Fuel Selection - Tech Controllers ST-976 User Manual

Water tank priority
In this mode, the water tank (DHW) pump operates until the pre‐set DHW temperature is reached (the valves
close to the maximum and the valve pumps are switched off). After the pre‐set temperature has been reached,
the pump is disabled and the controller activates the CH pump and the mixing valves. When the water tank
temperature drops below the pre‐set value minus hysteresis, DHW pump is enabled again and the valves are
disabled.
NOTE
If the pre‐set water tank temperature is higher than the pre‐set CH boiler temperature, the pump will
not be activated in order not to cool down the water.
Parallel pumps
In this mode the CH pump operates above the pump activation threshold. DHW pump is activated at the same
time in order to heat the water tank. Once DHW pre‐set temperature has been reached, DHW pump is
disabled. It is enabled again when the temperature drops by DHW hysteresis value.
NOTE
If current CH boiler temperature is lower than current water tank temperature, DHW pump will not be
activated to prevent the water in the tank from cooling down.
Summer mode
In this mode only DHW pump is active (enabled when the pump switch‐on threshold is reached) and the CH
valves are closed in order not to heat the house unnecessarily. If the CH boiler temperature is too high (when
return protection function is enabled), the valve will be open in an emergency procedure.
4.3.8
Fuel selection
This function is used to select the type of fuel used ‐ pellet or wood. Depending on user's choice, certain
factory settings change.
Automatic transition
This function involves automatic fuel change. If the CH boiler is fired with wood, once the wood has been burnt
up, it is possible to change the fuel type into pellet without the necessity of using Fire‐up function. When the
CH boiler is in operation mode and CH sensor detects that the temperature is lower than the pre‐set threshold,
the controller will empty the grate and start pellet fire up, after the time defined in Waiting time function.
20
Pellet
Wood
Automatic transition