The Big Equations in Energy Work

There are seven keys to the kingdom.

You can go to college and get an engineering degree, but the equations that are used most often in the energy conservation business are relatively few, and they are relatively simple to work with.  Indeed, I don’t see why someone without a degree could not learn these equations and become effective in using them pretty quickly.  I am not going to run through units right now, but we’ll get to that.  Let’s run through the big 7, shall we?

Thermal power in air and water flow is computed as:

  • Btuh = CFM * (To – Ti) * 1.08  (for Air)
  • Btuh = GPM * (To – Ti) * 500  (for Water)

Mechanical power for fans and pumps is computed as:

  • BHP =  (CFM * Pressure) / 6356 * Eff)  (for Fans)
  • BHP =  (GPM * Pressure) / 3960 * Eff)  (for Pumps)

Electrical Power

  • Watts = Volts * Amps * pf          (single phase, where pf is Power Factor)
  • Watts = Volts * Amps * pf * 1.7  (three phase, where pf is Power Factor)

Affinity Law

  • Power_new = Power_old * (Speed_new / Speed_old)^3

That’s really it.  You can do most energy engineering with these seven equations.


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