Section 4 — Commissioning
Part No. 750-363 4-19
“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 Figure 2-10 in this manual or to 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 (demand
input) is energized, the demand is enabled. The boiler then 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 “Local”. This setting should be verified
under the Falcon control’s Central Heat configuration group, “Central Heat>Modulation>Modulation Rate
Source”. For remote modulation this parameter should be set to “S2 (J8-6) 4-20 mA with sensor on-off.
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 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 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 Central Heat
configuration group. Change the setting of “Central Heat Configuration>Set Point>Set Point Source” to “S2
(J8-6) 4-20mA”. Next, the span of the 4-20mA needs to be established. The “20mA water temperature”
parameter determines the value for 20mA; “4mA water temperature” determines the value for 4mA.
Depending on the quality of the remote input signal, the modulation rate or operating set point may fluctuate
slightly because of small changes in the measured current signal or because of induced noise. 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 0.2mA
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” or
“LOCAL” 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.
Rate Limiting/Override
For safety reasons or to accommodate special operating conditions, the Falcon incorporates a number of
control functions that either limit the modulation range or set the firing rate to a specific value. These
functions include Delta T limiting, Slow Start, and Forced Rate. See Appendix A for a complete listing of
control functions with detailed descriptions and parametrization instructions.
Delta T limiting is designed to reduce the firing rate in case of an excessive difference between the inlet and
outlet temperatures caused by a mismatch between water flow rate and boiler firing rate. Sensor
connections to the Falcon are at J8-4 and -5 (inlet temperature) and J8-8,-9, and -10 (outlet temperature).
Delta T limiting includes an Inversion Detection mode which when enabled becomes active in case the inlet
temperature is higher than the outlet temperature (indicating reverse water flow through the boiler).
Forced Rate limiting causes the burner to stay at a fixed firing rate for a fixed time period immediately after
lightoff, following the Run Stabilization period (if any). The forced rate period is optionally followed by a
Slow Start function that limits the ramp-up speed of the firing rate whenever the water is colder than a user-
specifiable threshold. Slow Start can help reduce set point overshoot, high limit trips, and frequent cycling.
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