Patent Description:
Air conditioning systems for residential or commercial buildings typically include an outdoor unit and an indoor unit. The indoor unit contains an indoor heat exchanger, which absorbs heat from the air being passed through the system using a refrigerant when the system is operating in cooling mode. The outdoor unit contains an outdoor heat exchanger, which cools and condenses the gaseous refrigerant when the system is operating in cooling mode. This refrigerant, historically, has been provided as a fluid with a high GWP value such as R134A or R410A. Although these refrigerants are effective coolants, the effect they can have on the environment has led to the institution of requirements that new refrigerants, which have moderate-to-low GWP values, be employed instead.

Moderate-to-low GWP refrigerants (i.e. A2L refrigerants) can be mildly flammable, however, and thus their use in air conditioning systems can present risks that needs to be addressed. In particular, to the extent that refrigerant leaks are possible in air conditioning systems, it is desirable to have leak detection systems in place when A2L refrigerants are in use for indoor units for ducted residential heating, ventilation and air conditioning (HVAC) products and other similar systems.

One of the existing technologies available to detect refrigeration leaks is a nondispersive infrared sensor (NDIR). However, a current limitation of using a NDIR sensor is the high response time in comparison with other technologies. Such response time is critical to ensure effective safety measures. Accordingly, there remains a need to for a refrigeration detection assembly with an acceptable response time to detect leaks of A2L refrigerant.

<CIT> discloses an air conditioning system including a refrigerant detection sensor that is operable in a first mode in which a baseline response is established and a second mode in which refrigerant leak detection is executed based on the baseline response.

According to a first aspect of the invention, a refrigerant detection assembly is provided, in accordance with appended claim <NUM>, which includes a nondispersive infrared (NDIR) sensor for sensing a flammable refrigerant, a fan configured to continuously direct a sample to the nondispersive infrared sensor, and a controller operatively connected to the nondispersive infrared sensor and the fan. The controller is configured to operate the fan in constant operation and trigger a response when the sensor detects a concentration of at least <NUM>% of the lower flammability limit in the sample.

The nondispersive infrared sensor may be configured to detect a leak of at least one refrigerant of the class A2L according to ASHRAE Standard <NUM>.

The response may include at least one of: an alarm signal, a trigger for stopping operation of the system, a trigger for operating a zoning damper, and a trigger for operating an indoor fan of an air conditioning system.

According to another aspect of the present invention, there is proposed an air conditioning system as defined in claim <NUM>. A preferred embodiment of the air conditioning system is defined in claim <NUM>.

According to another aspect of the invention, a method for detecting a refrigerant leak using a refrigerant detection assembly is provided as defined in appended claim <NUM>. Preferred embodiments of the method are defined in appended claims <NUM>-<NUM>. The method provides for the operating of a nondispersive infrared sensor, directing of a sample to the nondispersive infrared sensor continuously with a fan, and triggering a response with a controller when the sensor detects a concentration of at least <NUM>% of the lower flammability in the sample. The refrigerant detection assembly includes the nondispersive infrared (NDIR) sensor, a fan disposed adjacent to the nondispersive infrared sensor, and a controller operatively connected to the nondispersive infrared sensor and the fan.

The controller is operatively connected to the fan to operate the fan continuously.

The response may include at least one of: an alarm signal, a trigger for stopping operation of the system, a trigger for opening a zoning damper, and a trigger for operating an indoor fan of an air conditioning system.

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The following descriptions of the drawings are by way of example only and should not be considered limiting in any way.

As will be described below, a refrigerant detection assembly, an air conditioning system for incorporating the same, and a method of detecting refrigerant leaks using the refrigerant detection assembly are provided. The refrigerant detection assembly enables the detection of leaks within ten seconds of being exposed to <NUM>% lower flammability limit (LFL). The refrigerant detection assembly utilizes a nondispersive infrared (NDIR) sensor. The refrigerant detection assembly overcomes the high response time traditionally associated with nondispersive infrared sensors by incorporating a fan to force a sample into the NDIR sensor. This sample will contain an air and refrigerant mixture when there is a leak in the air conditioning system. By forcing the sample into the NDIR sensor, the fan effectively reduces the amount of time it takes for the refrigerant to diffuse into the NDIR sensor thereby reducing the response time of detecting a leak. For example, the refrigerant detection assembly may be capable of detecting a leak of at least one A2L refrigerant.

