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Find Out Everything You Need to Know About Heat Exchangers


When you discuss your HVAC system with a technician, it can help to have a basic understanding of what the various parts do. When it comes to your furnace, there's no more crucial part than the heat exchanger. That's where most of the important work of producing heat occurs.


Quite simply, a heat exchanger is a set of tubes — also referred to as coils — looped through the furnace's air flow. The shape of the coils differs, depending on the model of furnace or the type of fuel your furnace uses.

Here's how it works: an igniter lights the burners in the combustion chamber. The heat that is generated is pushed into the heat exchanger, which becomes very hot. The furnace's blower motor blows air over the heat exchanger and once the air is heated, it is pushed into the ductwork and then distributed throughout the home.

Combustion gases that the burning fuel created are vented through a flue in the roof, or through a wall.


As you can imagine, the metal of the heat exchanger is subjected to considerable stress as it heats up and cools, expanding and contracting. Over time, small cracks can appear from which poisonous gases such as carbon monoxide may leak. Depending on the size of the crack, it may be necessary to replace the heat exchanger — which can be very expensive — or even replace the furnace.

However, make sure you consult with a reputable HVAC contractor about cracks in the heat exchanger, and do ask to see the cracks. Some signs indicating you might have heat exchanger damage:

  1. High levels of CO in the flue pipe
  2. Burner flames should be steady and blue; if they are yellow/orange and move around, the heat exchanger may be cracked.
  3. Soot buildup on internal parts

It's always a good idea to have a carbon monoxide monitor in your home to alert you when CO levels are too high.

For more information on heat exchangers, contact Valley Heating, Cooling, Electrical. We serve South Bay Peninsula and Santa Cruz.

Our goal is to help educate our customers in the South Bay Peninsula and Santa Cruz areas of California about energy and home comfort issues (specific to HVAC systems).

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