Does an air conditioner have to be perfectly level?

When installing an air conditioner, one of the most common questions is whether the unit needs to be perfectly level. The short answer is that while a small amount of tilt is acceptable, the air conditioner should be as close to level as possible for optimal performance. In this article, we’ll discuss the details around leveling air conditioners and the effects of having an unlevel unit.

Why Leveling Matters

Air conditioners, especially central air units and window units, have a compressor that circulates refrigerant through the system to cool your home. This compressor needs to be properly oriented to function. When an air conditioner is significantly unlevel, a few issues can arise:

• The compressor can wear out prematurely from vibration and added strain.
• Refrigerant may not circulate properly, reducing cooling efficiency.
• Condensation drainage can back up instead of flowing out the drain pipes as intended.
• The fans and airflow can be disrupted, leading to uneven cooling.

By ensuring the unit is as close to level as possible, you avoid these potential problems. The air conditioner will run smoother, last longer, and deliver more consistent cooling.

Acceptable Level Range

Most air conditioner manufacturers indicate the unit can tilt slightly and operate safely. A 3-degree tilt is usually the maximum acceptable amount. This equals around 3 inches of height difference over 5 feet of level.

Beyond 3 degrees of tilt, you risk the problems mentioned earlier. Any tilt over 5 degrees is almost certain to cause functional issues with drainage, the compressor, fan balance and more. However, a 1-2 degree tilt is unlikely to cause immediate problems in most cases.

How to Level a Window AC Unit

Window air conditioners need firm, level support underneath. Here are some tips for leveling them:

• Use a bubble level tool on the top of the unit to identify which direction it tilts.
• Lift the side that is low and place shims, such as plastic or composite under the base until it is closer to level.
• Recheck with the bubble level and add or remove shims until the bubble is centered.
• Consider using adhesive, brackets or supports to hold the shims in place over time.

Window units only have a couple of inches for adjustment, so you may not be able to fully level it if the window frame or sill is very unlevel. Get it as close as possible.

Leveling a Portable AC

Portable air conditioners have caster wheels underneath to roll them into position. Here are some tips for leveling portable units:

• Use shims under the wheels/casters on the low side to lift that part of the unit.
• If needed, use cinder blocks, wood or other materials to create a level platform for the entire ac unit to sit on.
• Check periodically to see if the unit has settled out of level and re-adjust as needed.

The rolling nature of portable air conditioners means they can shift out of position over time. Periodically double check the level and make adjustments to maintain optimal orientation.

Leveling a Through-Wall AC

Through-wall air conditioning units are installed in a sleeve through the wall. Here are some tips for leveling them:

• Check for level front-to-back and side-to-side inside the sleeve using a level tool.
• Shim underneath the rear and/or sides of the sleeve as needed to bring it to level.
• Make sure the outdoor condenser is also level for best performance.
• Use a level on the top of the AC unit itself once installed to double check.

Shimming the wall sleeve and outdoor base pad during installation is crucial to allow the AC system to be level.

How to Level a Central Air Conditioner

Central air conditioning systems have two main components to be leveled – the condenser outside and the evaporator coils/air handler inside. Here are some tips for both:

Outdoor Condenser

• Position the concrete pad for the condenser on level ground or make level with shims.
• Use a level tool on the top of the installed condenser to identify tilt direction.
• Lift the low side up and slip concrete paver stones, composite shims, or other sturdy materials underneath to bring it closer to level.
• Recheck periodically for settling and re-adjust as needed.

Indoor Evaporator or Air Handler

• Ensure the wall mounts or platform for the air handler are firmly installed and level.
• Use a level on the top and sides of the component once installed.
• Shim beneath the base pan if needed to bring it to level.
• Suspended air handlers should hang evenly to avoid tilt.

Taking the time to position both the indoor and outdoor units level is important for longevity and efficiency of the central air system.

Using a Leveling Device

A basic bubble level is usually sufficient for checking level on air conditioners. The bubble must be centered between the lines for the unit to be perfectly level. Laser levels can also be handy for leveling over longer distances.

Here are some other tips for using a leveling device on an AC:

• Double check both side-to-side and front-to-back orientation.
• Take measurements at different spots on the chassis when possible.
• Account for curvature or peaks in the chassis when taking readings.
• Avoid contact with moving parts or electrical components inside the AC.

Take care to get an accurate level reading to identify exactly how much and in what direction to shim the unit.

Signs of an Unlevel Air Conditioner

In addition to directly checking for level, here are some signs that your air conditioner may be tilted:

• Condensation leaking from the base.
• Gurgling noises from the drain line.
• The unit rocks or vibrates excessively when running.
• Fan sounds are uneven or blades scrape the housing.
• Airflow is weaker on one side of the output.
• Rooms on one side are warmer than the other side.
• The unit doesn’t sit squarely on the support pads.

Addressing these issues quickly by leveling the unit can restore normal operation and prevent worsening of any problems.

Conclusion

Having an air conditioning unit perfectly level is ideal, but a small amount of tilt up to about 3 degrees is usually acceptable. Anything beyond that can start to impact the AC’s performance and lifespan. Take the time to properly level window, portable, through-wall and central air conditioners and make periodic checks for shifting. Use a bubble or laser level and sturdy shims to bring the unit as close to perfectly level as realistically possible. Keeping the air conditioner level will help ensure it runs efficiently and reliably for many years.