A LONG, LONG TIME AGO
Cavemen already understood 10,000 years ago that the temperature underground (or in a cave) is constant year round no matter how cold or how hot the outdoor temperature is.
Geothermal heat pumps get their efficiency on the fact that the earth temperature remains warmer than the air above in the winter and cooler than the air above in the summer, very much like a cave.
The first geothermal heat pumps hit the market in the 1940s, but the benefits of geothermal heat pump still largely remain a mystery to the public.
WHAT IS THE DIFFERENCE BETWEEN A GEOTHERMAL HEAT PUMP AND A TRADITIONAL HVAC
Traditional HVACs are air-cooled systems while geothermal heat pumps are water cooled systems. Traditional air-cooled heat pump are subject to outdoor temperature swings; from 110°F in the summer to -20°F in the winter while geothermal heat pumps take advantage of 50-75°F water temperature year round. Depending on your region, the temperature 20' below the ground is around 50-75°F. In the Dallas-Fort Worth area the underground temperature is 70°F year round.
Geothermal heat pumps work just like traditional HVAC systems; they use the same compressor, same refrigerant, same evaporator coil, same blower, same controller and same thermostats. The only difference is that geothermal heat pumps use the constant ground temperature to heat the house in the winter and cool the house in the summer by running a series of closed loop pipes that carry water from the compressor to the ground.
The water inside the pipes works like a conveyor belt; carrying the heat out of the house in the summer and absorbing the heat out of the ground in the winter.
WHY GEOTHERMAL HEAT PUMP
All HVAC systems remove the heat out of the house in the summer due to heat gain and add heat into the house in the winter due to heat loss. HVAC units are rated in BTU (12,000 BTU = 1 ton).
The BTU rating indicate how much heat the A/C unit can remove in 1 hour when the outdoor temperature is 95°F. For heat pump in heat mode, it indicates how much heat the unit can add when the outdoor temperature is 47°F.
The capacity of ALL air-cooled HVAC system is affected by outdoor temperatures. In the summer a brand new perfectly installed 4 ton A/C unit can lose as much as 5% of its capacity when the outdoor temperature reach 100°F and the capacity keep decreasing as the outdoor temperature increase. The same goes on in the winter, as the outside temperature drop, the capacity of an air source heat pump drop significantly requiring an electric strip to offset the loss of capacity by the equipment.
Wear and tear also affect HVAC cooling and heating capacity to the point where a 10 year old unit may no longer have enough capacity to cool the house in the summer and heat it in the winter.
Outdoor temperature on the other hand has no effect on the efficiency of a geothermal heat pump; the geothermal heat pump uses the constant ground temperature as a heat exchanger; it dissipate the heat into the ground in the summer and it absorb the heat out of the ground in the winter.
To see how the outdoor temperature affect air-cooled A/C unit click on the image below. (Manufacturer's data for a SEER 21 unit)
HOW EFFICIENT REALLY ARE GEOTHERMAL HEAT PUMPS
Geothermal heat pumps are so efficient in North Texas there is no need for a back-up electric strip, saving a huge amount of money in the winter while keeping the house at a very comfortable 72°F.
In the summer geothermal heat pump offer plenty of capacity even when the outdoor temperature reach 110°F keeping the house at a comfortable 75°F while maintaining the humidity around 45-50%.
Due the extra capacity of geothermal heat pumps over air-cooled units, geothermal heat pumps must be sized with a proper load calculation.
Geothermal heat pumps come in package unit meaning that the compressor is only 2 feet away from the evaporator coil increasing the efficiency of the equipment and reducing significantly the amount of refrigerant necessary.
Because geothermal heat pumps do not use a fan, they are usually installed inside the conditioned space; there is no wear and tear due the weather and having the compressor and blower inside the conditioned space also increase the efficiency of the equipment.
The refrigerant running thru a geothermal heat pump is the same R410A as an air-cooled system but in a geothermal heat pump the compressor runs at much lower pressure and temperature putting less stress on the equipment.
Geothermal heat pump will also heat your water for free, saving another 30% on your energy bill.
GEOTHERMAL HEAT PUMPS ARE FULLY ASSEMBLED AT THE FACTORY; JUST ADD WATER.
Air-cooled system are composed of multiple elements assembled by the contractor on the jobsite increasing the risk of a bad installation. Each component (compressor, blower, furnace, evaporator coil) must be carefully chosen to obtain the published efficiency. Multiple configurations are possible making the process very complicated for the designer, installer and supplier .
Geothermal heat pumps come fully assembled from the factory making it much easier to obtain the published efficiency.
Would you rather buy your new car assembled at the factory or buy it in kit and have it assembled at the dealership?
To see inside a geothermal heat pump click on the picture below.
TRADITIONAL AIR COOLED SYSTEM SEER RATING COMPARE TO WATER COOLED GEOTHERMAL EER RATING
All air cooled HVAC systems are rated in SEER using 82°F outdoor temperature while water cooled HVAC systems are rated in EER using 95°F outdoor temperature. At 95°F outdoor temperature, a SEER 21 unit has similar efficiency as a SEER 13 unit (EER 13.2 VS. EER 11). Geothermal heat pump on the other hand have much higher EER rating at 19.20 and plus; that's almost 50% more efficient than a SEER 21 system and 75% more efficient than a SEER 13 system.
To see the AHRI SEER and EER certificate for air cooled equipment compare to geothermal equipment click on the image below.
REQUIREMENTS TO INSTALL GEOTHERMAL HEAT PUMP
Geothermal heat pumps require access to the underground constant temperature. There are different options when it comes to installing the "water side" necessary for a geothermal system. The "loop" design depends on your location, climate and land space. Knowing which option is best for you will maximize the efficiency of the system year round for a long time.
Here in the North Texas area drilling vertical borehole is the best available option. In some area where the soil stays compact and humid year round horizontal loop can be a great option as long as there is land space available. Another option available is the use of a lake, a pond or a large body of water; be very careful when choosing this option; in case of a drought the lake level could drop to the point where the system could fail.
The primary reason geothermal heat pumps do not perform to their capacity is due to bad installation, a bad installation will also affect the lifespan of the equipment.
A properly designed, sized and installed geothermal heat pump system will always outperform an air-cooled system hands down, no matter what SEER the air-cooled system is and that includes ductless systems. It's physics!
To see a video of a drilling job, click on the video below:
GEOTHERMAL HEAT PUMPS CAN BE RETROFIT OR INSTALL IN A NEW CONSTRUCTION
Since geothermal heat pumps operate just like traditional air cooled systems they can be retrofit to any homes as long as there is room to run a loop system. Geothermal heat pumps use the same duct system as air cooled systems.
A load calculation must be perform before sizing a geothermal heat pump for new construction or for retrofit.
BENEFITS OF GEOTHERMAL HEAT PUMP
GEOTHERMAL HEAT PUMP VS. AIR COOLED A/C COOLING CAPACITY COMPARISON
To see a comparison in capacity between a SEER 21 air-cooled HVAC unit and a geothermal heat pump click on the image below to see the manufacturer's data.