Planning Geothermal - Unit Selection and Loop Design

WaterFurnace has software for dealers to help select the needed geothermal equipment and design the loop.  The software is called GeoLink Design Studio.  This software’s input is very simple, the heat loss/gain figures from whatever load calculation method the dealer used.  I used ACCA’s Manual J and entered the heating load of 36,948 Btuh and the cooling load of 21,232 Btuh.  From this data I decided to pick the WaterFurnace Envision dual capacity 3-ton unit with hot water assist.

My existing Trane unit is a 2.5-ton unit, and the duct work I have will fit a 3-ton unit.  I need an extra outlet in my finished family room, so the extra size will help.  The Envision dual capacity compressor will run in low speed which is 69% of the capacity of the 3-ton total. To put this in a different way my Envision’s low speed is roughly equivalent to 2 tons. The advantage here is that the unit will produce cooling and heating Btuhs that are closer to what my home needs on typical summer or winter days, and will not use unnecessary energy as a 3-ton unit would use during the same period.

The software produces a BIN Chart which show how many Btuh my home needs at different temperature conditions.  The chart show how many hours in Richmond is typical (based on 20-yr weather data), and how much capacity the 3-ton has at each temperature BIN has. The chart is interesting in that it predicts when the house Btuh needs exceeds the unit’s capacity and electric strip heat is turned on.  On the chart this is at 17 degrees.  A typical conventional heat pump will start to need electric back-up at 32-37 degrees.


BIN Chart -

The typical loop design has ¾” PE pipe circuits, and 1 ¼” PE header pipe to carry the water from the circuits to the circulating pumps inside.  (Although there are many other design approaches depending upon field conditions and other factors). The pumps are often set next to the geothermal unit where pipes are then connected from the pumps to the unit’s heat exchanger. The recommended number of circuits is 1 per ton; odd tons either add or subtract one circuit.  My system will have 4 circuits and two wells.  The GeoLink software calculated 375 total feet of bore for my unit given my Manual J load and soil conditions (average rock for wells).  So I rounded up to 200 feet for each bore.

I had my geothermal loop installed on December 9 & 10, 2010, see my photos on this Blog. My area in Charlottesville, VA has a strong aquifer. My well driller's experience in this city helped him plan a water containment strategy to minimize the risk of flooding my neighbor's yard.  He took the extra precaution to build a containment pit and trench.  In most vertical geothermal projects, this is not needed.  However due to close quarters with my neighbors, this was well worth the extra effort. 

For more information about geothermal loop design see the FAQ section of the International Ground Source Heat Pump Association's (IGSHPA) website.  For additional information about geothermal heat pump technologies start at their home page.

For additional information about aquifers visit the USGS website.

Planning the Geothermal Heat Pump Installation – The Manual J

My home was built nearly 20 years ago.  The first heat pump installed only lasted seven years.  It was a “builder model” unit made by some obscure HVAC manufacturer.  The indoor coils failed.  At the time of failure I was working for a local Trane dealer, so I decided to upgrade to a 10 SEER Trane heat pump in 1997.  That unit has performed as expected with few problems.  However, it is showing its age, a minor refrigerant leak on the outside condensing coils, and just few weeks ago the blower fan had to be replaced.

If machines can read people’s minds then it must have happened with my Trane unit because the fan motor failed the day I ordered my new WaterFurnace geothermal heat pump.  I replaced the fan myself with advice from my friend who operates his own HVAC company over in the Shenandoah Valley of Virginia.

Ok, back to the planning…

To get started with a geothermal heat pump installation, it is very important for the heating contractor to first calculate a heat loss and heat gain analysis for the home. Actually this is important for any new or replacement HVAC in any home.  A big pet peeve of mine is that too often contractors guess that the existing equipment inside the home had been correctly sized.  No it has not! Not unless the original installing contractor used an approved method to calculate the building’s load.

The most popular method is to use the ACCA’s Manual J Method.  At one time this was done by hand, but no longer, the latest edition of Manual J, the 8th is nearly impossible to calculate by hand (we don’t live but for 70 some odd years) so a computer program is used.  This makes it easy the contractor because all he or she has to do is measure the rooms, windows, and determine the construction type of existing walls, ceilings and floors.  All that data is then crunched by a computer and the results become a fairly accurate heat loss heat gain in Btuhs.

