Village Hall Boiler

[Tristar]

We have been offered either an Ideal 18kw or Worcester Greenstar 18Ri heat only boiler to replace our ancient Vaillant in our Village Hall.
We would be grateful for advice on which one to choose, or whether another make might be preferable.
Thank you in anticipation

 

[sjmac]

Both boilers are fine, I'm assuming the Ideal is a Logic ? Double check the warranty on the Ideal, as there used to be a clause about the appliance being fitted in a domestic property only for the extended warranty

 

[Tristar]

Thanks, will check that.

 

[Tristar]

A second quote suggests that a Baxi is better, having a SS heat exchanger as opposed to aluminium, we are confused as to which we should choose as prices are similar.

 

[Gasguru]

Whenever any one tries to make out that SS is better than alu or vice versa they are ignorant and talking utter nonsense...just remember most installers are getting some
kind of kickback from the manufacturer to promote the boiler.

There are pros and cons to each material and each have had very successful and complete dogs of design.

eg. An aluminium disaster is Baxi Barcelona design used in many many models, or the Isar/Icos design.
On the other hand The Worcester CDi aluminium design has been around 20 years and is very robust, even the cheaper Ri heat exchanger is now 15 years old and still in production and not particularly problematic.

Many stainless designs use a French heat exchanger (that includes Vaillant and many Baxis). These are more prone to debris as the coils are in parallel.
However the stainless design found in Atags is entirely different, hasn't changed in design from launch and are very long lived.

Then you have oddballs like the Intergas...copper tubes enbedded in an aluminium heat exchanger...again a very robust design.

You need to check very carefully whether you will have an extended warranty with the new boiler (it not being in a domestic property) as there are some truly extortionate spares prices nowdays (even from the likes of Worcester and Ideal).

 

[bernardgreen]

Then you have oddballs like the Intergas...copper tubes enbedded in an aluminium heat exchanger...again a very robust design.

But like most aluminium heat exchangers can suffer from erosion when the boiler is condensing and producing condensate on the surface of the heat exchanger.

 

[Gasguru]

And? If it lasts 15/20 years it's done it's job. I look after many 1st gen Greenstars from 2002/3 containing the original CDi type hex.
There are plenty of SS heat exchangers that fail prematurely from blockage as the waterways are often very narrow.
As I said you can't say one material is better than the other.

IMHO much of the boiler industry chose the wrong direction but cheapness of design always prevails.
A traditional copper fabricated heat exchanger coupled with a stainless steel tubed coil recuperator would prove the most robust design. (A few band D boilers were of that design).
Then add in a premix burner for low NOx emmisions.
With careful temperature monitoring of combustion products (to protect the primary hex from condensing) a 5:1 turndown ratio can be achieved which is perfectly adequate.

 

[Tristar]

Very interesting comments people, still leaving it very difficult to choose, thanks anyway. As the man said: Yer pays yer money and makes yer choice!

 

[muggles]

But like most aluminium heat exchangers can suffer from erosion when the boiler is condensing and producing condensate on the surface of the heat exchanger.

View attachment 205167

Not much erosion there, and there are some still going strong after 25 years of use so it's not an issue

 

[ericmark]

Oh 15 and 20 years, I thought that was bad? Just renewed boiler in old house after 40 years, it had developed a slight leak.

 

[bernardgreen]

Not much erosion there, and there are some still going strong after 25 years of use so it's not an issue

I am led to believe that picture was taken when the boiler was 6 years in service.

I know the amount of erosion is greatly increased if the return water ( from rads ) is cool enough that liquid condensate is formed on the surface of the heat exchange.

If the return water is hot enough that condensing does not happen then there will be very little erosion.

Another factor is the layer of oxides and other compounds that form a layer of thermal insulation between flame and heat exchanger, How much does this affect the efficiency of the boiler ?.

 

[vulcancontinental]

Just to confuse the original poster further with more extraneous observations;

The hex in the photo could do with a service, all boilers need one annually stainless or aluminium.
The Atag has many more tubes of a far smaller bore than the French one mentioned, two narrow headers, meters of thin gasket and over 140 welds to boot.
A village hall maybe intermittent usage so prolonged running of the boiler to offset the poorer conductivity of stainless with weather compensation and OpenTherm may not be the way to go. If the heaters are radiators then fast high temp heat up ali would be a good bet run hot with no oxides through condensing.
I liked the point about the traditional copper fabricated exchanger with recuperator and variable fan speed linked to gas valve modureg but not premix - the Synergy and Syntesi were both the old Band A though not without faults like any boiler.
Anything that separates the combustion products from the system water will not help conductivity but with a factor of 13 times better thin wall ali has a bit of a head start over stainless and servicing properly maintains that advantage.


I'd say looking at the original question again and bearing the above in mind something one piece, no joints, no welds, extruded not cast, large bore, thin wall, low mass, high conductivity, long warranty, retarded flue flow in place of the recuperator and easy front servicing for the lazy service engineer would be something to consider.

 

[ianmcd]

Really bet you wish you hadnt asked now

 

[Tristar]

You’d win the bet!

 

[dilalio]

Nobody is going to invest in designing and manufacturing a boiler that will last 20+ years... Energy compliance rules are changing almost yearly now and this would not allow the manufacturer to continue selling the product, without "major" changes and add-ons every 2 or 3 years, to meet those regulations.
This would make it very difficult for them to get a return on their investment.