A method for controlling constant air volume of an ECM motor in an HVAC system. The method includes: a) acquiring a target air volume Q.sub.set input from an external, determining a function I.sub.tad=f(n) corresponding to the target air volume Q.sub.set by the microprocessor, in which I.sub.tad represents a bus current, n represents a rotational speed of the motor; b) acquiring a calculated bus current I.sub.tad according to the rotational speed n and the function I.sub.tad=f(n), and detecting a real-time bus current I.sub.bus; and c) comparing the calculated bus current I.sub.tad with the real-time bus current I.sub.bus by the microprocessor for closed-loop control; when I.sub.tad>I.sub.bus, increasing the rotational speed n of the motor; when I.sub.tad<I.sub.bus, decreasing the rotational speed n of the motor; and when I.sub.tad=I.sub.bus, stopping regulating the rotational speed n and returning to B) for continuing the control of the constant air volume.

A method for controlling air volume including: 1) inputting a target air volume into a microprocessor control unit of a motor controller; 2) starting a motor by the motor controller and allowing the motor to work in a steady state under a rotational speed; 3) recording the torque and rotational speed in the steady state, establishing a functional relation formula Q=F (T, n, V) for calculating the air volume, and calculating an air volume in the steady state; 4) comparing the target air volume with the calculated air volume; 5) re-recording a steady torque after the motor falls on a new steady state under an increased or reduced rotational speed, and recalculating the air volume in the new steady state; and 6) repeating steps 4) and 5) to adjust the rotational speed until the calculated air volume is equal or equivalent to the target air volume.

An air-conditioning apparatus detects refrigerant leak with high-accuracy even in a state in which an excessive liquid refrigerant is stored in an accumulator. The air-conditioning apparatus determines that leakage of refrigerant has occurred from a refrigerant circuit in an operating state in which an excessive liquid refrigerant is stored in an accumulator, after a part of the excessive liquid refrigerant stored in the accumulator is moved and stored into a condenser, with the excessive liquid refrigerant remaining in the accumulator as a reference amount, when the excessive liquid refrigerant is less than the reference amount.

A system and method for providing a substantially constant volume exhaust or ventilation air terminal system is shown for controlling exhaust and/or return airflow rates in a system having a central fan or ventilator. The system and method permits zone-by-zone or area-by-area airflow regulation or control in non-demand areas in response to a demand or call for ventilation in demand areas. In one embodiment, the system employs at least one constant airflow controller or regulator situated in a damper. In one embodiment, a terminal houses a plurality of sub-ducts each having an airflow regulator. At least one of the sub-ducts has a damper. When the damper is open, a maximum airflow through the terminal is a sum of maximum airflow permitted by the regulators.

A system and method for providing a substantially constant volume exhaust or ventilation air terminal system is shown for controlling exhaust and/or return airflow rates in a system having a central fan or ventilator. The system and method permits zone-by-zone or area-by-area airflow regulation or control in non-demand areas in response to a demand or call for ventilation in demand areas. In one embodiment, the system employs at least one constant airflow controller or regulator situated in a damper. In one embodiment, a terminal houses a plurality of sub-ducts each having an airflow regulator. At least one of the sub-ducts has a damper. When the damper is open, a maximum airflow through the terminal is a sum of maximum airflow permitted by the regulators.

A method and apparatus for balancing terminals of an HVAC system uses an air flow measuring device by inputting into a computer processing portion of the air flow measuring device predetermined target flows for each terminal; acquiring via the air flow measuring device initially measured air flows through each of the terminals, the initially measured air flows being provided to the computer processing portion; and adjusting the terminals in the HVAC system to flow set points according to instructions from the computer processing portion, the computer processing portion being programmed to calculate the flow set point for each terminal given current HVAC system load conditions, that will result in all terminals being set to target flow after all terminals have been adjusted as instructed.

A method for controlling air volume of an electric device to be constant, the device being adapted to exhaust or supply air, the method including: A) establishing M constant air volume control functions Qi=F(n) corresponding to M air volume points CFM.sub.i in the microprocessor of the system controller; B) allowing the microprocessor to receive or preset a target air volume IN-.sup.CFM; C) starting the motor, when the motor operates in a stable state, comparing M air volume points CFMi with the target air volume IN-.sup.CFM, and ensuring that the target air volume IN-.sup.CFM falls within two known air volume points CFMi and CFMi1; D) using the two known air volume points CFMi and CFMi1 to calculate a constant air volume control function Q0=F(n) corresponding to the target air volume IN-.sup.CFM by interpolation method; and E) controlling a motor parameter Q0 and a rotational speed n.