The best system diagnostic tool you can have as a GCHP system designer, a service technician, a building manager or owner, is an ongoing record of the fluid temperature leaving the GHX and entering the heat pump. This can tell you if the system is operating as it should or not. What does this mean for the different stakeholders of a system?
For the system designer: It means first of all, that the person running the system should have an operating manual that tells him or her what temperature the fluid from the GHX should be. With an hour by hour energy model of the building, there is software available that will calculate on an hour by hour basis, what the predicted temperature of the GHX fluid should be throughout the year. A chart should be provided to the building owner / operator that shows what the predicted operating temperature should be. Of course, weather conditions in a specific year will cause the predicted temperature to deviate a few degrees, but it will provide a fairly accurate annual temperature profile. It also means that the owner / operator should know which temperatures to record, or if it has a data logger or an automated control system, how to gain access to the information. Automated controls systems are available that provide the capability to input the predicted temperature profile and compare it to the actual operating temperatures and flagging deviations from the expected temperatures.
For the service technician: A record of the actual operating temperatures of the GHX provides a good diagnostic tool in comparison to the predicted temperatures can provide a good indication of what may be causing problems in system operation.
For the building owner / operator: It means that an ongoing record of the temperature data should be maintained. Something as simple as recording the fluid temperatures at approximately the same hour every day will provide an adequate trend line of the GHX operation. This can be invaluable in predicting potential operational problems and dealing with them well before they cause a system failure. It can also indicate potential problems that may be caused by changes in how a building is used and allowing changes to be made in the system operation to compensate before causing the system to fail.
Monitoring the operation of a system is discussed in detail in the Certified GeoExchange Designer course.
In my blog I'll be expressing my opinions about what I've the learned about ground coupled heat pump (GCHP) systems over the last 30 years. I've been very fortunate to work with many interesting people who are passionate about this technology...engineers, geologists, mechanical contractors, drillers, excavation contractors...in different parts of the world. I've learned a lot from them and will be using this forum to pass on some of the things I've learned and feel are important. Please feel free to use this information if you feel it's worthwhile...hopefully you can avoid some of the same mistakes I've learned from.