Leveling an air conditioning (AC) unit is crucial for its efficiency, performance, and lifespan. Using shims to level an AC unit prevents operational problems and expensive repairs. This guide explores why leveling matters, types of shims, step-by-step installation, safety considerations, and maintenance tips for homeowners and professionals.
Benefits Of Leveling An AC Unit
Proper leveling of your AC unit is more than just a technical requirement—it directly influences system health. Shims help keep your AC on a flat plane, reducing mechanical strain and avoiding inefficient operation.
- Prevents Compressor Damage: A tilted unit may cause internal compressor wear or oil starvation, leading to sudden breakdowns.
- Ensures Efficient Drainage: An unlevel AC can hinder condensate drainage, causing overflow or mold buildup.
- Reduces Vibration and Noise: Shims minimize rattling by stabilizing the base unit, leading to quieter operation.
- Keeps Warranty Valid: Manufacturers may void warranties if installation guidelines, like proper leveling, aren’t followed.
Types Of Shims To Level AC Units
Choosing the right shim type ensures effective and durable leveling. Each material has strengths and limitations in this context.
| Shim Type | Material | Ideal Use | Durability |
|---|---|---|---|
| Plastic Shims | High-Density Polyethylene (HDPE) | Corrosion-prone, outdoor settings | High |
| Composite Shims | Engineered Blend (plastic/resin) | Heavy loads, moisture-prone areas | Very High |
| Rubber Shims | EPDM, Recycled Tire Rubber | Vibration dampening | Moderate |
| Metal Shims | Galvanized Steel, Aluminum | Industrial/commercial, high compression | Very High |
| Wood Shims | Pine, Cedar | Temporary use, dry climates | Low (prone to rot) |
How To Know If Your AC Unit Needs Leveling
Recognizing signs of an unlevel AC unit can save you from bigger issues later. Routine checks—visually and with a level tool—are recommended.
- Noticeable Slant: If the unit appears uneven.
- Pooling Water: Water collecting under or beside the condenser.
- Abnormal Noises: Unusual rattling or humming sounds during operation.
- Poor Performance: Reduced cooling or ice formation on coils.
Step-By-Step Guide To Leveling An AC Unit With Shims
Leveling an AC unit is a manageable DIY task, but must be done carefully. Follow these steps to use shims properly and ensure your system runs optimally.
Tools And Materials Needed
- Bubble or digital level
- Selected shims (plastic, composite, or rubber recommended)
- Gloves and safety glasses
- Pry bar or heavy-duty flat screwdriver
- Stainless steel screws (optional, for fixing shims in place)
Leveling Instructions
- Turn Off Power: Always shut off electrical supply to the AC at the breaker box for safety.
- Check The Level: Place a level on top of the unit in multiple directions. Identify which side(s) are low or high.
- Prepare The Area: Remove debris, and ensure the pad is structurally sound.
- Lifting The Unit: With assistance, gently lift one edge of the unit just enough to insert the shim. Use a pry bar if necessary, but be careful not to damage refrigerant lines.
- Insert Shims: Slide the shim(s) under the base until the unit is level. For stability, consider placing shims at corners rather than the middle.
- Secure The Shims: If movement is possible, use a screw through pre-drilled holes to secure shims to the concrete or composite pad.
- Final Check: Re-check the level, adjust as needed. Restore electrical power once satisfied.
Choosing The Best Shims For Your Climate And Application
Your local environment impacts shim durability and effectiveness. Plastic or composite shims are best for American climates prone to moisture, insects, and sun exposure.
- Wet Or Humid Climates: Avoid wood due to rot; opt for plastic, rubber, or composite.
- Areas With Frequent Freezing: Composite shims resist cracking or shrinking.
- Vibration Concerns: Rubber shims can absorb shocks, protecting the unit.
- Heavy Or Oversized Units: Use composite or metal shims with high load ratings.
Maintenance Tips After Leveling With Shims
Regular maintenance and inspections will extend the service life of both your AC and shims. Periodic checks ensure the unit remains level despite soil movement or pad settling.
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- Annual Checks: Use a level each spring, especially after winter freeze-thaw cycles.
- Monitor For Settling: Soil or pads can sink over time, requiring adjustment or additional shims.
- Inspect For Deterioration: Replace cracked or crushed shims immediately.
- Clean The Area: Keep the base clear of leaves, debris, and standing water to avoid shifting.
Common Mistakes To Avoid When Using Shims
Improper shim use can compromise your AC’s stability. Avoid these frequent errors for safe and effective leveling.
- Using Inappropriate Materials: Never use soft woods or non-weather-resistant shims outdoors.
- Over-Stacking: Excessive stacking can lead to instability. Use fewer, thicker shims for higher lifts.
- Incorrect Placement: Place shims at pressure points (corners or main supports), not just under flimsy sheet metal edges.
- Skipping Security: Unsecured shims may shift over time. Fasten as needed, especially in high-wind or vibration-prone spots.
When To Call A Professional
While many homeowners can shim and level an AC unit, complex or heavy units, uncertain pad integrity, or signs of internal AC problems require professional assessment.
- Unusual Noises Or Vibrations Remain: Could indicate compressor or fan issues, not just leveling.
- Process Involves Lifting Large/Commercial Units: Risk of damaging refrigerant lines or base frame.
- Unit Remains Unlevel After Shimming: May need new support pad, ground regrading, or foundational repairs.
Sourcing Shims And Materials For Leveling AC Units
Obtaining quality shims is straightforward for most American homeowners. Home improvement stores and specialized HVAC suppliers offer weather-resistant shim options.
- Plastic And Composite Shims: Widely available at Home Depot, Lowe’s, or specialty online retailers like SupplyHouse and HVACDirect.
- Rubber And Metal Shims: Recommended for vibration-prone or commercial units. Check Grainger or HVAC supply centers.
- Custom Shims: For unusually heavy or custom units, request engineered shims through your installer or a local fabrication shop.
Frequently Asked Questions About Shims To Level AC Units
| Question | Answer |
|---|---|
| Can I Use Plywood As A Shim? | Not recommended outdoors, as plywood degrades quickly with moisture. |
| How Much Should I Lift The Unit? | Just enough to insert the shim and achieve level—typically less than 2 inches. |
| Will Shims Affect AC Warranty? | No, as long as they’re correctly installed and unit leveling meets manufacturer guidelines. |
| Is It Safe To Level A Running Unit? | Never work on a live unit—always turn off power at the breaker first. |
| Can Shims Fix Pad Or Ground Cracking? | Shims can compensate minor settling but won’t fix major foundational issues. |