CleaverBrooks CFC Operation, Service & Parts Manual page 174

CB FALCON
Parameter
DHW demand switch
DHW setpoint
DHW TOD setpoint
DHW off hysteresis
DHW on hysteresis
DHW hysteresis step time
DHW P-gain
DHW I-gain
DHW D-gain
DHW priority time ODR enable
750-265
Table 11. Domestic Hot Water Parameters.
DHW Sensor Only, DHW Switch, Auto-Sensor Only, EnviraCOM DHW Request, STAT, Auto
and EnviraCOM DHW, Plate Heat Exchanger, J7-3 120 Vac
This parameter selects the source of demand for the DHW system.
• If Sensor Only is selected, the burner on/off hysteresis levels also provide "pump
demand" or heat demand; there is no other switch-like input.
• If DHW Switch is selected, the S6 sensor (one half of the DHW sensor, which is S6S7)
acts as a switch. If it is shorted then there is DHW heat demand; if it is open then there is
no DHW heat demand.
• If either Auto DHW (S6) and EnviraCOM DHW Remote Stat or Auto: Sensor Only is
selected, the S6 sensor (one half of the DHW sensor, which is S6S7) is used for automatic
detection. In this case:
DHW high limit enable must be set to Disable (because it is not being used as a
•
safety sensor).
DHW connector type must be set to either "10K single nonsafety NTC" or "12K single
•
non-safety NTC"
DHW modulation sensor must be set to either "Auto DHW (S6) or Inlet," or "Auto
•
DHW (S6) or Outlet."
• If these are not as specified then a lockout occurs.
The behavior of the auto-detection is:
• If DHW (S6) is shorted or open then:
• DHW (S6) provides heat demand input and modulation is controlled by the input (Inlet or
Outlet) specified by the DHW modulation sensor parameter.
• ELSE (when DHW (S6) is providing a valid temperature) Modulation is controlled by the
DHW (S6) sensor, and if this DHW demand switch parameter selects:
Auto: DHW(S6) or Sensor Only then: The DHW sensor provides heat demand, as if
•
the "Sensor Only" option had been chosen.
Plate Heat Exchanger then the DHW heat demand operates as specified in the Plate
•
Heat Exchanger section.
STAT then the J8 terminal 3 input is the DHW heat demand signal.
•
J7 terminal 3 120 Vac
•
Degrees or None
This setpoint is used whenever the time-of-day switch is off or not connected (unused).
Degrees or None
This setpoint is used when the time-of-day switch (J10 terminal 2) is on.
Degrees or None
The off hysteresis is added to the setpoint temperature to determine the temperature at which
the demand turns off. Similarly, the on hysteresis is subtracted from the setpoint to determine
the temperature at which demand turns on.
However, these are adjusted at the time the burner changes from on to off, and from off to on
to give the PID algorithm some room to be more aggressive in tracking the load, which can
result in overshoot (undershoot). This adjustment is identical to that described for the CH
demand and rate source, except it is controlled by the DHW hysteresis step time. (see the
Setpoint and Hysteresis section, page 31)
seconds
The time for each step. A step time of zero disables this feature. (see the Setpoint and
Hysteresis section, page 31)
0-400
These parameters are the gains applied to the proportional, integral, and differential terms of
the PID equation for the DHW loop.
Disable, Enable
When enabled, the DHW priority override time parameter will be derated when the outdoor
temperature is below 32°F. When the outdoor temperature is 32°F and above, the
programmed time will be used as-is.
When the outdoor temperature is -40°F and below, the programmed override time will be
derated to zero (no override). Between 32°F and -40°F, a linear interpolation will be used. For
example, at the midway point of -4°F, the DHW priority override time is one half of the value
provided by the parameter.
Comment
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