Automated branch flow calibration in a HVAC distribution system

An apparatus for automatically calibrating air flow in at least one branch of a heating, ventilation and air-conditioning (HVAC) distribution system, the HVAC distribution system implementing a damper means in the at least one branch of the HVAC distribution system, the damper means being adjustable to a plurality of positions, the HVAC distribution system having a fan for distributing the air to the at least one branch, the apparatus comprising:

• means for selectively controlling the damper means to first and second positions;
• a first flow sensor for measuring a first and second air flow at an output of the fan, said first and second air flow at said output of the fan corresponding to said first and second positions of said damper means;
• a second flow sensor for measuring a first and second air flow at an input of the damper means, said first and second air flow at said input of the damper means corresponding to said first and second positions of said damper means;
• and
• means for calibrating the air flow in the at least one branch of the HVAC distribution system based on the measured first and second air flow at said output of the fan and the measured first and second air flow at said input of the damper means.

A method of automatically calibrating the fluid flow in at least one branch of a fluid distribution system, the fluid distribution system implementing a local control component in the at least one branch of the fluid distribution system, the local control component being adjustable to a plurality of positions, the fluid distribution system having a source component for distributing the fluid to the at least one branch, the method comprising the steps of:

• (a) instructing the local control component to first and second positions;
• (b) measuring a first and second steady state fluid flow at an output of the source component, said first and second steady state fluid flow at said output of the source component corresponding to said first and second positions of said local control component;
• (c) measuring a first and second steady state fluid flow at an input of the local control component, said first and second steady state fluid flow at said input of the local control component corresponding to said first and second positions of said local control component;
• and
• (d) calibrating the fluid flow in the at least one branch of the fluid distribution system based on the measured first and second steady state fluid flow at said output of the source component and the measured first and second steady state fluid flow at said input of the local control component.

A method of automatically calibrating the fluid flow in at least a first branch of a fluid distribution system of the type which has a first main duct segment between a source component for supplying fluid in said system and said first branch and a second main duct segment downstream of said first main duct segment and said first branch, and additional branches downstream of said first main duct segment, said system having a local control component in each said branch of the fluid distribution system, each local control component being adjustable to a plurality of positions, the method comprising the steps of:

• determining the flow coefficient for said first main duct segment by measuring the static pressure in said main duct segment and at said first branch at two different operating conditions, comprising different flow rates in said first main duct segment while keeping the flow rate through said first branch constant, and calculating the flow coefficient of said first main duct segment;
• determining the flow coefficient for said second main duct segment by measuring the static pressure at said source component and at said first branch at said two different operating conditions;
• setting said first branch local control component at a first predetermined open position while closing all other branch local control components, and calculating the velocity through the first main duct segment;
• calculating the flow rate through said first main duct segment;
• calculating the velocity through the second main duct segment;
• calculating the flow rate through said second main duct segment;
• subtracting the flow rate of said second main duct segment from the flow rate of said first main duct segment to determine the flow rate through said first branch.

A method of automatically calibrating the fluid flow in at least a first branch of a fluid distribution system of the type which has a first main duct segment between a source component for supplying fluid in said system and said first branch and a second main duct segment downstream of said first main duct segment and said first branch, and additional branches downstream of said first main duct segment, said system having a local control component in each said branch of the fluid distribution system, each local control component being adjustable to a plurality of positions, the method comprising the steps of:

• determining the flow coefficient for said first main duct segment by measuring the static pressure in said main duct segment and at said first branch at two different operating conditions, comprising different flow rates in said first main duct segment while keeping the flow rate through said first branch constant, and calculating the flow coefficient of said first main duct segment using the equation:
• ##EQU9## determining the flow coefficient for said second main duct segment by measuring the static pressure at said source component and at said first branch at two different operating conditions, comprising different flow rates in said second main duct segment while keeping the flow rate through said first branch constant, and calculating the flow coefficient of said second main duct segment using the equation:
• ##EQU10## setting said first branch local control component at a first predetermined open position while closing all other branch local control components, and calculating the velocity through the first main duct segment using the equation:
• ##EQU11## calculating the flow rate through said first main duct segment using the equation:
• Q.sub.fc =V.sub.fc *A.sub.fc
• calculating the velocity through the second main duct segment using the equation:
• ##EQU12## calculating the flow rate through said second main duct segment using the equation:
• Q.sub.cd =V.sub.cd *A.sub.cd
• subtracting the flow rate of said second main duct segment from the flow rate of said first main duct segment to determine the flow rate through said first branch.