An open loop heat pump is slightly different from closed loop heat pump. In closed loop system there is an anti-freezing solution circulating through it. This solution absorbs heat from the water or ground underneath the surface and carries it up to warm the houses. In open loop system instead of an antifreeze solution, water is circulated from the source through the geothermal heat pump's heat exchange coil and then returned to the earth. The heat of the water is then extracted for heating. In the cooling season it rejects heat from your home into the water.

If you have a well near your house, where you want to install an open loop ground source heat pump, here are three main criteria that your well should meet for smooth functioning of the geothermal heat pump-

What is the capacity of the well?

It has often been found that although some houses have wells near them but their capacity is hardly enough. A geothermal heat pump with open loop would need 1.5 gallons per minute for per ton of capacity. On average a moderately sized house requires three tons of heating and cooling unit. In that case it would be 4.5 gallons per minute. If the temperature of the water is lower than required, then it may increase the flow requirements. In warmer climates, when the pump is in cooling mode, the water flow rate may need to be increased so that the pump is able operate with efficiency. .

The annual amount of water used by a 3-ton geothermal heat pump is about one million gallons a year. However there is a brownie point. As ground source heat pump does not consume water, it gives back all the water that goes into it. The water is safety returned to the source to be used again. These pumps do not change the water quality, only water temperature is altered as the heat is extracted from it

How good is water chemistry?

Remember, the quality of the water should be good, otherwise it will frequently lead to scaling of the heat exchanger. This will need frequent professional intervention to clean with an acid flush. Bad water chemistry can also dissolve the water-to-refrigerant heat exchanger out of your geothermal heat pump. The mineral profile, pH, and temperature of the water must be within required limit to be compatible with the heat exchanger. Too high or too low pH level can dissolve the heat exchanger. Again, if the temperature of the water is too high, the acid or alkaline will dissolve the heat exchanger.

Feasibility

If the operational cost of the pump is too high then it is better not to install it. The main cost of open-loop heat pump is on account of the water being pumped against gravity, and the type of motor used in the pump. Previously submersible pumps that were used in open loop systems were powered by permanent split capacitor (PSC). Now ECM well pumps are available. These are quite efficient and cut the cost of pumping water by 60 percent, compared to a PSC motor. The only flip side is their cost. Depending on the model, the pump may cost $1200.00 to $1800.00.