When a Littleton homeowner needed a full HVAC overhaul for their large home, they called our team for a complete replacement of two aging Lennox furnace and air-conditioning systems. This extensive project included upgrading both systems to high-efficiency Carrier Infinity heat pumps and 96% Infinity furnaces, designed to deliver year-round comfort and reliable performance in Colorado’s climate.
Job Overview
- Location: Littleton, CO
- Client Type: Residential homeowner
- Scope: Replacement of two 90% Lennox furnaces and two AC systems with Carrier Infinity cold-climate heat pumps and 96% furnace
- Equipment Installed:
- Attic: 4-ton heat pump + 100,000 BTU furnace (upflow)
- Upper Floor: 3-ton system, 17” furnace
- Additional Work: Install new Infinity thermostats, CO detectors, flue rework, gas rework, drain line modifications, electrical panel verification and reconnection
- Why It Mattered: The home’s existing systems were outdated, inefficient, and no longer able to maintain reliable airflow or performance across this large property. Upgrading to modern heat pump technology ensures long-term energy efficiency, comfort, and code-compliant operation.
What We Found
The home contained two older Lennox 90% systems – one located in the attic and another in a second-floor mechanical closet. The attic system required special access modifications, including removing and reinstalling shelving and trim to safely move equipment. Both systems showed typical signs of age: declining efficiency, outdated venting, and undersized or worn components. Electrical panels in the basement needed verification to ensure proper reconnection of furnace and AC circuits across four panel locations. A full dual-system replacement was the safest and most cost-effective option, giving the homeowner modern comfort control and high-efficiency performance.The Solution
Our installation team completed both system replacements in a single-day, multi-team project. The attic system was replaced with an upflow 4-ton heat pump and 100k BTU furnace. To accommodate access, shelving and trim were temporarily removed and reinstalled afterward. The team set the new furnace on a short box/KGAD, installed a concentric flue kit, and fully reworked the flue, gas, and drain lines to integrate with the new Infinity system. On the upper floor, the team installed a new 3-ton, 17″ furnace system, including a new filter box. PVC flue venting was upgraded to 2″, and all gas and drain connections were reworked for proper fit and function. Both systems received new Carrier Infinity thermostats and CO detectors. Electrical work included verifying and reconnecting the furnace and heat pump circuits across four different panels in the basement to ensure everything met current code. Before leaving, the team walked the homeowner through thermostat functionality and system setup.Photo Highlights
