For many refrigeration applications, using solid state sensors will provide an economical and reliable gas detection solution. Solid state sensors are reliable if used in a clean area with very little temperature and humidity changes. Solid State refrigerant sensors should not be used where there are other chemicals or gases present (other than refrigerants), such as alcohol based cleaners, fumes from running engines, fuel storage containers, etc.

Using infrared sensor technology will ensure the highest degree of sensor accuracy if monitoring an area where there are other contamination gases or multiple refrigerants in the same area. Infrared refrigerant sensors should not be used in locations that have corrosive chemicals such as chlorine, ammonia and other oxidizers that are present, especially if there is a higher humidity level.

 

Comparison of CETCI’s Solid State Refrigerant Sensors and Infrared Refrigerant Sensors

 

CETCI’s Solid State Refrigerant Sensors

CETCI’s Non-dispersive Infrared Refrigerant Sensors

Mode of Operation

Metal oxide changes resistance in response to the presence of target gas. The change is measured by the electronics of the detector to determine the gas concentration.

Gas molecules absorb the infrared light of the optical sensor at a certain wave length. The wave length is measured by the electronics of the detector to determine the gas concentration.

Specific Refrigerant Gases Detected in CETCI Gas Detectors

R22, R134A, R402A, R404A, R407C, R410A, R422D, R438A, R507A

R22, R32, R123, R134A, R404A, R407A, R407C, R407F, R410A, R427A, R448A, R449A, R507, R422A, R422A, R452A, R513A, HFO1234YF, HFO1234ZE, FO1233ZD

Output

Non-linear

Linearized

Gas Detection Range (gas dependant)

0 – 2,000 ppm

0 – 3,500 ppm (0 – 1,000 ppm for R123)

Sampling Method

Diffusion

Diffusion

Life Expectancy

5-7 years

7 – 10 years

Maintenance

Low

Low

Calibration

Less calibration frequency required, every 12 months recommended.

Establish and maintain zero point and the accuracy of the detector remains intact. Less calibration frequency required, every 12 months recommended.

Sensitivity

High, detects low gas concentrations

High, detects low gas concentrations

Accuracy (gas dependent)

±15%

±5% (if calibrated to specific refrigerant)

Response Time T90

< 2 minutes (target refrigerant dependent)

< 5 minutes

Drift/Aging

Susceptible to temperature and humidity changes, require regular calibration to compensate for drift/aging

Less susceptible to temperature and humidity changes, little drift, moderate aging

Operating Temperature

-20°C to 40°C (-4°F to 104°F)

-30°C to 40°C (-22°F to 104°F)

Response to Temperature Changes

Sensitive to changes in temperature

Short term response to large changes in temperature

Operating Relative Humidity

15 - 90% RH non-condensing

5 - 90% RH non-condensing

Response to RH Changes

Sensitive to changes in humidity

High humidity can affect response and promote corrosion.

Wet Environments

Will shorten lifespan

Water or vapour condensation can impair the optics ability to function.

Dry Environments

Must be calibrated in the environment it will be operating in.

No problem in dry environments

Dirty, Dusty Environments

Will shorten lifespan and requires calibration more often.

Dust and dirt can coat the optics and impair the sensor response.

Time Required to Stabilize

New sensor is stable after 3 minutes; old sensor (ie. 5 yrs) may take 5 minutes.

Typically requires 10 to 20 minutes to equalize after a sudden variation in temperature. May take up to 30 minutes to stabilize from a change in humidity.

Presence/Absence of Oxygen (Air)

Requires oxygen for proper functioning.

No minimum level of oxygen required; operates in the absence of, or enriched presence of oxygen.

Cross Contamination

Non-specific, sensitive to many other gases, vapours and chemicals, susceptible to false alarms

Can be configured for broad range or gas specific, few false alarms. Cross sensitivity to other refrigerants.

Exposure to High Concentrations of Gas (poisoning)

Moderately resistant to poisoning

Will not burnout, immune to poisoning. May require a long time to clear before accurate readings can be taken again.

Continuous Exposure to Gas

Sensor reading will become unreliable after 15 minutes (will read higher than calibrated value).

Does not affect operation

Power Consumption

High

High

Cost

Economical

Can be expensive

  

Applications for Refrigerant Sensors: Recommendation by Sensor Type

Application Sensor Type Reasons

Boiler / Machinery Rooms

IR

No false alarms, longer life span, less maintenance

Breweries

IR

No false alarms, longer life span, less maintenance

Chiller Rooms

IR

No false alarms, longer life span, less maintenance

Convenience Stores

SS

IR usually too expensive

Hotels

SS 

Requires a small remote sensor on a cable for rooms with air conditioners

Shopping Malls

IR

No false alarms, longer life span, less maintenance

Supermarkets

IR

No false alarms, longer life span, less maintenance

Universities

IR

No false alarms, longer life span, less maintenance

Office Buildings

IR

No false alarms, longer life span, less maintenance

Hospitals

IR

No false alarms, longer life span, less maintenance

NOTE: Ammonia is commonly used as a refrigerant in very low temperature applications such as food/meat processing, ice making plants and ice arenas. Electrochemical sensors are required to ensure accurate monitoring in Ammonia applications.

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