Honeywell DHC, Service Manual

Page: 210 / 262

Hydraulic Components SDC / DHC
210 EN2H-0221GE51 R0812
Discharge control 2
The heating circuits are always supplied with energy from the
heat generator. As long as the buffer contains sufficient energy,
the heat generator will be heated via the buffer loading pump
instead of the burner. If the energy in the buffer is not sufficient,
the burner will be started.
If a heat generator disable is active (e.g. through external burner
disabling via contact or cycle disable (solid fuel/solar)), this will
only result in the suppression of the demand for the burner.
The buffer setpoint temperature is the temperature that the buffer
tank has to provide for supplying the connected heating circuits. It
corresponds to the highest demand value of these heating
circuits.
Example:
Demand value MC1 = 45°C
Demand value MC2 = 55°C
Demand value hot water = 65°C
=> buffer setpoint temperature = 65°C
A required offset value (e.g. hot-water load temperature offset)
has already been taken into consideration in the demand value of
the heating circuits.
When there is heat demand for the buffer tank from the heating
circuits or from hot water, this request will be maintained at least
to the minimum temperature limit. When the temperature drops
below this limit, the buffer tank is recharged by the heat generator
under the conditions of the buffer start-up protection.
If the buffer tank temperature exceeds the set value of the buffer
tank maximum temperature limit, forced switch-off of the buffer
loading pump occurs. The excess heat is dissipated into the
selected circuits (see forced dissipation). Forced dissipation is
disabled and buffer operation is resumed when the temperature in
the buffer tank drops more than 2 K under the set maximum
temperature limit.
NOTE
Buffer setpoint
temperature
Buffer minimum
temperature limit
Buffer tank maximum
temperature limit