Checking Gaskets And Thermal Insulation Components On The Boiler; Checking The Diaphragm Expansion Vessel And System Pressure - Viessmann Vitocrossal 300 Service Manual

Vitocrossal 300 CU3A 26 to 57 Service

Checking Gaskets and Thermal Insulation Components on the Boiler

Checking the Diaphragm Expansion Vessel and System Pressure

CAUTION
Unsuitable fill water increases the level of deposits and
corrosion, and may lead to damage to the equipment.
H Thoroughly flush the entire heating system prior to
filling with water.
H Only use water of potable quality.
H The water will have to be softened if it is harder than
8.77 grains / 150 ppm total dissolved solids.
H Inhibitors or antifreeze additives suitable for heating
systems may be added manually.
1. Check the gasket/seal on the flue gas collector A
between the flue gas collector C and the boiler body
B for tightness.
2. Check lip seal D of the boiler flue connection for
tightness.
Note: The seals/gaskets can also be checked under
full load with an inspection mirror. If required,
remove the thermal insulation components.
Traces of condensate on the outside of flue
gas collector C also point towards a leak.
3. If required, retighten the flue gas collector seal A
at the tensioning toggles E or replace. Replace lip
seal D in case it leaks.
Note: Prior to removing the flue gas collector,
pull the plug at flue gas temperature sensor F.
4. Check the fittings on the water side for leaks and
replace the seals/gaskets if required.
WARNING
There is a risk of injury when working on pressurized
components. Only open the connections on the heating
water side after the boiler has been depressurized.
Only drain the boiler with a suction pump when the
boiler air vent valve is open.
5. Check the boiler thermal insulation for good fit and
correct if required or replace if it is damaged.
Note: Carry out this test on a cold system.
1. Drain the system or close the cap valve at the
diaphragm expansion vessel to depressurize the
system until the pressure gauge indicates "0".
2. If the precharge pressure of the diaphragm expansion
vessel is lower than the static system pressure, top
up with nitrogen until the precharge pressure is raised
by 1.5 to 3 psi (0.1 to 0.2 bar).
3. Top up your heating system with water until the filling
pressure of a cooled system is 1.5 to 3 psi (0.1 to 0.2)
bar higher than the pre-charge pressure of the
diaphragm expansion vessel.
Max. operating pressure: 30 psi (2 bar)
Min. operating pressure: 14 psi (1 bar)
Service
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