When installing an air conditioner, one of the most important considerations is ensuring the outdoor AC unit is properly leveled. But does the AC pad underneath really need to be perfectly level? The short answer is yes – having a level AC pad is critical for optimal performance and longevity of your air conditioning system.
Page Contents
- 1 Why AC Pad Leveling Matters
- 2 How Flat Does the Pad Need to Be?
- 3 Using Shims to Level the AC Unit
- 4 How to Create a Level Pad
- 5 Using a Laser Level
- 6 Preparing Uneven Ground or Soil
- 7 Is the Pad Level with My Home? While the air conditioner pad must be level side-to-side and front-to-back, it does not necessarily need to be perfectly level with the ground around your home’s foundation. In fact, building codes often require the AC pad to be slightly lower than the immediate soil grade. This is to direct drainage away from the foundation wall. As long as the pad itself is flat and level, it’s acceptable for it to be 1 to 4 inches lower than entryways, garage floors, etc. Proper drainage slope is more critical than making the pad even with surrounding grades. Just focus on getting the pad surface as flat as possible based on the 1/4 inch levelness standard. Hiring a Professional
- 8 Conclusion
Why AC Pad Leveling Matters
There are a few key reasons why the AC pad or concrete slab that your outdoor condenser rests on should be level:
- Allows proper drainage – Air conditioners produce a lot of condensation from the evaporator coils when in cooling mode. This water needs to drain out of the base pan and away from the unit through the drain line. If the pad is uneven, water can pool in sections and potentially overflow the pan, leading to flooding, damage, and mold issues.
- Prevents vibration and noise – When an AC unit is not level, it can rock back and forth or side to side when the compressor is running. This vibration can cause annoying rattling noises and also put more strain on the internal components over time.
- Improves efficiency – A level condenser allows for optimal airflow through the coils and fins. If it is tilted in any direction, the airflow can become obstructed and cause the system to work harder to provide cooling, using more energy.
- Reduces wear and tear – An unlevel pad puts uneven stress on certain internal parts like the compressor and fan motor. It can also warp the sheet metal housing. This unequal distribution of weight decreases lifespan.
In essence, taking the time to correctly level your AC pad or slab during installation will maximize performance and minimize noise, drainage issues, and premature wear on parts. Your cooling system will run more efficiently and last longer.
How Flat Does the Pad Need to Be?
Most HVAC experts recommend the pad should be level within 1/4 inch (0.5 cm) from side to side and front to back. This tolerance helps ensure adequate drainage and prevent vibration. The 1/4 inch rule applies to both professionally installed concrete pads and prefabricated plastic or fiberglass pads.
Some building codes actually require air conditioner pads to be level within 1/8 inch rather than 1/4 inch, so it’s best to verify regulations in your local area. Either way, the surface must be very close to perfectly flat across the entire footprint of the outdoor condenser.
Using Shims to Level the AC Unit
If your existing pad or concrete slab is slightly uneven, you can use shims to level the condenser itself. Galvanized metal shims are inserted underneath the frame at certain points to bring the unit back to level. Shims should never exceed a 1/4 inch in height, or else they become ineffective.
While shimming is sometimes necessary for minor variations, the pad itself still needs to be as flat as possible. Shims are more prone to shifting and settling over time and should not be used as a shortcut for proper site preparation.
How to Create a Level Pad
When installing a new AC unit and pad, here are some tips for achieving a perfectly level surface:
- Dig out and prepare the site so it has a solid, well-compacted base without organic material.
- Form the pad using lumber or erosion control blocks to the desired size.
- Use a bubble or digital level tool on all sides to ensure the form is flat.
- Pour a concrete pad at least 4 inches thick into the form.
- As the concrete cures, recheck for level across the top and use a trowel to smooth any high spots.
- For fiberglass or plastic pads, check that the base is flat before installation.
Taking extra time to pour an accurately leveled pad will give your AC unit the best foundation. Follow all building codes for your area regarding concrete thickness and reinforcement.
Using a Laser Level
One of the best tools for checking AC pad levelness during preparation is a laser level. This projects a flat horizontal laser plane across the entire area. When placed on a tripod adjacent to the site, you can immediately see any high and low points on the pad surface to identify uneven spots that need correction.
Laser levels are extremely precise down to 1/16 inch or less. They eliminate any errors that can occur with standard bubble levels. Many concrete contractors will use laser levels when forming, pouring, and finishing outdoor AC pads.
Preparing Uneven Ground or Soil
If the AC unit will sit directly on the ground rather than a concrete pad, take extra care to achieve flatness across the installation footprint:
- Remove any organic material like grass or wood.
- Fill in low areas with compactible fill dirt.
- Tamp down and compact the soil until solid.
- Pour a thin layer of sand or gravel to fine tune the level.
- Recheck for flatness with a long level or laser level.
The ground underneath should meet the same 1/4 inch level tolerance as a poured pad. This prevents sinking, vibration, and improper drainage.