Why is steel a superior material to copper?
Steel is much more rugged than copper. The copper used in boilers is much thinner than steel, and less able to withstand extreme temperature fluctuations. It is also more sensitive to poor quality water, which can result in leaks. And finally, because of the way copper boilers are made, they are very sensitive to interruptions in water flow. Thus if a pump fails, there is a good chance the entire heat exchanger has failed.