By: Estatio Gutierrez, Building Engineer
October 31, 2016
When driving a car, you would never simultaneously hit the accelerator and brake with varying amounts of force to try and reach your desired speed. It would surely waste gas and add unnecessary wear-and-tear to your vehicle. The mental image of such a thing is quite comical. Now, imagine a commercial building instead of a car and it using simultaneous heating and cooling to reach the ideal temperature – it happens more often than you would think!
Over time buildings will naturally drift away from original operational targets. The systems that were once painstakingly commissioned and tuned will degrade due to a variety for reasons —from operational changes to maintenance issues to product failure. This was the case with Vista Peak Preparatory School in Aurora, Colorado. Within roughly four years, the school drifted away from LEED Gold certified operations and nearly doubled its energy intensity.
By deploying our technology-enabled services backed by our remote team of energy experts, data scientists and building engineers, provided the team at Vista Peak with the information and guidance needed to understand the building’s HVAC system at a granular level and pinpoint problems between equipment and programming, the detection of which would have otherwise been impossible. This access to previously unobtainable data uncovered the existence of simultaneous heating and cooling. The heating coil would control the heating in the morning and around noon turn to a pre-cooling function. The result was that during a short window of time the BMS system tried to both heat and cool the same space! (Read our Vista Peak case study to learn more).
This isn’t the only situation that could lead to the overlap of heating and cooling. Some more common situations that lead to this inefficient practice include:
- Overcooling at the Air Handler Unit (AHU) level could lead to electric reheats at the Variable Air Volume (VAV) level. This Issue could be addressed by implementing temperature and pressure setpoint resets, while keeping the VAVs satisfied.
- When heating equipment is turned on during the summer. This could lead the system to use simultaneous heating and cooling to meet the supply air temperature setpoints. It may seem logical, but this could be avoided by fully turning off the heating equipment during warm seasons and making sure the PID loops are tuned. The same principle applies during witner when cooling equipment should be turned off to avoid this issue.
- Overly tight humidity control settings. Humidity control involves some level of simultaneous heating and cooling. However, if the settings are too tight, it could also lead to an excessive amount of unproductive heating and cooling.
These situations would all translate to wasted energy and unnecessary increases in operational costs. The transparency that our 5i Platform offered in conjunction with our team of remote experts we have on call ensure that all aspects of a building’s HVAC system are working in harmony towards mutual energy efficiency and comfort goals.