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MAGNA3 INSULATED PUMPS INSTALLATION MANUAL
Determining the Pump Control Mode
The MAGNA3 has a number of control modes for a variety of applications. However, for geothermal installations there are only two
control modes that are applicable, Constant Pressure and Constant Curve. Most of the other modes are for boiler applications, and
are not recommended.
Constant Pressure:
A central variable speed pump is common for geothermal applications of three or more heat pumps due to the opportunity for
energy savings. Figure 2 provides an example piping diagram. The central pump is controlled based upon pressure differential.
As the water valves open and close based upon the operation of the heat pump, the system pressure changes, causing the
pump to adjust speed to attain the water flow needed. For example, if only one of five heat pumps is running, the pump speed
adjusts to the flow rate needed for the one heat pump, dramatically reducing pump Watts compared to when the pump is running
at maximum flow.
Constant Curve:
Because the MAGNA3 uses a very efficient motor, the pump may be used as a constant speed pump in applications where
variable speed is not necessary or desired.
Ground Loop Piping
Figure 2: Typical central pump application, using constant pressure control and modulating water valves.
Expan.
Tank
Modulating
2" 3-way valves
Water Valve
with flush ports
(2) FPL8
Two-Pipe System, Variable Speed Pump:
The central pump is controlled based upon pressure differential. As the modulating water valves
open and close based upon the operation of the heat pump, the system pressure changes,
causing the pump to adjust speed to attain the water flow needed for the number of heat pumps running.
VFD
PD
T
T
Heat
Pump
M
M
Automatic Flow
Ball Valve
Control Valve
6
T
T
M
M
M
T
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