CleaverBrooks CFC-500 Operation, Service And Parts Manual page 99

Section 4 — CFC Commissioning
The PID (Proportional-Integral-Derivative) load control operates to
generate the demand source's modulation rate. Under Central Heat
configuration, the PID gain values can be adjusted to match the
desired modulation response. The default gain value settings of
P=25, I=25 & D=0 have proven to work well with typical
applications.
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 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 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 active set point determines the value for 20mA;
"minimum water temperature" determines the value for 4mA.
Part No. 750-263 4-29