Decision-Making Aids Regarding Dhw Heating; Information About Water Quality - Viessmann VITODENS 242-F Technical Manual

Design information
■ Mixer PCB, capable of communicating with the Vitotronic 200 via KM
BUS
■ Adjustable bypass
■ Connection set for installation on finished or unfinished walls, with:
– Connecting pipes
– Shut-off valves for heating water flow and return with boiler drain
& fill valve
– 2 connectors for DHW
– 2 connectors for solar flow and return
– Gas shut-off valve (R ½) with thermally activated safety shut-off
valve
Boiler plinth
Part no. 7352 259

6.2 Decision-making aids regarding DHW heating

To provide the perfect solution for every situation, the Vitodens may
be supplied with an integral DHW primary store, an integral DHW cyl-
inder with internal indirect coil or an integral solar cylinder (see product
description).
Various factors must be considered when designing heating systems
and deciding between gas boilers with integral DHW primary stores or
integral DHW cylinders:

Information about water quality

6
Vitodens with primary store:
During DHW heating, settling of lime on the surfaces of the plate heat
exchanger cannot be totally prevented. The tendency towards lime-
scale build-up depends on various conditions, predominantly on the
substances contained in the water, the amount of water that is heated
(DHW consumption) and the DHW temperature.
Although generally scale deposits inside the plate heat exchanger are
minor enough not to cause any reduction in DHW output, such impair-
ment cannot be excluded with increasing water hardness. From a
water hardness of 20 °dH (3.5 mol/m
ommend the use of DHW cylinders with internal indirect coils or a water
treatment system in the cold water supply when heating DHW.
VIESMANN
66
(cont.)
3
) and higher, we therefore rec-
■ Flow temperature sensor
■ Cover with the same design as the appliance
■ Balanced flue extension, boiler flue connection
■ For the installation of the Vitodens on unfinished floors
■ Adjustable height, for screed floors from 10 to 18 cm
■ With spacers (for downward connection) for installation on finished
walls
■ DHW demand, convenience
■ Utilisation of the various connected draw-off points
■ Distance between the draw-off points and the boiler
■ System modernisation
■ Space requirement
■ Water quality
Please observe that frequently, regional water supply utilities specify
an average water hardness. In practical applications, therefore, higher
levels of water hardness may from time to time occur. This may make
the use of a water treatment facility advisable even from 17 °dH
(> 3.0 mol/m 3 ) upwards.
VITODENS