MAHLE RTI RHS780 - Manual (Page 4)

September 24, 1999 Page 3
USING THE RHS780
Note: The purpose of this discussion is to familiarize the user with the features and functions of the RHS780 Refrigerant
Handling Station. The procedures discussed in this manual assume that the RHS780 has been set up in accordance
with the figures which are referred to and that the RHS780 has been connected to the proper power supply. This
manual does not illustrate correct A/C service but rather how to correctly use the RHS780.
The RHS780 is microprocessor controlled with a menu driven user interface. All of the functions of the RHS780 are accessed
by pressing a few simple key strokes and following the prompts. See Page 4 items (2) and (6). The on board Charging
Cylinder is attached to a strain gauge measuring device and the weight is electronically displayed.
The RHS780 has a Fill Cylinder feature that allows refrigerant to be loaded directly into the Charging Cylinder without going
through the normal Recover/Recycle mode. When selected, this feature allows the RHS780 Charging Cylinder to be re-filled
in just a few minutes at which point it will automatically stop at approximately 13 lbs (6 Kg.)
The RHS780 Recovers and Recycles simultaneously in a true “single pass” through the filters and stores the refrigerant in
the Charging Cylinder where it is immediately available for use. This process automatically stop’s at 17.5 lbs (8 Kg) or when
a 15"Hg (-0.5 Bar) vacuum is sensed. The RHS780 will wait for a factory default of two minutes for “out gassing” and cold
refrigerant to raise the pressure back up to 3 psig (0.2 Bar) which would cause the Recover/Recycle process to start again
and reset this two minute Recycle Hold Timer before displaying that the process is complete. The Recycle Hold Timer can
be changed every time a Recover/Recycle procedure is run. Longer times should be selected on colder days or on A/C
Systems with large liquid capacities. Increasing this value may increase total time to Recover/Recycle while decreasing the
time may result in an incomplete Recovery of the A/C System. Refer to the chart below for guidelines on setting the Recycle
Hold Timer. The value entered is stored in the memory of the RHS780 and becomes the “default” value each time it is set.
Non-Condensable Gases are vented automatically during Recovery/Recycle. The Amount of refrigerant Recycled is displayed
at the end of the procedure. This value is added to the Total amount Recycled and stored in the memory of the RHS780 (see
Accessing Stored Data on Page 12.)
Temperature < 50F (10C) 50F (10C) to 80F > 80F (26.5C)
Recycle Hold Time 10 min 5 min 2 min
An integrated 3 CFM (1.4 L/s) rotary vane style Deep Vacuum Pump draws on both the High and Low Hoses, items (13) and
(14), ensuring complete evacuation of the A/C System. The amount of time that the Vacuum Pump has been programmed
to run will “count down” on the display (6). The value entered is stored in the memory of the RHS780 and becomes the
“default” value each time it is set. A special Vacuum Check Gauge (4) mounted between the High (5) and Low (1) Pressure
Gauges can be used to monitor a rise in A/C System pressure. An Auxiliary Vacuum Gauge Port(8) is also provided to attach
an external vacuum measuring device. When programmed to do so, the RHS780 will pause and start a “count up” timer
indicating how long the Vacuum Pump has been off, thus allowing the operator to determine if a vacuum leak is present
based on increasing pressure over time. A rapid rise in pressure indicates the presence of a large leak that should be
repaired. A slow rise in pressure may simply indicate that a longer Recycle Hold Timer or Vacuum Time value should have
been entered. A relatively constant vacuum reading over a long period of time (i.e. less than 2"Hg [0.05 Bar] rise over ten
minutes) is the most accurate way to check for vacuum leaks. The RHS780 can also be programmed to pause to allow oil
to be added, (9) and (16) to the A/C System after vacuuming and prior to Charging.
Charging is done via the on board Charging Cylinder. The A/C Capacity is entered via the Keypad (2). The value entered
is stored in the memory of the RHS780 and becomes the “default” value each time it is set. The RHS780 can dispense liquid
refrigerant through either the High (14) or Low (13) Side Hose by changing the position of a selector switch (10). As refrigerant
leaves the RHS780, the display (6) will show an increasing weight to the programmed charge amount plus a factory set 0.03
Kg (one ounce) Over Charge Amount necessary for compensation of refrigerant loss in the hoses. This Over Charge Amount
can be changed to accommodate different operating conditions (see Setting Over Charge Amount [only] on Page 13.) An
integrated Heater automatically engages whenever Charging occurs. The Amount of refrigerant Charged is added to the Total
amount Charged and stored in the memory of the RHS780 (see Accessing Stored Data on Page 12.)
The RHS780 can be programmed to perform the Recover/Recycle, Deep Vacuum and Charge in a completely Automatic
mode. The RHS780 will always go through the Recover/Recycle procedure, but will go immediately to the Recycle Hold Timer
if the A/C System is empty. The following matrix outlines the most commonly used options that can be programmed to occur
after the Recycle Hold Timer “times out”:
Recover/Recycle X X X X X X X X
Deep Vacuum X X X X X X
Vacuum Leak X X X
Add Oil X X
Charging X X X X X