PSA – Your Air-Conditioning Unit Must Always Be Level!

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Keeping your home or office cool in the middle of a heatwave or during high humidity is essential. When the temperatures are too hot, there is nothing worse than trying to stay cool and dry while the sweat drips down and you are trying to work. In these climates, buildings without air-conditioners are the exception rather than the rule.

The key to a functioning air-conditioning system is a perfectly level installation; this allows the oil to keep lubricating the motor, preventing damage. It stops the oil pooling in the system and makes the condensed water drain, which stops rust or mould from forming.

Properly installing a split air conditioner unit is not a job for an inexperienced do-it-yourself person. It involves bending and joining copper pipes, drilling large holes through your home’s outside walls as well as installing a hefty condenser unit, perfectly level, in a way that will keep it working for many years.

Air-Conditioners Must Always Be Level To Keep Them Working Well 

Two residential air conditioning AC units installed on a level outdoors
Two residential air conditioning AC units installed on a level outdoors

Correctly installed air-conditioners, positioned on a secure level surface, should work for years.

A split system includes the air handling unit (the part you see inside your home) and a compressor (the unit installed outside.)

The air handling unit consists of an evaporator, thermostat, control unit, and vents to let you point the cool air to wherever you want it. 

The magic happens in the compressor positioned on the outside wall, behind the control unit. The compressor is the part that makes the most noise and switches on and off as the temperature heats up or cools down. Like your fridge, the compressor has a motor (compressor) and a condenser (coils of copper tubing).

The compressor and the air handling unit must be installed perfectly level and very secure. The reasons for this are:

The Heart Of The AC System Is The Compressor

The compressor is a cumbersome, box-like unit installed on the outside wall. It consists of a motor and a condenser.

If the compressor is not level:

  1. It will compromise its efficiency, and it may not work as effectively
  2. The system contains oil to lubricate the motor. A small part of the oil runs through the system and returns to the motor. If the system is not correctly installed, the oil may drain to one side and be trapped in the piping.
  3. If the motor receives insufficient oil, eventually, it will fail.
  4. The high RPM motor may become slightly out of balance, which could cause vibration, and in an extreme situation, failure may occur.

If the compressor is not securely installed:

  1. It will start to vibrate. Vibration adds three potential failure points to a compressor.
  2. It may push the copper pipes out of alignment, preventing the refrigerant from moving.
  3. The pipes could fail if the vibration is strong enough, causing the expensive refrigerant to leak away.
  4. Constant vibration puts the whole compressor under pressure, and many parts within the unit may fail.

The Air Handling Unit Of The Air Conditioner

Someone installing an AC wall unit
Someone installing an AC wall unit

The inside unit is generally installed onto a wall inside a room that needs to be cooled. The air handling unit extracts moisture from the air, draining through the installed pipes to the outside. 

If the unit is not level, or the drainage pipes become blocked;

  1. The pooled water increases the humidity level, causing oxidation (Rust) of the metal components.
  2. Mould may develop, which is potentially harmful to the room’s occupants.
  3. Damp patches may appear on the wall behind the units, which can cause rising damp problems that need to be repaired and repainted.

How Do Air-Conditioners Work?

Why is it so crucial for air-conditioning units to be installed level?

Air-Conditioners works very much like a fridge. The instructions for your fridge instruct you never to lay it on its side or install it anywhere other than on a level surface; the same is true for an air-conditioning system.

Air conditioners work as follows:

  1. The compressor contains a refrigerant gas. 
  2.  When the unit is turned on, the compressor pumps refrigerant gas from the compressor.
  3. High pressure is created, which in turn compresses the refrigerant.
  4. The refrigerant leaves the compressor as a high-temperature, high-pressure gas.
  5. The gas travels through the condenser coils, condensing into a liquid.
  6. While in the condenser, the heat is released through metal grills to the outside atmosphere.
  7. After moving through the condenser and it has released the heat, it travels through the copper piping to the evaporator in the air handling unit.
  8. On its way, it passes through a small valve (which can be adjusted for the temperature). As the gas enters the valve, it is under pressure. Due to the small size of the hole in the valve, not all the gas passes through simultaneously.
  9. A low-pressure area is created on the other side of the valve, so the pressure drops, and the gas turns into a gas/liquid mix. 
  10. The liquid refrigerant evaporates and cools the coil in the condenser. 
  11. A fan blows the room’s air across the cool evaporator coil. The refrigerant absorbs the heat inside the air. 
  12. The cooled air is then circulated throughout the home while the heated evaporated gas is sent back outside to the compressor. 
  13. The cycle continues.

How Do You Know If Your Air-Conditioner Isn’t Level?

A contractor repairing an AC unit
A contractor repairing an AC unit

A few tell-tale symptoms will warn you that your air-conditioner is not level, either due to a faulty installation or the compressor’s movement over time.

The Compressor Starts Making A Noise

The air-conditioning compressor is a critical part of the overall system and the motor which drives the compressor needs oil to work correctly. If the air conditioner isn’t perfectly level, it won’t distribute the oil evenly; this could cause:

  1. The compressor to start making a grinding noise.
  2. The compressor begins to overheat.
  3. Your home to consume more electricity because the unit is not operating efficiently.

In the worst case, it could break entirely and need replacing.

Rust And Mold Appear

As the system draws moisture from the air it produces water which is a natural biproduct of the air conditioner’s cooling system. The subsequent water drains into a pan and then flows down a pipe to the outside of the home.

If the system is not perfectly level, the water will pool on the air-conditioners collector tray and not flow down the pipe. This could cause.:

  1. Water pooling around the air conditioner water tray.
  2. Rust and mold begin to appear.
  3. The coils inside the compressor become rusty and will not work as efficiently.
  4. Once again, your home’s electricity consumption goes up due to a less efficient air-conditioner.
  5. Damp patches, or peeling paint, appear on the wall behind the unit.

More Wear And Tear

As mentioned earlier, if the unit is not level, it might vibrate more than usual. Too much vibration could result in:

  1. Parts starting to wear out faster than expected.
  2. The refrigerant lines become loose and create a costly refrigerant leak.
  3. Over time the air conditioner installation sinks down and becomes even more off-kilter.
  4. The air conditioner wears faster than expected and eventually fails.

How To Level An Air Conditioner

Several large air conditioning (AC) units
Several large air conditioning (AC) units

A trained technician should only carry out an AC installation. It involves bending and welding copper pipes, ensuring the system remains closed. In addition, the technician must install each component entirely level.

The air handling unit is simple enough; however, creating the base for the compressor takes expertise. A suitably qualified installer will ensure that it is installed level and, just as importantly, stays level.


It is important, not at installation but also in the longer term that the air conditioner unit remains completely level. Failure to do so will result in;

  1. Higher electricity bills
  2. The unit failed faster
  3. Damp and Mold
  4. The unit is not operating to maximum capacity, which is frustrating on a sweltering day.
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About Charlie D Paige

Charlie is a massive DIY fan, with dozens of DIY projects under his belt - ranging from tiling to electrics, and concrete pads to walls. Charlie loves tinkering, seeing how things works, the outdoors and playing with power tools... so is it any wonder that he's completed so many DIY jobs over the years?

Charlie loves spreading his hard-won DIY experience with the world via this blog.