Lead-Lag - Honeywell EXCEL 5000 User Manual

ALPHABETIC REFERENCE
I/O Dialog Box
74-5577–33 (US)
EN2B-0184 GE51 R0518 (Europe)
Function This XFM controls two devices with lead-lag logic.
Inputs Ld Lead Device, 0 for first device, 1 for second
LdE Lead Device Enable, 1 to Enable, 0 to Disable
LdF Lead Device Failure, 0 is normal, 1 is failed
LgE Lag Device Enable, 1 to Enable, 0 to Disable
St1 Device 1 Status, 1 is On, 0 is Off
St2 Device 2 Status, same as St1
The lead enable input point, LdE, is a connection to a digital signal calling for
start-up of the lead device. A value of 1 turns the lead device on. A value of 0 turns it
off.
The lag enable input point, LgE, is a similar connection for turning on and off the lag
device. The connection should be made from an operator calling for the lag device
to be either on or off.
Outputs Ss1 Device 1 Start/Stop
Ss2 Device 2 Start/Stop
LdF Lead Device Failure
The point LdF indicates lead device failure. It is meant to be passed back into this
submodule or put through some other logic, then passed back into the submodule. If
the devices being controlled by this submodule are stand-alone or are meant to be
backed up individually you can pass the output LdF directly to the input LdF through
a VD point. If the devices are part of a system which is to fail if any component in the
system fails, there will be several module calls to the submodule and you will need
to look at all of these LdF points and create one new VD point to pass back into the
appropriate submodules.
When the LdE point is turned on, the lead device is started and a timer delay is
initiated. Time is set at Parameter P1. If any time after this time expires, the lead
device status is not true, the LdF point turns on. If the Ld point is changed while the
LdE is on, the LdF is reset to False and a new time delay is initiated. When the LdE
is turned Off, the Ss points that were on continue to run for the time set at
Parameter P2.
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EXCEL CARE CONTROL ICONS

LEAD-LAG