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maintenance
9 MAINTENANCE
A preventive maintenance schedule should be established as soon
as the STC Series unit is installed. The unit should be inspected
periodically for proper operation and build up of frost and debris.
WARNING: All power to the evaporator must be off before cleaning
or performing maintenance.
9.1 DRAIN PAN
Inspect and clean each drain pan to insure free drainage of
condensate. Drain pans should be cleaned regularly with warm
water and soap.
If a drain pan needs to be removed, support the long dimension of
the pan from underneath with a minimum of two 4x4s for one thru
four fan units, or two 6x6s for five and six fan units, so the outer
sheet metal skin does not buckle and become damaged. Do not
point load the center of the support beam. For longer pans more
than one lifting device may be needed to keep the pan balanced
when lifting. If the drain pan uses hot gas defrost make sure the
coil is completely pumped out and isolated with hand valves to
prevent refrigerant from escaping to the atmosphere. Remove
the hot gas piping or electric wires if the unit has a HTS or an
electric defrost drain pan. Remove the drain line so that it is out
of the way of the pan when it is being lowered. Remove the drain
pan attachment bolts from the bottom of the evaporator unit and
slowly lower the pan from the unit. Assemble pan in reverse order.
Replace hot gas interpiping gaskets before tightening flange bolts.
9.2 COIL AND CABINET
Clean coils, the fan cabinet, fan(s), and fan guard(s) with warm
water and soap. A low pressure water hose is recommended
to avoid water entering into electrical components and causing
equipment failure.
The evaporator coil should be checked once a month for proper
defrosting. Many variables affect coil frosting such as room
temperature, type of product being stored or processed, how
often new product is brought in, and the length of time the door
to the room remains open. Summer conditions of high humidity
can cause heavier frost loads and it may be necessary to change
the number of defrost cycles seasonally.
9.3 FAN GUARD REPLACEMENT
To remove a fan guard for fan-motor maintenance, or for guard
replacement, make sure all electrical power to the unit has been
turned off before any work is performed. While supporting the
guard to the unit remove nuts. Remove the guard. Reassemble
in the reverse order.
9.4 FAN REPLACEMENT
If a fan is out of balance, damaged, or needs to be replaced, the
unit does not need to be at floor level for maintenance. Make sure
all electrical power to the unit has been turned off before any work
is performed. Remove the fan guard as described in Section 9.3.
Loosen two bolts from the bushing that hold the fan onto the
motor shaft. Remove the fan. Clean and deburr the motor shaft
if necessary. Place the new fan onto the motor shaft and tighten
bolts. Reattach the fan guard.
9.5 MOTOR REPLACEMENT
Make sure all electrical power to the unit has been turned off
before any work is performed. To replace a motor a lifting device
may be required for heavy motors. Remove the fan guard and fan
as described in Sections 9.3 and 9.4. Remove the motor cover
and disconnect motor leads. Support the motor from the unit then
unbolt from the motor mount.
Assemble the replacement motor, fan and fan guard in the reverse
order.
When starting the motor make sure the fan is rotating in the
proper counter clockwise direction, when looking at the fan from
under the unit. If the fan rotates clockwise, stop the motor, shut
off all power to the unit, and change the motor wiring for counter
clockwise rotation.
9.6 ELECTRIC DEFROST HEATERS
Inspect the electric defrost heater ends to determine if they are
operating. A heater will be operating properly when the heater is
observed to be glowing during the defrost cycle. If a heater rod is
cold during the defrost cycle it will need to be replaced.
Coil heaters require horizontal removal from ends of the unit. See
Table 1 to determine if heaters have to be removed from one or both
ends of the unit. Turn off all electrical power on the unit. Remove
heater wires from the terminal block and note where original wires
were located. Rotate the heater rod so that the heater and retainer
clip can be slid through the coil endplate slot. Remove clip from the
old heater rod and install on the new heater rod in approximately
the same location as the original heater. Install new heater rod in
the original coil slot, rotate the rod 90°, and place new wires in
position of original wires in the terminal block.
Drain pan heaters require the drain pan to be removed. Support
the long dimension of the pan from underneath with a minimum
of two 4x4s for one thru four fan units or two 6x6s for five and
six fan units so the outer sheet metal skin does not buckle and
become damaged. For longer pans more than one lifting device
may be needed to keep the pan balanced when lifting. Remove
heater's wires from terminal blocks. Remove the drain line so that
it is out of the way of the pan when it is being lowered. Remove
the drain pan attachment bolts from the bottom of the evaporator
unit and slowly lower the pan from the unit. Remove clips from
the heater's hold down brackets and remove brackets. Replace
the heater. Replace hold down brackets and assemble the pan in
reverse order. Rewire heaters in original terminal blocks.
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