Heating Degree Days & Fuel Consumption: Part 4

Finally, let’s recalculate the HDD data and present in a pie chart that shows each month’s expected fuel consumption as a percentage of the yearly total:

 

While every boiler system is unique and has its own nuances, the historical monthly fuel consumption for heating purposes SHOULD follow these charts fairly close.  If you notice a significant discrepancy between your historical fuel consumption and the pie charts, there are a number of issues that may be affecting the performance of your boiler system:

  • Fireside fouling: Soot buildup on the fireside of the boiler significantly reduces heat transfer and efficiency, resulting in abnormally high fuel consumption.
  • Lack of condensate return: Malfunctioning condensate return equipment requires more fresh water makeup to be used, resulting in higher fuel consumption.
  • Poor control strategy: Multi-boiler installations need to be sequenced/staged properly to ensure that the appropriate amount of boilers is online. Too many boilers online will result in higher fuel consumption.
  • Rich combustion: When combustion is tuned too rich (low O2%), there’s more fuel entering combustion than is required for operation, resulting in higher fuel consumption.
  • Short-cycling: If the boiler is grossly oversized and doesn’t have sufficient turndown/modulation to react to the changing loads, the boiler will cycle on and off excessively, resulting in higher fuel consumption.
  • Waterside fouling: Scale buildup on the waterside of the boiler will reduce heat transfer and efficiency, resulting in abnormally high fuel consumption.