Data Flow Systems TCU800, Installation And Operation Manual

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C h a p t e r 4
External Phase Monitor
Phase Monitor Bypass
The TCU’s internal phase monitor can be bypassed (i.e., disabled) if it is not required. To bypass the TCU’s phase monitor,
connect a bias voltage (through a voltage-dropping resistor if required) directly into the EXT_PM terminal (P2-4). Use
the same bias voltage source that was used to bias the motor run (MTRx_RUN) inputs (P2-1, P2-2, P2-3). The return for
the bias voltage must be connected to the IN_COM_1 terminal (P2-5). The MTRx_RUN and EXT_PM input circuits are
internally connected to the IN_COM_1 terminal (P2-5). Note that the TCU’s Phase Monitor is designed for 200-240 VAC
or 480 VAC (using external resistors) 3-phase only.
If you are using an external phase monitor and would like to have the voltage values available to HT3 for monitoring and
trending purposes, you can wire the TCU’s three phase inputs. For this option to work correctly you must also configure the
TCU’s phase monitor range and alarm trip points. This is necessary, because if the external phase monitor trips, the TCU
will apply these user-configured, internal phase monitor settings when deciding whether or not to run the pumps. Consider
the acceptable run conditions for your system when selecting phase monitor settings.
Input commons on the TCU must be either AC neutral (with no voltage potential when referenced to earth
ground) or the negative terminal of a DC power supply.