Method and a system for preventing a freeze event using refrigerant temperature
A method includes measuring a saturated suction temperature, receiving actual temperature value reflective of the measured saturated suction temperature, and determining whether the actual temperature value is less than a first pre-determined minimum threshold temperature value. If the actual temperature value is less than the first pre-determined minimum threshold temperature value, initiating a timer to operate for a pre-determined time interval. Determining whether the actual temperature value is less than a second pre-determined minimum threshold temperature value and if the actual temperature value is less the second pre-determined minimum threshold temperature value, initiating the timer to operate for a modified time interval. If the timer has expired, the operation of the compressor is modified.
1. A method of mitigating a freeze event in a heating, ventilation, and air conditioning (HVAC) system, the method comprising:
utilizing a controller to perform the steps of:
receiving an actual temperature value reflective of measuring a saturated suction temperature measured by at least one sensor;
determining if the actual temperature value is less than a first pre-determined minimum threshold temperature value;
responsive to a determination that the actual temperature value is less than the first pre-determined minimum threshold temperature value, initiating a timer to operate for a pre-determined time interval;
determining if the actual temperature value is less than a second pre-determined minimum threshold temperature value;
responsive to a determination that the actual temperature value is equal to or above the second pre-determined minimum threshold temperature value, the timer;
responsive to a determination that the actual temperature value is less than the second pre-determined minimum threshold temperature value, initiating the timer to operate for a modified time interval;
determining whether the timer operating for the modified time interval has expired; and
responsive to a determination that the timer operating for the modified time interval has expired, modifying operation of a compressor.
2. The method of claim 1 , wherein the saturated suction temperature comprises a temperature of refrigerant within an evaporator.
3. The method of claim 1 , wherein the at least one temperature sensor comprises at least one of a thermocouple, a thermometer, and a thermostat.
4. The method of claim 1 , wherein the at least one temperature sensor is disposed on an exterior surface of an evaporator coil thereby using a surface temperature of the evaporator coil as a proxy measurement for the saturated suction temperature.
5. The method of claim 1 , wherein the first pre-determined minimum threshold temperature value comprises 32° F.
6. The method of claim 1 , wherein the second pre-determined minimum threshold temperature value comprises 33° F.
7. The method of claim 1 , wherein the pre-determined time interval comprises 180 seconds.
8. The method of claim 1 , wherein the modified time interval is calculated using the equation:
MODIFIED TIME INTERVAL=(T_DEF/LIMIT 3 )*SST 3 where
T DEF=180 seconds;
LIMIT=32° F.; and
SST is the saturated suction temperature.
9. The method of claim 1 , wherein the modifying comprises adjusting a speed of the compressor to a value between a maximum-rated speed and a minimum-rated speed.
10. The method of claim 1 , wherein the modifying comprises cycling a compressor between an activated state and a deactivated state.
11. The method of claim 1 , wherein the freeze event comprises ice buildup on an evaporator of the HVAC system.
12. The method of claim 1 , comprising, responsive to a determination that the actual temperature value is greater than the first pre-determined minimum threshold temperature value, repeating the measuring step.
13. The method of claim 1 , comprising, responsive to a determination that the timer operating for the modified time interval has not expired, repeating the step of determining whether the actual temperature value is less than the second pre-determined minimum threshold temperature value.
14. A heating, ventilation, and air-conditioning (HVAC) system comprising:
at least one temperature sensor associated with at least one component of the HVAC system, wherein the at least one temperature sensor is positioned on an evaporator coil;
a controller configured to communicate with the at least one temperature sensor;
wherein the controller is configured to:
receive an actual temperature value reflective of measuring a saturated suction temperature measured by the at least one temperature sensor;
determine whether the actual temperature value is less than a first pre-determined minimum threshold temperature value;
responsive to a determination that the actual temperature value is less than the first pre-determined minimum threshold temperature value, initiate a timer to operate for a pre-determined time interval;
determine whether the actual temperature value is less than a second pre-determined minimum threshold temperature value;
responsive to a determination that the actual temperature value is equal to or above the second pre-determined minimum threshold temperature value, reset the timer;
responsive to a determination that the actual temperature value is less than the second pre-determined minimum threshold temperature value, initiate the timer to operate for a modified time interval;
determine whether the timer operating for the modified time interval has expired; and
responsive to a determination that the timer operating for the modified time interval has expired, modify operation of a compressor.
15. The HVAC system of claim 14 , wherein the modified operation of the compressor causes the controller to:
adjust a speed of the compressor to a value between a maximum-rated speed and a minimum-rated speed; and
cycle the compressor between an activated state and a deactivated state.
16. The HVAC system of claim 14 , wherein:
the first pre-determined minimum threshold temperature value comprises 32° F.; and
the second pre-determined minimum threshold temperature value comprises 33° F.
17. The HVAC system of claim 14 , wherein the pre-determined time interval comprises 180 seconds.
18. The HVAC system of claim 14 , wherein the modified time interval is calculated using the equation:
MODIFIED TIME INTERVAL=(T_DEF/LIMIT 3 )*SST 3 where
T DEF=180 seconds;
LIMIT=32° F.; and
SST is the saturated suction temperature.
19. A method of mitigating a freeze event in a heating, ventilation, and air conditioning (HVAC) system, the method comprising:
receiving an actual temperature value reflective of measuring a saturated suction temperature measured by at least one sensor;
determining, using a controller, whether the actual temperature value is less than a first pre-determined minimum threshold temperature value;
responsive to a determination that the actual temperature value is less than the first pre-determined minimum threshold temperature value, initiating, by the controller, a timer to operate for a pre-determined time interval;
determining, using the controller, whether the actual temperature value is less than a second pre-determined minimum threshold temperature value;
responsive to a determination that the actual temperature value is equal to or above the second pre-determined minimum threshold temperature value, resetting, by the controller, the timer;
responsive to a determination that the actual temperature value is less than the second pre-determined minimum threshold temperature value, initiating, by the controller, the timer to operate for a modified time interval;
determining, using the controller, whether the timer operating for the modified time interval has expired; and
responsive to a determination that the timer operating for the modified time interval has expired, adjusting a speed of a compressor to a value between a maximum-rated speed and a minimum-rated speed.