Short cycling
Short cycling turns up in 2 fields: HVAC, boilers. Here is what it means to the people in each one.
Short cycling in HVAC
A compressor or system turning on and off too often, with run times too short to reach steady operation.
Each start draws locked-rotor current and stresses the compressor, and short runs never dehumidify properly because the coil does not stay cold long enough to drain. Causes include oversized equipment, a thermostat in the path of supply air, a pressure switch tripping on low charge or high head, iced coils and faulty controls. Most systems carry an anti-short-cycle delay of a few minutes to protect the compressor.
"It's short cycling on the low pressure switch, three minutes on and off, check the charge before you blame the switch."
Short cycling in boilers
A burner starting and stopping far too often, with short run times that waste fuel and wear parts.
Each cycle costs a purge that cools the boiler, an ignition sequence that wears igniters and valves, and minutes of inefficient warm-up, and non-condensing boilers condense flue gas during each cold start. Common causes are an oversized boiler, a narrow control differential, small zones calling alone, too little turndown, or a misplaced sensor. Fixes include right-sizing, wider differentials, buffer tanks and outdoor reset.
"Boiler's short cycling, eight starts an hour on a mild day, it's double the size of the heat loss."