Preparing Your Furnace for Iowa Winters
Quick Answer
Don't wait until it is -15°F in January. Here is the essential fall checklist to ensure your heat turns on and stays on.
When the first true cold front hits Des Moines, local HVAC companies immediately log hundreds of "No Heat" calls. The tragic reality is that 80% of these terrifying midnight emergencies could have been prevented with 15 minutes of proactive maintenance in October.
A gas furnace is a complex sequence of safety switches. If a single sensor detects a flaw, it immediately shuts down the gas valve to protect your family from carbon monoxide or fire. Here is what you must check before the snow flies.
1. The Flame Sensor (The #1 Culprit)
The most common cause of a "No Heat" call is a dirty flame sensor. This metal rod sits directly in the path of the gas burner. Its only job is to detect fire.
How It Fails:
Over years of burning natural gas, a microscopic layer of carbon soot builds up on the metal rod. When the thermostat calls for heat, the gas valve opens and the burners ignite. But because the flame sensor is coated in soot, it cannot "feel" the fire. Assuming the fire blew out, the furnace panics and instantly shuts the gas off to prevent filling your basement with explosive gas. The burners light for 3 seconds, then die. Over and over again.
The Fix:
- Turn off power to the furnace.
- Unscrew the single 1/4-inch screw holding the sensor.
- Gently rub the metal rod with light steel wool or a dollar bill (do NOT use sandpaper, it scars the metal).
- Reinstall. The furnace will now detect the flame.
2. Clearing the PVC "Snorkels"
If you have a high-efficiency (96%+) furnace, it does not vent through a metal chimney. It breathes through two white PVC pipes sticking out the side of your house: an exhaust pipe and an intake pipe.
| The Threat | The Consequence |
|---|---|
| Snow Drifts | A blizzard piles 3 feet of snow against the side of your house, completely burying the PVC intake pipe. |
| Critters & Leaves | During the summer, mice or wasps build nests inside the exhaust pipe, or autumn leaves blow into it. |
The Resulting Failure:
Inside the furnace is a Pressure Switch. It proves that exhaust gases are successfully leaving the house. If the outdoor PVC pipe is blocked by snow, the pressure switch trips. The furnace refuses to ignite because it assumes carbon monoxide is backing up into your basement. Always shovel a 3-foot clearance around your exterior PVC pipes.
3. The 1-Inch Filter Wall
We've said it before, but it bears repeating: A clogged furnace filter destroys heat exchangers.
- The "High Limit" Trip: The furnace generates a massive amount of fire. It relies on the blower motor to push cold house air over the metal heat exchanger to extract that heat. If a filthy filter blocks the airflow, the heat gets trapped inside the furnace cabinet. The internal temperature spikes to dangerous levels, tripping the "High Limit" safety switch and shutting the system down.
- The Permanent Damage: Repeated high-limit tripping forces the metal heat exchanger to constantly expand and contract violently. Eventually, the metal cracks. A cracked heat exchanger leaks carbon monoxide into your ductwork and requires a $2,500+ replacement. Change your filter monthly during the winter.