Routine Maintenance And Service; Air Cooled Condenser; Separator/Coalescer Drains; Recharging Dryer – Refrigerant, Oil And Dryers - AirTek SC Series Operator's Manual

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6.

ROUTINE MAINTENANCE AND SERVICE

Air Cooled Condenser

Very little routine care is necessary for the Airtek Dryer. The
most important step for an air cooled dryer is to keep the air
cooled condenser clean. The air is being taken in across
the condenser. Dirt from the ambient air will accumulate on
the finned tubes of the condenser coil. As the dirt will
accumulate on the rear of the condenser, blowing from the
inside out is most effective. In dusty areas the simple
inexpensive installation of a furnace filter will stop the
majority of dirt entering the dryer's condenser. This should
be changed when visibly dirty. If the condenser does
become dirty, an abnormally high refrigeration discharge
pressure will occur. The unit may shut down on high dew
point or high pressure. This will greatly reduce the life of
the refrigeration compressor and could lead to a voiding of
the warranty.

Separator/Coalescer Drains

Drains should be checked regularly. Failure of an auto-
matic drain can result in extreme amounts of water and
debris in your air system.
7. FOR THE REFRIGERATION SERVICE
TECHNICIAN
Airtek recommends that only qualified and experienced
refrigeration mechanics do repair work on these units.
This section is a list of hints and instructions for the skilled
serviceman and relating specifically to the Airtek Smart
Cycle and Cold Trap refrigeration systems.
Recharging Dryer – Refrigerant, Oil and Dryers
Refer to the dryer information tag on the front of the unit for
the approximate charge needed for each unit. The relatively
large charge is needed because of the flooded-shell
evaporators. Use the following to assess the adequacy of
the charge when unsure:
* Because of the widely fluctuating pressures occurring
when the Smart Cycle or Cold Trap system unloads, it
is impractical to use pressures or sightglass indica-
tions to determine correct charge. Gross undercharge
results in a hot suction line and overheated compres-
sor. Gross overcharge is indicated if the head and
suction pressure rises greatly when the unit is loaded.
Remember to clean the condenser before deciding on
the charge.
* The sightglass should stay filled most of the time
when the dryer has its customary air load. It is normal
for the glass to break up when the condenser fan
starts if the load is light or when the unit unloads. It
may take time to refill when it reloads. Don't charge to
clear the glass with no load; that will be too much.
* All units have a charging fitting on the evaporator shell.
The unit must be charged through this fitting and/or the
liquid line service valve. The best way is to dump liquid
into both ports with the dryer off, then start up and
continue feeding a full stream of liquid into the evapo-
rator until charged.
Do not charge vapor. You want the charge installed as fast
as possible so the oil will be returned.
Airtek 4087 Walden Avenue, Lancaster, NY 14086 TEL: (716) 685-4040 FAX: (716) 685-1010 E-MAIL: airtek@airtek.com
Additional oil is added at the factory to compensate for the
migration with the freon. If a compressor is replaced,
remove the drain plug from the evaporator shell to drain any
excess oil trapped. If that isn't possible, it may be neces-
sary to remove oil from the system after start-up. Excess oil
is indicated by noisy and vibrating compressor operation. If
a replacement evaporator is installed, oil should be added.
Prolonged operation with insufficient charge or a bad TXV
may cause oil to be trapped in the evaporator. If the
compressor is still good, this oil will return within a few
minutes of operation with the correct conditions. For R-22
applications use 150w refrigeration mineral oil, For R-134A
and R-404A, applications use synthetic refrigeration oil.
Replace both suction and liquid filter-dryers together
whenever the system has been exposed to air or water,
unless it's brand new or you know how much air has gone
through it. Solids will be caught in the suction drier even if
the system is dry.
NOTE: Magnum models do not have enough receiver
capacity to hold the whole charge. A complaint of pressure
tripping only on start-up is usually due to air through the
dryer when it is shut down or low cooling pressure rather
than overcharge. This causes refrigerant to migrate
backwards from the evaporator and overfill the high side of
the system.

Evaporator Leaks

If there is a leak between the tube and shell side of the
evaporator, the usual symptom is high head pressure,
because the air pressure is higher than the refrigerant
pressure.
To determine this, bypass air flow, stop dryer, and observe
head pressure after it stabilizes. 20 minutes is sufficient. If
the pressure is much higher than that corresponding to the
ambient temperature, there is air in the system. Purge air
at compressor discharge or receiver inlet to verify.
Gross leak-checking of the evaporator is done at the
separator drain with air pressure off and at least an hour
wait. If a leak is verified, it can often be fixed by removing
the bonnets, locating the leak with bubble soap and re-
rolling the leaky tubes. Split evaporator tubes can be
plugged with special tapered brass plugs.
WARNING: If the refrigerant has been seriously contami-
nated with water, you probably won't be able to dry it with
dryers and certainly not vacuum. Best to do solvent
cleanup on the evaporator and suction accumulator or
replace the evaporator. A flooded shell holds a lot of water
and is difficult to clean effectively.

Refrigerant Control Valves

Expansion valves: The superheat (+15º F) that the valve
controls is created in the control evaporator or suction line
heat exchanger. There is liquid or zero superheat at the
main evaporator outlet to facilitate oil return and keep the
shell flooded. If there is superheat at the main evaporator
outlet or if the suction line to the compressor is warm to the
hand, 1) check the charge. If the sightglass is full, 2) the
TXV may be defective or the liquid line is blocked. The TXV
superheat adjustment is not critical.
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