Issue:
Refrigerant charging table for a Uniflair Unit.
Product line:
T*DV, T*TV, T*AV, T*EV, T*WV.
Environment:
All Serials Numbers.
Cause:
Install.
Resolution:
Air-cooled DX units must be connected to a remote outdoor condenser. Systems with remote outdoor condensers must have discharge and liquid lines from the equipment to the condenser.
Note: Install all refrigerant lines in accordance with applicable industry guidelines as well as local and national codes and regulations.
General Guidelines:
• All refrigerant piping is type L ACR hard drawn copper pipes (soft copper is unacceptable).
• All refrigerant lines/chilled water piping are free from debris.
• All refrigerant lines should be short and direct as possible.
• All refrigerant piping joints must be made by brazing only; do not solder. Recommended brazing alloy is AWS A5.8 BCuP-5.
• All refrigerant pipes are installed with proper supports and approved refrigerant line clamps.
Caution: The laying of the lines and the refrigerant connections must be performed by a qualified technician. All lines must be properly supported, insulated and isolated to avoid
premature joint failures due to system vibrations.
Note: Isolate piping from structural surfaces using proper refrigeration/AC vibration clamps.
Note: When brazing field-installed copper refrigeration lines, use a nitrogen purge to minimize
contamination of the refrigeration system during the brazing process.
Equivalent Line Length of Fittings
Use the following table for reference when determining the total equivalent length of a pipe run.
Discharge Line Sizing
Caution: Discharge lines must be insulated where contact could be made to avoid a contact burn. Discharge lines must be sized such that refrigerant velocity in vertical lines is between 5 m/s
(1000 ft/min) and 15 m/s (3000 ft/m). Refrigerant velocity in horizontal lines should be a minimum of 2.5 m/s (500 ft/min). Refrigerant velocity must be high enough to keep oil entrained in the flow to ensure the proper flow of oil throughout the system, in particular when operating at partial load. If refrigerant velocity is too low, oil will not return to the compressor. If the refrigerant velocity is too high, both the noise level and pressure drop will increase. The acceptable pressure drops in discharge lines are up to 68.9 kPa (10 psi).
Note: Give consideration to the full and half load (or tandem) of the compressor to ensure that the operational range stays within these limits. Horizontal discharge lines must be pitched downward at a minimum of 10 mm per m (1.2 in per ft) to ensure proper oil return.Trap the discharge line at the base of the vertical riser to prevent oil from returning back to the compressor during shutdown
periods.
Calculating Total Discharge Line Size:
Use the following guidelines to determine the diameter of pipe:
• Use the formula:
Total Equivalent length = Vertical line length + Horizontal line length + Equivalent Length of Fittings
• Total equivalent length should not exceed 40 m (130 ft).
• For pipes running in a downward vertical direction, select pipe size from the horizontal sizing table.
Discharge Line Size—Vertical:
• Calculate equivalent discharge line length in vertical direction.
• Use the table below to determine pipe diameter for vertical pipes.
Note: Equivalent length in vertical direction cannot exceed 15 m (50 ft).
Discharge Line Size—Horizontal
• Calculate equivalent discharge line length in horizontal direction.
• Use the table below to determine pipe diameter for horizontal pipes.
Note: Equivalent length in horizontal direction cannot exceed 40 m (130 ft).
Liquid Line Sizing:
Liquid lines must be sized to ensure sufficient refrigerant flow to the expansion device and to minimize pressure drop.
Note: Excessively long liquid lines should be insulated from high ambient temperatures.
Refrigeration Circuits
Warning: Charging and maintaining the refrigeration circuit must only be performed by qualified personnel. The refrigeration circuit from the factory is pre-charged with nitrogen. Prior to evacuation a gross
pressure test should be performed to identify any leaks.
Gross Pressure Test:
1. Open any shut-off valves present in the system to ensure that all of the components will be tested.
2. Pressurize the system to 17.2 bar (250 psi) with nitrogen.
3. Leave the system pressurized for 24 hours.
4. After 24 hours, verify that no drop in pressure has occurred. After verifying the absence of leaks from the system, perform the system evacuation.
System Evacuation:
1. Open any shut-off valves present in the system to ensure that all of the components will be evacuated.
2. Connect a vacuum pump to the service ports on the system piping. Use of a core removal tool may reduce the time of the evacuation.
3. Pull the first vacuum down to 750 microns, then isolate the system from the vacuum pump.
4. Wait for an hour and check vacuum level. The vacuum should not rise above 1500 microns; if vacuum level exceeds this level, check system for leaks.
5. Break the vacuum with nitrogen.
6. Pull a final vacuum to below 500 microns. With the system isolated from the vacuum pump the system should not rise above 500 microns for a minimum of 2 hours.
Note: Install a ball valve before the micron gauge to prevent damage to the micron gauge during charging. After completing the vacuum seal, charge the system with refrigerant.
Refrigerant Charging:
- Calculate the total charge needed, using the reference table and formula:
Indoor Unit Charge + Liquid Line Charge + Condenser Charge = Total Charge
2. Connect the refrigerant cylinder to the service ports.
3. Break the vacuum by charging with liquid R410A.
.
Note: Charge R410A as a liquid only.
4. Charge to 80% of the calculated total.
Note: If the system is not ready for commissioning, then apply only a holding charge and record the amount charged.
5. Start the compressor, and complete the charging process.
Note: Perform a slow charge to avoid compressor damage.
Note: This charge calculation is used as starting point, please continue charging based on superheat and subcool.
Published for:APC Belgium
