CleaverBrooks CFC-500 Operation, Service And Parts Manual page 172

CB FALCON
Slow Start and Forced Rate limits (Hydronic Control)
The Forced Rate limit causes the burner to stay at a fixed firing rate immediately after lightoff, just after the end of the Run
Stabilization time (if any). This is optionally followed by a slow start function that limits the ramp-up speed of the firing rate when the
water is colder than a threshold, as shown in the following diagram.
IGNITION
PFEP/MFEP/DBI
LIGHTOFF RATE
FORCED RATE AND SLOW START
= A PROGRAMMABLE PARAMETER
NAME
= A PROGRAMMABLE PARAMETER THAT IS NOT
NAME
PART OF FORCED RATE OR SLOW START
Parameter
CH forced rate time
CH forced rate
DHW forced rate time
DHW forced rate
750-265
RUN STAB. FORCED RATE
CH FORCED RATE
DHW FORCED RATE
TIME
(0 = DISABLE)
(0 = DISABLE)
SETPOINT = OFF HYST.
SETPOINT
SETPOINT - OFF HYST.
Fig. 20. Slow Start and Forced Rate limits.
Table 23. Limits and Rate Override: Slow Start Limit Parameters.
MM:SS
This parameter determines the duration of the forced rate period, when firing for CH or LL
demand. If it is set to zero then this forced rate period is disabled.
RPM or %
This parameter provides the firing rate during the CH forced rate time. It is also the initial rate
for the CH slow start period (even if the forced rate time is zero).
MM:SS
This parameter determines the duration of the forced rate period, when firing for DHW
demand. If it is set to zero then this forced rate period is disabled.
RPM or %
This parameter provides the firing rate during the DHW forced rate time. It is also the initial
rate for the DHW slow start period (even if the DHW forced rate time is zero).
RUN
SLOW START
CH ENABLE
DHW ENABLE
CH TIME
ENDS WHEN OUTLET
DHW TIME
TEMP EXCEEDS
OPERATING
SETPOINT
MINUS
DEGREES
SLOW START DEGREES
OUTLET
TEMPERATURE
Comment
48
MODULATION
TURN-OFF ADJUSTMENT
STARTS WHEN FREE
MODULATION BEGINS.
SETPOINT - SLOWSTART DEGREES
(THIS THRESHOLD ALSO COULD BE HIGHER
THAN THE BURNER-ON THRESHOLD, IF THE
SLOWSTART DEGREES VALUE WAS SMALLER
THAN THE ON HYSTERESIS VALUE.)