Checking The Diaphragm Expansion Vessel And Pressure In The System Separation Circuit; Checking The External Diaphragm Expansion Vessel (Heating Circuits) And System Pressure; Checking The Safety Valve Function - Viessmann Vitovalor PT2 Installation And Service Instructions For Contractors

Checking the diaphragm expansion vessel and pressure in the system
separation circuit
Fig. 78
Checking the external diaphragm expansion vessel (heating circuits) and
system pressure
Note
The expansion vessel can lose some of its charge
pressure over time. When the boiler heats up, the
pressure gauge indicator may rise to 2 or 3 bar (0.2 or
0.3 MPa). The safety valve may also respond and dis-
charge the excess pressure.
Therefore check the expansion vessel pre-charge
pressure annually.
Check whether the installed expansion vessel is ade-
quate for the system water volume.
Carry out this test on a cold system.
1. Drain the system until the pressure gauge shows
"0".
Alternatively, close the cap valve on the expansion
vessel and reduce the pressure until the pressure
gauge indicates "0".

Checking the safety valve function

Note
Carry out this test on a cold system.
The system must be shut down.
The top panel can be removed for easier access. See
C
page 52.
1. Drain the system separation circuit at valve
2. Check the pre-charge pressure of the diaphragm
B
3. If the pre-charge pressure of the diaphragm expan-
4. Top up with water. Observe the specifications for fill
Note
If the diaphragm expansion vessel is being replaced:
A
Only use the gasket supplied with the spare part.
2. If the pre-charge pressure of the expansion vessel
3. Top up with water until the charge pressure of the
Commissioning, inspection, maintenance
pressure gauge indicates "0".
B
expansion vessel once a year. Set value: 1.0 bar
(0.1 MPa).
sion vessel is lower than this, recharge with nitro-
gen via connection .
C
and top-up water; see page 62.
Operating pressure: 1.5 to 1.6 bar
(0.15 - 0.16 MPa).
is lower than the static system pressure, top up
with nitrogen until the pre-charge pressure is 0.6 to
0.7 bar (60 to 70 kPa) higher than the static system
pressure.
cooled system is at least 1.7 bar (0.17 MPa), and
is 0.6 to 0.7 bar (60 to 70 kPa) higher than the pre-
charge pressure of the expansion vessel.
Permiss. operating pressure: 3 bar (0.3 MPa)
until
A
85