Method for Installation of HVAC System (Part-4)

HVAC Refrigerant  Pipe Testing:

(A) Refrigerant Piping (Leak Check) by Pressure Testing:

  •  Pressure testing helps ensure a leak free system, a critical component to a successful installation.
  • Max PSI and duration of pressure tests can vary between manufacturers and should be reviewed in the installation manual.
  • All VRV systems should be pressure tested to 550 PSIG and held for 24 hours.
  • Pressure testing process: Tighten down stop valves before any pressure testing to prevent nitrogen
  • From leaking back through condenser and contaminating refrigerant.
  • Pressure testing shall be done in three (3) steps.
  • Step 1 – Leak check 3 minutes at 150 PSI
  • Step 2 – Leak check after 5 minutes at 325 PSI
  • Step 3 – Leak check after 24 hours at 550 PSI (450 psi for systems with vertical Air Handlers)
  • After the gauge reading reaches 550 psig, isolate the system by first closing the gauge manifold, then close the nitrogen cylinder valve.
  • Check the flared and brazed connec­tions for leaks by applying a bubble solution to all joints.
  • The bubble solution must be a solution designed for refrigerant leak testing. Common soap solution must never be used on refrigerant piping as those contain chemicals that could corrode copper and brass, and cause product malfunction.
  • If the pressure does NOT drop for 24 hours, the system passes the test.
  • In this case, the pressure drop of 9.5 psig was due to temperature differences, therefore, there is no leak in the refrigerant piping system.
  • If the pressure drops and it is not due to ambient conditions, there is a leak and it must be found. Remove the bubble solution with a clean cloth, repair the leak(s), and perform the leak / pressure check again.
  • After the system has been thoroughly tested and no leaks are found, depressurize by loosening the charging hose connector at the nitro­gen cylinder regulator. When system pressure returns to normal, completely disconnect the charging hose from the cylinder, and release the nitrogen charge from all refrigerant piping. Wipe off any remaining bubble solution with a clean cloth.
  • Ambient Conditions and the Leak / Pressure Check
  • If the ambient temperature changed between the times when pressure was applied and when the pressure drop was checked, adjust results by factoring in approximately 0.79 psi for each 1°F / 1°C of temperature difference.
  • Correction formula: (°F / °C Temperature when pressure was applied – °F / °C Temperature when pressure drop was checked) x 0.79.
  • Example: When pressure (550 psig) was applied, temperature was 80°F / °C; 24 hours later when pressure drop (540 psig) was checked, temperature was 68°F / °C.
  • Thus, (80°F / °C – 68°F / °C) x 0.79 = 9.5 psig.

(B) Triple Evacuation (Vacuum)

  •  Why is a triple evacuation so important instead of a deep vacuum? Because the relationship between pressure and temperature with water.
  • When the first vacuum is pulled, some of the moisture in the lines boils and evaporates.
  • However, once it reaches a certain pressure the water will actually freeze and leave small ice crystals in the system. This is why a single deep vacuum is insufficient.
  • A triple evacuation of all piping should be performed to eliminate moisture in the system:
  • Do NOT open service valves until the deep vacuum of 500 microns or below has been achieved and the additional charge has been added
  • If Heat Recovery System connect to all three main refrigeration stop valves at outdoor unit.
  • Verify that the micron gauge is connected at a point where it can read the system’s pressure at all times during this process, even when the vacuum pump is not running during the hold test.
  • Evacuation procedures: Evacuation procedures shall be performed as follows:
  • Step 1- Operate the vacuum pump and evacuate the system to the 2,000 micron level.
  • Isolate the pump by closing the manifold gauges and the vacuum pump valve, and then watch the micron level. Micron level may rise a bit, but MUST eventually stop rising for fifteen (15) minutes.
  • If the micron level DOES NOT stop rising, there is a leak, and the leak test must be performed again. If the micron level DOES rise above 2,000 micron, re-open the manifold gauges and the vacuum pump valve and continue evacuation back down to 2,000 micron level.
  • If the micron level holds at 2,000 micron, Break the vacuum with dry nitrogen to a pressure of 2-3 PSI and hold for 15 minutes (this is to “sweep” moisture from piping).
  • Step 2- Evacuate to 1,000 micron level.
  • Isolate the pump by closing the manifold gauges and the vacuum pump valve, and then watch the micron level. Micron level may rise a bit, but MUST eventually stop rising for fifteen (15) minutes.
  • If the micron level DOES NOT stop rising, there is a leak, and the leak test must be performed again.
  • If the micron level DOES rise above 1,000 micron, re-open the manifold gauges and the vacuum pump valve, and continue evacuation back down to 1,000 micron level. If the micron level holds at 1,000 micron, Break the vacuum with dry nitrogen to a pressure of 2-3 PSI and hold for 15 minutes (this is to “sweep” moisture from piping).
  • Step3- Evacuate to static micron level ≤500.
  • Micron level must remain ≤500 for 24 hours. If the vacuum gauge rises and stops, the system may contain moisture, therefore, it will be necessary to repeat the steps of vacuum break and drying.
  • After maintaining the system in vacuum for 24 hours, check if the vacuum gauge rises or not. If it doesn’t rise, then the system is properly evacuated.
  • Close manifold gauges.
  • Shut the valve before turning off the vacuum pump.

