DHW POST PURGE
After DHW demand is removed, control performs a purge on
the boiler.
• Control shuts off boiler and continues to operate either the
DHW pump or DHW valve and primary pump (P3)
• Control purges residual heat from boiler into the DHW tank
• Control continues purge for a maximum of four minutes or
until boiler supply temperature drops 20°F (11°C) below
DHW Boil TRG temperature
• Control stops purge if boiler supply temperature drops
below current Boil TRG temperature
DHW MIXING PURGE
After DHW operation, the boiler is extremely hot, while heating
zones may have cooled off considerably after being off for a
period of time.
• To avoid thermally shocking the boiler after DHW priority, the
control shuts off the boiler, but continues to operate the
DHW while restarting the heating system
• Above step allows some of the DHW return water to mix with
the cool return water from the zones and temper the boiler
return water
66
CONTROL FUNCTION
OVERVIEW
CONTROL FUNCTION OVERVIEW - CONTROL FUNCTION OVERVIEW - Section C - Domestic Hot Water
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