5 = Duty backup and assist
First pump comes on, if it cannot cope, it goes
off and next pump comes on (duty backup). This
continues until the last pump comes on and if it
cannot cope the first pump comes back on to
assist the last pump (duty assist) if the level
continues to rise all other pumps will come on
(assist) in turn until the level decreases to the
pump off points. Each pump has its own
setpoints, (P2n3 & P2n4).
6 = Service ratio duty assist
All pumps are used to assist each other (run at
the same time) and each pump has its own
setpoints (P2n3 & P2n4). And a service ratio
setting. The third setpoint (P2n5) is used to set
the service ratio. Each time a pump is required to
start then the pump with the least running hours
(with respect to the service ratio) is started (i.e.,
the setpoints are re-assigned accordingly). For
example, if two pumps A and B have the service
ratio set to 2 and 1 respectively, then pump A
will operate for twice as many hours as pump B.
7= Service ratio duty
backup
If a pump fails to meet the demand (due to
malfunction, intake blockage and so on), then it
is stopped, and another pump shall take over.
Each time a pump is required to start then the
pump with the least running hours (with respect
to the service ratio) is started (i.e., the setpoints
are re-assigned accordingly). Each pump has its
own setpoints (P2n3 & P2n4). The third setpoint
(P2n5) is used to set the service ratio. For
example, if two pumps A and B have the service
ratio set to 2 and 1 respectively, then pump A
will operate for twice as many hours as pump B.
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