Refrigerant Charging:

  • Weigh in additional refrigerant with digital scales. Calculate charge based on total line length plus lb/ft of diameter. Check with each unit model for correct multiplier.
  • After the amount of refrigerant to be added is determined write it down on the label on the back side of the front cover. After the vacuum/drying is complete, charge the additional refrigerant in its liquid state through the liquid stop valve service port.
  • Make sure to use installation tools you exclusively use on R410A installations to withstand the pressure and to prevent foreign material from mixing into the system.

Gas Pressure For any Ton Capacity

Refrigerant Suction Pressure (PSI) Discharge Pressure (PSI) Standing Pressure (PSI)
R 22 60 To 70 250To 300 156
R 32 120 490 260
R 134A 35 158 To 199 95
R 290 65 275 To 300 125
R 404A 87 270 To 356 190
R 407C 63 247 To 307 153
R 410A 110 To 120 400 To 500 250
R 417A 65 261 140

Refrigerant Piping –Additional Refrigerant Charge:

  • Do NOT open unit service valves until additional refrigerant charge has been calculated, added and recorded.
  • Calculates the additional refrigerant charge based on the refrigerant piping layout. If at any time there is a change in the actual piping installation from the design layout, it must be reported back to the designer for verification.
  • Enter additional refrigerant charge amount -R410A.Lbs.
  • Record additional charge amount inside the outdoor unit using a permanent marker.

Additional Refrigerant Charged Volume

Liquid pipe Size R410A (kg/m)
6.4 mm 0.022
9.5 mm 0.057
12.7 mm 0.11
15.9 mm 0.18
19.1 mm 0.26
22.2 mm 0.37
25.4 mm 0.45

Split AC Copper Pipe Additional Refrigerant Charge

Total Pipe Length 50 Meter 60 Meter 70 Meter
Additional Refrigerant None 250 gm (25gm/Meter) 500 gm (25gm/Meter)

Electrical Connections:

  • Make all electrical connections in accordance with electrical codes and ordinances.
  • Multi-pole circuit breaker or disconnect is required to fully isolate the unit from all power.
  • Install circuit breakers/disconnects in accordance with local and national codes.
  • Select the power cable in accordance with relevant local and national regulations.
  • Unbalanced power must be maintained within 10% of supply rating among all indoor units or the unit will stop and an error code will be generated. (Significantly unbalanced power may shorten the life of the system.)
  • Ground the unit at an exclusive grounding terminal, at the electrical panel
  • The communication cable between single-phase outdoor units and between indoor and outdoor units has no polarity.

Testing of the System:

(A) Indoor Unit Cooling Measurement:

  • Measure Indoor unit Return Air Temperature or Room Temperature.
  • Measure Indoor Unit Grill Temperature.
  • Grill Temperature should be 10⁰C to 13⁰C less than Room Temperature in 10 to 15 min.

(B) Outdoor Unit Hot Air Measurement:

  • Measure Outdoor Atmosphere Air Temperature near Out Door Unit (Fan inlet Temperature).
  • Measure Outdoor Unit Fan Discharge Temperature.
  • Outdoor Unit Fan Discharge Temperature should be 11⁰C to 14⁰C higher Out Door Unit Fan inlet Temperature.

(C) Measure Suction Pressure and Discharge Press of System

  • Suction and Discharge Pressure should be according to Refrigerant Type.

(D)Measure Cuurent drawn by Compressor.

  • Ampere drawn by should be as per Manufacture recommended Current Rating.

(E) Fell Cooling of Discharge Line (Liquid Line)

  • Discharge line should be cool enough after starting of Compressor.

(F) System Cooling Problems

  1. Less or No cooling even though No Leakage in Refrigerant Pipe & Suction Pressure is OK.
  • Low Discharge Pressure
  • Weak Compressor.
  1. Ice accumulation on Discharge Line (Liquid Line / Small Line)
  • Less Gas Pressure
  • Capillary Problem.
  1. Ice accumulation on Suction Line (Gas Line / Big Line)
  • Less Gas Pressure
  • Indoor Air Filter chock up, Blower Not running, indoor unit cooling coil problem.
  • Outdoor unit Fan speed is too low, Capacitor Discharge, Refrigerant Pipe Bend or punch
  1. Ice accumulation on both Suction & Discharge Line
  • Not Cut Off Compressor,
  • Electrical Contactor stuck , Electrical Contactor coil not working
  • Problem in Sensor, Thermostats.
  • Machine is continuous working 

System Problems

System Problem Discharge Line Pressure Suction Line Pressure Suction Line Temperature Compressor Amp
Over Gas Charge High High Low (Ice on Suction Pipe) High
Under Gas Charge Low Low High Low
Capillary Block Low Low High Low
Less Air Flow on Evaporator (Indoor Unit) Low Low Low Low
Less Air Flow on Condenser (Outdoor Unit) High High High High
Dirty Condenser (Outdoor Unit) High High High High
Low Ambient Temperature Low Low Low Low
High Ambient Temperature High High High High
In sufficient Compressor Low High High Low

HVAC System installation & Testing Flow Chart

About Jignesh.Parmar (B.E,Mtech,MIE,FIE,CEng)
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical). He is member of Institution of Engineers (MIE) and CEng,India. Membership No:M-1473586.He has more than 16 years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He has published numbers of Technical Articles in “Electrical Mirror”, “Electrical India”, “Lighting India”,”Smart Energy”, “Industrial Electrix”(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

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