Where should Freezestat be located?
Placement. The freeze stat is frequently installed in the wrong location. Generally, freeze stats should either be located on the downstream side of the first heating coil or on the upstream side of the first non-heating coil that is to be protected.
Is a freeze stat normally open or closed?
closed
They can be normally closed (NC). The freeze stat is easy to understand on paper, because it is nothing more than a switch that will open if the air moving across the water coil should drop below a given setpoint.
What is a freeze stat used for?
A freezestat is a low-ambient-temperature-limit control device. It is the standard control used to achieve water-coil low-temperature protection. If air temperature at a coil drops to just above freezing, a freezestat changes over its contacts and initiates protective action.
How do you use a freeze stat on an air handler?
The sequence of operation for any freeze stat inside an air handler will include the following: Stop the blower. Close all outside air dampers. Open the return air dampers. Open all valves serving chilled water or hot water coils inside the air handling unit.
When to replace the freeze stat on an HVAC system?
If the HVAC maintenance department experiences nuisance trips that cannot be adjusted through the range settings on the freeze stat device then the freeze stat should be replaced with a new freeze stat rather than jumping out the device. It would be better to disable the economizer than to jump out of the freeze if a problem occurs.
What is the sequence of operation for a freeze stat?
The sequence of operation for any freeze stat inside an air handler will include the following: When these valves open the appropriate pumps should energize. The pumps respond so that the water will flow through the coils. This prevents a freezing coil which will likely burst open if it freezes.
How to test if a freezestat is working?
This can be tested by manually tripping the freezestat. And depending on how the system is wired will depend on whether the NO contacts are used or the NC contacts are used. It is possible the controls contractor technician used both sets of contacts.