Wait — Is That System Even Covered? The Residential Exemption That's Confusing Everyone

Over the past seven weeks, we've covered the full scope of Subpart C: the 15-pound threshold, leak rate calculations, documentation standards, repair workflows, and the 125% chronic leaker rule.

Throughout all of it, we've been referencing an exemption that's buried in the regulation — and it's the detail generating the most confusion in the field right now.

The question we hear every week: "Does this apply to the residential splits I service?"

The short answer is no. The longer answer is that the exemption is narrower than you think, and misunderstanding where it ends could mean treating a covered system as exempt — or wasting compliance effort on systems that don't require it.

The Exemption, In Plain English

Section 84.106(a)(3)(ii) exempts refrigerant-containing appliances used for the residential and light commercial air conditioning and heat pump subsector from all Subpart C requirements.

That means: no leak rate calculations, no 30-day repair clock, no chronic leaker tracking, no recordkeeping requirements under Subpart C. For systems that fall into this category, Subpart C simply does not apply.

So far, so simple. But here's where it gets complicated: Subpart C also defines a category called "comfort cooling" — and comfort cooling systems are fully covered with a 10% leak rate threshold.

The regulation defines comfort cooling as appliances used for air conditioning to control heat and humidity in occupied facilities, "including but not limited to residential, office, and commercial buildings." Comfort cooling explicitly includes "chillers, commercial split systems, dual-function heat pumps, and packaged roof-top units."

Read that again: the definition of comfort cooling includes residential systems. But the exemption removes residential and light commercial systems from Subpart C coverage.

So what's actually covered? Commercial comfort cooling that's not in the residential and light commercial subsector.

Where's the Line?

The EPA doesn't provide a bright-line definition of where "residential and light commercial" ends and "commercial" begins in Subpart C itself. But the term has a history in EPA regulation and industry usage that gives us working boundaries.

Here's a practical framework based on regulatory context and industry convention:

Exempt: Residential and Light Commercial

These systems are not covered by Subpart C:

Residential split systems and heat pumps. The 2-, 3-, and 5-ton splits you install in houses. These are squarely in the residential subsector regardless of charge size. Most residential systems hold well under 15 pounds anyway, but even a large residential system with 15+ pounds of refrigerant is exempt.

Window units and portable AC. These are explicitly listed in the residential and light commercial subsector in EPA documentation for the Technology Transitions Rule. Same subsector, same exemption.

Light commercial systems in small commercial applications. Think: a single packaged unit or split system serving a small retail shop, a hair salon, or a one-suite professional office. Equipment that is essentially residential in design and application, used in a light commercial setting.

Mini-splits and ductless systems. In both residential and light commercial applications, these fall within the exempt subsector.

Covered: Commercial Comfort Cooling

These systems are covered by Subpart C at the 10% leak rate threshold:

Packaged rooftop units on commercial buildings. The 5-, 7.5-, 10-, and 15-ton rooftop units sitting on top of strip malls, medical offices, schools, restaurants, and office buildings. This is the big one. These are commercial comfort cooling appliances, they frequently hold 15+ pounds of refrigerant, and they are fully subject to Subpart C.

Commercial split systems. Larger split systems designed for commercial applications — serving multiple zones, connected to commercial air handlers, or sized above typical residential applications.

Chillers. Water-cooled, air-cooled, centrifugal, scroll — all chillers used for comfort cooling in commercial settings are covered.

Commercial heat pumps. Heat pump systems in commercial buildings, including VRF/VRV systems in commercial applications.

Any comfort cooling system in a commercial building that doesn't qualify as "light commercial." The moment the application, the building, and the equipment move beyond what's recognizable as residential or light commercial, you're in Subpart C territory.

The Gray Zone: Five Scenarios

The boundary gets fuzzy in real-world applications. Here are five scenarios that come up constantly, with our best reading of where they fall:

Why This Matters for Small Contractors

If your business is primarily residential, here's the bottom line: most of your daily work is exempt from Subpart C. The residential splits, heat pumps, mini-splits, and light commercial systems that make up the majority of your service calls don't require leak rate calculations, 30-day repair timelines, or chronic leaker tracking under this rule.

That's genuinely good news. It means Subpart C is not a burden on every service call you run.

But here's the catch: if you also service any commercial accounts — and most small contractors do — you likely have systems in your customer base that are covered. The rooftop units on the strip mall. The 10-ton packaged unit on the medical office. The chiller in the small office building. Those systems need the full Subpart C treatment.

The risk isn't in your residential work. The risk is in assuming the exemption applies to everything you touch.

The Other Exemption: ODS-Only Systems

While we're clarifying coverage, there's a second exemption worth noting. Section 84.106(a)(3)(i) exempts appliances that contain solely an ozone-depleting substance (ODS) as a refrigerant.

Systems running only R-22, R-12, or other Class I or Class II ODS refrigerants are covered under the older Section 608 rules (40 CFR Part 82, Subpart F) — not Subpart C. Those systems have their own leak repair requirements with a 50-pound threshold.

This matters because there are still R-22 systems in the field, and they operate under different rules than the HFC systems covered by Subpart C. If a system runs R-22 and nothing else, Subpart C doesn't apply to it. If a system has been retrofitted to an HFC blend (like R-407C or R-422D), it falls under Subpart C.

A Decision Framework for the Field

Here's a quick-reference flowchart your techs can use to determine whether a system is covered by Subpart C:

Step 1: What refrigerant is in the system?

• ODS only (R-22, R-12, etc.) → Not Subpart C (covered by Section 608 at 50-lb threshold)
• HFC with GWP > 53 → Continue to Step 2
• Natural refrigerant (CO₂, ammonia, propane) → Not covered by either rule

Step 2: How much refrigerant does it hold?

• Less than 15 pounds → Not covered by Subpart C
• 15 pounds or more → Continue to Step 3

Step 3: What type of system is it?

• Residential or light commercial AC/HP → Exempt from Subpart C
• Commercial comfort cooling → Covered at 10% threshold
• Commercial refrigeration → Covered at 20% threshold
• Industrial process refrigeration → Covered at 30% threshold

Three questions. Ten seconds. Your tech now knows whether this service call triggers Subpart C obligations before they even open the access panel.

The exemption protects your residential work. It does not protect your commercial work. Every small contractor who services both needs to know where the line is — because the consequence of guessing wrong runs in one direction only.

What to Do With This Information

If you're a primarily residential contractor who occasionally services commercial accounts:

Audit your customer list this week. Identify every commercial account with equipment that's likely 15+ pounds and running HFC refrigerant. Those are your Subpart C accounts. Everything else is business as usual.

Train your techs on the three-question framework. Print the decision flowchart above and put it in the truck. The five seconds it takes to ask "what refrigerant, how much, what type" will save hours of unnecessary compliance work on residential calls — and prevent missed compliance on commercial calls.

Don't over-comply on residential. Subpart C documentation on a residential split system isn't required and isn't expected. If you're spending time and money tracking leak rates on 3-ton residential systems, you're burning resources that should be focused on the commercial systems that actually require it.

Don't under-comply on commercial. The flip side is equally important. If you assume "most of my work is residential, so I don't need to worry about Subpart C," you're one strip-mall rooftop unit away from a compliance gap.

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Next Monday, we're wrapping up this initial series with a complete Subpart C reference guide: every threshold, every deadline, every documentation requirement on one page. The kind of thing you print, laminate, and keep in the truck for the rest of the year. See you February 16th.