Do's & Don'ts Good Servicing Practices Do’s & Don’ts

Do's & Don'ts Areas of Focus Brazing Cleaning and Flushing Leak Testing Evacuation Measurement / holding of vacuum Charging of Refrigerant

Do's & Don'ts Essentials of Brazing Melts at temperature lower than that of base metals Rod should melt by contact with heated base metal Melted Rod Material flows into clearance between walls of the two tubes through capillary action Brazing Filler Rod TorchBase Metal Brazing Filler Rod

Do's & Don'ts Good Brazed Joints: Prerequisites Right technique Right temperature Right Joint preparation Surface preparation Joint clearances Right brazing alloys; Right Flux

Do's & Don'ts Suitability of Brazing Equipment Oxy Acetylene: Best suited Oxygen-LPG: Better suited than Air-LPG Air-LPG: May be inadequate, but O.K. for Cu tubes up to 3/8” with Swirljet (or Cyclone) Torches Kerosene Blow-lamp: Should be avoided

Do's & Don'ts Cleaning and Flushing  USE. Dry Nitrogen Trichloroethylene (for chemical cleaning) (ensure trichloroethylene vapourises and does not remain as liquid after cleaning, by application of gentle heat)  DO NOT USE CTC (Being phased out) Air (Contains moisture, lubricant & other gases, detrimental to the system) Oxygen – not O.K. for compressor oil Petrol (has a lot of impurities which can destroy the compressor)

Do's & Don'ts Leak Testing  USE. Dry Nitrogen (after the system has been reassembled)  Should have a dew point of at least C Commercial nitrogen with a drier (to reduce moisture content)  DO NOT USE Compressed air (Contains moisture, lubricant & other gases, detrimental to the system) Refrigerant

Do's & Don'ts Dry Nitrogen Different types of N 2 available For refrigeration service, following specification recommended : Purity : % Dew Point: -40 o C at least Approximate price: Rs. 325/- per cylinder of 7 m 3 (with security deposit ranging from Rs. 5000/- to Rs. 10,000/-) Makes: Bombay Oxygen, Inox & others

Do's & Don'ts Equipment for Evacuation DO NOT USE Refrigeration System’s compressor Other Hermetic / Semi Hermetic / Open Refrigeration compressors May lead to compressor failure as:  moisture gets deposited in compressor’s discharge chamber  there can be loss of lubricant  Creates inadequate vacuum for moisture to boil and vacate the system

Do's & Don'ts Why Vacuum Pump is needed

Do's & Don'ts CFM Pump (1/4 HP) 3 CFM Pump (1/3 HP) ½ HP Compressor Vacuum in Microns of Hg ,000100,0001,000,000 Comparison of Vacuum Pump vs Compressor

Do's & Don'ts Equipment for Evacuation (Cont) Use specially designed vacuum pumps, capable of developing blank off pressure of microns Hg Micron gauge capable of reading pressures in Microns range Most preferred: Two stage, Rotary, multi-vane pump

Do's & Don'ts Measuring Vacuum Accurately Use Pirani / Thermocouple vacuum gauge having a range from /10000 microns a.Evacuate to about 500 microns or lower b.Isolate the vacuum pump & observe the rise in the vacuum for 5-10 minutes c.Repeat (a) & (b) till the vacuum in (b) stabilises at around 1500 microns or lower. The lower the stabilised vacuum the better.

Do's & Don'ts If Micron Level Vacuum Gauge is not Used If micron level vacuum gauges are not available  Bourdon type vacuum gauges cannot read vacuum in microns – hence actual vacuum reached cannot be known  In the absence of a micron vacuum gauge, the vacuum pump should be run at least half an hour after the Bourdon type vacuum gauge reading shows -30” / -760 mm / 0 millibar (at sea level).  Neither the vacuum level nor vacuum holding can be known from this. Therefore superior quality of evacuation & assurance using micron gauge will be absent in this case.

