Geothermal Rescue – Closed Loop Circulator Too Small and Heat Pumps Won’t Work


This geothermal rescue involved a closed loop system that had 21 geothermal heat pumps that would not stay operating – they were going out on fault codes several times a week.  The fault codes were either low temperature in the winter or high temperature in the summer.  When we were called to evaluate this system, we were told that the heat pumps were all defective and unreliable.

But upon closer inspection, we determined that the heat pumps were fine; they were just not getting enough geothermal water to operate reliably – they needed more flow.  The original design was to have two loop circulators piped and controlled so that only one circulator ran at a time and that it would be large enough to meet the needs of all of the heat pumps.  We quickly realized that this original design and installation was woefully inadequate for the needs of all 21 heat pumps.

failed BG circ


The original circulators themselves (the blue circulator in the picture at left) were too small and couldn’t meet the needs of all of the heat pumps – which explained why different heat pumps would have fault codes at different times.  It all depended on how many heat pumps were working at a time and what the heating or cooling load was.


The documentation for the original design and specs were incomplete so we carefully inspected every fitting, every length of pipe, and every connection to each of the 21 heat pumps.  This allowed us to develop the true flow and pressure requirements needed by all 21 heat pumps.  We then added a safety factor to permit for future expansion.   We ordered the correct loop circulators and prepped the piping.

BG circ and Grundfos circ

Because the house was occupied, we had to make a seamless transition from the old inadequate blue circulators to the new correctly sized circulators.  We did this by removing one of the blue circulators so that we could install the new replacement circulator (larger black circulator on right) in its place.  We turned on the new circulator, turned off the old circulator, and all fault codes vanished.  All of the heat pumps worked correctly and reliably!



We then were able to install the other new loop circulator so that we would have redundant pumping capability from the tandem loop circulators.  Since this project was completed in 2012, we have had no flow related fault codes or loss of cooling or heating from any of the 21 heat pumps.



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