This past summer, complaints about the air conditioning were fairly abundant, and the electric bill was high. You just had a meeting with your boss and the plant controller. The controller did some homework prior to the meeting and presented the following facts:

  • The electric rate was the same as last summer.
  • The monthly electrical usage was significantly higher versus the same months last year.
  • The weather data might justify a little more cooling but definitely cannot account for this much difference.
  • The HVAC maintenance contractor’s reports show no coolant loss.
Your boss and the controller want you to look at the HVAC system and elsewhere to identify the source of the excess power usage. What are some things you need to do?

Did the controller happen to mention whether the HVAC maintenance contract had been scaled down from the complete service plan to the minimum for compliance with refrigerant control laws? HVAC systems can have inefficiencies due to factors other than leaking refrigerant. For example:

  • Condenser fins can fold over, resulting in reduced heat exchange. Solution: Use a fin comb to straighten these.
  • Condensers can clog with debris, such as cottonwood fiber, effectively insulating the heat exchanger coils. Solution: Wash down with a water hose; use other cleaning as recommended by the manufacturer.
  • Airflow across the coils may be incorrect. Solution: Adjust fan speed.
Your HVAC maintenance contractor should identify and correct such problems as part of maintenance. In addition, conduct vent pressure and vent flow tests, correct any losses in the air distribution system, and inspect:
  • Power quality at the compressor motors.
  • Integrity of building envelope (are you leaking conditioned air?).
  • Proper venting of heat sources.

Conduct a power quality survey of the entire facility to identify any non-HVAC power inefficiency issues. Before commissioning the survey, examine your largest loads with a power quality analyzer.