Vaillant auroTHERM VFK 900, Start-Up, Maintenance And Troubleshooting Manual

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39 Manual - Solar hot water systems 0020009607_02
Minimum diameter
of the discharge
pipe from the
tundish Maximum
permissible
total resistance,
expressed as
straight pipe
length (without
elbows
or bends) Resistance due to
each elbow or bend
22 mm Up to 9 m 0.8 m
28 mm Up to 18 m 1.0 m
35 mm Up to 27 m 1.4 m
Table 5.6 Air resistance
Examples:
22 mm discharge pipe with 4 elbows and of 7 m length
from the tundish to the discharge point:
Resistance for 4 elbows
per 0.8 m
= 3.2 m
Resistance for discharge pipe = 7.0 m
Total resistance = 10.2 m
The total resistance of the discharge pipe is higher
than the maximum permissible value for 22 mm
pipes (9 m). Base your calculations therefore on the
next largest pipe diameter.
28 mm discharge pipe with 4 elbows and of 7 m length
from the tundish to the discharge point:
Resistance for 4 elbows
per 1.0 m
= 4.0 m
Resistance for discharge pipe = 7.0 m
Total resistance = 11.0 m
The total resistance of the discharge pipe is lower
than the maximum permissible value for 28 mm
pipes (18 m),which means this pipe diameter can be
used.
metal discharge pipe from
temperature relief valve to
tundish
metal discharge pipe
from tundish with
continuous fall
tundish
discharge below
fixed grating
fixed grating
trapped
gully
safety device
(e. g. temperature
relief valve
ventil)
500 mm
minimum
300 mm
minimum
Fig. 5.17 Typical drainage installation
Water which is almost boiling may escape from the
discharge pipe in the event of an error.
H
Danger!
Risk of being scalded by escaping hot water!
Make sure the discharge pipe ends at a safe
point inside or outside the building (safe and
visible), where there is no risk of anyone coming
in contact with hot water.
A suitable point is, for example, under a fixed grating
above the trap of a trapped gully. Low discharge pipes,
for example up to 100 mm above external surfaces, such
as parking spaces, grasslands etc., can be used, provided
they are secured by a wire fence or something similar to
prevent children from coming in contact with the waste
water, and the system is visible. No valves or taps may
be installed in the discharge pipe.
• Make sure the discharge pipe is at a constant slope of
at least 1:200 from the tundish to the discharge point.
The discharge pipe from the pressure relief valve of the
Vaillant boiler can be connected to the horizontal
discharge pipe of the solar cylinder behind the tundish
with a T-piece.
5.7.2 High level termination
Providing that the point of termination is such that
persons in or around the building will not be endangered
should discharge take place, the method of termination
shown in fig. 3.1 is satisfactory. Examples of points to
consider when deciding whether a location for the high
level of discharge is suitable are:
– The possibility, taking into account wind effect, that
someone may be in the path of the water being
discharged and if so, whether the temperature of the
discharge water will have been sufficiently reduced to
not be dangerous. Thermal conductivity of the
structure's surface, climatic conditions and location
and orientation of the discharge pipe may or may not
have an effect on reducing the temperature of the
discharge water.
– The location of windows and similar openings.
– The likelihood of a pram being left beneath the point
of discharge.
– The ability of structures surface to withstand near
boiling water.
– The possibility of ice formation if water is discharged
onto pedestrian walkways.
Installation 5
600mm
Max pipe length