System, method, and apparatus for balancing an HVAC system

1. A method for balancing terminals of an HVAC system using an air flow measuring device, comprising:

inputting into a computer processing portion of the air flow measuring device a predetermined target flow for each terminal;

acquiring via the air flow measuring device an initially measured air flow through each terminal, the initially measured air flow through each terminal being provided to the computer processing portion; and

adjusting each terminal in the HVAC system to a calculated flow set point according to instructions from the computer processing portion, the computer processing portion being programmed to determine the calculated flow set point for each terminal that results in each terminal being set to its respective predetermined target flow after all terminals in the HVAC system have been adjusted as instructed by the computer processing portion.

2. The method recited in claim 1 , wherein adjusting each terminal in the HVAC system comprises:

positioning the air flow measuring device at a terminal under adjustment as instructed by the computer processing portion;

obtaining the calculated flow set point for the terminal under adjustment from the computer processing portion; and

adjusting the terminal under adjustment to the calculated flow set point.

3. The method recited in claim 2 , wherein the computer processing portion is programmed to determine current HVAC system load conditions that are used to determine the calculated flow set point for a first terminal under adjustment as a function of the initially measured air flows and the predetermined target flow for each terminal.

4. The method recited in claim 3 , wherein the computer processing portion is programmed to determine current HVAC system load conditions that are used to determine the calculated flow set point for terminals under adjustment subsequent to the first terminal under adjustment as a function of air flows resulting from prior adjustments to terminals of the HVAC system.

5. The method recited in claim 4 , wherein the computer processing portion is programmed to calculate the air flows resulting from prior adjustments to terminals of the HVAC system.

6. The method recited in claim 4 , wherein the computer processing portion is programmed to calculate the air flows resulting from prior adjustments to terminals of the HVAC system as a function of a resulting air flow measured at a terminal other than the terminal under adjustment.

7. The method recited in claim 2 , wherein after adjusting the terminal under adjustment, the computer processing portion is programmed to instruct a user to use the air flow measuring device to acquire a measured air flow through a different terminal, the computer processing portion being further programmed to:

calculate a predicted air flow through the different terminal;

compare the measured air flow through the different terminal to the predicted air flow through the different terminal to determine an error;

in response to the error exceeding a predetermined threshold, determining a recalculated flow set point for the terminal under adjustment; and

instruct the user to re-adjust the terminal under adjustment to the recalculated flow set point.

8. The method recited in claim 7 , wherein, to determine the recalculated flow set point for the terminal under adjustment, the computer processing portion is programmed to:

calculate a revised total flow for the HVAC system as a function of a previously determined total flow for the HVAC system and the error;

calculate flow ratios for each terminal as a function of a predicted flow for each terminal and the previously determined total flow for the HVAC system;

calculate revised predicted flows through each terminal as a function of the flow ratios and the revised total flow; and

determine the recalculated flow set point for the terminal under adjustment as a function of the revised total flow and the revised predicted flows.

9. The method recited in claim 2 , wherein after adjusting the terminal under adjustment, the computer processing portion is programmed to instruct a user to move the air flow measuring device to a next terminal, the computer processing portion being further programmed to:

calculate a predicted air flow through the next terminal;

determine a measured air flow through the next terminal;

compare the predicted air flow through the next terminal to the measured air flow through the next terminal to determine an error;

determine a recalculated flow set point for the next terminal as a function of the error; and

instruct the user to adjust the next terminal to the recalculated flow set point.

10. The method recited in claim 9 , wherein to determine the recalculated flow set point for the next terminal, the computer processing portion is programmed to:

calculate a revised total flow as a function of a previously determined total flow and the error;

calculate flow ratios for each terminal as a function of a predicted flow for each terminal and the previously determined total flow;

calculate revised predicted flows through each terminal as a function of the flow ratios and the revised total flow; and

determine the recalculated flow set point for the next terminal as a function of the revised total flow and the revised predicted flows.

11. The method recited in claim 1 , wherein adjusting each terminal in the HVAC system to a calculated flow set point according to instructions from the computer processing portion comprises adjusting the air flow through each terminal while using the air flow measuring device to monitor air flow through each terminal to determine when the flow set points have been reached.

12. The method recited in claim 1 , further comprising adjusting all terminals in the HVAC system to a fully open condition prior to acquiring via the air flow measuring device the initially measured air flow through each terminal in the HVAC system according to instructions from the computer processing portion.

13. The method recited in claim 1 , wherein the computer processing portion is programmed to identify one of the terminals in the HVAC system as a key terminal in the HVAC system, wherein the method further comprises leaving the key terminal fully opened throughout the balancing process according to instructions from the computer processing portion.

14. The method recited in claim 13 , wherein the computer processing portion is programmed to:

for each terminal in the HVAC system, determine a terminal error as a function of a ratio of its respective predetermined target flow and its respective initially measured air flow; and

identify the terminal for which the terminal error is the lowest as the key terminal.

15. The method recited in claim 14 , wherein the computer processing portion is programmed to identify an ascending order in which the terminals of the HVAC system are adjusted, wherein the ascending order is according to an order of magnitude of the terminal error.