Replacing The Expansion Vessel - Vaillant ecoTEC plus 937 Instructions For Installation And Servicing

• Pull the plug (4) out of the gas valve.
• Pull the plug (3) out of the fan.
• Unscrew the three screws (2) out of the thermo-
compact module (1).
• Remove the complete component group "gas valve/
fan".
5
Fig. 9.3 Gas valve/fan screwed joint
• Release both fixing screws (5) on the gas valve and
remove the fan from the gas valve.
• Replace the faulty component.
a Caution!
Danger of damage to the equipment!
Fit the gas valve and fan in the same position
as before.
• Screw the fan onto the gas valve.
Use new seals.
• Re-install the complete "gas valve/fan" unit in reverse
sequence.
• After completion of the work check the system for gas
leaks and carry out a function test (see Section 7.8).
9.4

Replacing the expansion vessel

d Danger!
Before replacing components ensure that the
safety instructions from Section 9.1 are
observed.
• Disconnect the appliance from the mains as described
in Chapter 9.1, and close the gas isolation valve in the
gas supply pipe.
• Close the isolation valves in the flow and return pipes
and drain the water out of the combi boiler.
ecoTEC plus 937 installation and maintenance manual
Replacing components 9
Fig. 9.4 Replacing the expansion vessel
• Unscrew the nuts (4) from the water pipe on the
underside of the expansion vessel.
• Unscrew the two screws (1) in the retaining plate (2)
and remove the retaining plate.
• Pull out the expansion tank (3) forwards.
• Guide the new expansion tank back into the appliance.
• Re-connect the new expansion tank using a new
gasket.
• Re-fit the retaining plate.
• Check the pressure of the expansion tank (minimum
pressure 0.75 bar).
If required, match the pressure to the static head of
the heating system.
• Fill and vent the combi boiler.
• After completion of the work check the system for gas
leaks and carry out a function test (see Section 7.8).
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