I just discovered that my recently-acquired '73 Europiccola has a burned-out 200W element. It's not a short: I took the machine apart and noted a couple of nasty splits in the smaller element. I'm wondering why these elements burn out when run dry in espresso machines, but not in ovens or stovetops. It's my understanding that they all use Calrod elements--insulated nichrome wire in a metal sheath--and it's obvious that stoves and ovens run dry for decades without issues. What gives?

Short answer is watt density.

Lower watt density can dissipate enough heat in air.

I would presume most oven elements are much larger (surface area) than comparable submersed elements of similar power.

An element for an espresso machine is created for the specific purpose of being used under water. Goals would be fast recovery and fast response. Water is very dense and can absorb the thermal energy quickly, particularly when the vessel is sealed and under pressure.

RE*AC*TOR wrote:Short answer is watt density.

Randy G. wrote:An element for an espresso machine is created for the specific purpose of being used under water.

+1

In addition to being able to use a somewhat higher watt density, water immersion elements can use a low temp sheath material like copper (350F) because the sheath is never much hotter than the surrounding water. Ovens would use alloy sheath materials that withstand much higher temperatures.