Grundfos PM Rain, Installation And Operating Instructions Manual

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English (GB)
10
7.2 Start/stop according to water
consumption
As default, the PM Rain is set to this operating
mode, i.e. DIP switch 5 set to "OFF".
7.2.1 Starting and stopping conditions
Starting conditions
The unit starts the pump when at least one of the
following conditions is fulfilled:
• The flow is higher than Q
min.
.
• The pressure is lower than p
start
.
The default start pressure is 2.5 bar (250 kPa)
and can be increased in steps of 0.5 bar (50 kPa).
See section 5.1 DIP switches.
Stopping conditions
The unit stops the pump with a time delay of
10 seconds when the following conditions are both
fulfilled:
• The flow is lower than Q
min.
: 1.0 l/h.
• The pressure is higher than p
start
:
2.5 bar (250 kPa) (factory setting).
See section 11. Technical data.
7.3 Start/stop with 1 bar (100 kPa)
differential pressure
This operating mode can be used in systems with
a pressure tank of a sufficient size.
In this operating mode, the pump is started and
stopped at a 1 bar (100 kPa) differential pressure,
which reduces the pump operating time. If the
pressure tank is of an insufficient size, it will cause
cycling of the pump.
To enable this operating mode, set DIP switch 5 to
"ON". See section 5.1 DIP switches.
7.3.1 Starting and stopping conditions
The conditions described below require that DIP
switch 5 has been set to "ON".
Starting conditions
The unit starts the pump when the pressure is lower
than p
start
.
The default start pressure is 2.5 bar (250 kPa) and
can be increased in steps of 0.5 bar (50 kPa).
See section 5.1 DIP switches.
Stopping conditions
The unit stops the pump when the pressure is higher
than p
stop
.
p
stop
= p
start
+ 1 bar (100 kPa).
7.3.2 Setting the precharge pressure of the
pressure tank
The precharge pressure should be 0.14 bar (14 kPa)
below the pump start pressure.
8. Functions
When the auto-reset function is enabled, cycling and
dry-running warnings will be automatically reset.
To enable the function, set DIP switch 6 to "ON".
See section 5.1 DIP switches.
8.1 Anti-cycling
To detect inadvertent starts and stops of the pump in
case of a failure in the installation, the anti-cycling
function can be enabled.
The function will detect cycling if it occurs and the
red "Warning" indicator light will illuminate.
When the PM Rain has been set to start/stop
according to water consumption, cycling may occur
in the following situations:
• In case of a minor leakage.
• If a tap has not been entirely closed.
When the PM Rain has been set to start/stop with
1 bar (100 kPa) differential pressure, cycling may
occur in the following situations:
• If the pressure tank has lost its precharge
pressure.
• If the size of the pressure tank is insufficient.
If the cycling warning has been activated, the pump
can be restarted manually by pressing [Reset].
When the auto-reset function is enabled, the pump
will be restarted automatically after 12 hours in
warning condition.
To enable the function, set DIP switch 7 to "ON".
See section 5.1 DIP switches.
8.2 Dry-running protection
The PM Rain incorporates dry-running protection
that automatically stops the pump in case of dry
running.
The dry-running protection functions differently
during priming and operation.
8.2.1 Dry running during priming
If the unit detects no pressure and no flow within
3 minutes after it has been connected to a power
supply and the pump has started, the dry-running
warning is activated.
8.2.2 Dry running during operation
If the unit detects no pressure and no flow within
40 seconds during normal operation, the dry-running
warning is activated.
Caution
With the default setting the pump will
not stop until it reaches its maximum
pressure.
Note
In case of a very small consumption,
the anti-cycling function may register
this as a minor leakage and stop the
pump inadvertently. If this occurs, the
function can be disabled.
Caution
If a dry-running warning has been
activated, the cause should be found
before the pump is restarted in order to
prevent damage to the pump.