Condensing: Stainless v Aluminium

[bogstandard]

What are the feelings in respect of condensing boilers using Stainless steel units versis Aluminium units ie
Stainless = Vallient/ Chaff/Halstead etc
Ali = Worcester/Ideal/Volera etc
I have seen a lot of degadation of Ali in the past!

 

[doitall]

Stainless steel every time, no contest in my book

 

[ChrisR]

I asked this questiopn of a number of mfrs at a phex recently. Got NO satisfactory answers. They usually said theirs didn't corrode, and that the grey aluminium goo in the condensate trap was nothing to worry about.

Not very convinced really, but Bosch etc have been doing it in Europe for years.

 

[bripl]

chris bosch heat exchanger is a hybrid ali/silicon not been running long enough stainless is the only way forward at this moment in time

 

[croydoncorgi]

Depends what you want to achieve...
Obviously (?) there WILL be situations whre aluminium will corrode and if you find grey goo in the trap, it must be from somewhere. OTOH, stainless will probably be more expensive. That said, note that many of the stainless burner units (Glowworm, Vaillant, ...?) all come from the same place (Giacomini?). I recently worked on a VERY expensive Atag boiler which not only had a stainless steel combustion chamber casing and HX. The blurb also maintained that it was 'special' so that crud would not stick to the internal surfaces. Can't remember if this was 'special steel' or additional surface treatment; anyway, the boiler was certainly much cleaner internally than I have come to expect from condensers.
So, as usual, you pays your money and takes your choice. And the more you pay, the better the result, within reason.

 

[ChrisR]

bripl
it was WB who said they've been using Al in Europe. Anyone ever actually known a Greenstar heat exchanger dissolve to the point where it needed replacing?

They add silicon to the alloy so it casts better, and is harder so threads can be tapped etc. It's quite detrimental to AL's corrosion resistance though.

Al (and its alloys) is VERY much better at conducting heat than steel. So easier to lift so cheaper to move prior to sale, install.

Maybe it's a bit like a car. The whole thing has a design life and there's no point making one bit last forever. Wouldn't be surprised if it's 10 years! (It used to be 60,000 miles for a Ford, now 100,000)

 

[htgeng]

imo, all will be stainless steel in 10 years time. The only thing the ally brigade is trying to do is to continue to shift their existing stuff while they changeover their design...