JOhNsON CONTROLs
18
FORM ET115.24-NOM5 (908)
sECTION THREE - NORMAL OPERATION & PERIOdIC MAINTENANCE
GENERAL
Each unit on a job will have its own unique operating
environment and conditions that may dictate a
maintenance schedule for that unit that is different
from other equipment on the job. A formal schedule of
regular maintenance and an individual unit log should
be established and maintained. This will help to achieve
the maximum performance and service life of each unit
on the job.
Information regarding safety precau
-
tions contained in the preface at the
beginning of this manual should be
followed during any service and main
-
tenance operations.
For more detailed information concerning service
operations, consult your Sales Representative or the
Factory.
MOTOR/BLOWER AssEMBLY
The type of fan operation is determined by the control
components and their method of wiring, and may vary
from unit to unit. Refer to the wiring diagram for each
unit for that unit’s individual operating characteristics.
Motors are permanently lubricated, PSC type and do
not require field lubrication.
Fan Deck
The fan assembly is easily removed from the unit
without disconnecting the ductwork for service access
to motors and blowers at, or away from the unit.
Should the assembly require more extensive service,
the motor/ blower assembly may be removed from the
unit to facilitate such operations as motor or blower
wheel/housing replacement, etc. Dirt and dust should
not be allowed to accumulate on the blower wheel or
housing. This can result in an unbalanced blower wheel
condition that can damage a blower wheel or motor.
The wheel and housing may be cleaned periodically
using a vacuum cleaner and a brush taking care not to
dislodge the factory balancing weights on the blower
wheel blades.
COIL
Coils may be cleaned in place by removing the motor/
blower assemblies and brushing the entering air face
between fins with a soft brush parallel to fins. Do not
brush perpendicular to fin orientation as damage may
occur. Brushing should be followed by cleaning with a
vacuum cleaner. If a compressed air source is available,
the coil may also be cleaned by blowing air through the
coil fins from the leaving air face. Vacuuming should
again follow this. Units provided with the proper type
of air filters, replaced regularly, may require periodic
coil cleaning.
ELECTRIC REsIsTANCE HEATER AssEMBLY
Electric resistance heaters typically require no normal
periodic maintenance when unit air filters are changed
properly. Other conditions and equipment may affect the
operation and service life in the system. The two most
important operating conditions for an electric heater are
proper airflow and proper supply voltage. High supply
voltage and/or poorly distributed or insufficient airflow
over the element will result in element overheating. This
condition may result in the heater cycling on the high
limit thermal cutout. Open wire type heaters provided
have an automatic reset switch with a back-up high
limit thermal switch. Automatic reset switches are as
the name implies; they reset automatically after the
heater has cooled down. High limit thermal switches
must be replaced once the circuit has been broken.
The high limit thermal cutout device is a safety device
only and is not intended for continuous operation. With
proper unit application and during normal operation,
the high limit thermal cutout will not operate. This
device only operates when some problem exists and
ANY condition that causes high limit cutout MUST be
corrected immediately. High supply voltage also causes
excessive amperage draw and may result in tripping
of the circuit breaker or blowing of the fuses on the
incoming power supply.
LD13896
