In general, any change out requires advanced planning for three elements, placement of the new equipment, duct modifications, thermostat wiring, and electric work. A geothermal system will require two extra steps. One is planning for the indoor geothermal pipe hook-up with the flow center (which circulates the loop water between outside and the heat exchanger located inside the geothermal unit). Two is planning for the hot water assist installation (if the unit comes with the optional hot water assist).
With my situation, the existing unit is a 2.5 ton air handler with a bottom return and top discharge. My new WaterFurnace Envision unit is a 3 ton with dual speed compressor, right return and top discharge. Since my existing duct work’s capacity is 2.5 ton, my contractor assisted with measuring the existing duct work to decide what modifications were needed to not only fit the new unit in place of the old, but to assure good air flow given I have a slightly larger unit.
My finished basement family room had always been cold in the winter; there is only one supply outlet for the room. In addition, one of the supply outlets to another room in the basement had been disconnected. The resulting comfort problems turned out perfect for directing extra supply air. I now have has a more inviting place to go relax as my family room will now become more comfortable.
At first fitting the new unit in place appeared it could be a challenge because the existing air handler was 21 x 21.5 inches, while the new Envision unit was 31.6 x 25.6 inches. The model unit needed for replacement has the compressor and heat exchanger on the bottom, and the air handler with coil on the top. In the HVAC world this type of unit is known as a “packaged” unit meaning everything is contained inside one piece. Other types are called split, where the compressor and heat exchanger are in one box, and the air handler is a separate box to allow placement in remote locations such as an attic. Copper line sets and a few wires will connect the split unit with the matching air handler.
The advantage of having a package unit allows for a compact design, while the split allows the flexibility to meet any challenge because of space constraints.
Back to the planning for my unit; the Envision unit is 50.4” tall, while the old air handler sits on top of a 21” air return box, and so that 21” plus the air handlers 63 inches. So there is a slight bonus with a shorter unit, this made it easier to modify supply discharge. The return opening on the Envision unit is 28” wide by 34” tall. The existing return box was 19” wide, and there is enough height to get the 34”. So my contractor and I decided to build a second return 11” x 34 inches, plug the existing basement return and open a new basement return using the 11 x 34 side. This modification will keep my system balanced and give me a little more air return than I had for the finished family room.
We removed the old unit just before Christmas and the new one installed on the same day. I had to run about two days on electric heat while the loop field and indoor piping was completed.
The route of the geothermal pipes also needs advanced planning to assure a smooth installation. The location of the geothermal circuits often will determine the best place to enter the home. The two geothermal wells were on the SE side of my house, just off the windows for our family room. Each well had two circuits. We decided to route the geothermal pipes to enter under the foundation at the laundry room. This allowed us to contain all work in the same room where the geothermal unit is located.
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| Drilling holes in the foundation |
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| Finished holes |
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| The indoor pipes |
The geothermal pump sits next to the unit, so the pipe enters from the foundation, goes up a wall (inside the 2 x 4 frame) then over an interior doorway to a point where the pipe drops down to the pump. We had to tear some drywall out, and will hide most of the ceiling routing with an extended soffit.
Finally, the new unit needs an additional 240 volt electric line to supply the compressor. The old heat pump’s compressor was outdoors so that electric line became useless. In addition, the new unit needed 45 AMPs vs. the 35 AMPs for the old unit. My contactor has a master’s electrician license so he was able to pull the new wire and replace my circuit breaker with the correct size.
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| Programmable Thermostat |
Finally my contractor planned out the water-pipe connections from the Envision unit to my existing hot water tank. WaterFurnace provides excellent shop drawings for this so it was very simple. Often a second tank is installed as a buffer tank, this enhances the efficiency of the hot water assist but my home has limited space so we did not install a buffer tank.
The unit installation along with all geothermal piping, and the hot water assist was completed by December 30th. In addition to this, we discovered that the geothermal heating produced much warmer air, and may wife requested humidification. I had my contractor install a remotely mounted Honeywell unit which produces steam.
Wow, it has been a week now and we are all amazed at how comfortable our home feels! Over the next few months I will monitor the electric bills and will compare what we are now experiencing with last year.
