HK1103555B - Method of zone damper fault detection in an hvac system and hvac system - Google Patents

Description

Method for detecting zone damper fault in heating, ventilating and air conditioning system and HVAC system

Technical Field

The present invention relates to a method and control for a heating, ventilation and air conditioning (HVAC) system in which there are multiple zones, each zone having a damper. The method and control enable a technician to determine the operational status of the damper at a remote location.

Background

In a typical ducted HVAC system, a blower located at an indoor air handler circulates treated air through ductwork to various locations in the home. In a zoned HVAC system, the duct is divided into zones, with one zone being associated with each part of the building that is desired to be controlled to achieve comfort independent of other areas. A set of dampers is installed into the duct section with at least one damper associated with each zone.

The dampers can be opened or closed to direct more or less air to a particular zone as needed to meet the desired comfort level for that zone. In more advanced systems, the dampers can not only be fully opened or fully closed, but they can also be adjusted to a number of intermediate positions to achieve a more accurate level of comfort control.

Typically, zoned HVAC systems are provided with electronic controls that send signals to each damper to open or close. In a typical HVAC system, such as found in most residential systems, the dampers implement "open loop" or do not provide any feedback to the electronic control regarding airflow position. In addition, if there is a fault in the damper, no feedback is provided to the electronic control. Therefore, the electronic control device is not aware that a failure has occurred even if the system fails to operate properly.

The damper failure may be due to a mis-installation (e.g., miswiring), a complete failure of the damper motor, a mechanical obstruction that impedes movement of the damper, etc. During installation and maintenance of a partitioned system, it is difficult and time consuming for a technician to ascertain the nature of any faults and the affected area.

Disclosure of Invention

A method and control apparatus capable of identifying a malfunctioning damper in a zoned HVAC system is disclosed. The method operates automatically according to the control. In addition, the control may identify which zone has a faulty damper and may provide some information about the failure of the damper. This information is provided to a technician at the control device to ensure quick, proper installation or maintenance.

The disclosed embodiments determine the condition of the dampers by looking at the varying characteristics of the air handler as each damper is moved between the open and closed positions.

These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

Drawings

FIG. 1 is a schematic view of the HVAC system of the present invention.

Detailed Description

Figure 1 schematically illustrates a multi-zone HVAC system 20. An indoor unit (furnace/heating coil) and/or an outdoor unit (air conditioner/heat pump) (collectively, the temperature conditioning components 22) is associated with the indoor air handler 24. The air handler 24 takes air from the return duct 26 and sends the air into a plurality of ducts 28, 30, 32 associated with different zones 1, 2 and 3 in the building. As shown, dampers 34 are provided on each of the zone ducts 28, 30 and 32. A system control (e.g., microprocessor control) 36 controls the dampers 34, the indoor air handler 24, the temperature conditioning components 22 and also communicates with user zone controls 130 associated with each zone. The control component 130 may essentially be a thermostat that allows the user to set a desired temperature, noise level, etc. for each zone relative to the other zones. Furthermore, the control unit 130 preferably comprises a temperature sensor for feeding back the actual temperature to the control unit 36.

In one embodiment, the control unit 36 is mounted within one of the thermostat control units 30 and communicates as a system control with all of the other constituent units via a control wiring diagram (such as that disclosed in co-pending U.S. patent application Serial No. _______ entitled "Serial communication HCACsystem," filed on 7.1.2004). The control component 36 is also preferably capable of receiving configuration information about each of these constituent units to enable the control component 36 to learn the individual characteristics of the constituent units 22, 24, 30 and 34. Details of this feature may be those disclosed in co-pending U.S. patent application entitled "Self-Configuring Controls for Heating," ventilatively and Air Conditioning systems, "serial No. ______, as filed on 7.1.2004. The disclosures of both applications are incorporated herein by reference.

The indoor air handler 24 has a variable speed blower motor that is capable of reporting its operating speed to the control component 36. In such a system, the speed of the blower motor is increased as the restriction in the duct increases due to the closing of the damper 34.

In the practice of the disclosed concept, the control 36 operates the indoor blower at a predetermined level, which may be an airflow level or a motor torque level. The control 36 then sequentially opens and closes the dampers 34 associated with a particular zone while recording the speed of the blower motor. The dampers for the other zones do not change during this sequence.

If the blower speed is greater when the damper 34 is closed than when the damper 34 is open, the damper operates properly. If the speed at which the damper opens and closes is the same (or within a measurement tolerance), the damper 34 is determined to be "unresponsive". This condition is defined as a fault. A damper is "flipped" or miswired if the speed at which it is closed is less than the speed at which it is open. Thus, not only the fault but also the nature of the fault is identified.

The sequence is then repeated for each region in the system. In this manner, the system may automatically determine whether all dampers are functioning properly or identify a particular damper as unresponsive or reversing.

The entire fault determination process may be conducted during the initial installation of the system and any resulting faults may be indicated to the installer. For example, an unresponsive damper may be due to loose wires, a faulty damper motor, or a mechanical obstruction to damper movement. The inverted damper may often be caused by miswiring the open and close signal lines. All of these, once identified, are easily corrected.

As shown, the control 36 may be integrated with a display panel 50. The display panel 50 may identify a particular damper 34 or a series of failed dampers that have been identified as being failed. The nature of the fault may also be identified. In the disclosed embodiment, the control 36 is incorporated into a thermostat and operates as the system control described above.

Additionally, the fault determination process may be periodically initiated after the system is operational. If a fault is detected, the system can alert the homeowner, provide the trouble details to the service personnel and confirm when the problem is corrected.

In the second embodiment, the indoor blower is also capable of maintaining airflow through the ductwork substantially constant, independent of the overall restriction in the duct including any partially or fully closed dampers 34. In addition, the control unit 36 is capable of calculating the duct Static Pressure based on the operating Air flow, the operating blower Motor Speed, and certain predetermined characteristics of the Air handler unit, each of which is disclosed in co-pending U.S. patent application entitled "Method of Determining Static Pressure in a Dual Air delivery System Using a Variable Speed Motor", filed on 30/4/2003, serial No.10/426,463. The entire disclosure of this application is incorporated herein by reference. Like the blower speed, duct static pressure increases when the damper is closed. Separately, duct static pressure may be a more accurate measure of duct restriction than blower speed. Thus, for this embodiment, duct static pressure replaces the blower speed in the damper failure detection method described above.

Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims (2)

1. A method of determining a damper condition at a remote location, comprising the steps of:

(1) providing a zoned heating, ventilation and air conditioning HVAC system comprising a plurality of zone ducts, each zone duct containing a damper, and providing a system control for operating each said damper;

(2) actuating one of said dampers between open and closed positions with said system control and monitoring system conditions during said movement of said damper; and

(3) if the system state does not change as the damper moves between the open and closed positions, a damper fault is identified.

2. A heating, ventilation and air conditioning HVAC system comprising:

an indoor air conveyor for conveying air to a series of ducts;

a series of dampers associated with a series of ducts; and

a control for controlling the dampers, the control having an algorithm for moving one of the dampers between open and closed positions and monitoring system conditions during said movement, the control identifying a fault on a particular one of the dampers that is moving between the open and closed positions if the monitored system conditions do not change as expected during movement of the damper.