A steam control cutting out at 2 psi with a 1 psi differential cuts back in at 1 psi; a hot water control set at 180 with a 15 degree differential brings the burner back at 165. Too narrow a differential makes the burner short cycle; too wide gives big swings. Depending on the control, the differential is added to or subtracted from the main scale setting, which trips up techs who don't read the label.
Differential's set at the minimum, so it's lighting off every three minutes, open it up to 10 degrees.
Also heard as
- diff
- swing
Related terms
Pressuretrol
Shop name for the pressure switch that starts and stops a steam boiler's burner to hold pressure in a set range.
Aquastat
Shop name for the immersion temperature control that fires and limits a hot water boiler.
Short cycling
A burner starting and stopping far too often, with short run times that waste fuel and wear parts.
Operating control
The automatic-reset control that cycles or modulates the burner to keep steam pressure or water temperature in range.