Chef Werner is furiously slicing carrots for his Saturday evening rabbit stew special. In his haste, he cuts a deep gash in his pointer finger. Instead taking a trip to his local ER, he covers it with a Band Aid and keeps right on slicing. In the coming days, he notices a red line running from the tip of his finger up to his elbow. He ignores it and continues on with his daily activities. Later that month, he decides to change the bandage. The offensive odor that permeates from his finger sends him over the edge and finally to the door of his doctor’s office.
What does this graphic story have to do with energy efficiency? Because Chef Werner covered the problem with a Band Aid instead of taking care of it correctly, he now has to have a costly surgery and missed work time to fix the gangrenous infection. This is not all that different from Band Aids being used on HVAC control systems – ok, maybe a little.
Dorothy in room 210 at ABC Inc. is cold and complains to maintenance. The building operator looks at the control system and notices the air flow is only at 30%. The operator “locks” the flow to 100%. Problem solved – Dorothy is comfy. Assuming she doesn’t get too warm or too cold again, this override remains and everyone is happy. Right? Not quite. The operator doesn’t realize how much this one small override (the Band Aid in this story) can increase the energy use of the building.
Changing airflow rates is not the only thing that can cause waste. Another recent example includes a facility with two large air handling units with 50-HP fans – two years ago during an evening meeting, someone overrode the scheduled unoccupied periods in an unusual place within the control system. This system has been operating the fan, heating, and cooling for 8,000 unnecessary hours since then. Everyone thought the system was scheduled, but it’s really banging away at 100% reheating all night long. Indeed, the system appeared to be scheduled, but the give away was the trend noted on the digital control system. If the fan is off, how can there be 2 inches of static pressure within the system throughout the night? It isn’t often that building operators check their control system at midnight to make sure the unoccupied controls are set correctly.
Overrides are seen quite often, and as a result, systems may operate inefficiently. If building operators don’t fully understand what the system is doing, advanced control strategies can easily become unintentionally disabled, leading to more waste. The bottom line – a building’s HVAC system is not a furnace in a basement – it’s fairly difficult to operate efficiently. Every time the system is overridden, it’s like a band aid is placed on that festering wound. It’s a quick fix but could lead to a nasty, expensive case of gangrene. Not a good situation for Chef Werner, or for building operators and owners.