Why do heat exchangers fail?

This is a simple example of how to destroy a furnace. Poor ducting. In this case the ducting should be changed to the correct size.
Here’s the simple version. If you’d like to learn more - watch the video.
Lack of air flow as a result of poor duct sizing or dirty filters
- Oversized or over fired equipment
- Lack of maintenance
- Poorly Engineered furnace or heat exchanger
- Incorrectly sized or incorrectly installed or both