The classification of refrigerant is based upon American Society of Heating, Refrigerating and Air-Conditioning (ASHRAE) Standard <NUM>. The standard evaluates each refrigerant's flammability and toxicity and gives it a class referenced as a letter and number combination. The letter refers to the refrigerants toxicity, and is based on the particular refrigerant's occupational exposure limit (OEL). An "A" is given to refrigerants with a <NUM> ppm or greater OEL. A "B" is given to refrigerants with less than <NUM> ppm OEL. The number adjacent to the letter refers to the refrigerants flammability, and is based on the burning velocity (BV), heat of combustion (HOC), and lower flammability limits (LFL) of the particular refrigerant. A flammability of "<NUM>" is the lowest, with a "<NUM>" being the highest. Recently the second class was broken into "<NUM>" and "<NUM>". A rating of "<NUM>" indicates that while the refrigerant is still considered flammable, its flammability is much lower than that of class <NUM> or <NUM>. It is envisioned that the refrigerant detection assembly described herein may be capable of detecting a leak and triggering a response of at least one A2L refrigerant when the NDIR sensor detects at least <NUM>% LFL in the sample.

A lower flammability limit (LFL) of a refrigerant is the minimum concentration limit that is required for the refrigerant to become potentially combustible. For example, R-<NUM>, which is an A2L refrigerant, has a LFL of <NUM>%. A <NUM>% LFL value is one quarter of the value of the LFL. For example, R-<NUM> has a <NUM>% LFL value of <NUM>%. For illustrative purposes, if the R-<NUM> were used as the refrigerant in the air conditioning system, the refrigerant detection assembly may be configured to trigger a response when the NDIR sensor detects at least <NUM>% of R-<NUM> in the sample. In certain instances, the refrigerant detection assembly may make it possible to trigger a response within ten seconds of the sample reaching <NUM>% LFL. For example, if using R-<NUM> as the refrigerant, the refrigerant detection assembly may make it possible to trigger a response within ten seconds of the sample containing <NUM>% R-<NUM>.

With reference now to the Figures, an air conditioning system <NUM> is schematically shown in <FIG>, which incorporates the refrigerant detection assembly <NUM> of <FIG>. As shown in <FIG>, the air conditioning system <NUM> includes a refrigerant detection assembly <NUM> located proximate to the indoor heat exchanger <NUM>. The air conditioning system <NUM> is provided for use within a building, such as a residential or commercial building, and may be configured as a ductless or ducted system. For purposes of clarity and brevity, however, the following description will relate to the exemplary use of the air conditioning system <NUM> as a ducted system.

In certain instances, the air conditioning system <NUM> includes an indoor unit and an outdoor unit, the indoor unit containing an indoor heat exchanger <NUM> and the outdoor unit containing an outdoor heat exchanger. When operating in cooling mode, the indoor heat exchanger <NUM> absorbs heat from the air being passed through the air conditioning system <NUM>. The cooled air is then circulated into the building by way of the air ducts. The outdoor unit, in addition to including an outdoor heat exchanger, also includes a fan and a compressor. When operating in cooling mode, the outdoor heat exchanger, in combination with the fan, operates to absorb heat from the refrigerant being passed through the outdoor unit. The compressor in the outdoor unit pumps the refrigerant in a cyclical manner through the air conditioning system <NUM>. This refrigerant may, in rare instances, leak into the air conditioning system <NUM>. When utilizing A2L refrigerants in the air conditioning system <NUM>, a leak of refrigerant could lead to undesirable consequences due to the mildly flammable nature of A2L refrigerants. To identify leaks in the air conditioning system <NUM>, the air conditioning system provides a refrigerant detection assembly <NUM> located proximate to the indoor heat exchanger <NUM>. In certain instances, the refrigerant detection assembly <NUM> is attached to the indoor heat exchanger <NUM>. For example, the refrigerant detection assembly <NUM> may be attached to the sheet metal of the coils delta plate of the indoor heat exchanger <NUM>.

An exemplary embodiment of the refrigerant detection assembly <NUM> is shown in <FIG>. As shown in <FIG>, the refrigerant detection assembly <NUM> includes a nondispersive infrared sensor <NUM>, a fan <NUM> disposed adjacent to the nondispersive infrared sensor <NUM>, the fan <NUM> configured to direct a sample to the nondispersive infrared sensor <NUM>, a controller <NUM> operatively connected to the nondispersive infrared sensor <NUM> and the fan <NUM>. The controller <NUM> is configured to operate the fan <NUM> in constant operation and trigger a response when the refrigerant detection assembly <NUM> detects at least <NUM>% lower flammability limit (LFL) in the sample. In certain instances, the controller <NUM> of the refrigerant detection assembly <NUM> is configured to trigger a response within ten seconds of the sample reaching <NUM>% lower flammability limit.

