TYPE 3 (Low-pressure)

Leak Detection

• Order of preference of leak test pressurization methods for low-pressure systems (first: hot water method or built-in system heating/pressurization device such Prevac; second: nitrogen)
• Signs of leakage into a low-pressure system (e.g., excessive purging)
• Maximum leak test pressure for low-pressure centrifugal chillers

Leak repair requirements

• Allowable annual leak rate for commercial and industrial process refrigeration
• Allowable annual leak rate for other appliances containing more than 50 lbs of refrigerant

Recovery Techniques

• Recovering liquid at beginning of recovery process speeds up process
• Need to recover vapor in addition to liquid
• Need to heat oil to 130F before removing it to minimize refrigerant release
• Need to circulate or remove water from chiller during refrigerant evacuation to prevent freezing
• High-pressure cut-out level of recovery devices used with low-pressure appliances

Recharging Techniques

• Need to introduce vapor before liquid to prevent freezing of water in the tubes
• Need to charge centrifugals through evaporator charging valve

Recovery Requirements

• Evacuation requirements for low-pressure appliances in each of the following situations:
• • Disposal
  • Major vs. non-major repairs
  • Leaky vs. non-leaky appliances
  • Appliance (or component) containing less vs. more than 200 lbs
  • Recovery/recycling equipment built before vs. after November 15, 1993
• Definitions of "major" and "non-major" repairs
• Allowable methods for pressurizing a low-pressure system for a non-major repair (controlled hot water and system heating/pressurization device such as Prevac)
• Need to wait a few minutes after reaching required recovery vacuum to see if system pressure rises (indicating that there is still liquid refrigerant in the system or in the oil)

Refrigeration

• Purpose of purge unit in low-pressure systems
• Pressure-temperature relationships of low-pressure refrigerants

Safety

• Equipment room requirements under ASHRAE Standard 15 (oxygen deprivation sensor with all refrigerants)
• Under ASHRAE Standard 15, need to have equipment room refrigerant sensor for 123