2 Safety information
3.7.2 Avoiding water-side corrosion
Corrosion is usually triggered by the available oxygen
in the water. This value can be brought into a safe
range with proper planning, design, installation and
maintenance of the heating system. A constant input
of oxygen should be avoided.
Important in this regard:
–
Expansion tank
: Air must be prevented from
being drawn in when the heating system is coo-
ling down. Ensure:
–
Correct planning and implementation of the
expansion tank.
–
Regular check of the system pressure, expan-
sion tank pre-pressure.
–
Immediate repair of leaks in the heating system.
–
In the case of older underfloor heating, ensure
pipes are diffusion resistant
Check the pH of the fill-up water
–
The pH value must be between 8.2 and 9.5.
–
If this pH value does not self adjust after a week of
operation, it must be raised by adding 10 g/m³ tri-
sodium phosphate (Na3PO4) or 5 g/m³ sodium
hydroxide (NaOH). Allow 2 to 4 weeks of ope-
ration before further corrections.
–
Exception: If aluminium materials are used in the
heating system, a pH from 8.2 to 8.5 must be met
(pH> 8.5 increased corrosion tendency).
Electrical conductivity
The probability of corrosion usually decreases with
decreasing electrical conductivity of the heating
water.
Low salt operation - filling with demineralised
water
, see VDI 2035 sheet 2.
Low salt
Electrical conductivity at 25°C
< 100 µS/cm
In the case of low-salt operation, feeding with non-
demineralised water can have a significant effect on
the pH value and push it into a critical range.
►
Check the pH value regularly.
3.8 Information about the hydraulic
connection
Return flow boosting (RFB)
–
Functioning: If cold heating water (temperature <
55°C) flows from the heating circuit or the buffer
tank into the hot boiler, the steam contained in the
flue gas condenses on the "cool" boiler heat
exchanger surfaces. In the long term this leads to
corrosion and damage in the boiler. To avoid this,
hot water from the boiler flow is added to the
boiler return.
–
Return booster modules with a motor-controlled
mixer perform this task more accurately and
reliably than thermally controlled modules.
–
In addition, they allow the use of residual heat: If
the boiler temperature rises again after the burner
has stopped, then the charging pump starts, the
mixer opens, and the residual heat from the boiler
is transferred to the buffer tank.
i
The
pellet
elegance
has integrated return flow
boosting as standard, i.e. no further measures
are required in this regard.
Provide shut-off options in the lines
–
Position shut-off valves for each section (in buffer
tank, etc.) in order to minimise the quantity of
water that needs to be replaced in the event of
repairs or system extensions (see: preventing the
ingress of oxygen, heating system's fill-up/make-
up water
).
Pressure equalisation through expansion tank
–
The expansion tank prevents air from being
drawn in when the system cools down (issue: oxy-
gen input, heating system's fill-up water
–
Dimension the expansion tank with a capacity of
12% of the total hydraulic system volume.
–
Secure the expansion tank against shut-off. To do
this, either use the shut-off options on the way to
the expansion tank as cap valves, or unscrew the
hand lever (handwheel) and attach it to the expan-
sion tank with the wire in a clearly visible position.
–
Installation of an expansion tank or a pressure
maintenance system is essential. Use of open
expansion tanks is not permitted.
–
The pressure in the heating system (can be read
off the manometer) and the set pre-pressure in
the expansion tank must be checked regularly.
Installation manual
pelletelegance
9
