Some of these questions may seem too technical and have you thinking “who cares”, but they’re really not.  It’s a good idea to educate yourself about this technology before making a substantial purchase.  I see it kind of like hiring an attorney.  You can drop off a stack of files, say take care of it, and then forget about it.  The results you get may not have your best interests in mind.  It’s always better to educate a little, and then help yourself as much as you can along the way.  Contractors will be eager to inform, and surprised by your knowledge base.  Good luck…

General

1. What factors will determine the size of equipment that best fits my needs?
2. Would my home benefit from a zone system?
3. Can the system adjust its output capacity and airflow to serve small zones?
4. Will my existing ductwork handle the system being proposed?
5. What impact does undersized ductwork have on the system?
6. Can I monitor the exact energy consumption of my system and compare to my power bill?
7. Try to compare bids “apples to apples”.  Does the system proposed:
   1. Have two-stage operation?
   2. Have a variable speed blower?
   3. Have a full 10 year parts and labor warranty?
   4. Include excavation / trenching / plumbing / electrical / zoning?
   5. Include ductwork modifications and what are they?
   6. Include the “Hot Water Generator” option and associated plumbing?

Open Loop System:

1. Who will be performing the water quality testing on my well water?
2. Is the testing directly related to the water quality specification provided by the equipment manufacturer?
3. Will there be water noise during operation?  How will this be addressed?
4. Will you (the heating contractor) be installing all plumbing & components to support the unit?
5. How will I know the water flow rate through my heat pump?
6. What is the required flow rate for my heat pump?
7. Where in the plumbing is the water control valve located and why?
8. How will we address discharge water location?
9. What do I need to monitor during the first few weeks after installation?

Closed Loop System:

1. How will my ground loop / pond loop be sized?
2. What are the maximum and minimum temperatures of my ground loop?
3. Is the old saying “1 loop per ton” adequate for my system?
4. How long is each loop?
5. How much does it cost for an additional loop?
6. Why should I care about how many loops my system has?
7. Is the fluid flow in my ground loop laminar or turbulent and how do we know?
8. Why do fluid flow properties matter?
9. What is used for freeze protection?  Why?  Down to what temperature?
10. How will a circulation pump be selected for my ground loop?
11. Will my ground loop have a hydration system?
12. Can I monitor the temperature of my ground loop year-round?

Auxiliary Back-up Strip Heaters:

1. How much aux. back-up heat do you recommend?  Why should it matter?
2. Can I turn the aux heaters off?
3. How will I know if the aux. heaters are running?
4. Can I still set my temperature back down to 60 degrees overnite & then back to 70 for the daytime?

Knowledge of the System & Equipment Being Installed:

1. What is Heat of Extraction / Heat of Rejection?
2. Why is Heat of Extraction less than the units rated capacity?
3. What diagnostics will be performed at start-up to verify operation?
4. Can a COP / EER or efficiency be calculated directly after install?

“Open loop” and “closed loop” refers to the source.  The source side is the location where the heat pump will be extracting or rejecting heat to.  The load side is the home we’re trying to heat or cool.  Let’s start by looking at the pros and cons for each geothermal source.  Remember that efficiencies for ALL water source heat pumps exceed that of any other heating system today:

Open Loop Source (“pump & dump” or “once-through”):

Refers to running domestic well water through the system and discharging somewhere

Pros:                                                                                         Cons:

Less expensive install costs                                            Increased well pump usage

• In most cases                                                         Water quality concerns

Consistent entering water temperature                          Additional water control valve required

Slightly more capacity in late winter                                Discharge water location / design required

                                                                                                Additional energy usage due to well pump

Closed Loop Source (Horizontal pit or trench, vertical bore, horizontal bore):

Refers to circulating the fluid out through the ground and back through the heat pump in a continuous loop with high density PE pipe

Pros:                                                                                        Cons:

Control over water / brine quality                              Typically higher initial install costs

No scaling or build-up concern                                 Requires yard space

Less maintenance                                                       Lower entering water temperatures (heating)

No water usage from well                                             

No well pump running

If a contractor tells you that open loop systems are more efficient, most likely they either don’t know how to, or don’t want to install a closed loop.  It’s much easier to set a unit, pipe water to it and be done.  Furthermore, designing a closed loop requires the installer to know more about the product they are selling.  So do they really know how to commission a system and verify proper operation (another another topic ”Selecting a Geothermal Contractor”)?

