CleaverBrooks CFC-500 Operation, Service And Parts Manual page 166

CB FALCON
Parameter
DHW frost protection enable
DHW frost overrun time
Frost protection method
750-265
Table 17. DHW Frost Protection Parameters.
Enable, Disable
The DHW frost protection feature is enabled or disabled by this parameter. See Fig. 18.
DHW frost protection will use the DHW sensor, if the DHW demand source parameter selects
a switch instead of a sensor.
When enabled, 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 45ºF
• Once turned on, the DHW pump remains on until the DHW temperature exceeds 50ºF.
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 burner demand if the DHW 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 DHW Frost
protection ends. DHW Frost protection ends when the DHW temperature exceeds 50ºF. If the
DHW sensor is invalid (e.g. disconnected) then it is ignored by DHW frost protection.
hr:mm:ss
This time indicates how long the DHW pump demand should continue to run after DHW frost
protection pump demand ends.
Min modulation continuous, Mid modulation at 5 min/hour
Determines what happens when Frost Protection (from any source) becomes active.
• Min modulation continuous
Burner demand, if/when it occurs as part of frost protection, is continuous until the Frost
Protection condition no longer exists.
• Mid modulation at 5 min/hour
Burner demand occurs for 5 minutes when Frost Protection burner demand first becomes
active, then thereafter it remains off for 55 minutes, then of for 5, off for 55, etc.
Comment
42