CleaverBrooks CFC User Manual

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Fig. 12. DHW frost protection.
CH FP pump overrun time MM:SS
This time indicates how long the CH pump should continue to run after CH frost protection
pump demand ends.
DHW frost protection enable Enable, Disable
The DHW frost protection feature is enabled or disabled by this parameter. See Fig. 12.
Additionally, DHW frost protection will use the inlet sensor rather than the DHW sensor, if the
DHW demand source parameter selects a switch instead of a sensor.
If it is enabled then, regardless of whether the boiler is firing or not, or whether DHW is in
control or not:
• The DHW pump is turned on if the DHW temperature is below 45°F
• Once turned on, the DHW pump remains on until the DHW temperature exceeds 50°F.
When this occurs then the DHW overrun timer is started. After the timer expires, the DHW
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 DHW pump.
Additionally, if the burner has no demand from any other source, then the frost protection
source generates a demand if the DHW temperature is below 38°F and it requests a firing
rate of 0% which will be converted to be the minimum modulation rate since this is the lowest
possible firing rate.
It maintains this demand until some other source of demand takes over—frost protection is
the lowest priority demand source—or DHW frost protection ends. DHW frost protection ends
when the DHW temperature exceeds 50°F. If the DHW Sensor is not valid (eg.
disconnected)then it is ignored by DHW Frost Protection.
DHW FP pump overrun time MM:SS
This time indicates how long the DHW pump should continue to run after DHW frost
protection pump demand ends.
Table 11. CH Frost Protection Parameters. (Continued)
Parameter Comment
M24979
DHW
DHW FROST PROTECTION
PUMP DEMAND
DHW FROST PROTECTION
BURNER DEMAND
DHW FROST PROTECTION
FIRING RATE
SET: < 45°F
CLR: > 50°F
FROST PROTECTION PUMP
DEMAND ALWAYS TURNS THE
PUMP ON; THIS IS NEVER
BLOCKED BY OTHER FUNCTIONS.
FROST PROTECTION BURNER
DEMAND IS LOW PRIORITY, BUT
IT WILL FIRE THE BURNER IF NO
OTHER SOURCE IS DOING THAT.
DHW FROST PROTECTION ENABLE
THE FROST PROTECTION FIRING
RATE IS ALWAYS THE MINIMUM
MODULATION RATE.
SET: < 38°F
CLR: > 50°F
DHW SENSOR IS OK
(OTHERWISE IGNORE IT)

CleaverBrooks CFC Specifications

General

Brand	CleaverBrooks
Model	CFC
Category	Boiler
Language	English