Method and apparatus for determining critical pressure of variable air volume heating, ventilating, and air-conditioning systems

Abstract

A strategy for determining the critical supply duct pressure in variable-air-volume heating, ventilating, and air-conditioning systems that compensates for duct leakage and variable loads, enabling its use during normal system operation. The strategy consists of a static pressure sensor, an airflow sensor, a supply fan, a fan modulating device, a controller coupled to the static pressure sensor and the airflow sensor, and a data processing algorithm for analyzing results from a function test using these components. The functional test involves changing the supply duct pressure setpoint, waiting for equilibrium, recording pressure, flow, and time, then changing the supply duct pressure setpoint to the next setting in the sequence.

Description

[0001]“This invention was made with State of California support under California Energy Commission Grant number 02-03. The Energy Commission has certain rights to this invention.”BACKGROUND [0002] 1. Field of the Invention [0003] The following invention relates to controls for variable-air-volume heating, ventilating, and air-conditioning (HVAC) systems, specifically to supply duct static pressure control. [0004] 2. Description of Prior Art [0005] Modern buildings typically have complex heating, ventilating, and air-conditioning systems to control indoor temperature, pressure, ventilation rate, and other variables in a way that makes efficient use of energy. One way to conserve energy in these systems is to use a so-called variable-air-volume design. Key components of a variable-air-volume system are a supply fan and terminal units. The supply fan is a prime mover that causes air to move. A terminal unit contains a throttling damper that regulates an amount of air supplied to a spac...

AI Technical Summary

Benefits of technology

[0012] Accordingly, a primary object of the present invention is to provide a strategy for determining the critical supply duct pressure of variable-air-volume heating, ventilating, and air-conditioning systems so that a static pressure reset strategy can be configured and optimized.

[0015] Another object of the present invention is to provide a strategy for determining the critical supply duct pressure of variable-air-volume heating, ventilating, and air-conditioning systems that can compensate for load changes that occur while the strategy is implemented.

Problems solved by technology

A problem with this strategy is that it is inefficient at part-load conditions, when the supply flow rate is significantly lower than a design flow rate, which is the flow rate at which the system should operate when the fan is running at full speed.

When the supply duct pressure is below the critical pressure one or more terminal dampers will be fully open yet unable to get enough air.

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