Type III: Low-Pressure Appliances and Chillers

Type III is about low-pressure appliances. The physics flips compared with Type II: a low-pressure refrigerant can sit below atmospheric pressure, so the danger is often air and moisture getting in, not refrigerant rushing out. The rules follow from that. Once you see why, the Type III numbers are easy to keep straight.

What counts as low-pressure

Under 40 CFR 82.152, a low-pressure appliance uses a refrigerant with a liquid phase saturation pressure below 45 psia at 104 °F. EPA lists R-11, R-123, R-113 and R-245fa as examples. Under 40 CFR 82.161, Type III certification is required for technicians who maintain, service, repair or dispose of low-pressure appliances.

Where do you meet them? EPA's definition of comfort cooling in 82.152 names chillers, along with commercial split systems and packaged rooftop units, as examples of comfort cooling equipment. Not every chiller is low-pressure, though. Check the nameplate: the refrigerant decides the category, not the type or size of the machine. A chiller charged with R-123 is low-pressure; one charged with R-134a is medium-pressure, which is Type II work.

Source: EPA Section 608, 40 CFR 82.152 and 40 CFR 82.161.

What the Type III test covers

EPA's test topics page lists for Type III: Leak Detection, Leak repair requirements, Recovery Techniques, Recharging Techniques, Recovery Requirements, Refrigeration, and Safety. Compared with Type II, the new heading is Recharging Techniques.

The evacuation level: 25 mm Hg absolute

In Table 1 of 40 CFR 82.156, every row is in inches of mercury vacuum except one. Low-pressure appliances must be evacuated to 25 mm Hg absolute, and the number is the same whether the recovery equipment was made before or after November 15, 1993.

Two different scales are in play. Inches of Hg vacuum measure how far below atmospheric pressure you are, so a bigger number is a deeper vacuum. Millimeters of Hg absolute measure up from a perfect vacuum, so a smaller number is a deeper vacuum. 25 mm Hg absolute is close to a full vacuum. Test writers like to put "25 inches of vacuum" next to "25 mm Hg absolute" in the same question to see if you notice the unit.

Source: EPA Section 608, 40 CFR 82.156(a), Table 1.

Opening a low-pressure appliance for a non-major repair

A major repair, in EPA's definition, involves removing the compressor, condenser, evaporator or auxiliary heat exchanger coil. For work that is not major and is not followed by evacuation of the appliance to the environment, 40 CFR 82.156(a)(1) says:

• Pressurize the low-pressure appliance to no higher than 0 psig before opening it, and cover openings when isolation is not possible.
• If the refrigerant boils at or below 85 °F at 29.9 inches of Hg, do not use methods such as nitrogen that would require purging afterward.
• If the refrigerant boils above 85 °F, use heat to raise the internal pressure as much as possible. Nitrogen may be used only to raise the pressure from the level reached with heat up to atmospheric pressure.

Why 0 psig? At 0 psig the inside matches the outside, so when you open the system, refrigerant does not push out and air does not get pulled in. With a medium-, high- or very high-pressure appliance, you get there by evacuating down. With a low-pressure appliance that is sitting below atmospheric, you get there by raising the pressure up.

Oil changes

Same section, same idea: to change the oil, evacuate or pressurize the appliance, or the isolated part of it, to no higher than 5 psig before opening it, or drain the oil into a system receiver held at no higher than 5 psig.

When leaks prevent evacuation

If leaks make 25 mm Hg absolute impossible, or reaching it would substantially contaminate the refrigerant, the rule in 82.156(a)(2) applies: isolate the leaking components where possible, evacuate the non-leaking parts to the required level, and take the leaking parts to the lowest level attainable without substantial contamination, but never above 0 psig.

Leak repair on low-pressure systems

Leak repair under 40 CFR 82.157 applies to appliances with a full charge of 50 lb or more of a class I or class II refrigerant. Among the low-pressure examples, R-11 is a CFC and R-123 is an HCFC, so leak repair applies to those systems when the charge is 50 lb or more. R-245fa is an HFC, a substitute, and since April 10, 2020 the 82.157 leak repair rules do not apply to appliances containing only substitutes. For a chiller doing comfort cooling, the trigger rate is 10 percent, with 30 days to repair. Full details are in the Type II and leak rules guide.

Source: EPA Section 608, 40 CFR 82.157.

Mothballing

EPA defines mothballing as evacuating refrigerant from an appliance, or an isolated section of it, to at least atmospheric pressure and temporarily shutting it down. EPA's leak repair page explains that leak repair timelines may be suspended while an appliance is mothballed, and resume when it is brought back online.

Recovery equipment rules still apply

As with every type, recovery must use certified recovery or recycling equipment, used according to the manufacturer's directions unless they conflict with the rule (40 CFR 82.156(g)). Recovered refrigerant can go back into the same appliance or another appliance of the same owner without recycling or reclamation.

A Type III question to try

Then try the three Type III questions in the free quiz.

Frequently asked questions

What is a low-pressure appliance?

One that uses a refrigerant with a liquid phase saturation pressure below 45 psia at 104 degrees F. EPA lists R-11, R-123, R-113 and R-245fa as examples.

What evacuation level is required for a low-pressure appliance?

25 mm Hg absolute, for recovery equipment made both before and after November 15, 1993, per Table 1 in 40 CFR 82.156.

Can I use nitrogen to pressurize a low-pressure appliance?

For refrigerants that boil at or below 85 degrees F, methods like nitrogen that require later purging are not allowed. For refrigerants that boil above 85 degrees F, use heat first; nitrogen may only take the pressure from the heat-attainable level to atmospheric.

What is different about the Type III test topics?

EPA's test topics list for Type III includes Recharging Techniques, which is not on the Type II list.