How to Measure the Input & Output of a Boiler

Newer systems operate far more efficiently than older models.

Knowing the input and output of your boiler will help you to determine the boiler's efficiency. Armed with this knowledge, you can assess if the boiler is still functioning at optimum levels, or if it is time to replace it. It will also tell you if a size adjustment is required for the amount of space it is heating. To determine input and output of a boiler system, it is necessary to know the type of fuel that is being consumed.

Things You'll Need

• Fuel flow meter
• Fuel rate meter

Instructions

1. 

   Natural gas is the most common fuel source.

   Determine the type of fuel used -- it may be gas, liquid or solid.

2. 

   A university or professional lab may be required to determine solid fuel values.

   Calculate the caloric value of the fuel and its flow rate. For gas fuel, these numbers can be obtained from the gas supplier. For liquid fuels such as fuel oil, a meter will need to be installed at the combustion source. For solid fuels like coal, it is difficult to assess without sending a sample to a lab for analysis. This is the boiler's input.

3. 

   Variable-orifice or vortex-shedding types of flow rate meters are the most accurate.

   Install a flow rate meter to determine the boiler's output. Consult the manufacturer's manual to determine if the output rate need be corrected for temperature or pressure.

4. 

   Calculate the efficiency in calories.

   Determine the boiler's efficiency. Divide the boiler's output by the boiler's input. Multiply by 100 to get the percent efficiency rate. Assess results.

Tips & Warnings

• Always consult a licensed HVAC professional if you are unsure of your ability to install meters or work around various fuel types.

References

• Arizona State University: Important Measuring Instruments of Boiler
• Bureau of Energy Efficiency: Energy Performance Assessment of Boilers
• Northwest Food Processors Association: What “Efficiency Testing” Means in Boilers
• University of Rochester: Optimal Boiler Size and Its Relationship To Seasonal Efficiency