Kettling happens when water flashes to steam at hot spots and the bubbles collapse, usually because scale or sludge has built up on the heat exchanger or because flow through it is too low. Low-mass and condensing boilers are especially prone. Fixes include descaling and flushing, restoring pump flow, cleaning strainers, and checking that the boiler is not firing with its circulator off.
Customer says it sounds like a teapot in the basement, that's kettling, check flow through the heat exchanger and plan a descale.
Also heard as
- kettle noise
Related terms
Scale
A hard mineral crust that forms on boiler heat transfer surfaces from calcium, magnesium and silica in the water.
Delta T
The temperature difference between supply and return water in a hydronic system.
Condensing boiler
A boiler designed to cool flue gas below its dew point so water vapor condenses and gives up its latent heat.
Short cycling
A burner starting and stopping far too often, with short run times that waste fuel and wear parts.