How Come My Furnace Is Making a Loud Noise When It Kicks On?

During the heating season, many Indianapolis homeowners contact us with a common complaint – their furnace is making a loud noise when it kicks on. In our most recent blog, the heating and cooling technicians at B&W explain the possible causes of loud sounds when the furnace starts a heating cycle.

1. Loud Bangs

When a homeowner calls us because of strange furnace noises when the unit starts a heating cycle, we want to know if the noise sounds like a loud bang. If the noise is a banging sound, it’s important to note where it comes from. It’s normal for loud banging sounds to originate from ducts as the furnace starts up – it’s just the sound of the metal ductwork expanding and popping. This is sometimes called oil canning.

When the bang is coming from your gas furnace itself, immediate attention is required. A bang during the furnace starts up is usually a sign of delayed ignition, which is a dangerous problem. Issues with the ignition system prevent the immediate combustion of gas entering the chamber – instead, gas builds up unlit. Once the ignition system does fire up, there is extra gas in the combustion chamber, which all ignites at the same time. The loud banging sound is really a small explosion and can damage the furnace. This issue needs to be repaired at once for your safety.

A delayed ignition can be caused by dirty or misaligned burners or a defective part.

2. Whistling

Whistling sounds are commonly caused by duct leaks. As the furnace begins to circulate air, pressure forces air through leaks that have developed in the duct system – this can produce a whistling noise. To stop the sound as well as the air loss, duct leaks need to be sealed.

A loose furnace door or dirty and clogged filters can also possibly lead to whistling sounds from your furnace.

3. Rattling

When your furnace makes a rattling noise when it kicks on, a loose access panel might be to blame. If your furnace was recently serviced, the panel may not have been reinstalled tightly. It is possible that a panel could have been knocked loose accidentally. Check the access panels to your furnace, and make sure each fits snugly and securely. Tighten any loose screws, if necessary.

A couple of other reasons furnaces might make a rattling noise include dirty burners, a cracked blower motor fan belt or a loose or broken blower motor bracket. If you’re unsure what the cause is, contact B&W Plumbing, Heating, Cooling and Drains to inspect the unit.

4. Squealing

If your furnace makes a screeching or a high-pitched squeal when it turns on, there could be an issue with the furnace’s blower motor or blower wheel. In older furnaces, a loose belt can produce this concerning sound, as well as defective bearings which are likely if your furnace was not professionally serviced this season. These issues need to be corrected to allow the furnace to function properly and prevent component damage.

Need Furnace Repair? Contact B&W Today

If your furnace is making a strange noise when it kicks on, never ignore it! Furnace sounds are often a warning from the system that something is wrong. Call B&W Plumbing, Heating, Cooling and Drains to schedule furnace repair in Indianapolis today. Our professional technicians can handle all of your home’s heating and cooling maintenance, repair, and installation needs. We also offer 24-7 emergency service in case your HVAC system breaks down in the middle of the night, on a weekend, or during a holiday.