Green Leaf Air

by Rifat A. in Blog, Heating, HVAC Tips 3 comments

Different types of furnaces function differently. This infographic highlights these furnace mechanisms and sheds light on the role of the pilot light in their operation.


Different Furnace Mechanisms & Role of Pilot Light

Types of Furnaces

There are two types of furnaces – forced air and water-based heating unit. The key difference between these two types is how they transfer heat in your space.

If you have a forced-air heating unit, it’ll deliver heat to your space in the form of hot air. It delivers hot air through vents and the floor. But if you have a water-based heating unit or hydronic system, it keeps your home warm by generating steam. It produces steam by using a radiator or a radiant floor.

No matter what type of furnace you use in your home, both furnaces get the power from combustion and are controlled by a thermostat.

During summer, usually, heating isn’t required, and most homeowners lower the furnace thermostat setting to all the way down. But don’t think that your furnace is turned off completely. If the furnace’s pilot light is on, it means that your furnace is still consuming energy and operating.

Mechanism of the Furnaces

In a water-based furnace, when the temperature goes below the desired temperature, the gas burner gets engaged. As soon as the gas is lit, the boiler inside the furnace starts heating the water. After heating the water, it circulates the steam in your house through a radiator or a radiant floor. This is a continuous process. When the water cools, it again goes back to the boiler, and the boiler starts heating the water.

In a forced-air furnace, the process is almost similar to water-based furnaces. But instead of circulating the heated water through the radiator, it circulates the steam by using pipes, and the pipes supply the steam to the radiator.


Which One to Purchase: Forced Air Vs Water Based Furnace

If you prefer soundless sleep at night, you must purchase a water-based furnace unit. This type of furnace doesn’t require any air ducts and the installation cost is very low. But the downside of this type of furnace is that it takes longer to make your space warn. Besides, you can only get heating from the water-based heating unit.

On the other hand, a forced-air heating unit provides an efficient way of heating your space. It can reach your desired heat setting within a few minutes. Besides, you can use the furnace air ducts to cool your space in summer. However, as it uses air ducts, air ducts can have leaks, and if you neglect air duct cleaning, dust and allergens can accumulate inside the air ducts.


Role of the Pilot Light in Furnace

If you’re using an old furnace, chances are your furnace has a pilot light. This light was installed in furnaces so that users don’t have to ignite the light manually every time. One of the downsides of this feature is that if the pilot light ever goes off, your furnace won’t restart. Besides, because of this pilot light, your furnace will consume energy throughout the year, which means your furnace will be functioning even after lowering the thermostat setting all the way down. Because of this, you’ll have to pay energy bills even when you don’t need to use the furnace for heating. As the furnace is turned on 24/7, it lowers the energy efficiency or AFUE rating too.

Furnaces with pilot lights usually have an AFUE rating of 60% to 70%. On the flip side, modern furnaces don’t have such a pilot light. Instead, it has an instant ignition system, which doesn’t need to stay lit all the time. And because of this, modern furnaces have an AFUE rating of more than 98%.

So, if you want to save energy, it’s advised to purchase a modern furnace unit that comes with an auto-ignition feature.


If you’re looking for a reliable HVAC store, Green Leaf Air is your go-to option. We sell all sorts of HVAC units, including air conditioners, furnaces, and heat pumps from brands like Goodman, MRCOOL, Trane, and RunTru. For more details, call 972-992-5006.


See the summary of this article here – Water-Based Furnace vs. Forced-Air Furnace [Infographic]


Water-Based Furnace vs. Forced-Air Furnace
Water-Based Furnace vs. Forced-Air Furnace
Rifat A.

HVAC Expert, Author & Mathematician... rifatahmed.com

3 thoughts on “Furnace Mechanism & Role of Pilot Light”
  • Sam November 21, 2022 at 10:24 am

    Gonna save more this winter

    • Rifat A. November 26, 2022 at 9:28 am

      All the best.


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