Introduction

Most equipment does not continuously operate at its rated, name plate capacity. A Load Factor is most often an estimate of some percentage, lower than 100%, to account for the equivalent Full Load Hours, or average energy usage. Some equipment may actually be “on” and may even be running continuously, but not drawing a full load.

General Procedure for Estimating a Load Factor

  1. Obtain the actual name plate rating of the equipment. For electric equipment, the rating may be in Horse Power, watts, or amps at a certain voltage. For gas equipment, the rating will be in BTUs.
  2. Through observation and/or questions, determine the “on” period of operation, in hours per day and days per week
  3. Determine how the equipment is controlled; ie: does it have an on/off cycle that is manual or automatic; does it have a less-than full-on ability, such as variable speed control or variable fire burner
  4. Count the number of motors/compressors/burners that the equipment has. For example, a chiller with two compressors and motors that both have variable speed will have a substantially different load factor than a unit with a single fixed-speed motor

 

RULEOFTHUMBGeneral Rules of Thumb

(Name Plate Rating Input) x (On-Hours per Day) x (Load Factor) = Average Usage per Day

 

 

 

 

 

 

Equipment

Load Factor

Comments

Space Heating 60% For equipment that actually runs; 0% for standby equipment; less for shoulder months
Air Conditioners 60% For mid-summer months; less for shoulder months.
Air Compressors 60 – 80% For heavy use applications;
Refrigeration 40 – 100% Lowest during winter months; consider volume of warm product moving in for production applications;
Food Preparation 30 – 80% Use lower number for average daily, and higher number for hours limited to peak service times
Lighting 100% Occupied hours and up to 50% for unoccupied hours depending on building use and cleaning schedule
Office Machines 10% Copiers, faxes, etc.
Computers 100% Servers and main frames are always on; desk top units may always be on but go into a power saver mode when not in use
Gas Process 20 – 100% Highly variable; batch processes with long cycle times tend to have lower load factors due to hold and cool-down parts of the   cycle. Continuous processes have load factors that resemble the amount of product throughput – the faster and higher volume of product, the higher the load factor. Batch process equipment tends to have larger burners for faster heat-up, therefore the average usage is lower over the full cycle.
Stamping and Milling Machines 40 – 60% Most electric motor driven equipment that cycles has less than a 50% load factor; even lower with variable speed drives

 

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