Sterling MS - Manual (Page 18)

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AIR HANDLING REQUIREMENTS
AND ADJUSTMENTS
Remove wooden shipping support
from beneath blower housing of Blower Section
(if applicable) to prevent possible unit damage or
improper unit operation.
Static Pressure through the unit should never exceed
2.0" W.C. (0.50 kPa). Units operate at a temperature rise
range of 20 to 90°F (11 to 50°C).
NOTICE: It is important that the fi nal temperature
leaving the unit does not exceed 160° F (71°C). When
fi nal air throughput adjustments are being made, a
check of the discharge air temperature should be
made after unit has operated for 15 to 20 minutes.
A unit should never be allowed to
cycle on the primary limit for a prolonged period of
time. It is a safety control to prevent a fi re. If cycling
on the primary limit is noted, corrective measures
should be taken immediately. Failure to do so could
result in unit damage or a fi re.
NOTICE: At initial unit installation, unit should be
started momentarily to confi rm proper blower wheel
rotation as the unit will deliver some air with the
blower wheel running backwards.
Two basic air control systems can be used to deliver
conditioned air to the occupied space: intermittent or
constant fan operation.
Intermittent Fan Operation: The unit employs an air
control system which utilizes a fan time delay relay to
operate the fan while in the heating mode. If equipped
with cooling, the thermostat controls the fan through
a relay when in the cooling mode. Refer to unit wiring
diagram.
Constant Fan Operation: The unit can be wired to give
an air control system which constantly circulates air
through the unit and occupied space with constant fan
operation. Refer to unit wiring diagram.
NOTICE: Check blower belt tension. Proper belt
tension is important to the long life of the belt and
motor. Proper belt tension will allow the belt to be
depressed 1/2" to 3/4".
It is important that the blower motor and the blower
wheel pulleys be in good alignment, with the motor and
blower shafts parallel.
Belt tension must be adjusted to give approximately
3 /
4
" defl ection of the belt when fi nger pressure is applied
to the middle of the belt (See Figure 17). Small changes
in this tension may be necessary for optimum operation.
Belts will stretch over a period of time, requiring an
adjustment to this tension. See MAINTENANCE section
for belt and pulley adjustments.
These units are set at the factory for the RPM required to
meet the air volume (CFM) and external static pressure
ordered. If the estimated external static is incorrect, or
changes were made to the duct system, the blower RPM
may need to be changed.
Both the Standard and High CFM Blowers use motors
which are equipped with adjustable pitch pulleys. After
removing belt(s), loosen the pulley set screw and remove
the key, turn adjustable half of a pulley clockwise to
increase RPM, or counter-clockwise to decrease RPM.
Insert key, tighten set screw and replace belt(s). Adjust
belt tension to give 1/2" to 3/4" belt play when depressed.
Blower motor full load amps should
never be exceeded. Improper unit operation or motor
failure could result.
After changing blower RPM, confi rm blower motor full
load amps have not been exceeded. See motor data
plate for maximum full load amps.
Figure 17
1/2" TO 3/4"