START-UP and PULL DOWN
A thorough leak test and evacuation must precede charging and start-up. Refer to the condensing unit or sys-
tem installation instructions. Check the compressor oil level before and during start-up. Check fan blades for
correct rotation. The control circuit should be energized at least 12 hours and preferably 24 hours before
charging and start-up to open the liquid line solenoid and turn on the crankcase heater. This will assist with a
good, deep evacuation and provide added compressor protection during charging and start-up.
Do not leave equipment unattended during start-up. Evaporator fan motors may require a jumper until the
room has cooled sufficiently to keep the fans from cycling. High moisture levels in new rooms can cause rapid
frost build up on the evaporator coil. It may be necessary to manually initiate a defrost. Do not allow the coil
to become completely blocked with frost.
EXPANSION VALVE ADJUSTMENT - EVAPORATOR SUPERHEAT
Expansion valves will usually need adjustment. Evaporator superheat should be approximately 6° to 12°F.
Low temperature evaporators will operate most efficiently with 6° to 8° superheat at design room temperature.
Obtain evaporator superheat by accurately measuring the suction line temperature at the expansion valve
bulb. Obtain pressure at the Schrader fitting on the suction connection. Convert the pressure to temperature
using a pressure-temperature chart. Subtract the converted temperature from the measured temperature to
obtain superheat. For close coupled systems with short line runs it may be necessary to slightly increase
superheat at the evaporator to insure the minimum desirable (25°F) superheat at the compressor.
The access panels on the evaporator must always be in place when the evaporator is operating. Do not leave
the access panels off after valve adjustment or service.
DEFROST TIMER ADJUSTMENT
Usually, 2 to 4 defrost per day will be satisfactory. In extreme cases 6 defrost per day may be necessary.
With a medium frost load, air circulation is still good and coils defrost best. Defrosting with a very light frost
load can cause steaming. Allowing a coil to become heavily frosted can reduce air circulation and reduces the
system capacity. After the room has pulled down to temperature and the evaporator has gone through 6 or 8
defrost, it should be thoroughly checked after a defrost to make sure the coil and drain pan are clear of all
frost and ice. Manually remove any ice accumulations. Fan blades and guards should also be cleared of frost
or ice. Defrost termination control adjustment may be necessary. The timer fail safe should be set about 6 to
10 minutes beyond normal termination time. The usual timer fail-safe setting for electric defrost evaporators is
30 to 40 minutes. For optimum system performance and efficiency, set the timer pins to initiate a defrost when
the coil has a medium frost load.
EVAPORATOR MAINTENANCE
Disconnect electrical power to the evaporator when inspecting or cleaning. Evaporators should be checked
occasionally and cleaned of all dirt or grease accumulation. Fan blades and guards may require more fre-
quent cleaning. DO NOT use ammonia or other cleaning chemicals that are corrosive to copper or aluminum.
The drain pan should be lowered and thoroughly cleaned to prevent any drain restriction. The drain connec-
tion must be open and clean. Coils must be power washed if they become dirty. We recommend using the
System Operation Check List on page 10. Using often can give indication of a problem before it becomes a
major issue. The Check List can also assure the owners that their equipment is in good condition and is being
maintained properly. The Check List should be retained as a permanent service record document for each
system.
REPLACEMENT PARTS
To order replacement parts always include the evaporator model number, serial number, and a complete
description of the part. Provide component model numbers, markings, size, function, and state the quantity
you are ordering. Providing complete information will insure prompt handling of your order. See page 2 for
unit model number and serial number information. See page 11 and 12 for replacement part numbers.
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