Installation of Water Sourced

Geothermal Ground source heat pump

in Maryland By G&S Mechanical 

Written by Scott Meenen N3SJH,
    The ground source or Geothermal heat-pump system is supposed to be the most energy efficient and cost effective means of heating next to a solar hotwater system or solar energy. If you do the math it is supposed to beat natural gas.
    The reason heat pumps get such a bad reputation is that they don't deliver the heat when you need it the most, because the outdoor coil is in the same air that is making your house cold. If it is 10 degrees outside the coil can be below 0 or -10. With geothermal you are dealing with ground or a body of water that is from 50 to 30. Thirty degrees may sound cold but when it is 10 out with the wind blowing and wind chill factors below zero then 30 is not so bad especially as far as your system is concerned.
    This Ground source system is installed in a house in Maryland that originally had just electric forced air heating. The electric bills were so high that the owners did not use the electric heat system except when they went on vacation to keep the house from freezing. Otherwise they just burned wood or kerosene a very inexpensive way to heat but a nuisance.
    Unlike most geothermal systems this one doesn't use vertical well or ground "slinkies". This one has the coils buried in a body of water in a river. The same system can be used in a pond. This way we can cheat and use only 500 total feet of polyethylene tubing for a 4 ton system instead of several thousand feet. The reason for this is that water has a very good thermal conductivity compared to dirt which is about R5 per inch.
    Since this system is using a body of water it is hoped the the temperature of the loop won't get below 40 degrees F where water is the densest. Many ground systems that are sized too small the loop temperature can get below freezing and not thaw out until cooling season. It turns out the water temperature runs about 30-35 when there is ice frozen on the top.
    This system is good study for a high school science fair project and for college study. I believe the University of Oklahoma has a course on the subject.
Ground source glycol loop pumped by a Grundfos 26-99 and a Amtrol expansion tank Refrigeration heat exchanger also known as a chiller

    Images of heat exchanging (also known as a chiller) portion of ground source heat pump. The coil is made of Cupernickle which is similar to copper. Notice heat exchanging coil to right and circulating pump (which is made of cast iron and steel) and expansion tank on left.
    This equipment is located in the customer's basement near the compressor. This geothermal system has been completely field built except for components like the pump, heat exchanger and expansion tank. This equipment doesn't have the refrigeration lines connected yet. I will show that in another picture.

Bleeding the air out of the glycol solution in the ground loop The author checking the refrigeration system and the Sporlan sight-glass and thermostatic expansion valve
    Purging the air from the glycol solution (Sierra Anti-Freeze) in the system before closing it up and doing a final pressurization. On the right the author checks for proper refrigerant flow through the sight-glass connected to the filter dryer. The 4 ton Sporlan thermostatic expansion valve is on the left.
    Being a field built system I placed the tev the best I could for installation and service. Not shown this system like any Real refrigeration systems have a liquid line solenoid valve. To turn this system on and off I do not stop the compressor but instead close off the refrigerant liquid line and pump out all the vapor from the low side and let the system go off of low pressure. To restart the system the solenoid valve coil is energized with 24 Volts AC. from the thermostat.

The results are in

    After running this system for one month (December 2000) the customer finally got their electric bill and the results are staggering. This month of 2000 was one of the coldest on record for Maryland and most of the country. Their normal electric bill in the winter averages from $80 to $100 keeping in mind that they have used the wood stove and kerosene heaters to keep the house warm for the last 15 years. They have electric hot water and no clothes dryer. During this month of December they kept the wood stove and kerosene to a minimum but did have to run an "ice eater" to break up ice near their piers.
    The resulting electric bill was $158.00 now keep in mind that they were not using electric heaters that would run up their bill other than the electric devices inside the house and that the domestic hot water was provided by the hot gas from the compressor most of the time. This means that their heating bill is $58 as opposed to the wood stove and kerosene. This is a fantastic result for a 4 tons system in a rather large home. To top it off I am having some problems with the refrigerant heat exchanger not being adequate (the suction pressure runs about 20psig) and I will make a custom new one soon. This system will also heat the swimming pool in spring)

  1. Blower: usually a squirrel cage centrifugal air moving device. Will move large volumes of air relatively quiet. Will use less energy with more back pressure.
  2. Fan: a paddle type air moving device used where noise is not a major consideration. Will use more energy with more back pressure.
  3. Combustion blower: A blower used on high efficiency furnaces or oil burners to move combustion air. usually 1/20 to 1/6  horsepower.
  4. OEM: Original equipment manufacturer.
  5. Horsepower: 746 watts (ENERGY OVER TIME)
  6. KW Kilowatt (1000 watts) or 3400 BTUs per hour. (ENERGY OVER TIME)
  7. KWH Killowatt-Hours (1000 watts for 1 hour) or 3400 BTUs. (WORK)
  8. RPM: revolutions per minute.
  9. Service factor: the extent to which a motor can be safely overloaded beyond its name plate ratting without over heating.
  10. Air over horsepower: The rating of a motor assuming air flow through the windings usually as a result of the air moving device.
  11. SAE: Society of Automotive Engineers.
  12. Ton: 12,000 btus of cooling per hour the name comes from melting one ton of ice per day.
    This page will be updated soon
 Good Luck Scott
If your heat pump forms ice outside in the heat mode click here.
If your air conditioner or heat pump ices up in the cooling mode click here.
If you have water leaking problems with your air conditioner  click here to solve it.
To learn about the best thermostats click here.
To learn the color codes of thermostat wiring click here
To learn more about heat pumps in general.
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Good luck Scott.

    If you were looking for Ice Machine repairs click here.

Written By:  Scott Meenen N3SJH of:
Specializing in Mechanical, Controls and Electrical Modifications Of
Heating, Air-conditioning, Refrigeration, Cold storage,
Ice Production and Food preservation.
Anything having to do with Heat and Energy.
Serving MD, DC, and Northern VA.
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                 This text written by: Scott Meenen * G & S Mechanical
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