Expansion Vessel; Pump Controlled Pressure Maintaining Systems - Viessmann Vitoplex 300 Service Instructions For Contractors

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 (0.02 MPa)
■
■ 110 °C: 0.7 bar (0.07 MPa).

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, provide individual protec-
tion by installing a diaphragm expansion vessel
for each boiler. This applies in particular to pump
controlled pressure maintaining systems with
integral deaeration.
This reduces the frequency and level of pres-
sure fluctuations. This in turn contributes signifi-
cantly to improved operational reliability and a
longer service life of the system components.
Boiler out- kW
put
Expansion l
vessel
Checking the setting of the temperature controller if a building management
system is used (DCC system)
!
Please note
Shutting down from full load can result in high
material stress and material damage to the
boiler.
If a system with a higher ranking building man-
agement system takes over the temperature
control of the boiler, adjust the settings at the
temperature controller TR. Set the electronic
temperature controller TR to at least 10 K below
the mechanical temperature controller TR of the
Vitotronic.
)
St
= p + sup-
0 St
Up to 300 Up to 500
50 80
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 (0.01 to 0.02 MPa) 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 (0.01 to
0.02 MPa) higher than the pre-charge pressure of
the expansion vessel.
Permiss. operating pressure: 4 bar (0.4 MPa)
For water quality requirements, see page 22.
!
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-venti-
lation of the heating system. They do not pro-
vide 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
faults, otherwise other heating system components
may suffer damage.
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