Checking The Expansion Vessel And System Pressure - Viessmann VITOPLEX 300 Service Instructions Manual

Commissioning, inspection, maintenance
Checking the function of the pressure switch
Installation instructions in the "pressure switch
set"

Checking the expansion vessel and system pressure

Observe the manufacturer's documentation for
the expansion vessel.
Expansion vessel
1. Drain the system until the pressure gauge shows
"0". Alternatively: 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 applies:
100 °C: 0.2 bar (0.02 MPa)
■
110 °C: 0.7 bar (0.07 MPa).
■
Pump controlled pressure maintaining systems
In heating systems with automatic pressure maintain-
ing systems also provide individual protection by instal-
ling an expansion vessel for each boiler. This applies
in particular to pump controlled systems with integral
deaeration.
Boiler output kW
Expansion l
vessel
The individual protection reduces the frequency and
level of pressure fluctuations. This significantly increa-
ses the operational reliability and service life of the
system components. Failure to observe these recom-
mendations may result in damage to the boiler or to
other system components.
Only use pump controlled pressure maintaining sys-
tems that are sealed to prevent corrosion. The pres-
sure maintaining systems must be protected against
oxygen ingress into the heating water. Otherwise dam-
age to the system through oxygen corrosion can result.
See chapter "Water quality requirements".
*1
14
)
St
= p + sup-
0 St
Up to 1000 Up to 2100
140 300
Note
Check when system is cold.
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
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: 6 bar (0.6 MPa)
Pump controlled pressure maintaining systems with
atmospheric deaeration through cyclical pressure
release effect a central post-ventilation of the heating
system. They do not provide oxygen removal in the
sense of corrosion protection as described in VDI 2035
Part 2.
Note
Check the pressure maintaining system in line with the
manufacturer's instructions.
!
Please note
Cyclical pressure fluctuations and more signifi-
cant pressure differentials point towards a sys-
tem fault. Such faults result in damage to other
heating system components.
Limit pressure fluctuations to the lowest possible
differential.
*1 until the charge pres-