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The decision on whether or not to attempt to start the failed pump on
subsequent pump cycles will be determined by P*300 Max. Attempts.
Once the number of attempts stipulated have been made the pump will be
put out of service until such time the Device Fail input is cleared by a Reset
(P*391 = 4) on Digital Input 7. Alternatively the key can be used as a as
a Hot Key, which when pressed, whilst the unit is in RUN, will give details
of any Device Fail and provides prompts to Reset any failures to the no
fault condition.
Duty
When this function is selected the digital inputs are used to determine, via an
‘auto/manual’ switch, which one of the devices, connected to the relay
outputs of the Twin, will be the “lead” or “duty” device.
Consider the example of an application using 2 pumps. Each pump is
connected and controlled by one of the Twin relay outputs, the pump duty
and setpoints have been programmed as detailed in Using the Relays,
earlier in this chapter. The signals providing details on the “lead” or “duty”
pump ‘status’ are connected to the digital inputs as described in Chapter 2
Installation, and the input Type P*372, 375, 378, 381, 384, 387, 390 is
configured as detailed in Input Type, earlier in this chapter.
Pump 1 is connected and programmed to operate on Relay 1
Pump 2 is connected and programmed to operate on Relay 2
Pump 1 Duty signal is connected to Digital Input 3
Pump 2 Duty signal is connected to Digital Input 4
The type of switch to be used to determine the duty is selected and
configured as detailed in P*301 Switch Mode.
Standard Switch Mode (P*301 = 0 Standard)
When a standard rotary type switch is used, to determine auto/manual duty
one input per device is required, with each input being assigned to the
appropriate device relay output that it relates to, this is determined by
Assignment P*374, 377, 380, 383, 386, 389, 392. In the case of our
example Digital Input 3 will be assigned to Relay 1 (P*380 = 1) and
Digital Input 4 will be assigned to Relay 2 (P*383 = 2).
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