➢ Starting the burner by demand from one sensor and shutting it down by another is called
using a holding circuit.
Start threshold = Set demand temperature + Diff. on at the T.dem. sensor
Shutdown threshold = Set shutdown temperature + Diff. off at the T.off sensor
➢ For a control function with start and shutdown thresholds on just one sensor, the Shutdown
temperature input variable must be set to unused. If the boiler sensor is entered instead of
the cylinder sensor, the result is modulating boiler operation. Set demand temperature
thereby receives a start differential and a stop differential alongside its threshold value:
Start threshold = Set demand temperature + Diff. on
Shutdown threshold = Set demand temperature + Diff. off
➢ A minimum temperature can be specified using the low end temperature T.dem. min.
If the set temperature for demand or shutdown is below that value, the low end temperature
is applied as the threshold value.
The low end temperature is only effective if the relevant set temperature is > 5 °C.
A value > 30 °C is only useful if the function is being used for modulating boiler operation. In
that case, the start and shutdown thresholds apply to the T.dem. sensor.
➢ If the generator temperature (boiler temperature) exceeds the value T.gen. max. + Diff. off,
demand will not be permitted and will be switched off even if the minimum runtime has not
yet finished.
Demand will not be re-enabled until the temperature falls below T.gen. max. + Diff. on. The
minimum runtime counter will then restart.
To Next Page
Loading...
Need help?
General
