In the posts leading up to this, I have been looking at how would deploy a limited number of data loggers to understand the system dynamics and energy consumption patterns of heating hot water system I am working with on a current retrocommissioning (existing building commissioning) project. In this post, I will look at how I decided what to monitor to help me understand the energy inputs into the system; i.e. the boilers, which are pictured below, along with the freestanding boiler room.
Having hung out in the boiler room a bit as I was developing the system diagram, I had noticed that the boilers seemed to short cycle. Specifically, they seemed to come on and fire for 5-10 minutes, then cycle off for 2 -3 minutes and then repeat the cycle. There are a number of undesirable issues associated with such an operating pattern, especially if it persists for a long time, so I was very interested in understanding that in addition to getting a feel for what was going on with the system in general.
In addition, until I was sure that the Newport ASOS site weather data was a reasonable reflection of what was going on at the lab, I felt that I should monitor the ambient temperature and relative humidity at the site.
After a bit of thought, I realized that I could use one of the loggers with the built
in temperature and relative humidity inputs as well as external inputs to monitor the ambient conditions and the boiler supply and return temperature, thereby painting a picture of the local environment and the general load on the boiler plant. This left me with one logger to use to understand how the three boilers were staging and get a feel for the energy input to the plant. (Remember, I had already dedicated one logger to monitoring the return temperatures from the HVAC loads and the current used by the HVAC hot water pumps, per the post titled Data Logging a Heating Hot Water System; Where’s the Load?)
After some consideration, I realized that the boiler room had a dedicated electrical panel and that the only loads on the panel were the boilers, the boiler pumps, the boiler controls, and some light lighting and receptacle loads. After taking a look at the boiler and pump nameplates, I as fairly certain that if I monitored the panel amps with a 50 amp CT, I would be able to identify the operation of each boiler and its pump. This would help me understand the short cycling phenomenon that I was already curious about as well as the number of boilers operating at any given time, which will be an indication of the energy input to the system.
So there you have it; the final details of my deployment plan for the heating hot water system. In the next post or two, I’ll put up some pictures of the actual deployment for
the heating hot water system and also touch on some issues that came up as I deployed loggers on the other systems in the facility. After that, once I have the data, I’ll share what I found out with you.
Senior Engineer – Facility Dynamics Engineering