Type III recovery: EPA 608 Practice Questions

To what level must a low-pressure appliance be evacuated before a major repair or disposal?

Table 1 requires 25 mm Hg absolute for low-pressure appliances, with recovery equipment of any age.

25 mm Hg absolute is about how many inches of mercury of vacuum on a compound gauge at sea level?

25 mm Hg is about 1 in Hg absolute; 29.92 − 1 ≈ 29 in Hg vacuum. That is a deep vacuum, close to the limit a compound gauge can show.

Does the required evacuation level for a low-pressure appliance depend on whether the recovery equipment was made before or after November 15, 1993?

Unlike the other rows in Table 1, the low-pressure level is the same for old and new recovery equipment: 25 mm Hg absolute.

When recovering refrigerant from a low-pressure chiller, what should be removed first?

Most of the charge is liquid in the evaporator, so recovering liquid first is much faster. Vapor recovery follows.

Even after all the liquid is removed from a large low-pressure chiller, why must vapor recovery continue?

The large shells of a chiller hold a significant mass of vapor. Recovery continues until the 25 mm Hg absolute level is reached.

During recovery from a low-pressure chiller, why should water be kept circulating through the tubes (or the tubes drained)?

As refrigerant pressure falls, its boiling temperature drops below 32°F and can freeze the water in the tubes, which may rupture them.

Recovery equipment made on or after January 1, 2017 for use with a low-pressure chiller (non-flammable refrigerant) is certified under which standard?

Recovery equipment made on or after January 1, 2017 for non-flammable refrigerants is tested under Appendix B3, which is based on AHRI Standard 740-2016. Appendix B4, with UL 1963 Supplement SB, covers flammable refrigerants; AHRI 700 is the refrigerant purity specification.

Before a non-major repair on a low-pressure chiller, with no release expected afterward, what pressure must the chiller be at?

For a non-major repair, a low-pressure appliance is brought up to (but not above) 0 psig, so air does not rush in and refrigerant does not rush out when it is opened.

An R-123 chiller (boiling point about 82°F) must be raised to 0 psig for a non-major repair. May nitrogen be used to do this?

For refrigerants with a boiling point at or below 85°F, nitrogen may not be used to pressurize; use heat such as warm water or heater blankets.

For a low-pressure refrigerant that boils above 85°F, how may the appliance be brought to 0 psig for a non-major repair?

Heat must be used first to raise the pressure as far as practical; nitrogen may then be used only from that level up to atmospheric pressure.

What pressure applies when changing the oil on a low-pressure chiller?

For oil changes, the appliance (or the receiver the oil drains into) is evacuated or pressurized to no higher than 5 psig.

Why is the oil in a low-pressure chiller heated before it is drained?

Refrigerant dissolves in oil. Warming the oil as the manufacturer directs releases that refrigerant so less of it leaves with the drained oil.

A low-pressure chiller has a leak that prevents reaching 25 mm Hg absolute without pulling in air. What does the rule require?

Leaking components are isolated and evacuated to the lowest level reachable without substantially contaminating the refrigerant. Non-leaking parts still go to Table 1 levels.

Which recovery equipment may be used to evacuate a low-pressure chiller to 25 mm Hg absolute?

Recovery equipment must be certified for the refrigerant and appliance type. A vacuum pump would vent refrigerant and is never a recovery device.

After a low-pressure chiller reaches 25 mm Hg absolute, the technician isolates it and the pressure rises within a few minutes. What should be done?

A pressure rise after isolation means refrigerant is still present. Continue recovery until the level holds.