Thermal Shock Steam Boiler

Long Beach Ed

For many years we've run hot water loops off the base of several steam boilers. They are piped well, maintained properly and are fairly modern. Most are Burnham Independence gas fired units.

The other day I got to thinking: What effect does 50 feet of cold water have when the circulator vomits the 1-1/2 gallons into the base of that 210 degree cast iron? I realize the 3/4" baseboard's contents immediately mixes with the 5 gallon of 200 degree boiler contents, but it probably does some quick cooling.

Never had a problem with this, but luckily these days I don't have too much to worry about so this came to haunt me. Any thoughts to share?

Eddie, Long Beach, NY

Jamie Hall

It's the mixing and time which keeps things from problems. And the fact that the water isn't really all that cold... but there is a cooling which takes place, and in the smaller volume of modern boilers it is significant. In your example, the boiler water temperature will drop to about 180 over a period of a minute or so, if the incoming water is around 100 or so (very rough numbers). Particularly if the hot water loop return is to the wet return, as it should be.