Armstrong 4280 - 5 Control Modes; Constant Flow; Constant Pressure; Linear Pressure

installation &
operating instructions
Design Envelope 4200h & 4280
End Suction Horizontal Pumping Units
35
5.0 control modes
5.1 constant flow
Design Envelope pumps can be configured to maintain a con-
stant pump flow in a system as the system head varies. This ef-
fectively simulates speed control by a flow meter in the piping.
0
0
20 40 60 80 100
200
400
600
800
1000
1200
120 140 160 180
head
flow
target curve
Constant Flow Control Curve
5.2 constant pressure
Design Envelope pumps can be configured to maintain a con-
stant pump head in a system as the demand varies. This eec-
tively simulates the mounting of a dierential pressure sensor
at, or near, the pump.
0
0
20 40 60 80 100
200
400
600
800
1000
1200
120 140 160 180
head
flow
target curve
Constant Pressure Control Curve
5.3 linear pressure
Linear Pressure Control is where the controller is set to control
the speed according to a control ‘curve’ between max and min
flow. This type of control will change the pump speed to ensure
the pump operates on the projected linear control curve, where
the pump head varies directly with the flow. This type of control
is well known globally and is eective as far as the straight lin-
ear line will allow. For more realistic hvac control with superior
energy savings, consider the following control recommendation
5.4 Quadratic Curve Control.
0
0
20 40 60 80 100
200
400
600
800
1000
1200
120 140 160 180
head
flow
target curve
Linear Pressure Control Curve
5.4 quadratic curve control
Quadratic Pressure Control is where the controller is set to con-
trol the speed according to a control curve between max and
min flow. It is widely recognized that fitting a dierential pres-
sure 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 eciency.
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 devel-
oped according to the pre-set control curve.
0
0
20 40 60 80 100
200
400
600
800
1000
1200
120 140 160 180
head
flow
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 in-
crease 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;
a A dry-contact relay is supplies which will close when
minimum flow is reached, which can be used for an alarm or
other device.
b 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, regis-
ters 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.
0
0
20 40 60 80 100
200
400
600
800
1000
1200
120 140 160 180
head
flow
target curve
Minimum Flow Setting