Patent Application
20160140822
The application pertains to control systems and methods for monitoring variable airflows which might impact operation of ambient condition detectors. More particularly, the application pertains to such systems and methods to improve operationality of aspirating smoke detectors in varying airflow environments.
Aspirating smoke detectors are known and useful in a variety of commercial and industrial environments. When commissioned, aspirating smoke detectors establish an airflow baseline for the air that flows through the devices. During the operating life of the product the current air flow is monitored and compared to the baseline that was established during commissioning. When the current flow measurement deviates from the baseline airflow established during commissioning a trouble conditions is reported to the operator of the equipment.
Aspirating smoke detectors are often used to monitor airflow on the return air grills for HVAC units. During operation HVAC units may continuously cycle on and off which can result in periods of high air flow followed by periods of stagnant air. These changes in airflow can cause an aspirating smoke detector to generate trouble conditions due to the current air flow when compared to the established baseline.
While disclosed embodiments can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles thereof as well as the best mode of practicing same, and is not intended to limit the application or claims to the specific embodiment illustrated.
In one aspect, embodiments hereof more than one baseline is established. For example a baseline for when the HVAC unit is running at its maximum velocity and a second when the HVAC unit is off, would allow the device to account for the large airflow changes and prevent false trouble conditions.
The aspirating smoke detector could have an input from the HVAC unit which would indicate when the system is running and the unit could determine which airflow baseline should be used for indicating a trouble condition if such a condition exists. Example inputs could be ‘airflow on’, ‘airflow off’, input from an anemometer, etc.
In yet another aspect, when initializing the device will establish two baselines, one when the HVAC unit is on and one when it is off. During normal operation the device will sample the current airflow and compare it to the appropriate baseline value. The device selects the baseline to compare the current reading to by reading the input from the HVAC unit or from an external flow monitoring sensor.
If the flow varies by a percentage indicative of a trouble condition then the device will report an airflow trouble condition.
Detector 12 is coupled to control circuits 16 by an output signal line 14d. As those of skill will understand, the signals on line 14d are indicative of smoke detected in chamber 14.
The control circuits 16 can be implemented at least in part by one or more programmable processors 16a which can execute instructions 16b located at the detector 12.
A storage element 18a is coupled to circuits 16, and provides storage for at least two different baseline values. Storage element 18b is also coupled to circuits 16 and provides storage for at least one trouble limit value. The usefulness of these stored values is discussed subsequently.
A flow monitor 22 can provide output signals, on a line 22a indicative of sensed flow in a target area or region such as region R. Line 22b can couple an on/off signal for the HVAC unit indicative of when it is energized and operating to provide heat, ventilation or cooling to the region R.
System 10 can operate in a variety of modes. One operational mode is illustrated in
Subsequently, when detector 12 is placed to service a region such as region R, a current airflow is sampled, as at 110, via a flow monitor such as 22. A determination is made, as at 112, as to the state of the HVAC unit. An electrical signal 22b indicative of this state can be coupled to control circuits 16. This signal provides information as to whether the HVAC unit is energized, and on, or, not energized, and off.
If the determination is that the HVAC unit is on, another determination is made, as at 114, as to whether a percentage change, the trouble limit value, from the high airflow baseline exceeds the trouble limit. If so, a trouble condition is indicated, as at 116. An indicium of this state can then be transmitted via interface 20a and medium 20b to a displaced monitoring or security location.
If the HVAC unit is not on, as at 112, a determination is made, as at 118, as to whether the percent change, the same or a different trouble limit value, from the low airflow base line exceeds that trouble limit. If so the trouble condition is indicated, as at 116.
Those of skill will understand that neither the specific details of the exemplary system 10, nor details of method 100 are limitations hereof excepted as described herein. If desired multiple pairs of baseline, and multiple trouble limit values can be stored in units 18a, b without departing from the spirit and scope hereof.
From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope hereof. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims. Further, logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be add to, or removed from the described embodiments.
