Chapter 19 Exercises: Air Conditioning and Cooling Systems

These exercises build practical skills in understanding, maintaining, and making informed decisions about residential cooling systems. Several require access to your actual AC equipment; others involve calculations and research.

Exercise 1: Identify and Document Your Cooling System

What to do: Locate every cooling appliance in your home and document it completely.

For each system (central AC, mini-split, window unit): - Manufacturer and model number - Tonnage or BTU capacity (central systems are usually 1.5–5 tons; 1 ton = 12,000 BTU/hour) - SEER or EER rating (on the label — if very old, it may not be listed) - Estimated age (decode from serial number) - Refrigerant type (R-22 for pre-2010 systems; R-410A for 2010–2024; check the label on the outdoor unit) - Last service date (look for contractor stickers)

Questions to answer: 1. What refrigerant does your primary cooling system use? What are the cost implications if it needs to be recharged? 2. How old is the system? Where does it fall on the typical lifespan table from Section 19.2? 3. What is the SEER rating? How does it compare to current minimum standards?

Exercise 2: Calculate Your Operating Cost

Using your cooling system's SEER rating and your utility bill data, calculate annual operating cost.

Formula: Annual kWh = (Capacity in BTU/hour × Cooling hours per season) ÷ (SEER × 1,000) Annual cost = Annual kWh × Your electricity rate ($/kWh)

Data gathering: - Find your system's BTU/hour capacity (from label or nameplate) - Estimate your cooling season length in hours (Dallas: ~1,400 hours; Minneapolis: ~400 hours; Atlanta: ~1,000 hours; Phoenix: ~2,200 hours — adjust for your location) - Find your electricity rate on your utility bill

Compare: - What your current system costs per season - What a SEER 14 replacement would cost - What a SEER 18 replacement would cost

Question: At current energy prices and your actual cooling hours, how many years would it take to pay back a SEER 18 system vs. a SEER 14 system?

Exercise 3: Spring Startup Inspection

Perform the full spring startup inspection described in Section 19.7.

Document each step: 1. Air filter condition — clean, dirty, or replacement needed? 2. Outdoor unit: any damage to fins? Vegetation intrusion? Clearance adequate (18 inches minimum)? 3. Suction line insulation: intact or damaged/missing? 4. Condenser coil: visible debris or dirt accumulation? 5. Condensate drain: any visible algae growth or blockage? 6. Test run results: did cold air come from registers? Any unusual sounds?

What you learned: Describe one condition you found that you hadn't noticed before and what, if anything, you did about it.

Exercise 4: The Refrigerant Identification Challenge

Research task: Determine the refrigerant implications for your specific system.

  1. Look up your system's model number on the manufacturer's website or call the manufacturer's consumer line.
  2. Confirm the refrigerant type.
  3. If the system uses R-22: research current R-22 prices in your area. Call one HVAC contractor and ask: "If my R-22 system developed a small refrigerant leak, how much would it cost to locate the leak, repair it, and recharge the system?"
  4. Compare that cost to a ballpark quote for system replacement.
  5. At what repair cost would replacement become the better economic choice?

Exercise 5: Diagnose Reduced Cooling Performance

Walk through the diagnostic sequence for a system that "isn't cooling as well as it used to."

Work through these in order (each is a potential cause):

  1. Check the air filter. When was it last changed? Hold it up to a light — can you see light through it? Replace if dirty.
  2. Check airflow from supply registers. Walk to each register with a piece of tissue paper. Is airflow strong in all rooms?
  3. Check the outdoor unit. Is the fan spinning? Can you hear the compressor running (a steady hum)? Is the coil visibly dirty?
  4. Check the suction line. Is the larger insulated copper line cool to the touch (normal) or warm (possible refrigerant issue)?
  5. Check register temperatures. Using a thermometer (an infrared thermometer works well), measure the temperature of air coming from a supply register. Compare to the return air temperature. A difference of 14–22°F is normal for a properly functioning system. Less than 14°F difference suggests a problem.

Report: What did each check reveal? If you found an issue, what did you do?

