26
Solution:
a. From Fig. 27 find that deflection force for type A,
super belt with 5-in. small sheave PD is 4 to 5
1
/
2
lb.
b. Deflection =
16
/
64
=
1
/
4
-in.
c. Increase or decrease belt tension until force
required for
1
/
4
-in. deflection is 5 lb.
Check belt tension at least twice during first oper-
ating day. Readjust as required to maintain belt
tension within the recommended range.
With correct belt tension, belts may slip and squeal mo-
mentarily on start-up. This slippage is normal and disap-
pears after unit reaches operating speed. Excessive belt ten-
sion shortens belt life and may cause bearing and shaft dam-
age.
After run-in, set belt tension at lowest tension at which
belts will not slip during operation.
START-UP
General —
Complete the start-up checklist on page CL-1
before attempting system start-up.
1. Set indoor thermostat system switch to OFF position
and fan switch to AUTO position.
2. Check all electrical connections, fuses, starter and pres-
sure control resets.
3. Turn on condenser water supply.
4. Set selector switch on thermostat to the ON position. Ad-
just evaporator fan speed if needed. If an airflow is not
specified, use the nominal airflow from Tables 4-9 and
adjust the fan speed to compensate for actual job condi-
tions. Use Table 1 to determine proper fan speed.
5. Set thermostat at a setting below room temperature. Com-
pressor will start. If compressor suction pressure does not
drop and discharge pressure does not rise to normal levels
at start-up, reverse any 2 compressor power leads and re-
store power to ensure compressor was not wired to run in
reverse direction.
6. Set thermostat as desired.
Compressor Rotation —
To determine whether or not
compressor is rotating in the proper direction:
1. Connect service gages to suction and discharge pressure
fittings.
2. Energize the compressor.
3. The suction pressure should drop and the discharge pres-
sure should rise, as is normal on any start-up.
4. If the suction pressure does not drop and the discharge
pressure does not rise to normal levels, the compressor
may be rotating in the wrong direction.
5. Since the compressor and fan motors are connected in
phase during production, it is likely that the evaporator
and condenser fans are probably also rotating in the
wrong direction.
6. Turn off power to the unit, lock and tag disconnect per
standard safety procedures.
7. Reverse any two of the unit power leads.
8. Remove lock and tag per standard safety procedures and
apply power to the unit.
9. The suction and discharge pressure levels should now
move to their normal start-up levels.
NOTE: When the compressor is rotating in the wrong direc-
tion, the unit makes an elevated level of noise and does not
provide cooling.
CAUTION
To prevent injury, ensure that ducting or wire fan guards
are installed on the condenser fan before starting the unit.