Do's & Don'ts Charging Charge the same weight of refrigerant in the system, as recommended by the appliance manufacturer instead of charging by feel (To ensure good cooling performance and low energy consumption) Charging apparatus must provide for accurate weighing scales or calibrated charging cylinders (HFC-134a & HCs particularly are even more sensitive to charge quantity than CFC-12)

Do's & Don'ts Use of Anti-Moist Don’t Use Anti-Moist It has a harmful effect on compressor motor (Causes embrittlement of insulation leading to premature motor failure) Strictly prohibited for HFC-134a systems Instead, evacuate system properly and use the appropriate drier

Contamination & Cross Contamination Contamination by : Moisture Non-condensables Chemical residues Dirt, dust metal particles Organic contaminants Cross-Contamination through: Import of contaminants from other systems or servicing equipment Contaminants: Other refrigerants, other lub. Oils, chemical residues from other systems

Cross-Contamination due to Refrigerant Mixing Even at 10-20% of CFC-12 in HFC-134a & vice- versa, the azeotrope formed will have properties quite different from either This will seriously affect appliance performance Similar problems will arise with mixtures of CFC-12 & HCFC-22 or HCFC-22 & HFC-134a As full data on HCs / CFC-12 or HCs / HFC-134a mixing is not available, it is better to avoid their mixing. CAUTION: Ensure that refrigerants do not mix. AVOID.

Likely Sites for Refrigerant Cross-Contamination Charging stills of E&C units, used for multiple refrigerants Recovery & R&R machines used for multiple refrigerants Recovery cylinders Hoses & Manifolds Old systems retrofitted with non-CFC refrigerants

How to avoid Refrigerant Cross-Contamination (Cont) Ensure that all traces of the previous refrigerants is removed from the charging still / recovery machine & the unit is evacuated to a deep vacuum (1000 microns) before switching to a new refrigerant If possible use separate E&C & Recovery machines for each type of refrigerants Use separate recovery cylinders for each refrigerant

Wrong Installation Gap is less than 2”, after some time wall will be hot

Wrong v/s. right Installation

√ U Trap is must for drains Wrong v/s. right Installation X

Do's & Don'ts LET US INSIST ON GOOD SERVICE PRACTICES WITH PHD. THANKS!!

Do's & Don'ts Contamination & Cross Contamination Contamination by : Moisture Non-condensables Chemical residues Dirt, dust metal particles Organic contaminants Cross-Contamination through: Import of contaminants from other systems or servicing equipment Contaminants: Other refrigerants, other lub. Oils, chemical residues from other systems

Do's & Don'ts Cross-Contamination due to Refrigerant Mixing CFC-12 & HFC-134a when mixed, form high pressure azeotropes with pressure higher than either refrigerant Even at 10-20% of CFC-12 in HFC-134a & vice-versa, the azeotrope formed will have properties quite different from either This will seriously affect appliance performance Similar problems will arise with mixtures of CFC-12 & HCFC-22 or HCFC-22 & HFC-134a As full data on HCs / CFC-12 or HCs / HFC-134a mixing is not available, it is better to avoid their mixing. CAUTION: Ensure that refrigerants do not mix

Do's & Don'ts Cross-Contamination due to Refrigerant Mixing

Do's & Don'ts Likely Sites for Refrigerant Cross-Contamination Charging stills of E&C units, used for multiple refrigerants Recovery & R&R machines used for multiple refrigerants Recovery cylinders Hoses & Manifolds Old systems retrofitted with non-CFC refrigerants

Do's & Don'ts How to avoid Refrigerant Cross-Contamination (Cont) Ensure that all traces of the previous refrigerants is removed from the charging still / recovery machine & the unit is evacuated to a deep vacuum (1000 microns) before switching to a new refrigerant If possible use separate E&C & Recovery machines for each type of refrigerants Use separate recovery cylinders for each refrigerant

Do's & Don'ts Common Practices Use of blow lamp Brazing with Cu electrode for brazing Cu tubes Bundy/steel tubes Flushing with air / refrigerant Use of CTC / petrol for cleaning Leak testing using air/refrigerant Self-evacuation using system compressor or old / used compressor as vacuum pump Improper assessment of vacuum achieved Charging by feel (inaccurate) Use of anti moist Contamination / Cross Contamination of Refrigerants

Do's & Don'ts Essentials of Brazing (Cont) Melted Filler Rod material wets base metal and penetrates surface & forms metallurgical bond. Boundary locking layers (dotted) show metallurgical bond Outer tube end (swaged) Filler material Spigot (inner tube) Tube hollow

Do's & Don'ts Temperatures for Brazing Desired temperature range for Phos Cu Alloys Average temperature for Phos Cu Alloys Right temperature for Cu Ag alloys (Ag >35%) C C C C