Worcester Greenstar CDI Heat Exchanger Life

[JCK1]

My combi boiler is approx. 14 years old . Worcester Greenstar CDI 35kW (I think it a very early version of what they now seem to call the Classic). It gets a service now about every two years. I live in Manchester which has a water supply from the lake district with very low total dissolved salts and alkalinity. The system has a magnetite filter (TF1 compact) on the return since 2017, and Spirotech Deaerator on the flow (this year added) . I replaced all the house radiators 5 years ago (old ones were early 1980s), I drain down the system once per year and refill , adding Sentinel X100 inhibitor since the boiler was installed. The TF1 filter collects almost nothing when I inspect every 6 months. The only problem in 14 years was the flow adaptor on the flow turbine disintegrating 2 years ago, taking out diverter motor (my gas boiler guy tells it is common with these).
My questions are a) what causes the corrosion on the condensate side (see some limited aluminium debris in condensate trap when boiler guys services) , is it carbonic acid or is nitric acid from impurities in the natural gas. or both ? b) Condensate corrosion should have predictable rate of corrosion. therefore what is the life of the heat exchanger if there is no significant corrosion on the system water side. ?

 

[Gasguru]

Stop replacing the system water each year, it's unnecessary and each time you're introducing fresh oxygen into the system. Just top up the inhibitor to maintain the dose when required.
The CDi heat exchanger first appeared back in 2002/2003 AFAIR. Working on these early models suggests the heat exchanger should carry on for many years yet.
The condensate is a little acidic and the aluminium is sufficiently thick to allow gradual corrosion of the surface to have little consequence.
Make sure the heat exchanger fins are properly cleaned of oxide say every 5 years.

 

[muggles]

Stop replacing the system water each year, it's unnecessary and each time you're introducing fresh oxygen into the system. Just top up the inhibitor to maintain the dose when required.
The CDi heat exchanger first appeared back in 2002/2003 AFAIR. Working on these early models suggests the heat exchanger should carry on for many years yet.
The condensate is a little acidic and the aluminium is sufficiently thick to allow gradual corrosion of the surface to have little consequence.
Make sure the heat exchanger fins are properly cleaned of oxide say every 5 years.

Agree with all of this