Applications Manual Bosch Geothermal Heat Pumps
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Bosch Thermotechnology Corp.
Data subject to change
All Bosch water-to-water geothermal heat pumps are
equipped with two (2) oversized coaxial water-to-
refrigerant heat exchangers as standard issue. Customers
can choose cupronickel coils if the system is connected
to an open-loop system to offset any water quality issues.
Both copper and cupronickel coils are designed to allow
optimal heat transfer while offering extremely low pressure
drop. This unique low pressure ow design reduces the
amount of pumping power necessary to achieve optimum
water ow in order to maintain the ef ciency of the unit.
Coaxial heat exchangers are not as susceptible to clogging
and freezing as are plate heat exchangers. All Bosch water-
to-water geothermal units come standard with wrapped
insulated coaxial heat exchangers. This insulation wrap
prevents condensation from forming in low temperature
operation.
As shipped, all Bosch water-to-water geothermal heat
pumps are equipped with controls internal to the system
similar to the Bosch water-to-air units. Customers may
order an optional external heat pump controller for a
more visual control approach (Fig. 118). This controller
is recommended in most cases and offers a low cost,
simple solution to the control of the water-to-water unit.
The control is con gurable to provide cooling only, heating
only or auto change over control strategies based on the
application of the unit in a given system, and has multiple
features, including a selectable mode of operation, an
adjustable temperature differential for heating and cooling
set points, an adjustable auto changeover set point,
intelligent auto reset to avoid nuisance hard lockouts, an
LED display of control temperature and set points and
con gurable operation for continuous or cycling operation
of the compressor.
Fig. 118
16.2 Bosch Geothermal Water-to-Water Heat
Pump Sizing Criteria
When sizing a Bosch geothermal water-to-water heat
pump, the same guidelines apply as with Bosch
geothermal water-to-air heat pumps. An accurate heat loss
and heat gain load calculation still must be completed.
The only signi cant difference is the delivery method for
heating and cooling. Like Bosch water-to-air heat pumps,
economics must be considered for Bosch water-to-water
applications.
Bosch geothermal water-to-water heat pumps sizing is
dependent upon the type of hydronic system application
(load side - indoor) and the type of ground loop system
(source side - outdoor). Since the capacity and ef ciency
of the Bosch geothermal water-to-water heat pump is
directly related to the entering source temperature, care
should be exercised to insure that the water-to-water heat
pump will provide adequate capacity at design conditions.
The complexity of the ground loop sizing can be simpli ed
with the use of the Bosch Geo Solutions software which
allows the user to enter the heat loss/heat gain, the water-
to-water heat pump size, and the ground loop parameters.
An analysis based upon bin weather data is calculated with
the software that allows the user to size the equipment/
ground loop and obtain annual operating costs. All Bosch
geothermal contractors and dealers can acquire and/
or access the Bosch Geo Solutions software through the
Bosch Way to Grow website or by contacting their Bosch
sales representative.
Although there are numerous water-to-water systems
installed that provide 100% of the heating load, a larger
system and ground heat exchanger is required, increasing
installation costs. If the water-to-water system is not sized
for 100% of the application heating load, a method of
backup heat must be selected.
Just like Bosch water-to-air geothermal heat pump
systems, which typically have some type of backup heating
capability, Bosch water-to-water geothermal heat pump
systems can also bene t from the use of supplemental
heating to help lower initial installation costs. Design
temperatures are usually chosen for 1%, meaning that 99%
of the time, the outdoor temperature is above the design
temperature. If the Bosch water-to-water geothermal heat
pump is designed to handle 100% of the load, it is larger
than required 99% of the time. Bosch Geo Solutions can
determine an economical balance point that will allow
the Bosch water-to-water geothermal heat pump to be
downsized when a backup boiler or water heater is used
for supplemental heat.
Often, central cooling is not always desired with radiant
heating systems. A Bosch water-to-water geothermal
heat pump system can provide chilled water to cool the
structure, as well as hot water for the heating system.
Homes with fan coil units can generally be retro tted for
cooling quite easily. However, problems could arise if the
