Why We Trend Data and Why It's Important
RCx for the Rest of Us Session 3
Think of trending data as an EKG of your building’s critical systems. Each part of your facility has a history of data to pull and collecting that informa
tion from the beginning is a critical step in finding which measures were successfully implemented. When the data is taken a year or two from the date of implementation, the data will show if there was persistence in the commissioning measures. Ultimately, data trending allows us to determine whether or not the program implementation was a success and helps us to keep a finger on the pulse of overall building health.
According to David Perry, Field Manager, Energy Efficiency Programs, at PECI, “Trending data is like taking a snapshot of the building every 10 or 15 minutes. It helps us answer critical questions that can affect a system’s operations such as; what is the outside air temperature?; what chillers, pumps, and boilers are operating?; what speed are the fans and the position of the economizer?; what is the pressure in the duct?”
Perry said, “All of these data ‘points’ (and more) can be graphed together and analyzed, helping engineering to identify retro-commissioning measures and potential energy savings.”
To capture this information we commonly use data loggers:
A data logger records data over time with a built in instrument or sensor based on a digital processor similar to a computer. Data collected can be for general or highly specific purposes. For retro-commissioning projects, data loggers are generally set to collect data for approximately two weeks, possibly longer if it is over a holiday break or outside temperatures are outside the “norm”.
Some of the common data trending for retro-commissioning includes:
- Load profiles for energy consumption management
- Temperature, humidity and power use for heating and air conditioning efficiency studies
- Outside weather recording (wind speed, wind direction, inside and outside temperature, relative humidity, solar radiation)
recording (water level, water depth, water flow, water pH, water conductivity)
- Gas pressure recording
- Monitoring for maintenance and troubleshooting applications
All data collected during retro-commissioning eventually ends up at the sponsoring utility and the Public Utility Commission (PUC). Data is used not only to benchmark the buildings, but can also calculate the cost savings/sq ft and energy savings/sq ft. average, can be used in measurement and verification processes, can provide the results or persistence of the commissioning, and since the utility programs are funded by tax dollars, the PUC uses the findings to either keep funding the programs or steer the dollars to a better program.
According to Perry, “Trending data is an integral part of any retro-commissioning project.” So keep your finger on that pulse and trend the data of your building, you may be surprised at what you discover.
Please feel free to email me with specific questions and I can help guide you through the process. firstname.lastname@example.org
Introduction January 21, 2011:
Retro-commissioning (RCx) for the Rest of Us
Session One February 18, 2011 :
To commission or not to commission?
I think I want to participate, but I don’t understand the process…
Session Two March 18, 2011:
Qualifying a RCx provider for your RCx
Engineers, don’t take offense!
Session Three April 22, 2011:
Why we trend data and why it’s important
Session Four May 20, 2011:
The Hidden Measures That Can Pay Off in Energy Savings
June 17, 2011 July 15, 2011:
The importance of persistence in RCx
Session Six July 22, 2011: