Technical Data
VITOROND 200, VD2A
11
New Casting Design and Therm-Control Functionality
A specific, matching boiler control is part of the standard equipment of the Vitorond 200, VD2A.
Boiler protection is assured by the following:
- Therm-Control logic
- Control of a shunt pump
- Flow rate reduction in the heating circuits
- Constant return temperature control
The cast iron mid-sections were re-designed
to increase the heat exchanger surface area
and water volume, and the number of cast
iron sections was reduced by one section.
Together with the redesigned return water
distribution system and the Therm-Control
low-temperature protection logic, this
eliminates the need for a minimum return
water temperature.
The larger water volume and increased
width of the flue passages also ensure even
heating of the water and reduced burner
cycling.
A new tongue-and-groove system with
silicone sealant replaces the fiber-rope seal
between sections used with the VD2 Series.
Redesigned Return Water Distribution System
System return water enters the cast iron
sections of the VD2A boiler via a return
water distribution tube now located at the
top of the cast iron block (see Fig. 8).
Heated supply water flows at the bottom of
the cast iron block towards the rear section
and upward to the supply connection. The
return water temperature is elevated when
passing through the rear cast iron section
where the supply water flows upward to the
boiler supply connection.
The pre-heated return water is then
distributed to the cast iron sections through
two upward-pointing openings in the
distribution tube at each section. The size of
the opening is proportional to the amount of
heat input of each cast iron section. In each
section the return water flows downward
and mixes with heated water. Once fully
heated, the supply water flows through the
bottom of the cast iron block up the rear
section and out the boiler supply to the
system.
The even temperature distribution ensured
by this design reduces the thermal stress on
the heat exchanger and, in conjunction with
the Vitotronic Therm-Control logic, prevents
the formation of flue gas condensate at all
return water temperatures, eliminating the
need for a shunt pump or return temperature
elevation provided by a Low Temperature
Protection (LTP) Package.
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Fig. 6
VD2 cast iron section
Fig. 7
VD2A cast iron section
Fig. 8
Boiler supply
Boiler return
Therm-Control sensor
Return water distribution tube
Fig. 8
