ROTHENBERGER Digitales Monteurhilfe Set - Manual (Page 14)

12 ENGLISH
Vacuum gauge operation fig. A
 Press the POWER button to turn the unit ON. Allow 10 seconds for the unit to initialize.
 Close both valves.
 Connect the vacuum cable to the manifold.
 Connect the other end of the vacuum gauge to the side port on the manifold. Press the VACUUM
button.
 Connect the high side and low side hoses to the system and the yellow hose to the vacuum pump.
 Start the vacuum pump and open the low side valve.
The vacuum countdown will start from atmospheric pressure 00000. Depending on the size of the
system, the lines on the LCD display will disappear one by one. Once all lines have disappeared, the
numerical reading will appear on the LCD. The numbers descend from 25000 MICRONS or
corresponding units.
 The unit will shut down after 15 minutes automatically. Press the POWER button again.
Allow 30-45 seconds for initializing and the correct vacuum reading to appear.
 Once the target vacuum is reached, close the low side valve and disconnect the vacuum gauge port
from the manifold.
 Press the POWER button to turn the unit off. (If pressure, temperature or deep vacuum is being
used for extended periods of time turns the unit off and turns back on again when reading
is required
)
WARNING!! Never stop the vacuum pump unless the vacuum gauge is disconnected. Failure to
do so may cause oil to enter the sensor chamber.
Measuring actual superheat and subcooling fig. B
Superheat is the difference between the actual temperature (sensor temperature) of the refrigerant
(gas) as it leaves the evaporator and the boiling point temperature of the refrigerant in the evaporator
coil (saturated temperature).
After boiling, the refrigerant continues to warm up.
The number of degrees it “warmed up” after boiling is called the superheat. Under worst-case
conditions (low load for fixed orifice systems), the refrigerant in the evaporator boils off near the end of
the evaporator coil.
To make sure liquid doesn’t enter the compressor under the worst case condition, the AC manufacturers
publish charts. The charts indicate what the superheat should be at a given indoor wet bulb
measurement and outdoor air temperature. Measuring superheat is your best indication on a fixed
orifice system of the proper refrigerant charge and operating conditions.
If everything else is working properly and the actual superheat is too high, add refrigerant. If it’s too low,
remove refrigerant.
Subcooling is the difference between the boiling point of the refrigerant in the condenser (saturated
temperature) and the actual temperature (sensor temperature) of the refrigerant as it leaves the
condenser. The degree that the refrigerant “cools down” below the boiling point is the sub-cooling.
Under worst case scenario low load for thermostatic expansion valve systems (TXV) the subcooling will
continue to rise.
If the subcooling rises too high, liquid may be backed into the compressor causing damage and failure.
WARNING! Use caution whenever working with electricity and high-pressure liquid or gas.
Always wear safety glasses and gloves.
Follow all instructions provided with equipment being serviced or installed.