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Verfügbare Sprachen
Verfügbare Sprachen
8.1 DOL pumps
Each DOL pump is switched on by a contactor controlled by the digital output DOL1 and DOL2 present in the IPFC.
IPFC relays driving the DOL pumps are relays with no voltage contacts. Max voltage to the contacts is
250 V, max current 5 A.
Two pumps are connected in parallel, with one pump (pump 1, P1) run by the inverter, while the second pump (pump 2, P2)
is directly connected to the main power ("Direct On Line" connection). Start/Run of the second pump is controlled by the
relay DOL1 (allowing a third pump to be controlled by the relay DOL2).
H
P2
P1
If pump 1 (P1) is already running to maintain the desired set pressure (red line) , an additional water request changes the
system curve from C1 to C2 ; since pump 1 (P1) is running at maximum speed, it is not possible to maintain the set pressure
by increasing the speed, so the system pressure will drop till reaching the new working point 2.
If pressure at the point 2 is (set value – delta control), IPFC will run the DOL by relay DOL1. The DOL pump will run at its
nominal speed while the pump 1 will drop it speed equal to the P1 pattern to maintain set pressure.
If water demands decreases, returning to the system curve C1, pump 1 will reduce the pump speed to maintain constant
pressure in the system. When pump 1 reaches a frequency equivalent to the minimum frequency, while still maintaining set
pressure, the DOL pump will be switched off and pump 1 will increase the speed to maintain the p_set in the system.
H
P2
P1@f min Q=0
If two pumps are connected in parallel, the first driven by IPFC and the second with a DOL
connection, it is necessary makes sure that the value "delta control" will be sufficiently high to
ensure the first pump, once the DOL pump is switched on, will reach a frequency higher than its
minimum frequency value.
By proper setting of the minimum frequency, excessive pump ON/OFF cycling is avoided, thus
preventing damage to the DOL pump.
C1
C2
3
1
2
P1+P2
C1
C2
P1+P2
delta start pres.
Q
Q
33
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