Data Flow Systems TCU800, Installation And Operation Manual

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C h a p t e r 7
If an AC power fault alarm occurs at a TCU that is connected to a backup battery:
• Check that all circuit breakers are on.
• Check if any circuit breaker has tripped. If a station control panel breaker has tripped, resolve the problem.
• Check if the TCU’s replaceable fuse has blown.
Auxiliary Input Alarm
The TCU monitors the AUX_IN terminal (p2-12), and it can be configured to activate the AuxIn alarm when the terminal
is open or closed. If the auxiliary input alarm has been enabled and AUX_IN enters its configured alarm state (open or
closed), an auxiliary input alarm is generated.
DC Bias Fault
The ISO+24V voltage, which is provided for biasing the digital monitor inputs and/or powering up to two analog
transducers, is monitored by the TCU. If a fault occurs with the ISO+24V voltage, the DCBias alarm is activated.
If a DC bias fault alarm occurs, measure the voltage between the ISO+24V and ISOGND terminals. The voltage should
be 20-24 VDC.
• Check for a short circuit condition between the ISO+24V and ISOGND terminals if the measured voltage is 0 (zero)
VDC.
• If the voltage is low, check the current load on the ISO+24V source. It should be less than 100 mA. If the current load
is excessive, disconnect and isolate ISO+24V and ISOGND terminals to determine if the fault is with the bias source
or in the external circuitry. If the fault appears to be with the external circuitry, try isolating each input connected to the
ISO+24V voltage until the problem is found. If the problem cannot be isolated, the TCU may require factory service.
See “Appendix H: Support, Service, and Warranty” for removal, replacement, and servicing instructions.
Float Sequence Fault
If the TCU detects floats out of sequence, it issues a FltSeq alarm. A FltSeq fault is not cleared at the TCU until the alarm
message is viewed or after 24 hours have passed. A float sequence fault that is reported through telemetry clears on the next
valid pump cycle (one without a float sequence fault).
Be sure that STRT_PWR (P1-24) and AC_PWR (P1-5) are both connected to the station’s control power. This ensures
that all pumps under local control receive an emergency shutdown when AC power drops. If this is not done,
multiple pumps could be commanded to start at the same time.
ISO+24V is provided only for biasing the 12 digital monitor inputs of the TCU and/or powering up to two analog
transducers while not exceeding the maximum current of 300 mA.