7 mistakes to avoid when DIY installing a heat pump (2026)
Reading time: 8 minutes
Installing your own heat pump is perfectly feasible — thousands of Canadians do it every year. But certain mistakes can turn a simple installation into a costly nightmare.
After helping hundreds of customers with their DIY projects, we've identified the 7 most common mistakes . Avoid them and your installation will go smoothly.
Mistake #1: Choosing the wrong capacity (BTU)
The problem
This is the most costly mistake because it cannot be corrected after installation. A heat pump that is too small will run constantly without ever reaching the desired temperature. A heat pump that is too large will cycle on and off too frequently, prematurely wearing out the compressor.
Signs of poor ability
- Too small: The unit runs constantly, the room never reaches the desired temperature, resulting in high electricity bills.
- Too large: Short cycles (less than 10 minutes), high humidity in summer (not enough time to dehumidify), temperature variations.
The solution
Use a BTU calculator that takes into account:
- The room's surface area
- The ceiling height
- The number of windows and their orientation
- The level of insulation
- The climate of your region
General rule for Quebec: Allow approximately 30-35 BTU per square foot for a well-insulated space, up to 45 BTU/sq ft for average insulation.
Error #2: Ignoring the level during installation
The problem
The indoor unit produces condensate (water) during operation. This water must drain into the drain pipe. If the unit is not level—or worse, if it is leaning to one side—the water will accumulate and eventually overflow into your wall or onto your floor.
The consequences
- Water damage to walls and floors
- Mold behind the unit
- Unpleasant odors
- Damage to the unit itself
The solution
- Use a good quality spirit level when installing the wall bracket.
- Check the level in both directions : horizontally and from front to back.
- The unit should have a very slight backward tilt (drainage side) — about 2-3 degrees.
- Double-check after hanging the unit on the bracket.
Simple test: Before closing everything up, pour a glass of water into the tray of the indoor unit and check that it drains properly to the outside.
Mistake #3: Bending the refrigerated lines too tightly
The problem
Refrigeration lines are made of flexible copper, but they have their limitations. A bend that is too tight can:
- Pinch the tube and block the flow of refrigerant.
- Create a weak point that could leak over time
- Reduce system efficiency by 20-30%
How to recognize a bad crease
Run your fingers along the line. If you feel any flattening or distortion, the crease is too tight.
The solution
- Make smooth curves with a minimum radius of 10 cm (4 inches).
- Never bend at a right angle — always in a curve.
- If you need to make a sharp turn, use a bending spring (available at hardware stores).
- Plan your route before you start to minimize turns.
Pro tip: Fully unroll the lines and let them "relax" for 30 minutes before installation. They will be easier to handle.
Error #4: Incorrectly positioning the outdoor unit
The problem
The location of the outdoor unit directly affects its performance and lifespan. An incorrect position can cause:
- Overheating in summer (if poorly ventilated)
- Snow blockage in winter
- Excessive defrosting cycles
- Disturbing noise for you or your neighbors
Common positioning errors
- Too close to the ground: Snow accumulates and blocks the unit.
- Under a dripping roof: The falling water freezes on the unit.
- Against a wall with no clearance: Not enough air to dissipate the heat.
- In full summer sun: The unit has to work harder to cool down.
- Under a bedroom window: The noise disturbs sleep.
The solution
- Height: Raise the unit by a minimum of 30-45 cm (12-18 in) in Quebec.
- Clearance: 50 cm in front, 30 cm on the sides and above.
- Protection: Sheltered from falling snow/ice from the roof.
- Orientation: Avoid having the fan face the prevailing winter winds.
- Base: Stable and level surface (concrete slabs, wall support, or anti-vibration pads).
Mistake #5: Neglecting to seal the wall hole
The problem
The 3-inch hole you drill for the lines is a direct breach in your home's thermal envelope. A poorly sealed hole lets in:
- Cold air in winter (heat loss)
- Hot air in summer (loss of air conditioning)
- Humidity (risk of mold)
- Insects and rodents
The solution
Use a two-layer approach:
- Inside the hole: Fill the space around the lines with low-expansion foam (high-expansion foam can distort the lines).
- Exterior: Apply a bead of silicone sealant around the lines to seal against rain.
Pro tip: Install a wall sleeve (included with some models) for a clean finish and better sealing.
Error #6: Incorrect tightening of fittings
The problem
The fittings on the refrigeration lines must be tightened "just enough". It's a delicate balance:
- Not tight enough: Refrigerant leak = loss of performance, then complete failure.
- Too tight: Damage to the fitting or thread = possible leak.
How can I tell if it's tight enough?
Kanartic DIY systems use quick-connect fittings that simplify this step. Here's how:
- Align the fittings and screw them in by hand until they resist.
- Use a wrench to make an additional 1/4 to 1/2 turn .
- Stop when you feel firm resistance — no need to force it.
Leak testing
After installation, check your connections:
- Mix water with a little dish soap.
- Apply to each joint with a brush.
- If bubbles appear, there is a leak — tighten slightly.
Mistake #7: Forgetting the test before closing everything
The problem
You've just spent four hours on the installation. Everything seems perfect. You seal the hole, put away your tools, and turn on the heat pump for the first time... and something isn't working. Now you have to take everything apart to find the problem.
The solution: The 5-point test
Before sealing and closing everything up:
- Drainage test: Pour water into the tray of the indoor unit. The water should flow freely outwards.
- Visual check: Inspect all fittings, electrical connections and communication cable.
- Electrical test: Turn on the circuit breaker and check that the unit turns on (indicator light).
- Functional test: Operate the unit in ventilation mode for 5 minutes.
- Mode test: Briefly test the air conditioning mode AND the heating mode.
Only after these 5 tests: Seal the hole and do the finishing.
Summary: Error-proof checklist
Print this list and check each item:
☐ I calculated the BTUs needed for my space
☐ The indoor unit is perfectly level
☐ All curves in the lines have a radius of at least 10 cm
☐ The outdoor unit is elevated and well clear of the surroundings
☐ The hole in the wall is sealed (foam + caulking)
☐ The fittings are properly tightened (checked with soapy water)
☐ I tested the drainage, electricity, and modes before shutting everything down
Need help?
Have a question during installation? Our technical team is available via chat to guide you. Don't hesitate to contact us—a 2-minute question can save you hours of trouble.
