Technical data

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Vitorond 200, VD2A Technical Data
Technical Data
Therm-Control Low-Temperature Protection Logic
A specific, matching boiler control is part of the standard
equipment of the Vitorond 200, VD2A. Boiler protection
is assured by the following:
H Therm-Control logic
H Control of a shunt pump
H Flow rate reduction in the heating circuits
H Constant return temperature control
Therm-Control is an integrated low-temperature
protection logic provided by the Vitotronic control.
The control uses a Therm-Control temperature sensor
specifically positioned in the casting close to the boiler
return (shown in Fig. 8 on page 11) to capture the
thermal state of the boiler (i.e. the temperature of the
system return mixed with the boiler water) and react
as early as possible. The Therm-Control Logic shuts off
the system pump (and, if applicable, closes the mixing
valve) and brings the burner to full fire until the boiler
minimum setpoint temperature is reached during start-up,
preventing the formation of flue gas condensation and
allowing for maximum heat transfer to the system.
This ensures steady supply temperatures with only
minimal fluctuations, and eliminates the need for a shunt
pump or return temperature elevation provided by a
Low Temperature Protection (LTP) Package.
Example:
Take a heating system with one heating circuit and
a mixing valve.
In the start-up phase, the set Therm-Control temperature
is not achieved at the Therm-Control sensor.
The mixing valve downstream of the boiler receives
a signal via the control to reduce the flow rate and to
operate the burner at full fire (Phase 1 as shown).
The boiler temperature and that captured by the Therm-
Control sensor now rapidly rise. The mixing valve opens
when the set temperature is exceeded at the Therm-
Control sensor, and the flow rate (in this example 50 %)
inside the boiler is steadily increased (Phase 2).
The return water temperature rises after a certain time has
elapsed which is a function of the system water volume.
As the return temperature rises, the mixing valve opens
further until the maximum flow rate (100%) is achieved.
Now the control will modulate the burner firing rate to
achieve the required setpoint (burner modulation), and
weather-responsive boiler water temperature modulation
will take place.