Lets get back to comparing these two source options.  From the list above, open loop systems have the benefit of a consistent entering water temperature (EWT).  Your well water temp doesn’t change much year-round.  The output heating capacity of the system is dependant on the EWT.  The unit is extracting heat from the entering water, so if the temp of that water is higher, it has more capacity to heat your home (and consequently, it will also operate more efficiently).  Closed loop systems circulate the same freeze protected fluid (brine) forever.  This brine is extracting heat from the earth and EWT’s can get down to 30 degrees in late winter.  For example, let’s look at the spec book and examine the heating capacity and efficiency of a 4-Ton unit and assume it’s late winter:

                                               Open Loop                        Closed Loop

EWT:                                    50 degrees                        30 degrees

Heating Capacity:          47,800 Btu/hr                       37,500 Btu/hr

Power:                                3.22 KW                                2.97 KW

COP:                                     4.35                                    3.71

So the open loop system is providing 10,300 more BTU’s than the closed loop system due to the elevated EWT.  Open loop system is 435% eff vs. the closed loop operating at 371% eff.  The thing that’s missing is the well pump.  The well pump runs 100% of the time that the heat pump is running (obviously turns off when the heat pump shuts down).  A residential variable speed well pump will draw ~ 5 amps or more at lower flow rates.  This equates to another 1.2 KW and takes the total COP down to 3.12. (or 312% eff).  At this rate the closed loop system is more efficient with less operating costs.  It’s the turtle that wins the race in this example.

Our experience has been great with both open and closed loop systems.  We have learned that open loops require a little more attention in the weeks directly following install.  It’s good to check a new system frequently.  Inspect the flow meter to verify correct water flow.  This is important in the spring when sprinkler systems come on.  Sprinklers, or other large water demand on the well, can reduce the water flow rate through your heat pump.  Sprinkler system start-up can also send quite a large amount of sand or other sediment up the pipe.  You’ll want to check the sediment trap at the unit location and clean when needed.  Once dialed in the system typically runs good with simple filter changes every 3 months.

The install cost is another factor worth discussing.  Just because you already have a well doesn’t mean the open loop will always be the cheapest to install.  Finding a good way to discharge the water can also cost money.  One method is to take a backhoe and dig a big hole, backfill with washed rock, and then see if the ground will take it all back in.  This works well in sandy soils but could still cost you $1,500 in backhoe time and labor.  If you have a surface pond you could discharge in there pretty cheap.  We have had customers who want to drill both a supply and discharge well for an open loop.  The cost of that would be equal to or more than simply installing a ground loop.

At the end of the day both systems are going to far exceed the efficiency of anything else you could install.  Air-source heat pumps have come a long way.  However, they’ll never achieve the eff of a geothermal system because it’s just too difficult to extract heat from air that’s 20 degrees (winter in Idaho).  It’s ~ 30 times easier to transfer heat using water than with air.  Water source heat pumps are moving onward as well.  We already have systems rated up to 500% eff.  The next generation has new design features that will significantly increase even this number.

Simply put “geo” means earth and “thermal” means heat. Therefore, geothermal heating and cooling transfers heat from the earth to the home or office when using a water source heat pump (WSHP).  Due to the constant temperature of the earth…

geothermal heating can achieve an efficiency (COP) of up to 5.0. This means that for every unit of energy put into the WSHP, it can remove up to 5 units of energy to utilize for space conditioning.

Benefits of geothermal heating and cooling include:

1. Energy savings up to 70%- compared to gas furnaces and air conditioners

2. Improved aesthetics- geothermal heating and cooling systems utilize a packaged unit that eliminates the need for an outdoor AC. this reduces noise and ear and tear.

3. Longer Life- water source heat pumps have a much longer life expectancy than conventional systems. They have a lower maintenance cost

4. Eco friendly- Water source heat pumps are recognized by the DOE and the EPA for their superior efficiency.

5. Positive Cash Flow- The monthly utility  savings often are greater than the added cost of a system.