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The answer can be found at my neighbour's house. Three metres 15mm² pipe has to be emptied of cold water before any hot water can reach the sink. Then there is another metre or two of water before the heat exchanger in the boiler can put any heat into the DHW that is flowing through the heat exchanger
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That is very interesting and thanks for posting but with a cohort size of 4, there's no possibility of detecting a difference of less than 10% and gaining statistical significance with a confidence of >80%, so it all has to be treated as anecdotal.
Did the person who analysed the graphs make any comments about statistical significance?
Any testing I'm involved in we need thousands of samples to detect a difference like that and it's very common, in fact almost inevitable to see a big difference pale into nothing after a decent number of samples start to come in. However i realise that there are a lot of variables that affect how much data you would need in your case.
Did the person who analysed the graphs make any comments about statistical significance?
Any testing I'm involved in we need thousands of samples to detect a difference like that and it's very common, in fact almost inevitable to see a big difference pale into nothing after a decent number of samples start to come in. However i realise that there are a lot of variables that affect how much data you would need in your case.
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It's not obligatory to agree or disagree, someone was asked to supply data, he did as best he could and a little better than the usual anecdotal data we're fed.
Correct, and Bernard did not have to post these figures for us. However the data, methods of analysis and systems are open to scrutiny. What also has to be taken into account is the ongoing service costs. Cylinder systems, unvented and vented have more parts involved which are future failure points adding more costs. Unvented with their annual service costs. One good point about Ferroli Modena and Intergas combis is that they use far less electricity in summer when only supplying DHW - the pump is not used. But the overall annual running and services costs matter with an eye to expensive failures in the future - cylinders, 3-ways valves, cylinder stats, etc, when they add no extra value over a well made, well designed, well sized, quality combi.
Scrutiny was applied.
and that elusive item is ?
They may use less electricity (*) but that cost saving is insignificant when compared to the cost of gas wasted when a combi is fired up to supply a few litres of hot water.
Compare the volume of gas used to provide 100 litres of water at X°C in a single long draw with the volume of gas used to provide 100 litres of water at X°C in 50 draws each of 2 litres with a gap of 1 minute between draws. For this test the delivery point is 500 mm from the DHW outlet of the boiler and water less than at X°C is not included iin the 100 litres.
The heat loss from 100 litres of hot water in a cylinder can be added into the equation but even then 100 litres into a bath from the cylinder costs less then 50 washing up bowls of 2 litres each
(*) do not forget the fan may have to run at full speed to purge the combustion chamber after DHW flow is detected and before ignition occurs
( X°C because I cannot recall the target temperature ).
The prime point in costs of overall running is annual running costs inc' servicing. Then future potential costs like failures of cylinders, 3-way valves, pressure valves on unvented cylinders, etc, which can be high unexpected expenses being high cost replacements.
Other points are that combis deliver infinite hot water giving valuable space saving in tiny UK homes, having no cylinders with less overall in the system to go wrong.
A quality combi? ATAG iC Economiser 39 Plus @ 17 litres/min DHW flowrate. 10 yrs guarantee with a heat exchanger 'lifetime' replacement guarantee. That will deliver about the same flowrate of hot water infinitely as a vented tank/cylinder system. It will deliver in 30 minutes 510 litres of hot water. Look at the large physical size of a 500 litre cylinder! A modern 120 litre bath will be filled in 7 minutes - quicker in summer. Two showers can be delivered simultaneously - two definitely using aerated Raindance types of shower heads. Is it big? No, the same size as most other combis: 700mm x 440mm x 355mm.
I doubt any cylinder system will be cheaper to run than the ATAG combi.
Other points are that combis deliver infinite hot water giving valuable space saving in tiny UK homes, having no cylinders with less overall in the system to go wrong.
A quality combi? ATAG iC Economiser 39 Plus @ 17 litres/min DHW flowrate. 10 yrs guarantee with a heat exchanger 'lifetime' replacement guarantee. That will deliver about the same flowrate of hot water infinitely as a vented tank/cylinder system. It will deliver in 30 minutes 510 litres of hot water. Look at the large physical size of a 500 litre cylinder! A modern 120 litre bath will be filled in 7 minutes - quicker in summer. Two showers can be delivered simultaneously - two definitely using aerated Raindance types of shower heads. Is it big? No, the same size as most other combis: 700mm x 440mm x 355mm.
I doubt any cylinder system will be cheaper to run than the ATAG combi.
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H
Hot&Cold
how does the atag compare to your other favourite boiler https://www.diynot.com/diy/threads/navien-combi-boilers.507427/
I have an Atag IC Economiser and it performs very well. DHW output is excellent.
Very well. But I do not go to sleep with the manual under my pillow yet. I have a few favs of course. ATAG Control system is getting simpler. But very expensive to buy.how does the atag compare to your other favourite boiler https://www.diynot.com/diy/threads/navien-combi-boilers.507427/
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What kW size?
Just out of interest. Would one ( or more ) of the informed people explain exactly what does a boiler's "efficiency rating" refer to.
Is it combustion efficiency ( as measured by the oxygen content in the flue gases ? ? ) or percentage of available heat that is transfered to the heating and/or hot water circuits.
D. A. Wulfinghoff, Energy Efficiency Manual, Energy Institute Press, Wheaton, Maryland USA makes for interesting reading
Is it combustion efficiency ( as measured by the oxygen content in the flue gases ? ? ) or percentage of available heat that is transfered to the heating and/or hot water circuits.
D. A. Wulfinghoff, Energy Efficiency Manual, Energy Institute Press, Wheaton, Maryland USA makes for interesting reading
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