The age of your boiler makes it possibly on the cusp of whether it has the old seal fitted or indeed the new graphite seal. Only a visual inspection of the retaining nuts on the burner would confirm.
The new seals are supplied with nuts that have a 'rubber' locking ring around the inner outside.
As Tony says this should have been serviced at approx 12 months as they do have a tendency for the co2 % to creep up over the year, therefore making the boiler run too powerful and we all know that the Giannoni HE doesn't like too much heat (French carp )
The new seal is supposed to last 5 years as long as it is not disturbed. I for one do not agree with this for various reasons, so my personal policy is to replace at least every 3 years.
The new seals are supplied with nuts that have a 'rubber' locking ring around the inner outside.
As Tony says this should have been serviced at approx 12 months as they do have a tendency for the co2 % to creep up over the year, therefore making the boiler run too powerful and we all know that the Giannoni HE doesn't like too much heat (French carp )
The new seal is supposed to last 5 years as long as it is not disturbed. I for one do not agree with this for various reasons, so my personal policy is to replace at least every 3 years.