37
Cleaning Steam Coils —
If proper filtration is main-
tained in the unit it should not be necessary to clean steam
coils. However, if the coils become dirty or greasy, film forms
on the fins. Proper cleaning can restore the coil heating
performance.
For best results wash coils from discharge side and wash
back toward the fan or unit return filters. Clean coils with a
vacuum cleaner, fresh water, compressed air, or a bristle brush
(not wire). Backflush coil to remove debris. Commercial coil
cleaners may also be used to help remove grease and dirt.
Steam cleaning is NOT recommended. Units installed in
corrosive environments should be cleaned as part of a planned
maintenance schedule. In this type of application, all accumu-
lations of dirt should be cleaned off the coil.
Use a fin comb with teeth of the correct fin spacing when
straightening bent or mashed fins.
During heating operation, the vacuum-return system is rec-
ommended since it helps eliminate any residual condensate
from the coil.
The steam distribution coils have a significantly reduced
possibility of freeze-ups. They are still susceptible to freezing,
however, if a minimum steam quantity is not maintained where
air over the coil approaches 32°F, or if they are not properly
pitched, drained, trapped and controlled.
The following points should also be considered for freeze
protection of steam distributing coils.
In cases where outside air is admitted to the unit, it should
be sufficiently mixed with return air before reaching the coil in
order to avoid cold spots on the coil. It is important that a mini-
mum steam quantity be maintained when heat is called for to
prevent water remaining in the tubes and possibly freezing.
The ON-OFF type of steam control is preferred over modulat-
ing control where air temperature over the coil approaches
32°F. Make sure that closed outside air dampers are sufficiently
sealed to prevent air leakage. Low leak style dampers are
recommended.
Make sure that the coil is properly pitched, drained, and
trapped so that condensate drains out of the coil whenever the
control valve shuts off the steam supply.
Checking System Charge —
The 50XCW units are
shipped with full operating charge. If recharging is necessary:
1. Insert thermometer bulb in insulating rubber sleeve on
liquid line near filter drier. Use a digital thermometer for
all temperature measurements. DO NOT use a mercury
or dial-type thermometer.
2. Connect refrigerant pressure gage to discharge line near
compressor.
3. After unit condition have stabilized, read head pressure
on discharge line gage.
NOTE: Operate unit a minimum of 15 minutes before
checking charge.
4. From standard pressure-temperature chart for R-410A,
find equivalent saturated condensing temperature.
5. Read liquid line temperature on thermometer; then sub-
tract from saturated condensing temperature. The differ-
ence equals subcooling temperature.
6. Compare the subcooling temperature with the normal
temperature listed in Table 13. If the measured liquid line
temperature does not agree with the required liquid line
temperature, ADD refrigerant to raise the temperature or
REMOVE refrigerant (using standard practices) to lower
the temperature (allow a tolerance of ± 3°F).
Example:
Head pressure (from gage) . . . . . . . . . . . . . .416.4 psig
Saturated condensing temp (from chart) . . . . . . 120°F
Liquid line temp (from thermometer) . . . . . . . . 100°F
Subcooling (by subtraction) . . . . . . . . . . . . . . . . . 20°F
Table 13 — Subcooling Temperature
*Saturated condensing temperature at compressor minus liquid line
temperature.
NOTE: Do not vent or depressurize unit refrigerant to atmo-
sphere. Remove and recover refrigerant following accepted
practices.
Access Panel Removal
TOP PANEL — Remove 3 to 6 screws, pull out panel and
remove.
CONTROL PANEL — Remove 4 screws and remove panel.
BOTTOM PANEL — Remove 3 to 6 screws in bottom panel
and lift up to remove panel.
Evaporator-Fan Motor Removal
NOTE: Motor power wires need to be disconnected from con-
trol box terminals before motor is removed from unit.
1. Shut off unit main power supply. Lock out power supply
and tag disconnect locations.
2. Loosen bolts on mounting bracket so that fan belt can be
removed.
3. Disconnect motor power wires from motor terminals.
4. Remove the 4 motor mounting bolts from bottom of
motor.
5. Remove motor. Rest motor securely on a high platform
such as a step ladder. Do not allow motor to hang by its
power wires.
Pressure Relief Device —
All units are equipped with
a fusible-plug type safety relief device on the refrigerant tub-
ing. The relief setting is 210°F.
Current Protection Device —
All units are
equipped with a current-sensing lockout relay on each circuit.
This device will lock out the compressor after any safety trip
(high-pressure switch, low-pressure switch, or internal over-
load of the compressor) for 5 minutes. Check reason for lock-
out before resetting the device. To reset, turn the thermostat
system switch to OFF, then back to COOL position.
High and Low-Pressure Switches —
The high-
pressure switch is located on the compressor discharge line.
The low-pressure switch is located on the suction line.
Oil Charge —
All units are factory charged with oil (see
Table 1 for compressor model number). It is not necessary to
add oil unless the compressor is removed from the unit. If addi-
tional oil is needed, do not use mineral oils. Only synthetic oils
are satisfactory.
UNIT 50XCW
SUBCOOLING*
06-24
12°F
WARNING
To prevent personal injury, wear safety glasses and gloves
when handling refrigerant. Do not overcharge system —
this can cause compressor flooding.
CAUTION
Before attempting to remove fan motors or motor mounts,
place a piece of plywood over evaporator coils to prevent
coil damage.