The SOX3 Combustion Check is a great tool to easily tune furnaces when a full combustion analysis isn't necessary. Designed specifically for HVACR pros, the SOX3 provides all the essential measurements needed to tune most combustion equipment. It directly measures %O2 and flue temperature, and calculates %CO2, %Excess Air, and combustion efficiency. With three common fuel types, as well as a custom fuel input, you can work on any combustion equipment you may encounter.

Like all Fieldpiece products, the SOX3 Combustion Check Tool was designed to help HVACR professionals do more with their tools. From custom fuels to field-replaceable oxygen sensors, the SOX3 can be trusted to measure up for any furnace tuning job.

• Automatic Electric Pump with Pause - Pump works automatically so there's no hand pumping, and techs can pause the pump at any time to save battery life of SOX3 Combustion Check Oxygen Sensor
• Field-replaceable Oxygen Sensor - The SOX3 Oxygen Sensor indicators tells techs when a new sensor is needed. With calibration data stored on the sensor, it can be swapped out in seconds, so there's never a need to send your instrument in for calibration
• Hands-free Testing - The threaded R-cone holds the barrel firmly in the flue, and the strong magnet on the back of the SOX3 holds the instrument firmly to the side of the flue, while the internal electric pump does all the work. Techs simply view the results on the triple line display
• Combustion Efficiency - Quickly calculated and displayed on the screen, the SOX3's combustion efficiency calculation is great measurement to help determine the health of a furnace
• Custom Fuels - Not only does the SOX3 test Natural Gas, Oil #2, and Propane, it can be quickly, and easily programmed to test any type of fuel, making non-conventional furnaces just as easy to tune as standard units

Combustion Basics

Combustion is the rapid oxidation of fuel. Oxygen from air (20.9% oxygen & 79.1% nitrogen) is used to burn fuel which produces heat. The appliances installed and serviced by technicians rely on clean efficient flames to produce the energy needed to heat homes, water, etc. Combustion testing is necessary to maximize the efficiency of the combustion systems and to minimize the harmful emissions produced such as carbon monoxide and carbon dioxide. Proper tuning of the combustion process by combustion testing reduces the production of harmful carbon monoxide and decreases the amount of fuel burned due to increase in efficiency.

Combustion efficiency can typically be increased by creating a more balanced air to fuel ratio. The ratio of air to fuel determines how much CO is produced and how efficient the flame is.

Tuning the O2, CO2 excess air, stack temperature, and temperature rise to match the appliance manufacturers specifications will increase the efficiency and help to maximize the performance and life expectancy of the equipment. A properly tuned natural gas appliance will have between 6-9 O2% in the flue while an oil appliance will have 3-7 O2%.

Adjustments to the combustion process ensure that the highest combustion efficiency is safely achieved, thereby reducing the overall amount of fuel used in producing the energy needed. It is still necessary to test and adjust the appliance to the manufacturer’s specification for airflow in the duct system, temperature rise across the heat exchanger and anything else that may need testing. Testing and balancing appliances to meet manufacturers’ specifications helps to ensure maximum system efficiency and equipment longevity.

Combustion testing does not take into account start up losses, standby losses, cabinet/boiler body losses, or distribution losses in ducts or piping.

The diagram below is a simplified representation of the relationship between the various combustion parameters, and how a change in one parameter affects the others.