Excerpt_from_GreenChill.pdf
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- Replace Compressors for Constant Temperature Rooms in the NLGRP Federal contract opportunity
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- 128KAP18R0003
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Excerpt from GreenChill
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Excerpt from
GreenChill Best Practices Guideline Ensuring Leak-Tight Installations of Commercial
Refrigeration Equipment https://www.epa.gov/sites/production/files/documents/leakguidelines.pdf
Pre-Evacuation Nitrogen, air, and moisture can remain in the system if the system is not properly evacuated. Moisture causes expansion valve ice blockage, wax build up, and acid in the oil.
Before beginning the evacuation process, make sure you observe the following:
• ensure system is completely depressurized;
• plan procedures so breaking the vacuum with refrigerant does not introduce contaminates into the system;
• the evacuation pump should be connected to three points on the rack, unless the system is small (if the system is small, the evacuation pump may only need to be connected at 2 points); o the 3/8 inch flare ports are ideal for these connections, o copper lines are preferred over hoses, and o if any hoses are used, they must be special vacuum hoses, as standard pressure hoses tend to collapse under high vacuum and increase the time required to fully evacuate the system;
• Vacuum pump: o Vacuum pumps should be rated at 8 cfm or larger. Pumps should be connected to several branch circuits to access all components of the system.
∗ Be sure each pump is tested prior to use and vacuum sensors are in working order. The pump must be able to achieve a vacuum of at least 300 microns. Test vacuum gauges and vacuum sensors according to manufacturer’s instructions.
o Use clean vacuum pump oil as recommended by the pump manufacturer.
o Make sure electrical connections to the pump are secure and uninterrupted.
o Check all vacuum pump connections for leaks.
o Monitor the pump for signs of normal operation (e.g. “vapor” from the pump exhaust early in the procedure that tapers off).
• Lines and valves: o Use all copper lines or hoses that are suitable for vacuum duty.
o Use packless valves.
o One large vacuum pump can be used, if a header is connected to three different points on the system.
o All schrader valve caps need to be properly tightened and checked. Check the condition of o-ring in Schrader valve caps.
o All access valves need to be properly tightened and o-rings intact. In a deep vacuum, the stems will draw in and cause a loss of vacuum. This will not be noticed during a pressure test.
• Micron vacuum gauge (digital, analog, LED) o Before beginning evacuation, calibrate the micron gauges per manufacturer’s instructions.
o Verify with a gauge that the vacuum pump can pull a vacuum of at least 300 microns.
o Measure vacuum at a minimum of two locations. These two locations must be at the most extreme positions of the system.
7. Stairstep Evacuation Procedure Vacuum requirements may be dictated by customer and/or code requirements.
• Pull a system vacuum down to at least 1000 microns (+/- 50 microns) and close the vacuum header valves. If the system cannot pull a vacuum at any step and returns to atmospheric pressure, which is an indication of a leak, test for and repair the leak using the previously described procedure with tracer gas.
• If the 1000 micron vacuum holds for 30 minutes, break the vacuum with dry nitrogen to a pressure of 2 psig ∗ Do not exceed micron gauge transducer limits or transducer will be damaged!
• Install system suction and liquid drier cores.
• Pull a second vacuum to a minimum of 500 microns.
• Close vacuum header valves.
• If the 500 micron vacuum holds for a minimum of 30 minutes, then break the vacuum with the refrigerant to be used in the system to a pressure of 2 psig.
• Pull a third vacuum to a minimum of 300 microns.
• Close vacuum header valves and allow system to stand for a minimum of 24 hours.
• If the 300 micron vacuum holds for 24 hours with a maximum drift of 100 microns over the 24 hour period, then the system is ready to be charged with refrigerant.
• Break the vacuum with the refrigerant to be used in the system and charge the system with refrigerant.
• Add oil to the compressors, oil separator and oil reservoirs, if equipped.
https://www.epa.gov/sites/production/files/documents/leakguidelines.pdf
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