: Unless specified otherwise, disconnect all
electrical power including remote disconnect and
discharge all energy storing devices such as capacitors
before servicing. Follow proper lockout/tagout
procedures to ensure the power can not be
inadvertently energized.When necessary to work with
live electrical components, have a qualified licensed
electrician or other individual who has been trained in
handling live electrical components perform these
tasks.
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
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 18; 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
Oring is even with the top of the next belt or even with
40
Step 1a by 64; the
Step 1b.
a straightedge placed across the fan and motor
sheaves. Refer to Figure
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.
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
two to three days of operation. Belt tension may
decrease until the new belts are "run in".
Figure 18. Belt tension gauge
Table 6. Belt tension measurement and deflection
ranges
Deflection Force (lb)
Super
Belts Small P.D.
Gripbelts (in.) Gripnotch (in.)
Cross Range
Section (in.) Min.
3.0–3.6 3 4-1/2
A 3.8–4.8 3-1/2
5.0–7.0 4 5-1/2
3.4–4.2 4 5-1/2
B 4.4–5.6 5-1/8 7-1/8
5.8–8.8 6-3/8 8-3/4
18.
(Step 5) with the
Table 6. If the
Table 6.
Steel Cable
Gripbelts (in.)
Max. Min. Max. Min.
3-7/8 5-1/2 3-1/4
5 4-1/2 6-1/4 3-3/4
5 6-7/8 4-1/4
5-3/4 8 4-1/2
6-1/2 9-1/8 5-3/4
7-3/8 10-1/8 7
RRU-SVX02F-EN
Max.
4
4-3/4
5-1/4
5-1/2
7-1/4
8-3/4