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.