Case Study: Residential AC Replacement on Locust Street, Carter Lake

This case study documents a straightforward residential AC replacement for a Carter Lake home on Locust Street, the residential corridor running through the heart of this small Iowa community of approximately 3,000 residents. The work involved replacement of a 14-year-old R-410A AC with modern R-454B equipment at standard tier specifications appropriate for the property and customer situation. The case illustrates standard residential AC replacement workflow including refrigerant transition planning, equipment selection, and MidAmerican Energy customer rebate coordination.

Customer Situation

The property is a 1985 ranch home on Locust Street in Carter Lake, 1,400 sq ft on a 6,500 sq ft lot with attached single-car garage. The customers (couple in their mid-50s with adult children no longer living at home, husband works construction in Council Bluffs, wife is a Carter Lake elementary school teacher) had owned the home for 14 years (purchased 2011 shortly before the 2011 Missouri River flooding which caused minor damage to the property). They had completed substantial flood remediation including basement sealing improvements after 2011 and again after the 2019 flood event.

Equipment situation:

• 2011 Goodman 13 SEER R-410A AC, 3 ton, 14 years old (approaching end-of-life)
• 2011 Goodman 92% AFUE furnace, 14 years old, operating well (replaced after 2011 flood damage)
• AC operating but with diminished cooling effectiveness during summer 2025
• Customer experienced 22% increase in electricity costs compared to prior summer (despite similar usage patterns)
• Several developing component issues observed during August service call

Diagnostic Assessment

Assessment by Krystal Bauer (IAQ Lead with substantial cooling expertise). Service call time approximately 60 minutes during August service request.

Equipment Condition

• 2011 Goodman GSX13 14 years old, beyond average residential AC lifespan
• Capacitor measuring 38 microfarads (below acceptable 45 rated range)
• Compressor amperage elevated suggesting developing inefficiency
• Contactor with substantial pitting indicating approaching end-of-life
• Refrigerant pressures within acceptable range but indicating aging operation
• Realistic remaining useful life: 1-2 cooling seasons before major component failure

Customer Decision Process

Customer presented with options:

• Option A — Component repair — replace capacitor + contactor: approximately $385. Addresses immediate issues but compressor inefficiency continues. Equipment still 14 years old with limited remaining lifespan.
• Option B — Standard tier replacement — Lennox ML17XC1 16 SEER2 R-454B single-stage AC: $5,800 total. Modern A2L refrigerant compliance plus efficiency improvement.
• Option C — Mid-tier two-stage — Lennox EL18XCV 18 SEER2 R-454B two-stage AC: $6,400 total. Additional comfort benefits and efficiency improvement.

Customer selected Option B (standard tier replacement) based on:

• Equipment age and component issues making repair temporary
• Property value tier and modest cooling load suggesting standard tier sufficient
• $600 cost savings vs mid-tier two-stage option
• Single-stage adequate for Carter Lake climate conditions

Equipment Selection

• Lennox ML17XC1 single-stage AC — 16 SEER2 R-454B, 2.5 ton (right-sized from prior 3 ton via Manual J)
• New A2L-compatible evaporator coil — matched to AC
• New A2L-compatible refrigerant line set — required for A2L refrigerant compatibility
• Standard programmable thermostat — replaced existing basic thermostat

Project Execution

Single 6-hour service visit:

• Hour 1 — R-410A refrigerant recovery to EPA Section 608 standards; old outdoor unit and evaporator coil removal
• Hour 2 — Old refrigerant line set removal; new A2L-compatible line set installation
• Hour 3 — New Lennox ML17XC1 outdoor unit positioning on existing concrete pad; new evaporator coil installation in existing air handler; electrical connections
• Hour 4 — R-454B refrigerant charging to manufacturer specifications; system pressure testing; leak verification
• Hour 5 — System startup and commissioning; performance testing across cooling cycle; temperature drop across evaporator verification (18°F appropriate)
• Hour 6 — New programmable thermostat installation; customer walkthrough including operation and maintenance discussion

Results

• Modern A2L refrigerant equipment — R-454B compliance for 15-20 year equipment lifespan
• Cooling efficiency improvement — 16 SEER2 vs prior 13 SEER produces estimated 23% cooling efficiency improvement
• Right-sized equipment — 2.5 ton matched to actual cooling load vs prior 3 ton oversized
• Customer cooling cost reduction — subsequent month electricity cost approximately 25% lower than prior comparable period
• Modern equipment warranty — 10-year manufacturer registered warranty
• MidAmerican Energy rebate — $400 for qualifying SEER2 16+ equipment
• Customer satisfaction — substantially improved cooling effectiveness with right-sized equipment

Pricing

Total project cost: $5,800

• Lennox ML17XC1 AC (2.5 ton, 16 SEER2, R-454B): $3,600
• A2L-compatible evaporator coil: $785
• A2L-compatible refrigerant line set: $385
• R-410A refrigerant recovery and disposal: $165
• R-454B refrigerant charge: $185
• Standard programmable thermostat: $145
• Installation labor (6 hours): $385
• Old equipment removal and disposal: $150
• MidAmerican rebate application coordination: included

Net cost after MidAmerican Energy rebate:

• Project cost: $5,800
• MidAmerican Energy rebate: -$400
• Net cost: $5,400

Federal tax credit not applicable for standard AC replacement (federal Section 25C focuses on furnaces and heat pumps; standard split-system AC doesn’t qualify).

Why Right-Sized Equipment Matters

Customer’s previous 3 ton AC was oversized for actual cooling load of this 1,400 sq ft home:

• Manual J cooling load: approximately 22,000 Btu/hr (about 1.8 tons)
• Original 3 ton (36,000 Btu/hr) was approximately 65% oversized
• Right-sized 2.5 ton (30,000 Btu/hr) provides appropriate capacity with reserve for peak conditions
• Oversized equipment produces shorter cycles, worse humidity management, increased equipment cycling stress
• Right-sized equipment produces longer steady-state cycles with better moisture removal and more even comfort

Lessons from This Project

• 14-year-old residential AC equipment is at typical replacement consideration point; multiple developing component issues confirm appropriate timing
• Standard tier (single-stage) equipment is appropriate for moderate residential properties; mid-tier two-stage provides modest improvement but isn’t essential
• Right-sizing based on Manual J calculation produces substantially better outcomes than maintaining original equipment sizing
• R-410A to R-454B refrigerant transition affects all new equipment installations through 2050+ regulatory horizon
• MidAmerican Energy customer rebates provide modest incentive ($400) for qualifying efficiency tier equipment
• Standard tier replacement workflow is straightforward 6-hour single-day project for typical residential properties

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Contact Omaha Heating and Air Conditioning

For Carter Lake Locust Street area AC replacement, R-410A to R-454B refrigerant transition consultation, right-sized equipment installation, or MidAmerican Energy customer service, call our 24/7 line.

• Emergency Line (24/7): (402) 258-6703
• MidAmerican Energy Emergency: 800-595-5325 (Iowa gas/electric)
• 911: for CO detector alarms or fire/smoke situations
• Address: Lake Regency Building, 450 Regency Pkwy #370, Omaha, NE 68114
• Email: info@omahaheatingairconditioning.xyz
• Iowa Plumbing & Mechanical Systems Board License: #B-027841
• EPA Section 608 Universal: #608U-2014-227841

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