Quick answer
A straight swap — a heat pump replacing an existing air conditioner on a working furnace — takes one day, usually six to nine hours on site. Replacing the furnace or air handler at the same time makes it two days. A single-zone ductless system is about a day, and electrical panel work is normally a separate visit before or after.
Heat pump installation takes about a day for the common case, and the day is longer than an air conditioner changeout because the system has to be commissioned in two modes rather than one. What follows is what actually happens between the truck arriving and the crew leaving, and the specific things that push a job into a second day.
The one-day changeout, start to finish
- Early morning: floors and stair edges protected, power and gas isolated, and the refrigerant in the old system recovered into a cylinder — venting it is illegal and a licensed technician will not do it.
- Mid-morning: old condenser and indoor coil out, pad or stand set. In snow country the outdoor unit belongs on a stand or bracket clear of the drift line, not on the ground the AC sat on.
- Late morning: new coil fitted to the plenum, line set run or the existing one assessed, brazed under flowing nitrogen so the inside of the copper stays clean.
- Early afternoon: pressure test with nitrogen, then evacuate the system down to roughly 500 microns and confirm it holds. This step is where installs quietly go wrong, and it cannot be rushed.
- Mid-afternoon: refrigerant weighed in to the manufacturer's charge, thermostat and outdoor sensor wired, staging and lockouts configured.
- Late afternoon: commissioning — heating mode, cooling mode, a forced defrost, airflow and static pressure measured, backup stage proven, then a walkthrough of the thermostat and filter with you.
What turns one day into two
- Replacing the furnace or fitting an air handler at the same time — the sheet-metal transitions and venting add most of a day.
- A new line set through finished walls, or a longer run because the unit is being relocated away from a bedroom window.
- Duct modifications the load calculation called for: a larger return, a resized trunk, or a new run to a room that was always cold.
- A dedicated circuit or a panel upgrade. Electrical work in Ontario needs an Electrical Safety Authority notification and inspection, and that is scheduled around the mechanical work rather than squeezed into it.
- Condensate routing where there is no floor drain nearby, or a pump that has to be added.
A ductless install takes a day per head, roughly
A single-zone ductless system — one outdoor unit, one indoor head — is a comfortable day, and much of it is careful drilling, hanging the bracket level, and running the line set and condensate in a tidy exterior chase. Each additional head on a multi-zone system adds several hours, so a three-head install is realistically two days. A head on a second storey or across the house from the outdoor unit takes longer than one on the wall directly behind it.
The parts of the project that are not install day
Site visit and load calculation come first — see what size heat pump do I need — then equipment ordering, which is where lead time lives: cold-climate models in specific capacities are not always on the shelf, and the busy weeks in October and in the first heat wave stretch everything. Municipal permits are pulled before work starts: the City of Burlington, Town of Oakville and City of Hamilton each run their own building department process. The rebate application uses the invoice and the equipment's performance listing, and the current program sets its own order of steps, so we handle that filing rather than leaving it to you. See HVAC permits in Burlington for how the permit side is handled.
Will the house be without heating or cooling?
Only during the working hours of the changeout. On a hybrid install the furnace is usually available the same evening even if commissioning continues, and on an all-electric system the backup elements are wired and proven before the crew leaves. If your existing system has already failed in a cold snap, say so when you book — that changes how the job is scheduled, and emergency service exists for the gap.
Questions worth asking before install day
- Where exactly is the outdoor unit going, at what height, and which way does the fan discharge?
- Is the existing line set being reused, and if so how is it being cleaned and proven?
- Who pulls the permit, and who notifies the Electrical Safety Authority if a circuit changes?
- What will be measured at commissioning — charge by weight, subcooling, airflow, static pressure — and will those numbers be left with me?
- What happens to the old equipment and refrigerant?
For a fuller picture of the project, read heat pump installation day: what to expect. ZK Mechanical books installs from the shop on North Service Road across Burlington, Oakville and Hamilton — see heat pump installation in Oakville or get a date on the calendar.