Mastercool 99773-AR HVAC Digital Manifold - Manual (Page 4)

4 www.mastercool.com
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.
NOTE: 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 an extended period of time turn the
unit off and turn 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.
VACUUM LEAK TEST
When checking a system for leaks under high vacuum (less than 1000 microns), connect
the vacuum gauge directly to the system. If additional connections are required use cop-
per tubing (do not use rubber hoses) and high vacuum shut-off valves. Standard hoses
and manifold gauge set shut-off valves may have a small amount of leakage under high
vacuum. When initiating a high vacuum test, the vacuum gauge reading may “drift” higher
until the system has equalized. After this short stabilization period (5 minutes) the vacuum
reading should hold steady. An upward “drift” of the vacuum gauge reading may indicate a
leaking system.
CLAMP-ON THERMOCOUPLE CALIBRATION (PAIRING)
Each thermocouple has been calibrated (paired) to this manifold in the factory for accurate
readings. Replacing the thermocouple will require pairing. Please follow the directions
indicated.
1. Connect the thermocouple to the manifold and attach the clamp to an accurate source
of temperature (reference source.)
2. Remove the rubber cap from the back of the manifold (located next to the battery
compartment under the rubber boot.
3. Use a flat miniature screwdriver to adjust the temperature.
4. Replace the plug.
MEASURING ACTUAL SUPERHEAT AND SUBCOOLING (SEE FIG. C)
��������
������
�
�
��������� ����������
����������
���������������������������������������������
������
����������������
�����
������
����������������
�����
������������������������������
����������
��
�������������
���
���������������
�
����������������
����������������
����������������
����������
��
�������������
���
������������������������������
FIG. C
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.