installation &
operating instructions
Design Envelope 4312 and 4392 vertical in-line
twin pumping unit with ivs drive
33
5.4 quadratic curve control
Quadratic Pressure Control is where the controller is set to
control the speed according to a control curve between max
and min flow. It is widely recognized that fitting a dierential
pressure sensor at the most remote load, across the supply
piping and return piping encompassing the valve and coil set,
is the benchmark scheme for energy eciency.
Design Envelope pumps can replicate this control without
the need for the remote sensor. As the flow required by the
system is reduced, the pump automatically reduces the head
developed according to the pre-set control curve.
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target curve
Quadratic Control Curve
5.5 quadratic curve control with
minimum flow protection
This configuration is designed for hvac hydronic systems
where flow sensitive equipment required a minimum flow for
equipment stability; such as a chiller that cannot tolerate flow
below a certain volume. This control will take advantage of
the 5.4 Quadratic Curve Control mode, where the pump will
increase speed to maintain a minimum flow setting as the
system load is shutting down.
Pump controls can only control the flow to the maximum
speed or motor limit;
5.5.1 A dry-contact relay is supplies which will close when
minimum flow is reached, which can be used for an alarm
or other device.
5.5.2 When ordered, a minimum flow breach can be controlled
by opening a customer supplied 2-way (normally closed)
system bypass valve. The valve will be opened and closed
as system flow, which is also monitored by the controls,
registers below or above the pre-set (adjustable)
minimum flow value, using the built-in outputs and relays
in the Design Envelope pumping unit on-board controls.
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target curve
Minimum Flow Setting
5.6 quadratic curve control with
maximum flow protection
This configuration is ideal for hvac hydronic systems where
pumps are generally oversized and a flow limit is required
for system equipment stability and resulting energy savings.
This control will take advantage of the 5.4 Quadratic Curve
Control mode, where the pump will decrease speed to main-
tain a maximum flow setting. This will prevent over-pumping
and save energy costs. Over-pumping is common in hvac
systems as pumps are typically oversized for the application.
Pump controls can only control the flow to a minimum speed;
thus a dry-contact relay is supplies which will close when
maximum flow is reached, which can be used for an alarm or
other device.
0
0
20 40 60 80 100
200
400
600
800
1000
1200
120 140 160 180
target curve
Maximum Flow Setting
5.7 quadratic curve control with mini-
mum & maximum flow protection
This control mode combines the control logic of 5.5 & 5.6
which takes the values of the quadratic control curve and
protection for both the maximum & minimum flow limits.
Pump controls can only control the flow to the motor limit
or maximum / minimum speed limits of the unit, thus a dry-
contact relay is supplies which will close when either the
minimum or maximum flow is reached, which can be used for
an alarm or other device.
0
200
400
600
800
1000
1200
target curve
Minimum & Maximum
Flow Settings
5.8 parallel sensorless pump control
(pspc)
This configuration maps the quadratic control curve into the
pump controls and ensures the system flow requirements are
met, while staging the pumps on and o to maintain opti-
mum pump energy usage. This is accomplished by operating
the pumping units at the best pumping eciency level for the
required flow.
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