Heat Exchangers Decoded
What is a Heat Exchanger?
The heat exchanger is a series of sealed chambers in your furnace that separates the combustion process from your breathing air. The combustion process begins at your burners and ends where your exhaust is vented from your home (either your chimney or PVC venting). The air is heated as it blown across your hot heat exchanger. The heated air is then distributed throughout your home via your ductwork. If you need more background on furnaces it can be found here.
Without an airtight seal on your heat exchanger your home is susceptible to being exposed to the poisonous gases of the produced from combustion. Cracks or holes can result in the poisonous gases being mixed with the air being distributed throughout your home. Extended exposure to these gases, carbon monoxide included, can lead to health risks or potentially death.
Why do heat exchangers fail?
Most heat exchanger will fail eventually due to metal fatigue. Rapid expansion and contraction of metal adds wear and tear. Over time, the fatigue eventually creates cracks or holes. A good way to think of this is a paper clip. Bend a paperclip back and forth, the more it’s bent the less resistance there is. Eventually the paperclip breaks, the same concept applies to your heat exchanger.
Heat exchangers are designed to last the lifetime of your furnace, 15-20 years, but there a few factors that may lead to early failure. Any combination of oversized equipment, poor system design, lack of air flow or poor maintenance can result in premature failure of a heat exchangers.
How do I know when my heat exchanger fails?
There are two tests that can be performed depending on the efficiency of your system:
80% efficient furnaces: visual inspection is needed to identify & confirm cracks. In most cases your technician will crawl under your furnace and examine the heat exchanger with a mirror.
90% efficient furnaces: cracked heat exchangers can be identified with a CO test on the exhaust of your system.
What are my options now?
1. Replace the heat exchanger. This is the optimal option only if your heat exchanger is under warranty, otherwise you may be putting money into a sinking ship. Ask you technician if its under warranty!
2. Replace your furnace. There are couple factors that go into this decision: age of system, heat exchanger warranty, and money saved with an energy upgrade.
3. The least recommended choice, our technician will leave your furnace OFF for the safety of your family. WE HIGHLY DISCOURAGE YOU FROM TURNING YOUR FURNACE BACK ON.
How do I know there is actually a crack or hole in my heat exchanger?
Short of ripping apart your entire furnace there is no way to show the cracks in a 80% efficient furnace until it is pulled out for replacement. Once the unit is out we show all of our customer the cracks to ensure you made the right decision (no one like buyers remorse). With 90% efficient furnaces a simple CO test will be showed to you to confirm the diagnosis. \
If it has been a while since you’ve had routine maintenance done on your unit, we suggest scheduling routine maintenance for a thorough examination of your heat exchanger.
For all of your heating and HVAC needs call Chris Mechanical Services Inc.