Data Logging a Heating Hot Water System; An Overview of the Targeted System

I recently initiated a string of posts on the topic of deploying data loggers and began the string with a discussion of how I developed my monitoring plan on a current existing building commissioning project1.  One of the systems I decided to focus on was the heating hot water system which is illustrated in the system diagram below.  I’ll use this post to familiarize you with the system a bit and then discuss my logging targets in subsequent posts.


Reducing that to a size that will fit on the web probably makes it hard to read, so you can use the preceding to get a feel for the general arrangement and the cropped out portions below to see the details of the boiler plant;


the HVAC loads and related pumps;


and the process loads and related pumps.


This is my first pass at developing a system diagram;  not a lot of detail yet but it does show the general arrangement of  things and will allow me to highlight some of the things that caught my eye about the system and influenced my decisions about what points to pick up with the loggers I had available.

My challenge was to use the three loggers I had available to me to my best advantage to help identify opportunities to improve system performance and optimize energy consumption.   I had at my disposal:

The boilers serving the system are located in a stand-alone boiler room.  Each boiler is equipped with a circulating pump that runs any time the boiler runs. Originally, the process water system was served by an independent heat source from the one serving the HVAC systems, but a recent project that replaced the original heating equipment interconnected the process heating water system with the HVAC heating water system and served them both from a common boiler room.

Heating water pumps serving the HVAC processes are located in one of the main mechanical rooms where they circulate water from the boiler plant to preheat coils in the air handling systems and reheat coils located through out the facility.

Heating water pumps serving lab process loads are located in a different mechanical space serving the pollution abatement equipment associated with the marine water that the labs use for their research.  The process hot water pumps circulated hot water to various laboratory loads associated with the various research projects that are going on in the lab.

All of the pumps need to operate continuously given the nature of the research and the nature of the make up requirements associated with the lab hoods and laboratory air handling systems.  Thus, there is a year round load on the boiler plant as illustrated in the average daily consumption graph below. This graph is discussed in detail in a post last July on the topic of Average Daily Energy Consumption Analysis.


You will notice that the baseline consumption for the system is 35-40% of the peak consumption.  Thus, the base load consumption of the plant represents a significant portion of the over-all energy use. 

This is a bit of a necessary evil given the nature of the labs and research, but it was my hope that we could optimize it once we understood what was going on.  Gaining such an understanding is the underlying goal of my data logging effort on the hot water system, which I will begin to describe in detail in the next post. 

David Sellers
Senior Engineer – Facility Dynamics Engineering

1.    Existing building commissioning is also known as retrocommissioning or RCx to many folks, but the industry is moving away from that terminology for a number of reasons.

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