Method and apparatus for reheat dehumidification with variable air volume

1. A heating, ventilation, and air conditioning (HVAC) system for regulating humidity of an enclosed space, the system comprising:

an evaporator coil;

a metering device fluidly coupled to the evaporator coil via a distribution line;

a variable-speed circulation fan for circulating air around the evaporator coil;

a temperature sensor thermally exposed to the distribution line;

at least one controller operatively coupled to the temperature sensor and to the variable-speed circulation fan;

wherein the at least one controller is configured to:

determine a latent cooling load based on a relative-humidity setpoint;

determine an optimal distributor line temperature that corresponds to the latent cooling load;

compare a measured distributor line temperature to the optimal distributor line temperature;

responsive to a determination that the measured distributor line temperature exceeds the optimal distributor line temperature, reduce a speed of the variable-speed circulation fan; and

responsive to a determination that the measured distributor line temperature falls below the optimal distributor line temperature, increase the speed of the variable-speed circulation fan.

2. The system of claim 1 , comprising:

a condenser coil fluidly coupled to the metering device;

a compressor fluidly coupled to the condenser coil and the evaporator coil; and

a condenser fan for circulating air around the condenser coil.

3. The system of claim 1 , wherein the at least one controller is configured to detect a relative humidity of the enclosed space.

4. The system of claim 3 , wherein the at least one controller is configured to calculate the optimal distribution line temperature based on the relative humidity of the enclosed space.

5. The system of claim 4 , wherein the at least one controller is configured to modulate the speed of the variable-speed circulation fan to maintain the optimal distribution line temperature.

6. The system of claim 4 , wherein the optimal distribution line temperature is calculated based on at least one of indoor dry-bulb temperature, relative humidity, and outdoor temperature.

7. The system of claim 1 , wherein the temperature sensor is configured to measure the distribution line temperature as a proxy for an evaporator coil surface temperature.

8. The system of claim 1 , wherein the HVAC system comprises a rooftop unit.

9. The system of claim 1 , wherein the at least one controller is configured to communicate with at least one of a monitoring device and a communication device.

10. The system of claim 1 , wherein the at least one controller is configured to reduce the speed of the variable-speed circulation fan thereby lowering a temperature of the evaporator coil.

11. The system of claim 1 , wherein the temperature sensor comprises a thermistor.

12. A method of regulating humidity of an enclosed space, the method comprising:

measuring a distributor-line temperature associated with a heating, ventilation, and air conditioning (HVAC) system;

determining, via at least one controller, a latent cooling load based at least in part on environmental conditions;

calculating, via the at least one controller, an optimal distributor-line temperature corresponding to the latent cooling load;

comparing the measured distributor-line temperature to the optimal distributor-line temperature;

determining if the measured distributor-line temperature exceeds the optimal distributor-line temperature;

responsive to a determination that the distributor-line temperature exceeds the optimal distributor-line temperature, adjusting, via the at least one controller, a speed of a variable-speed circulation fan to lower an evaporator coil surface temperature; and

wherein the adjusting the speed of the variable-speed circulation fan increases a latent capacity of the HVAC system.

13. The method of claim 12 , wherein the step of measuring comprises measuring a saturated suction temperature of the HVAC system.

14. The method of claim 12 , wherein increasing the latent capacity of the HVAC system facilitates dehumidification of conditioned air without an associated change of temperature of the conditioned air.

15. The method of claim 12 , comprising detecting, via the at least one controller, a relative humidity of an enclosed space.

16. The method of claim 15 , wherein the at least one controller is configured to modulate the speed of the variable-speed circulation fan to maintain the optimal distributor-line temperature.

17. The method of claim 12 , wherein the adjusting comprises decreasing a speed of the variable-speed circulation fan.

18. The method of claim 12 , comprising, responsive to a determination that the distributor-line temperature does not exceed the optimal distributor-line temperature, maintaining, via the at least one controller, a speed of a variable-speed circulation fan.

19. A heating, ventilation, and air conditioning (HVAC) system for regulating humidity of an enclosed space, the system comprising:

an evaporator coil;

a metering device fluidly coupled to the evaporator coil via a distribution line;

a variable-speed circulation fan for circulating air around the evaporator coil;

a temperature sensor thermally exposed to the distribution line;

at least one controller operatively coupled to the temperature sensor and to the variable-speed circulation fan;

a condenser coil fluidly coupled to the metering device;

a compressor fluidly coupled to the condenser coil and the evaporator coil;

a condenser fan for circulating air around the condenser coil;

wherein the at least one controller is configured to:

determine a latent cooling load based on a relative-humidity setpoint;

determine an optimal distributor line temperature that corresponds to the latent cooling load;

compare a measured distributor line temperature to the optimal distributor line temperature;

responsive to a determination that the measured distributor line temperature exceeds the optimal distributor line temperature, reduce a speed of the variable-speed circulation fan; and

responsive to a determination that the measured distributor line temperature falls below the optimal distributor line temperature, increase the speed of the variable-speed circulation fan.