Geostar ASTON SERIES Installation Manual page 29

Refrigeration cont.
Leak Testing
The refrigeration line set must be pressurized and checked for
leaks before purging and charging the unit. To pressurize the line
set, attach refrigerant gauges to the service ports and add an inert
gas (nitrogen or dry carbon dioxide) until pressure reaches 60 to
90 PSIG. Never use oxygen or acetylene to pressure test. Use an
electronic leak detector or a good quality bubble solution to detect
leaks on all connections made in the field. Check the service
valve ports and stem for leaks and all connections made in the
field. If a leak is found, repair it and repeat the above steps. For
safety reasons do not pressurize the system above 150 psi. Purge
pressure from line set. The system is now ready for evacuating
and charging.
System Evacuation
Ensure that the line set and air coil are evacuated before opening
service valves to the split unit. The line set must be evacuated to at
least 200 microns to remove the moisture and air that may still be
in the line set and coil. Evacuate the system through both service
ports to prevent false readings on the gauge because of pressure
drop through service ports.
Charge Amount When Using GAH Air Handler
The Aston Series Split is shipped with a factory pre-charge.
This volume of refrigerant is not sufficient to run the system and
additional refrigerant must be added. If using an GAH Air Handler
please refer to the Line Set Sizes table for charge amounts to
be added. The "Factory Charge" column is the charge amount
the compressor section/split is shipped with from the factory. The
"Charge Amount with GAH Air Handler" column is the total amount
of charge for the GAH Air Handler + Compressor section/split. This
column does not factor in additional refrigerant needed for the line
set. The installer of the system must add charge appropriately for
the specific length of the line set. A 3/8 in. liquid line is calculated
at 0.50 oz. of charge per linear foot, and a 1/2 in. liquid line
is calculated at 1.0 oz. of charge per linear foot using R-410A
refrigerant. The suction line will not hold "liquid" and should be
ignored for the charge calculation.
Example: 103*036/GAH036 with 20 ft. of 3/8 in. liquid line.
Remember that when using the GAH Air Handler, the
column "Charge Amount with GAH Air Handler" will be
used. Now calculate for the additional 20 ft. line set.
Additional refrigerant to be added = (20 ft. x 0.5 oz.)
Solution: 10 oz. should be added to the recommended charge
of 86 oz. found in the "Charge Amount with GAH Air
Handler" column for a total charge of 96 oz.
After initial charge, the system should be operated and the
system subcooling and superheat verified to the Unit Operating
Parameters table.
If an air handler manufactured by others is used then refrigerant
should be added to the Aston Series Split factory pre-charge.
Refrigerant should be added for liquid line length. This should
result in a slightly under-charged system exhibiting low subcooling
and high superheat. As charge is added, the subcooling should
rise and the superheat should fall.
Charging the System
Charge Method – After purging and evacuating the line set, fully
open the service valves counterclockwise. Add R-410A (liquid)
into the liquid line service port until the pressure in the system
reaches approximately 200 PSIG. Never add liquid refrigerant
into the suction side of a compressor. Start the unit and measure
superheat and subcooling. Keep adding refrigerant until the unit
meets the superheat and subcooling values on the Operating
Parameters tables.
Checking Superheat and Subcooling
Determining Superheat
1.
2.
3.
4.
Superheat Adjustment
TXVs are factory set to a specific superheat; however, the
superheat should be adjusted for the application. To adjust the
TXV to other superheat settings:
1.
2.
3.
= 10 oz.
29
ASTON INDOOR SPLIT SERIES INSTALLATION MANUAL
Measure the temperature of the suction line at the point where
the expansion valve bulb is clamped.
Determine the suction pressure in the suction line by
attaching refrigeration gauges to the Schrader connection on
the suction side of the compressor.
Convert the pressure obtained in Step 2 to the saturation
temperature by using the R-410A Pressure/Temperature
Conversion Chart.
Subtract the temperature obtained in Step 3 from Step 1. The
difference is the amount of superheat for the unit. Refer to the
Operating Parameters tables for superheat ranges at specific
entering water conditions.
Remove the seal cap from the bottom of the valve.
Turn the adjustment screw clockwise to increase superheat
and counterclockwise to decrease superheat. One complete
360° turn changes the superheat approximately 3-4°F,
regardless of refrigerant type. You may need to allow as much
as 30 minutes after the adjustment is made for the system to
stabilize.
Once the proper superheat setting has been achieved,
replace and tighten the seal cap.
WARNING: There are 8 total (360°) turns on the
superheat adjustment stem from wide open to
fully closed. When adjusting the superheat stem
clockwise (superheat increase) and the stop is
reached, any further clockwise turning adjustment
will damage the valve.