Weather Changes – a reason to monitor your GHX?

The size and configuration of a ground heat exchanger (GHX) for a ground source heat pump (GSHP) is designed for the energy loads of the building(s) it is heating and cooling. Energy loads for a proposed new building are calculated by simulating the building in a computer model, taking into consideration building construction, how it will be occupied, the design of the mechanical system, how the building and system is operated, and the weather that is expected. Weather files used in computer simulations are based on a Typical Meteorological Year (TMY). They represent a single “typical” year in the given location. But as we all know, weather changes from one year to the next. 2012 was the warmest year on record in Winnipeg. Two years later, 2014 was the coldest year in over 100 years. The average annual temperature was more than 6°F warmer in 2012 than 2014. Changes in weather affect the temperature and performance of a GHX. This graph shows the average monthly temperature of heat transfer fluid delivered to a 50,000 ft2 office building in Winnipeg, MB over several years. During the coldest year on record, the average temperature of the GHX was about 10-15°F colder than the temperature during the warmest year in 2014. An Ensure® Predictive Monitoring package measures the hourly energy transfer to and from the GHX as the weather changes. It sends a signal to the building automation system to activate a discretionary heating or cooing load to either: • Add heat to a GHX if the predicted temperature is decreasing, or • Remove heat from a GHX if the predicted temperature is increasing. Ongoing monitoring allows the Ensure® Predictive control system to proactively manage and optimize the temperature of a GHX rather than having to react to a system that has failed.