Geothermal Revised Strategy

The Original Geo-Thermal Design Concept :

The original concept design was to feed this home with a 10 ton Geo-thermal loop using approximately 3,000 linear feet of exchange piping. This plan called for the installation of two five ton heat pumps to control two separate zones in the home since we already had a difference between the basement and main floor with radiant floor supplementary heat versus the second floor which had no supplementary heat from the radiant system.

It was later recommended from the manufacturer/supplier to combine the two loops into one large 10 loop. This would allow the heat pumps to extract and reject energy from a larger surface area, most of the year. The goal of this strategy would have resulted in improved COP’s (efficiency) of the units.

We proceeded with the requirement for a 10 Ton loop which is approximately 9,000sqft. This was achieved with an approximate 30’ wide x 300’ long area buried in the Island under the over-burden that sits above the footing levels and water table. This does not include the header piping leading from the loop field to the mechanical room of the dwelling. This approach minimized or eliminated the need for excavation, trenching, backfilling, tree removal etc. because the building the Island was required anyway to deal with swamp-like conditions.

Ultimate revision and final decision regarding the Geo-Thermal Strategy within the submission from the sub-contractor.

Even though the system as defined within the design drawing documentation would have conditioned the space geo-thermally, we fully expected that there would be opportunities to better align the equipment selection and configuration to optimize home owner comfort and minimize hydro consumption. We welcomed different geothermal strategies that would enable an overall lowered capital expenditure without a utility savings compromise.

This decision included revisions to the ground loop (Geothermal) system to supply the key components as follows:

1.0 In-floor heating

2.0 Domestic Hot Water

3.0 Heating, Ventilation and now Air Conditioning (Client's insistence on a back-up system to the natural cooling envisioned).

The Geothermal system submitted by the sub-contractor recommended a water to water heat pump (TMW) units as a central heat pump unit for all three systems mentioned above with fan coils for the HVAC unit facilitating the heating or cooling exchange.

The details on this approach were as follows:

1.0 We used a water to water heat pump (TMW) unit as a central heat pump

unit for the in-floor heating. This method supplied lower water temperature to the in-floor heating loop. Therefore, it required less pipe spacing and longer pipes in order to achieve the same heating output.

2.0 We also used the same water to water heat pump (TMW) as the above, to

pre-heat the domestic hot water and with electric hot water tank to provide domestic hot water supply at 140 deg. F.

3.0 The Heating, Ventilation and Air Conditioning system remained setup as per the original design drawings, i.e.: The ground loop was connected directly to each heat pump unit for heating and cooling. We made these adjustments and decisions because in our opinion, the system as described above was much simpler to install and operate. We also found the system to be less expensive to install which is a welcome improvement.