Bosch Geothermal Heat Pumps Applications Manual page 40

4 0 | Bosch Geothermal Heat Pumps
Scaling potential should be assessed using the pH/
Calcium hardness method. If the pH <7.5 and the calcium
hardness is less than 100 PPM, scaling potential is low. If
this method yields numbers out of range of those listed,
the Ryznar Stability and Langelier Saturation indices
should be calculated. Use the appropriate scaling surface
temperature for the application, 150°F for direct use
(groundwater/open loop) and HRP (desuperheater); 90°F
for indirect use. A monitoring plan should be implemented
in these probable scaling situations. Other water quality
issues such as iron fouling, corrosion prevention and
erosion and clogging are referenced in Table 21.
Typical open loop piping is shown (Fig. 25). Shut off
valves should be included in the open loop piping array
at the unit for ease of servicing. Boiler drains or other
valves should be placed into the lines to allow ushing of
the heat exchanger if necessary. Shut off valves should be
installed to allow ow through the coaxial heat exchanger
via the boiler drains without allowing ow into the piping
system. Pressure/Temperature (P/T) ports or plugs should
be installed so that pressure drops and temperatures can
be measured during waterside diagnostics, and gallons
per minute (GPM) can be determined from manufacturer's
speci cations. Due to pressure and temperature extremes,
PVC SCH40 is not recommended.
Fig. 25 Well water application
Data subject to change
In Bosch open-loop geothermal heat pump system
applications, water pressure must always be maintained
in the water-to-refrigerant coaxial heat exchanger. This can
be accomplished with either a control valve or a bladder
type expansion tank.
One method of ow control and regulation is by adjusting
the ball valve or water control valve on the discharge
line. Measure the pressure drop through the unit heat
exchanger, and determine the ow rate (GPM) from tables
in the installation manual of the speci c unit. Since the
pressure is constantly varying, two pressure gauges may
be needed. Adjust the valve until the desired ow of 1.5 to
2 GPM per ton is achieved.
A second method of ow control requires a ow control
device mounted on the outlet of the water control valve.
The device is typically a brass tting with an ori ce of
rubber or plastic material that is designed to allow a
speci ed ow rate. On occasion, ow control devices may
produce velocity noise that can be reduced by applying
some back pressure from the ball valve located on the
discharge line. Slightly closing the valve will spread the
pressure drop over both devices, lessening the velocity
noise.
When EWT is below 50°F, 2 GPM per ton is
always required for an open-loop geothermal heat
pump system.
Applications Manual
Bosch Thermotechnology Corp.