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English
L-2091 Operation
• The third mode is the differential and is accessed by press-
ing SET again. The differential is the temperature between
when the unit cycles off at SETPOINT and when it cycles
back on.
• Pressing the SET key again will bring you to the cooling/
heating mode. For correct operation, the thermostat should
be set at ‘C1’.
• By pressing the SET key once more, you will return to the
box temperature display.
• If, after pressing the SET key again, you return to the F/C
mode, keep pressing until you return to the temperature
display.
If you have a two-stage control (designated by “S2” in the
display) and the thermostat has an external toggle switch, then
your system is set up to function as a refrigerator or freezer.
Set two setpoints, one for use as a refrigerator (S1) and one
for use as a freezer (S2) and use the toggle switch to select
one or the other. To set the second setpoint (S2) follow the
same directions as the fi rst setpoint. See Figure 5.
Servicing Your Refrigeration System
Refrigerant
This refrigeration system uses R-134a refrigerant. With
a properly designed system, R-134a will perform well for
temperatures down to -6°F/-21°C. R-134a is a single compo-
nent refrigerant and should never be charged in the liquid
phase while the unit is running.
R-134a Tools
You should use a dedicated R-134a gauge set. This system
uses the common R-134a automotive type quick connects for
the gauge connections. They help ensure that only R-134a
tools are used. If you need a gauge set to fi t the connections,
contact your dealer and ask for part A-134A.
Care must be taken when using vacuum pumps and recovery
equipment with R-134a and other refrigerants. See the
manufacturer’s manuals before operating this type of equipment.
Constant Pressure Valve (CPV)
One feature of the CPV is that the system is not overly charge
sensitive; the high side pressure does not vary with charge.
The downside of this is that you cannot charge by pressure.
When charging a unit with liquid, the unit must be off and
remain off for at least 20 minutes after charging to assure that
no liquid exists at the suction valves of the compressor. The
sight glass is also a reliable indicator to use for charging. The
high side pressure does not tell you much about the refrigerant
charge, but rather refl ects the condensing temperature.
Correctly charge the unit by one of the following:
1. Evacuate and re-charge with the correct amount of
refrigerant (see dataplate). (BEST Method)
2. Listen to the CPV with a mechanic stethoscope or other
device. The CPV should make a steady, hissing sound. If
the valve is quiet, then the unit is very low on refrigerant. If
the valve is making a lot of sputtering noises, then the unit
is a little low. Charge until most of the sputtering gives way
to constant hissing. (Very Good Method)
3. Charge slowly looking for frosting of the CPV. When the
frost lines in the box are becoming constant and defi ned,
you are getting close. Never continue charging after the
sight glass becomes full. (Good Method)
Thermostatic Expansion Valve (TXV)
In the event that the frost line does not settle into a acceptable
range within twelve inches past the sensing bulb, and the sight
glass does not indicate moisture (in which case a drier change
out or re-evacuation of the system is necessary), an adjust-
ment on the valve may be necessary.
Confi rm that the sensing bulb is tight and not kinked or
ruptured and that the capillary tube is not touching any other
components.
Quick-Connect Fittings
QCs may be used in a similar manner as base valves. To check
compressor suction valve integrity, remove the liquid line QC
from the condensing unit. In 15-20 minutes or less, the unit
should be pulling a vacuum in the 25-27 in. HG range. You may
also use the QCs to troubleshoot leaks by narrowing down the
search to individual parts, such as the liquid line, suction line,
box, and condensing unit. Disconnect the QCs, and pressur-
ize all parts separately. Use of the Dometic part A-134VB will
allow you to connect your gauges to the QCs on the linesets
and the box.
Recharging the System
System Shutdown
It is best if the system can be turned off for 8-12 hours prior to
servicing to allow the refrigerant to reach ambient temperature.
This will expedite the recovery of the refrigerant.
Evacuate Refrigerant
1. Connect manifold gauges to both high and low side ports.
Attach center line of gauge set to recovery apparatus. On
the WAAF033T unit, off seat service valves 1 - 2 turns
(clockwise). The service ports on the WAR050T unit have a
Schrader valve and are always open to the system.
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