Understanding energy use in existing, old buildings can be an extremely complicated undertaking. Without detailed meters throughout the systems it can be an extreme challenge to find where energy is being wasted.
In a recent project evaluating an existing building we found heat flow reversed in a tertiary hydronic loop. This led to temperatures on the return side of the heating hot water system actually being greater than the supply temperature.
Is this bad? Yes!
Is this normal? No!
Check out the image below from the energy dashboard we created. The data was trended using external sensors with a capture rate of a couple seconds.
Return temperatures should (normally) be below supply temperatures in heating systems. If you have temperatures that are flipped like this - make sure you dive into them to understand what's going on! Trending temperatures is one of the BEST and simplest trends to evaluate and a great way to understand how a building is actually programmed to operate.
The above scenario can occur if a building has cross connections, reversing flow due to odd piping arrangements, if control sequences are not optimized... any number of reasons.
Diving into the details of building management system (BMS) data is crazy fun, and challenging. We've found that the best approach is to take weather data, correlate it against a building's operating schedule and trended data, as well as any other BMS data that you can easily get. Since all the buildings we work on are unique and require custom solutions, we've built a set of Python libraries that allow us to analyze the data quickly, and explain the data succinctly.
We've built our analytics into a package named Mizan, which is fully automated. Our client's BMS systems send us a daily email of trends for the previous day, Mizan analyzes the data, makes recommendations, and suggests possible problems in an email which it sends directly to the client. This approach gives our clients the ability to take proactive actions to correct problems that don't generate alarms, that they otherwise wouldn't have known existed.