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Checking the expansion vessel and system...
Expansion vessel
1. Drain the system until the pressure gauge indi-
cates "0" or close the cap valve on the expansion
vessel and reduce the pressure in the expansion
vessel.
Note
The pre-charge pressure of the expansion vessel
(p
) is made up of the static system pressure (p
0
(= static head) and a supplement (p
plement).
The supplement depends on the high limit safety
cut-out setting. The following high limit safety cut-
out settings apply
■
100 °C: 0.2 bar (20 kPa)
■
110 °C: 0.7 bar (70 kPa)
Pump controlled pressure maintaining systems
!
Please note
Pressure fluctuations may cause damage to the
boiler or to other system components.
In heating systems with automatic pressure
maintaining systems, and in particular pump
controlled systems with integral deaeration, we
recommend the installation of a diaphragm
expansion vessel (DEV) as individual boiler pro-
tection.
This reduces the frequency and level of pres-
sure fluctuations. This contributes considerably
to improved operational reliability and a longer
service life of the system components.
Boiler heating out-
put
Expansion vessel
capacity
Checking the firm seating of electrical plug-in connections and cable
grommets
St
= p
+ sup-
0
St
kW
up to
up to
up to
300
500
1000
l
50
80
140
Commissioning, inspection, maintenance
(cont.)
2. If the pre-charge pressure of the expansion vessel
is lower than the static system pressure, top up
with nitrogen until the pre-charge pressure is 0.1 to
0.2 bar (10 to 20 kPa) higher.
The static pressure corresponds to the static head.
3. Top up with softened water until the charge pres-
)
sure of the cooled system is 0.1 to 0.2 bar (10 to
20 kPa) higher than the pre-charge pressure of the
expansion vessel.
Permiss. operating pressure: 4 bar (0.4 MPa)
Note
Observe chapter "Water quality requirements".
!
Please note
The ingress of oxygen can result in system dam-
age as a consequence of oxygen corrosion.
Only use pump controlled pressure maintaining
systems that are sealed against corrosion. The
pressure maintaining systems must be protected
against oxygen ingress into the heating water.
Pump controlled pressure maintaining systems with
atmospheric deaeration through cyclical pressure
release bring about central post-ventilation of the heat-
ing system. They do not provide oxygen removal in the
sense of corrosion protection as described in
VDI 2035 Part 2.
Carry out all checks in accordance with the manufac-
turer's instructions. Limit pressure fluctuations to the
lowest possible differential. Cyclical pressure fluctua-
tions and more significant pressure differentials point
towards a system fault. Immediately remedy such sys-
tem faults, otherwise other heating system compo-
nents may suffer damage.
13
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