Furnace Installation

Furnace Installation

What Happens When You Replace Your Furnace (And What Should Happen)

Your furnace burns fuel to make heat. That's the simple version. The actual system includes a combustion chamber, heat exchanger, blower motor, control board, safety switches, venting, and gas piping—all working together thousands of times per year.

When furnace replacement becomes necessary, you're making decisions about equipment that will heat your home for the next 15-25 years. Getting it right matters more than getting it cheap.

When Replacement Makes Sense

Not every furnace problem requires replacement. But some situations make repair the wrong choice:

Replace, Don't Repair

Cracked heat exchanger

The heat exchanger separates combustion gases (including carbon monoxide) from the air that blows into your home. A crack allows those gases to mix. Significant cracks mean replacement—heat exchanger replacement on an aging furnace costs nearly as much as a new system for only 5-7 more years of life.

20+ years old with major failure

A 22-year-old furnace needing a major component? Replace. That part might last another 10 years, but the rest of the furnace is on borrowed time. You'll likely face another major repair within 3-5 years.

Repair cost exceeds 50% of replacement

When repairs approach half the cost of a new system, the repair-versus-replace calculation favors replacement sooner than most people think.

Repeated repairs in recent years

Three service calls in two years on a 15-year-old furnace? The system is telling you something. Each repair fixes one component while others continue aging.

Current furnace is significantly undersized or oversized

If your existing furnace was wrong from the start, replacement is an opportunity to get it right.

Repair, Don't Replace

• Furnace under 10 years old with single-component failure: Replace the failed part.
• Minor repairs: Flame sensors, ignitors, pressure switches fail before furnaces wear out.
• First major repair on a well-maintained system: 18-year-old furnace with annual maintenance? Fix it.

Understanding Furnace Types

Standard Efficiency Gas Furnaces (80% AFUE)

How they work: Natural gas burns in a combustion chamber. Heat transfers through a heat exchanger to air. A blower pushes heated air through your ducts. Combustion gases vent through a metal flue.

The number: 80% AFUE means 80 cents of every dollar you spend on gas becomes heat. 20 cents goes up the flue as hot exhaust.

Best for: Mild climates, situations where electrical upgrades would be costly, or tight budgets (lowest upfront cost).

High-Efficiency Gas Furnaces (90-98% AFUE)

How they work: Same combustion process, but a secondary heat exchanger extracts additional heat from exhaust gases. This cools exhaust below the condensation point—"condensing" furnace.

The numbers: 96% AFUE captures 96 cents per dollar. The difference between 80% and 96% efficiency means 20% lower gas bills.

Why condensing matters: Cooled exhaust (around 100°F vs. 350°F+) can vent through PVC pipe rather than metal. This allows sidewall venting, more flexible installation, and no existing chimney required.

Best for: Cold climates with high heating loads, newer homes with PVC venting infrastructure, homeowners prioritizing efficiency.

Sizing: Why It Actually Matters

Furnace sizing isn't about square footage. It's about heat loss calculation.

What Affects Heating Load

• Insulation levels: Better insulation means less heat loss
• Window type and area: Single-pane windows lose 20x more heat than insulated walls
• Air infiltration: Leaky houses lose heat through gaps
• Climate data: Your local winter design temperature matters

Manual J Calculation

The right way to size a furnace is Manual J—a software calculation that accounts for all the above factors, plus duct losses, building orientation, and local climate data. Manual J takes 30-60 minutes when done properly. If a contractor quotes you without measuring your home, they're guessing.

What Happens With Wrong Sizing

Undersized: System runs constantly during cold snaps, can't maintain temperature when design conditions hit.

Oversized: Short-cycles (wastes fuel), temperature swings, humidity problems, premature wear, higher upfront cost for equipment you don't need.

Most furnaces are oversized by 20-50%. Properly sized systems run longer cycles, distribute heat more evenly, and cost less upfront.

Installation Process: What Should Happen

A quality furnace installation takes 6-10 hours for a straightforward replacement. Here's what's involved:

Step 1: Pre-Installation Assessment

• Manual J calculation (not a rule-of-thumb)
• Ductwork inspection for sizing and condition
• Gas line sizing verification
• Venting route planning

Step 2: Equipment Removal

Old furnace safely disconnected and removed. Revealed components inspected (ductwork, flue, platform).

Step 3: New Installation

• Unit positioned level with proper clearances
• Ductwork connected with mastic seal (not tape)
• Gas line with drip leg, leak tested
• Proper venting (metal or PVC per efficiency type)
• Condensate drainage for high-efficiency

Step 4: Startup and Testing

Gas pressure verification, combustion analysis (CO levels under 50 ppm ideal), airflow verification, safety controls tested, thermostat calibration.

Step 5: Customer Education

Filter location and changing, thermostat operation, warning signs to watch for, maintenance requirements, and warranty information.

What Quality Installation Looks Like

When the crew leaves, here's what you should see:

The Furnace Itself

• Level, with proper clearances
• Secure, not wobbling
• Clean, no debris, protective films removed

The Connections

• Ductwork sealed with mastic or metal tape (not cloth duct tape)
• Gas line with drip leg and accessible shut-off valve
• Proper venting slope and termination
• Dedicated electrical switch within sight of furnace

Our Installation Guarantee

Every furnace we install includes:

• Proper sizing: Manual J calculation, not guessing
• Licensed installation: By our own employees, not subcontractors
• Permit and inspection: Where required by local code
• Combustion analysis: Documented and provided to you
• Satisfaction guarantee: If something isn't right, we make it right

If your furnace is approaching end of life, or you're ready to explore replacement, schedule a free consultation. We'll provide Manual J-based sizing, equipment options, and a complete proposal—no pressure, no rush.