Fresh Air Intake Rooftop Unit

Section 8.0 Choosing a Geothermal Heat Pump System

The type of geothermal heat pump system that is suitable for a given building must be chosen carefully. The normal process is a collaborative effort involving the owner, the architect and the consulting engineer. Each different geothermal heat pump configuration will affect the architecture and the ability to define climate control zoning. At present the commercially available heat pump types and the major physical implications for the building layout and operation are described here. The consulting engineer and the architect will collaborate in generating a systems comparison study that details the advantages and disadvantages of each mechanical system being considered. This study should compare performance, architectural implications, capital costs, operating costs and maintenance.

Water to air geothermal heat pumps:

A Partially exploded view of a console style geothermal heat pump. The controld, airside coil and compressor are visible.

Courtesy: Climatemaster

A Partially exploded view of a console style geothermal heat pump. The controld, airside coil and compressor are visible.

Courtesy: Climatemaster

Climatemaster Heat Pump Unit

Each water to air type of geothermal heat pump is connected to the well water circulating loop. The conditioned air must be distributed through a ducted distribution system. Each unit that requires fresh (ventilation) air will need to have a ducted supply of outside air brought to it. This ducted outside air distribution system should be fan forced, filtered and possibly tempered. If perimeter tempering is required, this may be accomplished with console style units.

The mechanical space requirements are modest given that the heat pumps are distributed throughout the building. The units may be ceiling hung with limited duct runs, or grouped in mechanical rooms. Unit sizes range from one ton (12,000 Btu/hr, 400 cubic feet per minute) to 20 tons. The unit distribution dictates the well water loop configuration. Generally a piped distribution system is less expensive than a ducted one, and the piping is considerably less bulky.

Each heat pump is able to operate in the heating or cooling mode at any time. During the spring and fall when some spaces may require heating and others cooling, this operating mode will be used. Similarly, if large interior zones exist, these may require cooling and ventilation only, even during the heating season. Again, this operating mode will be used. The net load the wells and earth see will be reduced if there is simultaneous heating and cooling.

Water to water geothermal heat pumps:

Water-to-water geothermal heat pump. The water connection for well water and the chilled/hot water supply and return for the load (building) side loop are visible.

Courtesy: Climatemaster

Climatemaster Water Water Heat Pump

Each water to water type of geothermal heat pump is connected to the well water circulation loop. The chilled or hot water generated is then distributed as required to fan coil units, or heating only applications such as radiant floors or heating elements. The chilled water temperatures available are conventional (40-55 deg. F), while the heating water temperatures are approximately 115 to 125 deg. F. Given that most heating elements are rated at higher temperatures, the heat output at these temperatures must be checked with the heating element manufacturer, and overall heating element sizes will be larger than in installations using higher temperature heat sources. Fan coil units are available in all sizes, and can be ducted units or console style. The console style is available in smaller sizes ranging from approximately 8,000 to 24,000 Btu/hr.

Fan coil units and air handling units, as the larger sizes are called, distribute the conditioned air through ducted distribution systems. Each unit that requires ventilation air will need to be supplied by a ducted outside air distribution system, which should be filtered, but may not need to be conditioned.

The water to water geothermal heat pumps are usually grouped together in a mechanical space, and can be treated as a conventional heater/chiller plant insofar as the distribution systems are concerned. The unit sizes range from three tons to 30 tons, but the market is in flux, with many new variations on this product being developed.

Water to water heat pumps can be piped so that all units operate together which then allows the building to operate either in the cooling or the heating mode. Simultaneous heating and cooling are not possible. Multiple unit installations can be piped in groups to allow simultaneous heating and cooling, but this requires a costly pipe distribution system.

Rooftop Geothermal heat pumps:

Hvac Rooftop Unit Economizer
Rooftop geothermal heat pump. These units are substantially similar in appearance to conventional rooftop units, but use geothermal wells as a heat source and sink. the fresh air intake/economizer cycle hood, filters, fan and the fan motor are visible.

Courtesy: Climatemaster

Rooftop geothermal heat pumps are similar in all respects to conventional rooftop units, except that the circulating well water loop must be brought to each unit. The rooftop units are capable of taking in the required ventilation air and do not require a separate system. Commercially available rooftop geothermal heat pumps are available in the 15 to 30 ton sizes, but new models are currently being introduced.

Mechanical space requirements for the units themselves are restricted to the rooftop, and the ducted distribution system may be interior or exterior.

Simultaneous heating and cooling from the same rooftop unit are not possible. If multiple zones are required that have different heating and cooling needs, such as interior and perimeter areas, various rooftop units can be used to meet these needs.

Split type water to air geothermal heat pumps

Stackable powder coated heavy gauge galvanized cabinet

Easily removeable com ml box

Hi^h lilficiency Scroll Compressor

Reversible Heat Pumps Rooftop

1" Swivel Water Fittings (FPTon commercial)

----BackSeating Brass

Service Valves with Serv ice Port

- Compressor Control Module

Reversible Heat Pumps Rooftop

The compressorized well-side module of the split type geothermal heat pump. Note the similarity to the water-to-water type, but with the refrigerant line connections at the bottom right. The reffrigerant lines can be run to a remote dirrect expansion/condensing section shown below.

Courtesy: Climatemaster

The air-side of a split-type geothermal heat pump. The fan section and the refrigerant coil are visible. The reversible refrigerant cycle allows the coil to heat or cool, as called for by the thermostat.

Courtesy: Climatemaster

The split type water to air geothermal heat pump is the water to air type 'split' into the condenser/compressor and coil/blower sections. The reason this configuration exists is that compressorized section which is the source of most of the noise generated by the unit can located remotely. The discussion of the packaged water to air unit above applies in all other respects.

Back up Heating Requirement

In geothermal systems having only one well pump the failure of this pump will leave the climate control system inoperable. Multiple well systems with multiple pumps do not run the same risk since the failure of one pump will not incapacitate the whole system. While the loss of air conditioning in summer is uncomfortable, it is less serious than the loss of heating during cold weather.

In projects where heating back up is warranted, the solutions can be various. The sizing of the back up heating system can be prudently set to provide adequate heat for the average winter temperature, which in New York City is approximately 36 deg. F.

The type of back up heating system used should be the one with the lowest first cost, as the use will be restricted times of pump failure, which are very infrequent.

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  • marja
    Does a geo thermal unit require fresh air intake?
    2 years ago
  • Jade
    Do geothermal systems require a fresh air intake valvue?
    4 months ago
  • marisa
    What is the air intake call on a roof top unit?
    2 months ago

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