'It lit, so it's fine': the Live Oak furnace belief that hides cracked heat exchangers

What “it lit” actually tells you

Ask a Live Oak homeowner in December how the furnace is doing and the answer is usually some version of “it came on, so it’s fine.” It is an understandable belief in a county where the furnace works a few dozen mornings a year and then sits idle from March to November. Ignition is the one thing a person can see. The flame comes up blue, warm air arrives at the register, and the house is comfortable by breakfast.

But a furnace is a box that burns gas inside your house and sends the fumes up a pipe, and whether it lights has almost nothing to do with whether it is doing that safely. A heat exchanger with a hairline crack lights beautifully. A flue that has rusted through at the roof lights beautifully. A propane regulator weeping at a fitting lights beautifully. The flame is the easy part. The parts that matter are the ones you cannot see from the hallway, and in this town they belong to furnaces that are old enough to deserve a real look.

The sequence on a furnace call

Cook’s works a furnace repair in a fixed order, and the first two steps happen whether or not they are what you called about.

1. Carbon monoxide first. A detector comes into the house before the furnace panel comes off. If it reads anything, the furnace goes off and stays off until the source is found.
2. Combustion and the heat exchanger. A combustion analyzer in the flue and a camera into the exchanger cells. Cracks, rust-through and flame rollout are the things that make a furnace dangerous, and they do not announce themselves.
3. The ignition chain. Thermostat call, inducer motor, pressure switch, igniter, gas valve, flame sensor, in that order, watched through a full cycle. Most “no heat” calls are a failure somewhere on this chain.
4. Gas supply. Manifold pressure with a manometer, and on propane systems in the county, the regulator and the flex connector leak-checked.
5. Airflow and limits. Filter, blower, limit switch. A furnace that lights and then shuts off after a few minutes is usually overheating on a starved return.
6. The ducts. Especially under older downtown homes, where the furnace sits in a crawlspace and the supply trunk has been breathing damp air for seventy years.

What we find behind the burner door in this county

Suwannee County’s furnaces run on three fuels and the findings sort by fuel.

City gas, inside Live Oak. The downtown bungalows between Ohio Avenue and the courthouse square, and the older ranches, have natural gas furnaces that are often twenty to thirty years old. The common finds are a flame sensor coated in residue, a cracked hot-surface igniter, a rusted heat exchanger from decades of damp crawlspace air, and flue connections that have separated. Several of these furnaces are sitting where a floor furnace used to be, with ductwork improvised around them.

Propane, in the county. Farmhouses around McAlpin, O’Brien and Dowling Oaks, and the acreage homesteads out toward Wellborn, heat with propane. The furnaces themselves are the same machines, but the gas side is different: regulator failures, connector leaks after a summer of disuse, and orifices never converted from natural gas when the furnace was installed, which produces a lazy yellow flame and soot.

Electric, in manufactured homes. Nearly half the county’s housing is manufactured, and most of it heats with an electric furnace or heat strips in a package unit. Open elements, burnt sequencers, limit switches tripping on dirty filters, and relays cooked by generator power after the Idalia outage are the regulars. No combustion, so the safety check here is electrical.

Call Cook's for furnace repair

What a furnace repair runs, in bands

You hear the price once the fault is found and before a tool touches the part, as a flat line that includes the part and the labor.

The high band is where repair and replacement meet, and we say so out loud.

When a repair is throwing money at a rusted box

A furnace is worth repairing when the part is in the low or middle band and the heat exchanger is sound. It is not worth repairing when:

• The heat exchanger is cracked or rusted through, which ends the conversation on safety grounds regardless of age.
• The furnace is past about twenty years and needs anything in the middle band.
• It is a propane furnace in a county house and the owner is paying propane prices for twenty mornings a year, where a heat pump would heat the house for a fraction of the fuel cost.
• It has needed two repairs in two winters.

In those cases you get a free estimate on the replacement, which in this county is as often a heat pump as a new furnace, and the option to spread a new system over monthly payments. If the furnace is unsafe you also get it tagged and shut off, and a plan for staying warm in the meantime, because a cold house in a 25-degree snap is its own emergency.