A freezestat must be field-supplied and field-installed.
When 24 VAC is not present on terminal FSHW and the outdoor air temperature is greater than 40°F, no action is taken and the unit operates normally.
When 24 VAC is not present on terminal FSHW and the outdoor air temperature is 40°F or less, the hot water valve opens 100%, the indoor fan de-energizes, the economizer outside air damper is fully closed, and all other fans de-energize.
The control returns to normal if either 24 VAC is present on terminal FSHW or the outdoor air temperature rises above 40°F.