Exercise 6: Ice Formation Drill

Scenario exercise (observation or simulated): Understand ice formation on evaporator coils.

If your system has accessible panels to the air handler: 1. Locate the evaporator coil and determine how to safely view it. 2. Identify where ice would form first if airflow were restricted (the lower/upstream portion of the coil). 3. Find and verify the condensate drain pan location and drain outlet.

Conceptual questions: 1. If you came home to find your AC running but barely cooling, and then saw ice on the copper suction line where it exits the air handler, what are the two most likely causes? 2. You identify a dirty air filter as the cause. What is the correct procedure for restoring operation? 3. Why should you not simply set the thermostat higher to "let it thaw while cooling"?

Exercise 7: Mini-Split Assessment

For your home or a hypothetical room:

Identify one space in your home (or a room you know well) that would be a good candidate for a mini-split — perhaps a room that's always too hot or cold, an addition, a finished attic, or a garage workshop.

Research task: 1. Measure or estimate the room's square footage. 2. Using a rule of thumb of 20–25 BTU/hour per square foot, estimate the required cooling capacity. 3. Research three mini-split units (indoor + outdoor) in that capacity range. Compare: - SEER2 or SEER rating - Sound level (sones or dBa) for indoor unit - Cold-weather heating capability (if applicable) - Price (check online HVAC supply retailers for equipment cost; add $500–1,500 for professional installation) 4. Get one contractor quote for a similar installation.

Question: How does the DIY-kit price compare to the contractor-installed price? What work could you do yourself and what would require a professional?

Exercise 8: R-22 Decision Tree

Work through this decision scenario:

Situation: Your neighbor has a 2003 central AC system with R-22 refrigerant. Last summer it cooled poorly. An HVAC technician diagnosed a refrigerant leak in the evaporator coil. The coil repair and recharge quote is $1,800. A new R-410A (or R-454B) 3-ton, SEER 15 system would cost $5,200 installed.

The system currently has SEER 10 efficiency. His annual cooling bill averages $620. A new SEER 15 system would reduce that by approximately 33%, saving roughly $205/year.

Your analysis: 1. If the repair holds for 3 more years before the system fails anyway, how much total did he spend? (Repair cost + 3 years of higher operating cost vs. new system) 2. If the repair holds for 6 more years, does that change the analysis? 3. What non-financial factors would you weigh? 4. What would you recommend, and why?

Exercise 9: Seasonal Shutdown Checklist

At the end of cooling season, perform (or plan) the following: 1. Clean the outdoor condenser unit — remove leaves, debris, rinse coils. 2. Check the condensate drain pan for standing water or algae (treat with bleach solution). 3. Turn the AC breaker off at the main panel to prevent the system from attempting to start on unseasonable warm days. 4. If using a cover for the outdoor unit, install only a breathable cover designed for the purpose (never an airtight tarp). 5. Note any performance issues from the season in writing for next spring's service call.

Documentation exercise: Create a simple log sheet for your AC system — a piece of paper kept with your HVAC records — listing the system details from Exercise 1, this year's shutdown notes, and a reminder to schedule spring service.

Exercise 10: Cooling System Replacement Planning

For systems over 12 years old:

Put together a preliminary replacement plan so that when the time comes (or when the system fails on the hottest day of the year), you're not making decisions under pressure.

  1. Confirm the system's age and current condition.
  2. Identify a preferred HVAC contractor (licensed, with verifiable references). Note their contact information.
  3. Decide on your efficiency tier preference: minimum code (SEER2 ~14), mid-grade (~SEER2 16), or high-efficiency (~SEER2 18–21). Know why you're choosing each.
  4. Check current federal tax credits (25C credit provides 30% of costs up to $600 for central AC, no limit for heat pumps). Update this annually — incentives change.
  5. Check your utility's rebate programs for high-efficiency cooling equipment.
  6. Know your approximate budget range so you can respond quickly to a contractor quote.

Reflection: Write two to three sentences about what you found and what your plan is if your current system fails this summer.