Wolf CGB-2 Service Instructions Manual page 19

13. Cleaning the heat exchanger
If you notice a loss of water, check the expansion
vessel pre-charge pressure.
The connection valve is at the top rear
and is secured with a protective cap.
When the heating circuit is depressurised, the
pre-charge pressure should be about 0.75 bar.
Replace the top and bottom combustion chamber
gaskets.
After installing the gaskets, lubricate them with
silicone grease on the outside.
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