Crest Audio FBN0751 Service Manual page 23

1
Service
(continued)
Modulation Factor
The modulation factor is used to slow down the aggressiveness
of the temperature regulation routine. This can be useful in
systems with low system flow, or in Cascade systems with more
boiler capacity than the system needs. The installer can adjust
this parameter by accessing parameter F16.
Minimum Boiler Rate
The minimum boiler rate parameter allows the installer to raise
the low fire rate. This setting is adjusted by accessing parameter
F17.
Freeze Protection Pump Differential
Once the pump has started running due to low inlet temperature,
the inlet temperature must increase by this amount before the
pump turns back off. The installer can adjust this differential by
accessing parameter 4DJ using the PC program.
G/H: SH/HWG Night Setback
The installer may adjust the space heating night setback offset
by accessing parameter G1 and the HWG night setback offset by
accessing parameter H1.
Once the internal clock has been set correctly, the SH night
setback feature can be used to program a lower set point. The
value of this parameter will be subtracted from the normal set
point to determine the set point used during night setback.
This parameter can be changed by the user or the installer by
accessing parameters G2 through G15 and H2 through H15.
The temperature range for this parameter is 0°F to 90°F (50°C).
The feature is turned off with a setting of 0°F.
I: ModBus/BACnet
ModBus (Active / Inactive)
When BMS is set to ACTIVE (see BMS Active / Inactive) and
the boiler is being controlled through ModBus or BACnet,
set parameter I1 to ACTIVE.
parameter to INACTIVE. Note that the boiler can still be
monitored through ModBus or BACnet with this parameter set
to INACTIVE.
ModBus Out of Order Timer
When the boiler is being provided with certain commands and
temperatures through ModBus or BACnet, this information
must be updated frequently. If it is not updated before this
timer expires, the boiler will revert back to its own internal
readings and control. This parameter is adjustable by the
installer by accessing parameter I2.
Otherwise, set the ModBus
J: Cascade
Cascade Active / Inactive
The boiler is part of a group of units sequenced together. The
designated Leader unit determines the total output needed
from the group based on the set point and controlling sensor
reading. It assigns portions of the output to itself (Leader) and
the Member units. When Cascade is active, each boiler in the
group requires a unique address. This setting is adjustable by
the installer by accessing parameter J1.
Cascade Address
The boiler designated as the Leader needs to be programmed
with address 0. All the Member boilers require addresses from
1 to 7, and the addresses must be different for each Member.
The addresses can be in any order, regardless of the order in
which the units are wired together. This parameter is adjustable
by the installer by accessing parameter J2. The outdoor air
(if used) and system supply sensor must be connected to the
Leader boiler.
Cascade Offset
This parameter determines how much the temperature
can go above set point before the lead boiler will turn off.
This parameter can be adjusted by the installer by accessing
parameter J3.
Cascade Off-On Differential
This parameter determines how much the temperature must
go below the turn off temperature (Set point + Offset) before
the lead boiler turns on. This parameter can be adjusted by the
installer by accessing parameter J4.
Maximum Boiler Set Point for Cascade
This parameter determines the set point used by the individual
boilers in a Cascade. When a boiler is commanded to fire by
the Leader boiler, it will attempt to achieve this temperature
at its outlet. If any of the boiler outlet temperatures reach the
maximum cascade set point, the boiler will then modulate
down on its own in order to keep its outlet temperature within
the maximum cascade set point. Therefore, this parameter
can be used to limit the outlet temperatures of all the boilers
in a Cascade. Note that this parameter does not apply when
the boiler is heating an indirect HWG tank. This parameter is
adjustable by the installer by accessing parameter J5.
Cascade Type
The two (2) types of Cascade control are listed below:
Efficiency Optimization
This method is used when it is desired to have the most efficient
system. When the first boiler reaches a certain rate (default =
80%), it lowers its rate to 40% and turns on the next boiler
at 40%. This parameter can be adjusted by the installer by
accessing parameter J9.
Service Manual
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