What is a freezestat alarm?
What is a freezestat alarm?
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.
What causes a freezestat to trip?
The freezestat will “trip” if any section of the temperature sensor element drops below the setpoint. The sensor element can be various lengths, often up to 20ft long,, and will trip if any 12” to 18” length goes below the setpoint.
How does a freeze switch work?
When the temperature reaches a specific setpoint, the pressure in the diaphragm will trip a switch which typically shuts down the flow of outside air while the capillary bulb’s temperature is at or below the setpoint.
Where is a freezestat located?
Normally the freeze stat goes on the leaving face of the heating coil set at 38F. Sometimes with a hot water coil there will be a small freeze protection pump as part of the piping system to rat race water around at the coil to keep it from freezing in the event of a heating plant failure.
How do you size a Freezestat?
1. Mount the body of the unit outside of the ductwork and near the top. The rule of thumb is that each sensor is about 20 feet long (exact lengths may vary) so at a ratio of 1 linear foot of element per 1 square foot of coil, one sensor should cover about 20 square feet.
What is the most vulnerable portion of a water coil to freezing?
The answer is fairly simple and consists of two main factors: The circuitry of the coil where the pressure builds, and the weakest point in that circuit. Extensive testing has shown that the failure will appear as a bloated area in the tube header or bend that has expanded.
What is a Frostat?
A Frost Stat is a Thermostat for the Pump that detects when the air temperature drops below a certain temperature and then activates your Pump to prevent freezing in the pipework. It works in the same way as your central heating thermostat.
How do you check if coils are frozen?
Signs of a Frozen AC Coil
- AC unit runs but doesn’t emit cold air.
- Ice is visible on the indoor or outdoor coils.
- Visible extra moisture/condensation around your AC system or home.
- Ensure the air filter is new and clean.
- Turn off the thermostat setting and turn the fan on.
What is a evaporator defrost control?
The evaporator defrost control (EDC or FrostatTM) is in- stalled in the evaporator (Indoor) coil face area. It’s purpose is to cycle the compressor when the evaporator frosts under low outdoor ambient cooling conditions or low airflow appli- cations.
Where to place the freezestat?
Also, the AC mechanics have already lowered the freeze stat trigger point as low as possible. Joe, for the averaging/controlling sensor, it would be a better idea to move it downstream so it feels less of a stratification effect. The freezestat should also be just upstream of the next coil, not at the immediate outlet of the heating coil.
What to do when freeze stat element senses below setpoint?
Usually if any one-foot section of freeze-stat element senses below setpoint, the unit trips. First thing I would recommend is that face and bypass dampers be used if at all possible. Steam valves should be fully open below 35-40°F outside and the F&B dampers should modulate to maintain discharge temperature.
How do I know if my freezestat is bad?
The freezestat should cover as much of the next coil area as possible. It could be faulty. Replace a suspected one with one you know works. You may also be able to test one by dipping it in & out of a bucket of ice water & connecting the terminals to an ohmmeter.
Is it possible to lower the trigger point of the freeze stat?
If not, what type of cheap alternative may be an option. Also, the AC mechanics have already lowered the freeze stat trigger point as low as possible. Joe, for the averaging/controlling sensor, it would be a better idea to move it downstream so it feels less of a stratification effect.
