Geothermal Rescue – Closed Loop Too Small and System Won’t Cool – West Tisbury


This is an on-going geothermal “rescue” that involves increasing the cooling and heating power of a large geothermal system.  The original system was designed for a cooling setpoint of 76 F which meant that the outside geothermal field was quite small.  Cooling the house to 72 F or 70 F was a strain on the outside geothermal field (the geothermal water got warmer and warmer) and on the aging R22 geothermal heat pumps.  During the peak heat in summer, the heat pumps would go off on faults because the incoming geothermal water temperature was too high (around 105 F).

There were two directions to take to resolve this situation – add more closed loop geothermal wells or install a fluid cooler.  Both directions would be effective in dropping the temperature of the geothermal water, but a fluid cooler was less invasive, easier to site, and ultimately less expensive.

As the project progresses, we will add more pictures and descriptions.

The equipment in the picture above is the 25 ton fluid cooler that will drop the geothermal loop temperature 10 F.  It has three cooling fans that will be driven with a variable speed drive to ensure quiet operation.


We had to rework the inside geothermal piping near the loop circulators to accomodate the added flow necessary for the remotely located fluid cooler.





We had to install a sturdy support structure of unistrut to accomodate the weight of the balancing valves.





Careful alignment was necessary to get the balancing valves located correctly so that we could adjust them and yet fit all piping into a tight footprint.





We were very pleased with the final result – both balancing valves were aligned and easy to adjust.





The balancing valve on the left is for the existing closed loop geothermal well system and the balancing valve on the right is for the new fluid cooler.  (55 gpm and 40 gpm respectively)





Once we received the fluid cooler, we opened it up for inspection.  Solid copper fins were spec’d for resistance to our salt air environment.   This fluid cooler has a capacity of 25 tons of cooling power and weighs 1300 pounds.




We installed 1-1/2″ black poly well pipe supply and return lines from the back of the carriage house to the remote location of the fluid cooler.  Here we can see the copper pipes coming through the shingles and immediately dropping below grade.






The fluid cooler was about 80 feet from the back of the carriage house so we had to size the circulator pump for the friction loss of the pipe and the fluid cooler. Here we are using large rocks to hold the stiff plastic pipe in place until we can backfill the trench with fill.





To prepare the fluid cooler for the move to its final location, we removed the three fan blades and fan guards.





We then used a Bobcat (skillfully piloted by Russell) to carefully lower the fluid cooler into its upright position.





To provide the necessary rigidity during the transport to its final location, we placed a 16 foot long timber across the top of the fluid cooler and assembled ratchet straps to the timber.





We carefully lifted the fluid cooler and adjusted the ratchet straps to ensure that the unit was not sagging or bowing.  The fluid cooler itself was almost all copper inside and any tweaking of the alignment of the body would result in a permanent deflection.  This we wanted very much to avoid as it would lead to broken braze joints and fan clearance issues.  Andrew Kahl looks on to ensure a straight and even lift.



Russell carefully crept forward with the fluid cooler trying to minimize swinging and jerking of the fluid cooler / timber assembly.  John Cotterrill serves as Russell’s eyes for obstructions ahead.




While the fluid cooler was being rigged and slowly transported, the NMD team was prepping the landing area with concrete blocks carefully leveled.  A lot of measurements were made to ensure that the installation of the fluid cooler could be done in one move. Mariah, Nate, and Dan did a great job of aligning all of the blocks.




The move slowed as the Bobcat, fluid cooler, and timber approached the stone wall.  Russell had to carefully lift the fluid cooler as he was going up hill but had to minimize swaying of the unit.




The critical part of the move was approaching as Russell started to lift the fluid cooler above the stone wall.  We had made extensive measurements of the reach of the Bobcat’s forks at different elevations but wouldn’t know for sure until we were over the wall.





Russell carefully lifted the fluid cooler above the stone wall and slowly advanced with the heavy load





Success!  The fluid cooler cleared the wall and we had it lined up with the landing pad.  Now we could extend the steel legs to the correct final height.





Once the legs were bolted at the correct height, Russell lowered the fluid cooler onto the concrete blocks and we unstrapped the long wooden timber.






We carefully measured the fluid cooler and determined that there was no deflection in the body and the top and sides were level and plumb – no damage to braze joints or seams.





Here is a shot of fluid cooler behind the stone wall.  Enough room was left between the wall and the cooler to permit planting of shrubs and trees to further hide the unit from the driveway.





We assembled a framework of strut to support the supply and return connections as they were exposed and vulnerable to damage.





We made the final connections to the 1-1/2″ plastic poly supply and return pipes using the ProPress copper connection tool and fittings.






2017-09-29 13.31.38We completed the repiping of the Carriage House mechanical room to accomodate the installation of a fluid circulator that would move 40 gallons per minute of geothermal water through the fluid cooler.   We also installed a booster circulator in the Main House mechanical room to circulate the 40 gallons per minute from the Carriage House fluid cooler system into the main geothermal system.



We adjusted the three cooling fans in a thermal cascade – each fan would turn on if the water was 2 degrees hotter than its setpoint.  We found that the system was able to run using only two fans for most of the summer due to our generous sizing of the fluid cooler.


Our goal is to be Martha’s Vineyard’s premier plumbing and HVAC shop – we appreciate the opportunity to show you some of our work.