System design
The Vitopend is only suitable for pumped hot water heating sys-
tems (sealed systems).
The circula tion pump is an integral part of the equipment.
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Minimum system pressure 0.8 bar.
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The boiler water temperature is l imited to 84 °C in heating mode
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The boiler water temperature is l imited to 87 °C in DHW mode
To minimise distributio n losses, we recommend that you size the
heat distri bution s ystem to a max. flow temperature of 70 °C.
Chemical anti-corrosion agents
Corrosion is generally avoided in properly installed and operated
sealed heating systems.
Never use chemical anti-corrosion agents.
Some manufacturers of plasti c pipes recommend the use of che-
mical additi ves. In such cases, onl y use anti-corrosion agents
offered by t he heating trade, which have been approved for boilers
with DHW heating via single-wa lled heat exchangers (plate-type
heat exchangers or cylinders)(DIN 1988-4). O bserve the
VDI gui deline 2035 [or local regulations].
Heating circuits
For heating systems w ith plasti c pipes, we recommend the use of
impermeable pipes to preven t the infusion of oxygen through the
pipe wall s. Provide system separation in heating systems with
permeable plastic pipes (DIN 4726). We deliver a separate heat
exchanger for this.
Underfloor heating circuit
Install a temperature limiter into the fl ow of the underfl oor heating
circuit to limit the maximum temperature. Observe DIN 18560-2.
The underfloor heating circuit should be connected via a mixer.
For this see the Vitoset techni cal guide, chapter "Control of under-
floor heating systems".
Low loss header
We recommend the use of a low loss header for systems with a
water conten t greater than 10 litres/kW.
Plastic pipework for radiators
We also recommend the installation of a temperature limiter to
limit the maximum temperature of plastic pipes in heating circuits
with radi ators.
Attic boiler room
The install ation of a low water indicator, compulsory according to
the DVGW [Germany], is not required when i nstalling Vitopend
boilers in an atti c heatin g centre.
Vitopend boilers are protected against low water l evels to
EN 12828.
Safety valve
A safety valve is already integrated into the Vitopend (opening
pressure 3 bar).
Route the blow-off line in accordance with EN 12828 into a drain
outlet (drain outlet set available as an accessory). The drain outlet
incorporates a siphon as stench trap.
Overflow valve
The overflow valve integrated i nto the Vitopend opens when the
thermostat val ves on the r adiators open or close.
This reduces the noise developed by your heating system.
The opening pressure of the overflow valve is 300 mbar.
5822 335-1 GB
30 VIESMANN VITOPEND 222
Design information (cont.)