Envision Peripherals Series Leak Testing, System Evacuation, Initial System Charge Calculation

NS SPLIT INSTALLATION MANUAL

Refrigeration (continued)

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 pres- sure 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 pres- surize 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 sys- tem through both service ports to prevent false readings on the gauge because of pressure drop through service ports.

Initial System Charge Calculation

The Envision unit comes with a factory pre-charge. This volume is not sufficient to run the system. Additional refrigerant must be added for the lineset. This additional charge added to the factory pre-charge of the Envision unit should be esti- mated using the following equation:

Addition to Factory Charge = (lineset length x oz. per ft) + (20 oz. for accumulator)

The lineset charge should be calculated by multiplying the length times 0.5 oz./ft for 3/8” liquid line and 1.0 oz/ft for 1/2” liquid line in R-410A systems. The suction line will not hold ‘liquid’ and can be ignored for the calculation. This should result in a slightly under-charged unit exhibiting low subcooling and high superheat. As charge is added, the subcooling should rise and the superheat should fall until 8-16 degrees of superheat is reached when the TXV should be metering the system. See operating details in the startup section of this manual for exact superheat and subcooling values.

Example: 038 with 40 foot of 3/8” liquid line.

Additional to be added = (40 ft x 0.5 oz./ft) + (20 oz. for accumulator) = 40 oz.

Solution: 40 oz. should be added to the existing 56 oz. of factory charge as an initial charge.

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 refrig- erant until the unit meets the superheat and subcooling values on page 24.

Checking Superheat and Subcooling

Determining Superheat

1.Measure the temperature of the suction line at the point where the expansion valve bulb is clamped.

2.Determine the suction pressure in the suction line by attaching refrigeration gauges to the schrader connection on the suction side of the compressor.

3.Convert the pressure obtained in Step 2 to the saturation temperature by using the R-410A Pressure/Temperature Con- version Chart on page 23.

4.Subtract the temperature obtained in Step 3 from Step 1. The difference is the amount of superheat for the unit. Refer to tables on page 24 for superheat ranges at specific entering water conditions.

Superheat Adjustment

TXV’s 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.Remove the seal cap from the bottom of the valve.

2.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.

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