In instances where the refrigerant detection assembly <NUM> detects a leak (ex. when the refrigerant detection assembly <NUM> detects at least <NUM>% LFL in the sample) in the air conditioning system <NUM>, the response triggered by the controller <NUM> may include at least one of: an alarm signal, stopping operation of the air conditioning system <NUM>, operating a zoning damper <NUM>, and operating an indoor fan <NUM> of the air conditioning system <NUM>. For example, the controller <NUM> may encourage the dilution of refrigerant in the building or air conditioning system <NUM> by directing the air from the air conditioning system <NUM> outside the building. In certain instances, the controller operates both the zoning damper <NUM> and the indoor fan <NUM> of the air conditioning system to direct the air from the air conditioning system <NUM> outside the building. By utilizing a zoning damper <NUM>, the air conditioning system <NUM> is capable of redirecting air outside the building when potentially hazardous conditions are present. In certain instances, the stopping operation of the air conditioning system <NUM> triggered by the controller <NUM> includes at least shutting off of the compressor in the outdoor unit to discontinue the circulation of refrigerant between the outdoor unit and the indoor unit.

To ensure that the air conditioning system <NUM> is effectively monitored for leaks, the fan <NUM> of the refrigerant detection assembly <NUM> is operated in a continuous manner by the controller <NUM>. The continuous operation of the fan <NUM> should not be interpreted as operating for a brief period of time in order to establish a calibration (ex. calibration of the NDIR sensor), but instead should be interpreted as the uninterrupted running of the fan <NUM> by the controller <NUM> to constantly direct a sample toward the NDIR sensor <NUM>. By running in a continuous manner, the refrigerant detection assembly <NUM> enables a reduced response time for detecting a leak in the air conditioning system <NUM> than what otherwise would be possible without the use of a fan <NUM>. In certain instances, the refrigerant detection assembly <NUM> triggers a response when the NDIR sensor <NUM> detects at least a <NUM>% LFL in the sample. This <NUM>% LFL in the sample may be reached by a leak of at least one A2L refrigerant. The configuration and method in which the refrigerant detection assembly <NUM> is used reduces the response time for detecting a refrigerant leak such that effective safety measures can be initiated.

The method of detecting a refrigerant leak using the refrigerant detection assembly <NUM> is illustrated in <FIG>. As shown in <FIG>, the method <NUM> includes step <NUM> of operating a refrigerant detection assembly <NUM>, the refrigerant detection assembly <NUM> including a nondispersive infrared sensor <NUM>, a fan <NUM> disposed adjacent to the nondispersive infrared sensor <NUM>, and a controller <NUM> operatively connected to the fan <NUM>. The method <NUM> further includes step <NUM> of directing a sample to the nondispersive infrared sensor <NUM> continuously with the fan <NUM>. To ensure that the fan <NUM> is operated continuously, in certain instances, the controller <NUM> is operatively connected to the fan. The method <NUM> further includes step <NUM> for triggering a response with the controller <NUM> when the sensor <NUM> detects at least <NUM>% lower flammability limit in the sample. The <NUM>% LFL in the sample may be reached by a leak of at least one A2L refrigerant. In certain instances, the response is triggered within ten seconds of the sample reaching <NUM>% LFL. When the sensor <NUM> detects at least <NUM>% LFL in the sample, the response triggered by the controller <NUM> may include at least one of: an alarm signal, stopping operation of the air conditioning system <NUM>, operating a zoning damper <NUM>, and operating an indoor fan <NUM> of the air conditioning system <NUM>. The response may make it possible to mitigate the potentially hazardous conditions.

Claim 1:
A refrigerant detection assembly (<NUM>), comprising:
a nondispersive infrared sensor (<NUM>) for sensing a flammable refrigerant;
a fan (<NUM>) configured to continuously direct a sample to the nondispersive infrared sensor (<NUM>); and
a controller (<NUM>) operatively connected to the nondispersive infrared sensor (<NUM>) and the fan (<NUM>), the controller configured to:
operate the fan (<NUM>) in constant operation, and
trigger a response when the sensor (<NUM>) detects a concentration of at least <NUM>% of the lower flammability limit in the sample.