If you're an HVAC contractor working in California, you've probably heard the term "altered system" come up when discussing Title 24 compliance. But what exactly qualifies as an altered system, what does the inspection involve, and what does the system need to pass? This guide breaks it all down, including the key testing standards that apply under the 2025 California Energy Code.
What Is an "Altered System" Under California Title 24?
California Title 24 Part 6 (the Energy Code) defines an altered system as an existing HVAC system or duct system that is modified, replaced, or extended. This is distinct from new construction, where an entire new system is installed in a building that didn't previously have one.
Common examples that trigger an altered system ECC inspection include:
- Full HVAC system replacement — new furnace, air conditioner, or heat pump
- Replacing only the AC condenser or heat pump outdoor unit
- Replacing the air handler or furnace while keeping the existing ductwork
- Installing new ductwork or extending existing ducts by more than 25 linear feet
- Adding a split system to a room or addition
Key point: The ECC inspection must be completed and filed with the HERS data registry before the building permit can close. This applies whether the permit was pulled by the homeowner, the contractor, or the HVAC company. No certificate on file = no permit closeout.
Some very limited scope work — like a straight-swap replacement of identical equipment with no duct changes — may qualify for an exemption depending on the local building department's interpretation. When in doubt, check with your local jurisdiction or call an ECC rater before assuming no inspection is needed.
The Four Tests Required for Most Altered Systems
The specific measures required for your project are determined by the CF-1R — the compliance form that was submitted with the permit. That document spells out exactly which ECC measures must be verified. That said, most full HVAC replacement jobs in California require some combination of these four tests:
1. Duct Leakage Test
The duct leakage test measures how much conditioned air is escaping the duct system into unconditioned spaces — attics, crawlspaces, wall cavities. A calibrated blower is attached to the supply or return system to pressurize it, and airflow is measured at a standard pressure of 25 Pascals (hence the unit CFM25).
Under the 2022 California Energy Code (the code in effect as of 2025), altered duct systems must meet the duct leakage requirement specified in the CF-1R. For most residential systems, the target is expressed as a maximum CFM25 leakage relative to the system's airflow capacity. Systems that don't pass must have leaks located — typically using a smoke pencil or duct pressurization along with physical inspection — and sealed before a re-test.
Contractor tip: If you're installing all new ductwork, seal all connections with mastic or foil tape before the rater arrives — not just the obvious joints. The duct leakage test catches small leaks at flex duct collars, boot connections, and plenum transitions that look sealed but aren't.
2. Fan Watt Draw (Fan Efficacy Verification)
Fan watt draw — also called fan efficacy verification — measures the actual electrical consumption of the air handler fan while it's running. The result is expressed as watts per cubic foot per minute (W/CFM). Title 24 sets a maximum W/CFM limit depending on the system type; a fan that draws more power than allowed fails the test.
This test matters because the air handler fan runs constantly whenever the system is in heating or cooling mode. An inefficient motor — one that draws more watts per CFM than the code allows — wastes energy continuously over the life of the system. The watt draw measurement is taken with a power meter connected directly to the fan circuit, and the fan must be running at its normal operating speed during the test.
Fan watt draw failures are most commonly caused by:
- An air handler with a PSC (permanent split capacitor) motor installed where the compliance documents specified a high-efficiency ECM (electronically commutated motor)
- Restrictive duct systems that force the fan to work harder and draw more power
- Incorrect speed tap settings on multi-speed motors
3. Refrigerant Charge Verification
Refrigerant charge verification confirms that the AC or heat pump system is charged to the manufacturer's exact specification. An improperly charged system — whether overcharged or undercharged — can lose significant efficiency and, in some cases, cause compressor damage over time.
California Title 24 allows charge verification using two accepted methods:
- Subcooling method — Used on systems with a thermostatic expansion valve (TXV). The rater measures the difference between the liquid line temperature and the saturation temperature at the measured liquid line pressure. The result must fall within the manufacturer's specified subcooling range.
- Superheat method — Used on systems with a fixed orifice metering device. The rater measures the difference between the suction line temperature and the saturation temperature at the measured suction pressure. The result must fall within the manufacturer's specified superheat range.
