750-265 32
Slow Start and Forced Rate limits
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 limit that limits the ramp-up speed of the firing rate
when the water is colder than a threshold. These functions will be implemented as shown in the following diagram.
Fig. 14. Slow Start and Forced Rate limits.
Table 15. Limits and Rate Override: Slow Start Limit Parameters.
Parameter Comment
CH forced rate time 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.
CH forced rate 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).
DHW forced rate time 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.
DHW forced rate 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).
PFEP/MFEP/DBI RUN STAB. FORCED RATE SLOW START MODULATION
ENDS WHEN OUTLET
TEMP EXCEEDS
OPERATING
SETPOINT
MINUS
TURN-OFF ADJUSTMENT
STARTS WHEN FREE
MODULATION BEGINS.
(0 = DISABLE)
SETPOINT = OFF HYST.
SETPOINT - OFF HYST.
A PROGRAMMABLE PARAMETER
A PROGRAMMABLE PARAMETER THAT IS NOT
PART OF FORCED RATE OR SLOW START
=
=
FORCED RATE AND SLOW START
SLOW START THRESHOLD
OUTLET
TEMPERATURE
SETPOINT
(0 = DISABLE)
IGNITION RUN
LIGHTOFF RATE
TIME
NAME
NAME
TEMP.
CH FORCED RATE
DHW FORCED RATE
CH TIME
DHW TIME
CH ENABLE
DHW ENABLE
RAMP
M28039
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