Commissioning
4-28
750-382
CBT
Remote enable and remote 4-20mA input
Remote enable and Remote 4-20mA input allow the boiler to be sequenced and/or controlled from a separate
boiler room controller or building management system. The 3-position Demand switch at the front of the control
panel determines whether the boiler is off, in local, or under remote control. When in the “LOC” (local) position,
the boiler operates on its own set point and ignores any remote signal connections. When in the “REM” (remote)
position, the boiler can be enabled and modulated by remote discrete and analog (4-20mA) inputs, respectively.
When in the “OFF” position, the boiler will not operate.
Refer to Figures 2-7 & 2-8, or your specific boiler wiring diagram, for remote enable and remote 4-20mA input
connections. For simple remote on-off sequencing, only terminals 24 and 25 (Falcon J8-1 & J8-3) need to be
connected to dry enable contacts at the remote controller. When terminal 25 (steam demand input) is
energized, the steam demand is enabled. The boiler operates on its local set point and PID modulating control
settings.
For remote modulation (firing rate) control, both the remote enable and remote 4-20mA input connections must
be made. The default setting for the 4-20mA remote input is “Modulation”. This setting should be verified under
the Falcon control’s Steam configuration group, “Steam 4-20mA remote control”. To avoid nuisance operating
limit shut downs of the boiler, the Falcon’s normal operating set point should be adjusted to a value that is
greater than the system header set point.
With steam demand present and completion of a successful trial for ignition sequence, the boiler will modulate
according to the 4-20mA input signal provided: 4mA = minimum modulation rate (low fire); 20mA =
maximum modulation rate (high fire). The boiler will continue to modulate until the steam demand is removed,
the operating limit is reached, LCI is opened (e.g. low water condition), or a Falcon lockout alarm occurs (e.g.
ILK opens on a High Limit trip).
To configure the boiler for remote set point control, navigate to the Falcon control’s Steam configuration group.
Change the setting of “Steam 4-20mA remote control” to “Set Point”. Next, the span of the 4-20mA needs to
be established. The steam set point determines the value for 20mA; “minimum steam pressure” determines
the value for 4mA.
Depending on the quality of the remote input signal, the modulation rate or operating set point may fluctuate
unnecessarily because of small changes in the measured current signal. Under the Modulation configuration
group, the “4-20mA input Hysteresis” setting may need to be adjusted to avoid undesired fluctuations in the
either the modulation rate or operating set point. The default setting is 0.1mA and can be increased to
essentially filter out small fluctuations of the input signal. It may take some trial and error to establish the
optimum input hysteresis setting for a particular system.
If at any time the remote 4-20mA input signal is disconnected, the Falcon control will indicate “OPEN” under
the 4-20mA input value at the operation screen. The boiler will then operate on its local set point and PID
modulation control. Once the 4-20mA signal is reestablished, the boiler will resume operation under remote
control.
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