A technician recovers R-22 from a rooftop unit that holds 150 pounds using equipment made after November 15, 1993. To what vacuum must the system be evacuated during recovery?

解析

An R-22 unit is a high-pressure appliance (40 CFR §82.152), and at 150 pounds it is under the 200-pound line. §82.156 Table 1 then requires 0 inches Hg (atmospheric pressure) with recovery equipment made on or after November 15, 1993. (a) 10 inches Hg is for high-pressure appliances of 200 pounds or more, or medium-pressure ones under 200; (b) 4 inches Hg is a pre-1993-equipment figure; (d) 15 inches Hg is only for medium-pressure appliances of 200 pounds or more.