Last reviewed: September 2026 · By the HVAC Brief Editorial Team · Our sourcing and editorial standards
A correct installation includes a load calculation, a permit where the jurisdiction requires one, and a commissioning step where the installer measures the system rather than assuming it. The measuring is the part most often skipped, and it is the part that determines whether you got what you paid for.
Most of what separates a good install from a poor one is invisible once the panels are back on, which is why it is worth agreeing the checklist beforehand.
What should happen, in order
- Load calculation before equipment is ordered. Capacity should follow from a room-by-room calculation, not from the size of the old unit. See why that matters.
- Permit application where required. Requirements vary by jurisdiction, and permitted work is inspected work.
- Duct evaluation. Static pressure measured before the new equipment goes on, so the ductwork is not silently inherited as a constraint.
- Removal and recovery. Refrigerant recovered, not vented. This is a federal requirement under 40 CFR part 82 regardless of system size.
- Installation and line set decisions. Whether existing line sets are reused, flushed or replaced should be stated, not assumed.
- Commissioning. Charge verified by measurement, airflow measured, static pressure rechecked, and the results written down.
- Documentation handed over. Load calculation, commissioning readings, warranty registration and permit sign-off.
What to get in writing before work starts
| Item | Why it matters |
|---|---|
| Equipment and labour as separate lines | Equipment is the line that has moved most since 2019 |
| Whether ductwork is included | The usual reason one quote is far below the others |
| Refrigerant type | Pre-2025 R-410A inventory is cheaper and legally installable, with a phasedown attached |
| Line set treatment | Reuse, flush or replace changes both cost and risk |
| Permit responsibility | Who applies, who pays, who schedules inspection |
| Commissioning readings | Written proof the system was measured, not assumed |
| Warranty registration | Often required within a window or the term shortens. See what warranties cover |
Ask what the measured airflow and static pressure were after commissioning, and ask for the numbers. An installer who measures will have them. One who does not will explain why they are unnecessary, and that answer tells you what kind of installation you bought.
Frequently asked questions
What should happen during an HVAC installation?
A load calculation before equipment is ordered, a permit where the jurisdiction requires one, duct evaluation including static pressure, refrigerant recovery rather than venting during removal, a stated decision on line sets, and commissioning where charge and airflow are measured and written down.
Do I need a permit to replace an HVAC system?
Requirements vary by jurisdiction and we cannot state a universal answer. Where a permit is required, permitted work is inspected work, which is a check on the installation you otherwise have no way to obtain. Agree in advance who applies, who pays and who schedules the inspection.
Can the installer reuse my existing line set?
Sometimes, depending on condition, sizing and the refrigerant involved. What matters is that the decision is stated rather than assumed: reuse, flush or replace each carry different cost and risk. Ask which was done and why before work starts rather than afterwards.
How do I know the installation was done correctly?
Ask for the commissioning readings: measured airflow, static pressure and verified charge, in writing. An installer who measures will have the numbers. Most of what distinguishes a good installation is invisible once the panels are back on, which is why written readings matter.
Methodology and limitations
Refrigerant recovery requirements are from 40 CFR part 82. Load calculation procedure is ACCA Manual J, a private standard we name but do not reproduce.
- Permit requirements vary by jurisdiction and we do not summarise them. Confirm locally.
- We publish no installation costs or durations, as no federal series measures them.
- Nothing here is engineering advice for a specific installation.
Sources
- US Environmental Protection Agency, 40 CFR part 82 subpart F, refrigerant recovery and technician certification.
The HVAC Brief is an independent trade publication. We do not sell equipment, take manufacturer advertising, or accept payment for placement in our research. Corrections welcome.
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