As you may have guessed, I know how to calculate Manual J’s and have been doing them for years.  So I measured my home, entered the data and received the following building loads for my home:

Heating Load = 36,948 Btuh
Cooling Load = 21,232 Btuh

The weather zone used is Richmond, VA (55 miles east of my home) with a winter design of 17 degrees Fahrenheit and summer design of 95 degrees Fahrenheit.

Next I will explain how I picked my unit and designed the loop.

For more information on what a homeowner should look for from a qualifed heating contractor visit the Air Conditioning Contractors of America's (ACCA) website.

To find a qualifed geothermal dealer near your home visit the WaterFurnace website's dealer locator and enter your zip code.

Planning a Geothermal Installation – Outline of Steps

Making plans for the installation of a geothermal heat pump system is really very simple.  The approach is very similar to any other conventional HVAC replacement or new installation project.  Here is an outline of what a heating contractor normally follows when planning a geothermal system project:

Property Visit – Determine type of geothermal system to recommend. The dealer will also measure for placement of equipment, needed electric and other mechanical components.

Present Proposal - Heating contractors will work on a detailed proposal for the homeowners.  The next steps follow the acceptance of the proposal. (In many cases the next step listed, heat loss/gain, has already been caclulated prior to the proposal.) 

Heat Loss/Gain – Will assist with selecting correct equipment, loop design and energy projection.

Install Loop – If the loop is closed loop the dealer will either subcontract to install the loop or will install the loop themselves.

Order Equipment – WaterFurnace equipment is made per order and delivered to the dealer normally within 5 business days from the date of order.

Install Equipment – Once the loop field has been completed the removal of the older equipment and installation of the new WaterFurnace system takes no longer than any conventional system.  After the equipment is installed the dealer’s technician commissions the unit with a start-up procedure outlined by WaterFurnace.

Post Check-up – The dealer should return after six months to check the air filter and determine the operating performance of the loop and equipment.  The dealer returns again after one year to do the same inspection.

Annual Maintenance – WaterFurnace units are shipped with 10-year all parts and 10-year labor allowance as standard.  These units require very little maintenance other than annual check-ups to make sure the equipment is operating at factory specifications and the air filters are clean.

Why Geothermal

I saw my first geothermal installation back in the mid 1980’s while performing an energy audit for a Virginia Power customer near Lexington, VA.  This customer’s bills were very low, and during my 1 ½ hour drive to his home, I was wondering why his electric bills were so low.  Did he give me the wrong square footage for his home?  So after the audit and my first ever look at a geothermal heat pump, I asked him, why did you call us out here?  He kind-of stuck his chest out and said, “I just wanted to see how much I was saving so I can brag to my friends.” 

Later Virginia Power incorporated the geothermal heat pump in their energy efficiency programs, and we promoted the system in the Shenandoah Valley and Central Virginia regions.  From those early days to today, where I now work for WaterFurnace International (a major manufacturer of geothermal heat pumps), I have met hundreds of satisfied homeowners who have a geothermal system.  What I am consistently told by these homeowners is 1) the system is more comfortable than the one I had or was used to, and 2) my energy bills are much lower.  When they tell me this it is nearly the same order every time.

I like to say I have met many people who spent big money on fancy cars and later regretted the purchase, but rarely meet people who spent the money for geothermal and had any regrets.

Geothermal heat pumps are good for the environment, and are the most efficient way to heat and cool a home, period.  The added hot water assist is icing on the cake, saving hundreds for heating domestic hot water while adding to the summer efficiency of the geothermal heat pump. Geothermal heat pumps last nearly twice as long as conventional systems, up to 24 years or even more.  They eliminate the noisy outdoor unit (those big units with the fan often spoil summer evening parties in the backyard).

Today, the Federal Government has backed the ideal with a very strong endorsement, a 30% tax credit on the total cost to install a geothermal system in your home.  Many states and electric utilities also kick in a few bucks too.  In Maryland, the state currently has a grant of $500 per ton of geothermal up to $2,000.  The Federal Tax Credit is good until 2016. 

This blog starts with the geothermal system I am installing in my own home.  Follow this blog as I plan for and then have my geothermal system installed.  This is a living and unfolding example, and this blog will report my travel on the road to and then with my new geothermal system as well as others.

For infromation on Federal, state and local geothermal incentives visit DSIREUSA.org.

Visit the WaterFurnace website for additional information about geothermal systems and products.