CleaverBrooks CFC-500 Operation, Service And Parts Manual page 165

Parameter
CH Frost protection enable
CH Frost Protection outdoor
setpoint
CH frost overrun time
DHW FROST PROTECTION
SELECTED DHW
MODULATION
SENSOR
Table 16. CH Frost Protection Parameters.
Enable, Disable
When enabled, regardless of whether the boiler is firing or not or whether CH is in control or
not:
• The CH pump is turned on if the CH control temperature is below 45ºF, using the active
CH sensor: Header or Outlet
OR
• The CH pump is turned on if the outdoor sensor is valid and the temperature is below a
programmed frost protection level provided by the CH frost protection outdoor setpoint
parameter.
Once turned on, the CH pump remains on until:
1) the outdoor temperature is above the programmed frost protection level + 4ºF, and
2) the outlet temperature exceeds 50ºF. When both of these have occurred, then a CH frost
protection overrun timer is started. After the timer expires, the pump reverts to normal
operation.
This source of pump control has the highest priority and cannot be overridden by any
subsystem (e.g. anticondensation) that wants to turn off the CH pump.
Additionally, if the burner has no demand from any other source, then the frost protection
source generates a burner demand if the outlet temperature is below 38ºF and it requests a
minimum modulation firing rate.
It maintains this demand until some other source of demand takes over—frost protection is
the lowest priority burner demand source—or CH Frost protection burner demand ends.
CH Frost protection burner demand ends when both of these occur:
1) the outlet temperature exceeds 50ºF.
2) the inlet temperature is greater than 41ºF.
If the CH control sensor (Outlet or Header) is invalid (e.g. disconnected) then it is ignored by
CH frost protection.
If the Inlet sensor is invalid (e.g. disconnected) then frost protection ignores that sensor and
operates only on the CH control sensor.
If the Outdoor sensor is invalid it is ignored without issuing an alert.
Degrees or None
CH Pump is turned on when the temperature is below the programmed frost protection level.
hr:mm:ss
This time indicates how long the CH pump demand should continue to run after CH frost
protection pump demand ends.
DHW SENSOR IS OK
(OTHERWISE IGNORE IT)
SET: < 45°F
CLR: > 50°F
SET: < 38°F
CLR : > 50°F
Fig. 18. DHW frost protection.
Comment
SLAVE STATUS
FROM CH
FROST PROTECTION
BURNER DEMAND
OVERRUN TIME
LOAD
THE FROST PROTECTION FIRING
RATE IS ALWAYS THE MINIMUM
MODULATION RATE.
41
CB FALCON
DHW FROST
PROTECTION
ENABLE
DHW FROST
PROTECTION
PUMP DEMAND
FROST PROTECTION PUMP
DEMAND ALWAYS TURNS
THE PUMP ON; THIS IS NEVER
BLOCKED BY OTHER FUNCTIONS.
DHW FROST
PROTECTION
BURNER DEMAND
FROST PROTECTION BURNER
DEMAND IS LOW PRIORITY, BUT
IT WILL FIRE THE BURNER IF NO
OTHER SOURCE IS DOING THAT.
CH FROST
PROTECTION
FIRING RATE
750-265