A sensing bulb sits in a well in the boiler water, and the control breaks the burner circuit at a high limit and remakes it after a set differential. Combination aquastats also hold a low limit for a tankless domestic coil and switch the circulator. Like pressuretrol, the word started as a brand and now covers any boiler water temperature control.
Aquastat high limit's at 200 with a 25 degree differential, no wonder the house feels like it's cycling hot and cold.
Also heard as
- boiler aquastat
Related terms
High limit
A safety control that shuts down the burner if pressure or temperature rises above the normal operating range.
Operating control
The automatic-reset control that cycles or modulates the burner to keep steam pressure or water temperature in range.
Differential
The gap between the point where a control turns the burner on and the point where it turns it off.
Outdoor reset
A control strategy that lowers hot water supply temperature as outdoor temperature rises, following a set curve.