Intergas...but which...

[Dan Robinson]

have not adopted or retained them but persist with a plate heat exchanger

Patents are a bugger like that I suppose

 

[hard-work]

Well it's drifted into farce but perhaps a question to be answered might be why other manufacturers, some having marketed dual pass heat exchangers in the past, in a very competitive market have not adopted or retained them but persist with a plate heat exchanger.

But some good lectures came out of the farce with some buffoons slapped down and spanked big time. Some makers just got it wrong. Ideal made a tube-in-tube which was an abortion. Ferroli always made one. The great thing about the Intergas is that the heat exchanger is the whole back panel of the boiler giving easy access to the burner and pump at the front.

You can make a combi case (or have a sheet metal outfit stamp them for you), you can buy all the stock parts and put them inside and make a combi. That describes most combis on the market. Makers just screw bits together, test it, box and ship it out. That is one reason why we do not see too many tube-tube-in-tube heat exchangers as none are available on the open market. Another is scaling up. Changing plate heat exchangers is a simple task and all the scale will have gone in a few minutes as its accumulates in the plate. I can't see why makers like Ferroli and Intergas do not build-in de-scaling connections into their combis. Ferroli boasts that both sides of their heat exchanger can be de-scaled in-situ.

How many use the Gianonni heat exchanger? Lots. Now if Gianonni made a tube-in-tube heat exchanger and sold it to all makers, we would see lots of 4 moving part combis. Patents are a big part of it though. This is why patents should only last 5 years. They hold back advancement. Patents and copyright is a form of economic rent seeking (unearned income). James Watt delayed the introduction of the steam engine for 10 years because of him wanting to secure patents. He dropped down the list of my engineering heros.

 

[bernardgreen]

Well it's drifted into farce but perhaps a question to be answered might be why other manufacturers, some having marketed dual pass heat exchangers in the past, in a very competitive market have not adopted or retained them but persist with a plate heat exchanger.

If it is to be answered can we define terminology first.

dual pass heat exchangers

The way I see it both Intergas ( separate tubes ) and Ferroli ( tube in a tube ) are dual circuit , single pass heat exchangers.

 

[hard-work]

If it is to be answered can we define terminology first.
View attachment 115248
The way I see it both Intergas ( separate tubes ) and Ferroli ( tube in a tube ) are dual circuit , single pass heat exchangers.

Bernard, the Intergas appears to be `dual pass single circuit`on the CH side. The 1" looking pipe coils in and out of the heat exchanger a number of times. I would say the Intergas is "dual circuit multi-pass." on the CH and single circuit single pass on the hot water. A hybrid.

 

[bernardgreen]

This is why patents should only last 5 years. They hold back advancement.

They can also promote creativity in devising a product that provides the required function without infringing patents. Some outstanding advances have come from that type of situation.

I can't see why makers like Ferroli and Intergas do not build-in de-scaling connections into their combis.

I may be wrong but from school chemistry I recall heating water with the exhanger temperature below 100°C does not create much if any scale on the surface between heat source and the water being heated. Where the heat source is above 100°C the interface layer of water between heat source and the bulk of the water will produce scale. The extremely thin layer in contact with the heat source boils and the scale comes out of solution but the steam is immediately condensed back to water by the bulk of water. This creates a slight noise while the evaoparing layer is very thin with cold bulk water. As the bulk of water heats up and is thus less effective at condensing the steam the evaporating layer becomes thicker and the noise increases. Eventually the bulk water is too hot to condense the steam and the water is boiling and steam is ejected from surface of the bulk water. ( kettle is now boiling, time for tea )

 

[bernardgreen]

I would say the Intergas is "dual circuit multi-pass." on the CH and single circuit single pass on the hot water. A hybrid.

Disagree slightly

Dual circuit, yes, circuit 1 for the CH and circuit 2 for the DHW

Multi pass, yes it is multi-pass both on both circuits IF you consider each tube through the aluminium core as a separate heat exchanger module (*) AND the tubes are connected in series AND the cold water entry is into the tube furthest from the burner.

(*) The separate modules being fused together as a solid block of cast aluminium

 

[hard-work]

`This creates a slight noise while the evaporating layer is very thin with cold bulk water`. Bernard this known as `kettling`. It happened a lot in open vented boilers. Chemicals were needed to treat it.

 

[bernardgreen]

a slight noise while the evaporating layer is very thin

Bernard this known as `kettling`

Kettling is when the evaporating layer is thick enough to produce more water vapour than adjacent water can condense. The excess vapour has to escape and reach some point in the system where the water is cool enough to condense the steam / vapour back to water .

 

[hard-work]

Note to Steelmason
Look up the Teknigas G800 series of valves.

Yep still available today:

 

[transam]

combi with a plate may be cheaper to manufacture

intergas combi can also be used as a water heater only i.e not connected to a primary circuit , hence the need to have a heat exc that can with stand dry firing

Gloworm made a non plate afaik there was an issue with an intial sting of very hot water which could occur when a hot tap was opened

after the heating had been on for a while ? afaik there were some complaints.

Which required a re-work or alteration ??

 

[hard-work]

combi with a plate may be cheaper to manufacture

intergas combi can also be used as a water heater only i.e not connected to a primary circuit , hence the need to have a heat exc that can with stand dry firing

Gloworm made a non plate afaik there was an issue with an intial sting of very hot water which could occur when a hot tap was opened

after the heating had been on for a while ? afaik there were some complaints.

Which required a re-work or alteration ??

Intergas and I assume Ferroli have the same initial hot water draw-off problem. It can be got over by installing a blending valve on the DHW outlet. Few manufacturers make their own heat exchangers. Giaonnni and AIC make a lot of them. If a maker can make its own heat exchanger that does CH & hot water they can cut down on components making the boiler cheap to make.

 

[Dan Robinson]

It can be got over by installing a blending valve on the DHW outle

Only 8f you want to overcomplicate things

 

[bernardgreen]

hence the need to have a heat exc that can with stand dry firing

One assumes that dry firing would only occur as a result of a fault in the boilers control system.

What would happen if there was static water in the heat exchanger when the burner was burning gas due to a fault ? Could it boil and create high pressures ? Maybe forcing hot water / steam back along the cold water mains supply.

At what temperature would expansion of the metals in the dry fired heat exchanger result in degredation of the bonding of aluminium to copper and would that result in a permanent reduction in heat transfer from aluminium block to copper tube when the boiler was restored to normal working.

 

[Corgigrouch GTi]

Bernard, under what circumstances do you envisage this catastrophic event? Shall we throw in the water meter having a non return valve in it?

 

[Dan Robinson]

And this bonding.... What bonding are you referring to?