Honeywell SDC Service Manual page 209

SDC / DHC
NOTE
EN2H-0221GE51 R0812
Loading control
The supply of energy from a controlled heat generator to the
heating circuits is realised through loading the buffer. The buffer
control ensures that the buffer is supplied with sufficient energy
from the heat generator, via the buffer loading pump.
With buffer discharge controls, it must be ensured that the
residual energy from the buffer can be transported to the heating
circuits if a controlled heat generator is not available. With control
mode 3 and 4, the buffer loading pump output must be switched
for this purpose in this case. With control mode 6, only the burner
demand is suppressed with a heat generator disable.
If a heat generator is not available and the actual buffer
temperature is below the minimum buffer temperature while buffer
start-up protection is active, the buffer loading pump output
remains switched off (priority).
A heat generator is not available if:
• An external heat generator disable is active at a variable input
• Heat generator cycle disable is active via configuration in the
"Solid Fuel" menu, parameter 05
• Heat generator cycle disable is active via configuration in the
"Solar" menu, parameter 07
• A heat generator is not present in the system (e.g. purely solid
fuel buffer combinations)
Discharge control 1
The heating circuits are supplied with energy either from the
buffer through discharging the buffer tank via buffer loading pump,
provided the buffer tank contains sufficient energy, or through
direct supply from the heat generator.
If a heat generator disable is active (e.g. through external burner
disabling via contact, cycle disable (solid fuel/solar)), the energy
contained in the buffer, independent of the current buffer level, is
dissipated into the heating circuits by enabling the buffer
discharge channel (e.g. switching on the buffer loading pump or
switching over the buffer loading pump valve). The buffer
minimum temperature is monitored. Hot-water loading is enabled
under the conditions of buffer/tank discharge protection.
Hydraulic Components
209