HVAC Start-up & Commissioning Checklist
A practical pre-start and first start-up checklist for packaged units and light commercial systems — so the system is set, measured, and verified before you leave.
- Interactive decision labs
- Built by working technicians
- Path-based verifiable certificate
- Exam preparation only
- Worldwide online
Why start-up discipline matters
Most of the equipment failures that come back as warranty calls were created in the first hour the unit ran. A compressor started on reversed rotation, a coil loaded during construction, a charge adjusted to hide an airflow problem — none of those are service faults, they are start-up faults wearing a service uniform. Commissioning discipline is what separates an installer who leaves and an installer who never gets called back. It also protects you: readings recorded at start-up are the evidence that the system left your hands correct.
Pre-start checklist
Nothing on this list requires the unit to be running. Work it before you make a call.
- Power confirmed at the disconnect, correct voltage and phase, and the disconnect locked out while you work.
- All panels, screws and covers accounted for; nothing left loose on the roof or in the closet.
- Filters installed, correct size, correct direction, and the filter rack sealed against bypass.
- Condensate line run, trapped correctly for draw-through or blow-through, tested with water and terminating legally.
- Outdoor clearances checked — service access, coil airflow and no recirculation off a parapet or wall.
- Refrigerant circuit verified: pressure test held, evacuation to spec, charge weighed in and recorded.
- Control wiring landed and rung out against the diagram; thermostat or DDC inputs configured for the equipment.
- Belt tension, sheave alignment and blower rotation checked by hand before energising anything.
First start-up sequence
Order matters. Each step proves the conditions the next step depends on.
- 1Energise the unit with no call and let crankcase heat build where the manufacturer requires it.
- 2Fan only (G): prove supply fan rotation, direction, and that air is actually moving at the diffusers.
- 3Measure total external static pressure in fan-only before you add a single stage of heating or cooling.
- 4First cooling call (Y1): watch the contactor pull in, confirm the condenser fan runs and the compressor sounds correct.
- 5Let the circuit stabilise, then read pressures, superheat and subcooling against the equipment data plate.
- 6First heating call (W1): prove the draft, ignition, flame signal and fan-on delay in that order.
- 7Cycle the unit through satisfaction and back to prove staging, off-delays and safeties behave as designed.
- 8Set the thermostat or controller to the customer's operating schedule and confirm it holds.
What to measure and record
Voltage and amp draw
Supply voltage under load, compressor RLA vs nameplate, fan motor amps, and any voltage drop across contactors.
Airflow indicators
Total external static, filter and coil pressure drop, supply and return temperatures, and the resulting temperature split.
Refrigerant-side numbers
Suction and liquid pressures with saturation temperatures, superheat and subcooling, and the charge weighed in.
Combustion and heat
On gas heat: manifold pressure, temperature rise against the rated range, flame signal in microamps and draft proving.
Controls and setup
Stage timings, changeover settings, economizer setpoint and damper travel, and the final schedule left with the customer.
The record itself
Photograph the data plate, log every reading against it, and leave a copy with the customer — commissioning that is not recorded did not happen.
Common start-up failures
Wrong rotation
Three-phase equipment started on reversed rotation moves almost no air and can destroy a scroll compressor in seconds. Check rotation first, every time.
Restricted airflow at start-up
Construction dust, shipping blocks, closed dampers and unopened registers all read as high static. Fix the restriction before you touch the charge.
Low or unbalanced voltage
Long runs, undersized conductors and loose lugs show up as hot terminals and nuisance trips weeks later. Measure under load, not at rest.
Control miswire
A swapped Y and W, a missing common, or an unconfigured heat-pump changeover produces symptoms that look like equipment faults but are wiring.
Charge chased instead of set
Adding refrigerant to fix a superheat number caused by low airflow is the single most common start-up mistake — and the most expensive one.
Condensate ignored
An untrapped or unpitched drain passes start-up and floods a ceiling in the first humid week.
Stop and diagnose vs the install is not ready
If the unit runs but the numbers are wrong, stop and diagnose — that is your work. If any of the conditions below are true, the install is not ready and starting the equipment makes the problem yours.
- Refrigerant circuit not pressure-tested, evacuated or documented — do not start it.
- No permanent power, temporary generator power, or voltage outside the nameplate range.
- Ductwork incomplete, unsealed or open to a construction space that would load the coil.
- Missing safeties, jumpered controls, or a heat exchanger you cannot visually verify.
- Gas piping not pressure-tested, or no combustion air / venting path finished.
- Any condition where starting the unit would transfer someone else's incomplete work onto your ticket.
Prove it on a live call
Two free labs put start-up thinking under pressure: a rooftop unit that will not cool, and a system where the numbers say airflow long before they say refrigerant. No account needed.
Path D — Installation, Start-up & Commissioning is in progressive development. This checklist is the first public piece; modules and graded commissioning labs release path by path.
Regional exam-prep notes
- United States
- Supports preparation for EPA 608 (Type II / Universal) and related NATE content. We do not issue the EPA or NATE credential.
- South Africa
- Aligns with safe-handling expectations under SAQCC Gas / SARACCA pathways. We prepare; SAQCC Gas issues the authorisation.
- Kenya / East Africa
- Supports good-servicing practice and RAC technician competence relevant to NITA / EPRA-adjacent work. Official authorisations remain with the relevant bodies.
- India
- Aligns with ESSCI RAC Service Technician (NSQF) and HPMP Good Servicing Practices orientation. ESSCI and the Ozone Cell issue official credentials.
Always verify current requirements with the authority in your jurisdiction.