The system must be running at steady-state — typically 15 to 20 minutes of operation — before measurements are taken. Outdoor ambient temperature and indoor return air conditions are also recorded to confirm the test was conducted within acceptable operating parameters.
Important: The refrigerant charge verification must be performed by a licensed ECC rater — not the HVAC technician who did the install. The rater documents the measured values on the CF-2R form and files it with the HERS registry.
4. Airflow Verification
Airflow verification measures the actual cubic feet per minute (CFM) of conditioned air delivered by the system and compares it to the design airflow specified on the CF-1R. Correct airflow is essential for the HVAC system to perform as designed — too little airflow starves the refrigerant circuit and reduces efficiency; too much can cause comfort problems and increased energy use.
Airflow is typically measured using a calibrated flow hood placed over a supply or return register, or calculated using a fan curve method based on external static pressure. The measured value must fall within an acceptable range of the design airflow from the compliance documents.
This test is almost always performed in the same visit as refrigerant charge verification — the two tests are closely related, since correct airflow is a prerequisite for an accurate refrigerant charge measurement.
Quick Reference: Altered System Tests at a Glance
| Test | What It Measures | Typical Trigger |
|---|---|---|
| Duct Leakage | Air escaping ducts to unconditioned space (CFM25) | Any ductwork alteration or new duct installation |
| Fan Watt Draw | Air handler fan efficiency (W/CFM) | HVAC system replacement |
| Refrigerant Charge | Subcooling or superheat vs. manufacturer specs | Any AC or heat pump installation |
| Airflow Verification | Actual CFM vs. design CFM from CF-1R | HVAC system replacement |
What Happens If the System Fails?
If a system fails any of the required tests, the ECC rater documents the failure and cannot file a passing certificate. The contractor is responsible for correcting the issue — whether that's sealing duct leaks, adjusting refrigerant charge, or swapping out an air handler — and then scheduling a re-inspection.
Re-inspections are common and nothing to be alarmed about. The most frequent failures we see are:
- Duct leakage above the required threshold due to incomplete sealing at boot connections or flex duct collars
- Refrigerant charge outside the acceptable range because the system wasn't fully charged at time of inspection
- Fan watt draw failures when a lower-efficiency motor was installed than the compliance documents specified
In most cases, corrections can be made the same day and the re-test completed on the same visit or within a day or two. The key is making sure the installation is complete before calling the rater — a system that isn't fully operational cannot be tested.
How to Prepare for Your Altered System ECC Inspection
A little preparation goes a long way toward getting through an altered system inspection without delays. Here's what to have ready before the rater arrives:
- System fully installed and operational — The HVAC system must be running and at steady-state. Don't schedule the inspection until the install is complete.
- CF-1R on hand — The compliance form from the permit tells the rater exactly what needs to be verified. Have a copy available or know where to pull it up.
- Equipment specs accessible — Manufacturer documentation with the subcooling or superheat target range helps the rater verify charge quickly.
- Clear access to the air handler and duct system — Attic access hatches unobstructed, air handler accessible, all registers open and unblocked.
- System has been running — Refrigerant charge tests require the system to be running at steady-state for 15–20 minutes before measurements. Start the system before the rater arrives.
Need an Altered System ECC Inspection?
Roo's Ratings performs all required altered system measures — duct leakage, fan watt draw, refrigerant charge, and airflow — with same-day certificate filing. Serving Sacramento and a 75-mile radius.
Don't Forget: Same-Day Filing Matters for Permit Closeout
Once an inspection is complete and the system passes, the ECC rater files the CF-2R (field verification form) with the HERS data registry. The building department can then pull that record to confirm compliance before closing the permit.
At Roo's Ratings, we file certificates the same day as the inspection — so your customer doesn't have to wait days for paperwork to clear before their permit closes. If you're an HVAC contractor looking for a reliable rater to partner with on your Sacramento-area jobs, give us a call. We make the compliance process as straightforward as possible so you can focus on the install.
Questions about what your specific project requires? Call us before you schedule — we can review the CF-1R with you and confirm exactly which measures apply so there are no surprises on inspection day.