Condensing Boiler Heat Exchanger - aluminium or stainless?

[jimmygibb]

Hi, Anyone any advice on whether one or the other is better/worse? I have heard that there are potential problems with corrosion in aluminium heat exchangers in condensing bolilers because the condensate is corrosive. Does anyone have long term experience of how well the two perform?

Cheers

Jim

 

[baxpoti]

Your quite right.

Go for stainless

 

[megawatt]

Does anyone have long term experience of how well the two perform?

Nope, they haven't been around for long enough.

 

[gas4you]

Stainlees steel evey time

You wouldn't even consider aluminium if you had seen the amount of 'dissolved aluminium' that has to be cleaned out of the Ideal Isar boilers I service

 

[simond]

Well, I am not convinced that aluminium is a bad idea.

Dave, I'm sure you are aware that Vaillant make most of their commercial condensers out of ali rather than stainless steel.

 

[gas4you]

No I didn't Simon. I know nothing at all about the commercial boiler range from Vaillant or any manufacturer come to that

I deal only in 100% domestic market.

 

[mehran]

it comes down to price, it is cheaper to simply make thicker alu heat exchanger, the stainless steal ones costs a hell of a lot more. in the commercial world that really adds up with the massive kw loads.

i have seen a few alu heat exchangers fail now, i don't think the current cast alu hx boiler will be around in 10-15 years. where the steel one will IMO.

now the alu alloys maybe a different kettle of fish...like what vokera use, only time will tell i guess.

btw there are a few people that are trying different designs of stainless steel hx to the Giannoni ones. hopefully we will get a bit of variety back in the boiler world

 

[chrishutt]

I've noticed quite alarming rates of corrosion in aluminium heat exchangers on Ideal Isars and some WBs, at least judging by the amount of debris that can be brushed out on servicing. Even if the HEx lasts 10 years the costs of servicing will be higher because it really will need doing every year, including clearing the condensate syphon.

 

[megawatt]

Which WB's Chris?

 

[chrishutt]

I think one was a Greenstar Junior 24i. I wouldn't like to swear on how bad it was - my memory of each boiler I see isn't what it was.

 

[simond]

We have seen flakes in the UK heat cell design condense traps.

The square 'Junkers' HE in the CDi models doesn't seem as affected.

Worcester offer 10 years on their HEs so I can't really see any major concerns if I had one.

 

[jimmygibb]

Lots of speedy replies! You guys should get out more

Think I'll opt for a stainless hx then. The boiler being replaced is at least ten years old and I'd hope the next one lasts longer rather than shorter. Now that latent heat's being extracted from the flue gas and most boilers are modulating I'd say there's not much further to go efficiency-wise so longevity is something to aim for.

Thanks

Jim

 

[baxpoti]

Flush out a trap on an Envoy or Barcelona!