combi versus conventional boilers

You have probably had this discussion here many times before but is there a perceived wisdom about which is better?
The subject arises as my grown up daughter has just moved into a house with a conventional boiler and she was going on about what a nuisance it was that the house did not have a combi boiler. My initial thoughts were why complain? - is the combi so good that you'd choose to be with one instead of conventional boiler?
I have never found it very satisfactory whenever I have come across a combi boiler but on this occasion kept quiet as I imagined that things had improved since my last experiences. And anyway who wants a Dad who is out of touch.
Pro combi boilers: Less capital expenditure than conventional No hot water cylinder Usually controls are within the combi casing including pump which saves wiring and /or space and helps to keep cost down. Mains water is used to supply the hot water so that it can be reasonably powerful once set up. Saves heating a (perhaps) unwanted cylinder of hot water which may be a waste of fuel.
Pro conventional boilers No need for a constructed airing cupboard ( the ones I have come across have a very small radiator at the bottom) - build one over the cylinder. Heating of space at the same time as the heating of water to supply hot water. (In my case a considerable advantage as it is at night when the whole family wants a bath or shower in readiness for the next day). (This allows me to go into a heated room to get dry and dressed which is a nicety but also allows the bathroom to be prepared for the next person - also the house does not go a bit colder.) Filling of a bath from a cylinder can be quicker than a combi can fill the bath. Often cited as the solution to a longer boiler life than the combi and also may be needed for larger houses or condensing boilers. Allows a cylinder full of water to use if needed when the water supply becomes very poor. (Boil for drinking or use for flushing). Also allows for hot water and heating if needed if the mains supply pressure or flow rate drops e g. in some London flats in summer drought mind you there are solutions suggested for low flow rate.
I suppose my primary motivation for asking how people regard them is the fact that we recently rented a house for a month and it had a combi boiler. No doubt the owner saved quite a bit putting that in. The hot water in the bathroom was always OK and the house was warm and cosy but the pipe route and the boiler settings meant that the kitchen was a pain in the neck for hot water - always needing great care in hot water use and despite an econo setting had to be run to get hot.
--
PK
Remove the xtra y from my name in the email address if replying

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Some combis can fill 3 baths simultaneously.

Want a combi that is ultra reliable? They have them. Try an Atmos, even with an integral weather compensator. Others, Viessmann, ECO-Hometec, Atag, even Vaillant aren't bad.
Want one that fills a bath as fast as cylinder? Mainly floor mounted: ACV Heatmaster, Gledhill Gulfstream, Viessmann 333, etc. Wall mounted: Alpha cd50, Viallant 937.
Want one that delivers water instantly without the combi lag? Many around with integral small water vessels.
Combis are so go these days that if you have good mains pressure and flow it is difficult to justify other forms of CH and DHW. Just get the right flowrate and a high quality product. Get one that is undersized in flowrate and poor quality and you have problems - same as any other product.
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Yes it did sound like a relaxed sort of troll - sorry I do not post enought to be on my guard. It was a genuine enquiry.
Obviously conventional and combi have their own supporters and it is still a live subject after all these years - glad I do not have to make decisions now.
But I will tell my daughter how wrong she is.
Now here comes the troll:
Could it be that those who are in favour of one sort or another are simply justifying their own decision. A bit like my car is great because I have one.
In any event thanks for all the thoughts - very enlightening. The spirit of usenet is still alive!
--
PK
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Not really - it's simply impossible to get the same flow at the same temperature of say 60C from a combi as you can from a half decent storage system. And when filling a bath this can make a real difference to the time you have to wait. It's also easier to design a storage system so you don't get so much interaction when other taps in the house are used.
Of course this may not matter to some, but it's as well to be aware of it since prats like dribble simply lie about their flow rates. And quote the upper end models as being representative. I've never quite worked out why he feels the need to tell lies so often.
--
*Those who live by the sword get shot by those who don't*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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It is a matter of getting the best solution for the needs, not pushing a whim. Those who say only a tank and cylinder is the way know sweet nothing about heating and water systems.

She is not wrong at all. Take note of professionals like me, not know-it-all amatures.

Those who say one thing and only that will do, know nothing of the industry.
The point is that if you have good mains pressure and flow a combi should be the first on the list in an assessment. They range from small one flat jobs to large three bathroom models and a plethora of models between. They do deliver the DHW, and save space in small UK homes. They are improving all the time and some the latest models are superb. Like any other product, price usually dictates quality and reliability.
Read my posts on the subject.
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Why do you assume everyone lives in a rabbit hutch like you?
--
*Why is a boxing ring square?

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

Please eff off as you are a plantpot.
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As opposed to living in one, weed.
--
*Pentium wise, pen and paper foolish *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

Please eff off as you are a plantpot.
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Ah, you might have hit the nail on the head there
They prolly put a bit of skunk in his cocoa last thing at night to pacify him
... which would explain the reason he lives in a different universe
--
geoff

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Maxie, you are a breath of fresh air.
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Paul Kelly wrote:

I think that is probably the case.
When I built here, I had no idea what was good bad or ugly. I did the research, talked to the BM's heating engineers, talked to the builders and plumbers, and arrived at a solution that suits ME.
I would happily recommend a combi for a small flat, with maybe two adults maximum.
I would not recommend a non stored solution for bigger households. The combi gets huge, expensive, and still can't do the peak flow rates.
A pumped cold water tank solution gets noisy and expensive, but if the mains pressure is crap, it works better than a pressurized HW setup.
Likewise if the mains pressure is good, a pressurised system turns out as cheap as a decent pump and gravity system, and its a lot nicer.
Nowhere is there a 'best' solution'. Just solutions that fit differing circumstances.
I have yet to see any advantage to a heatbank with a combi tho. Or two combis.

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Paul Kelly wrote:

My advice would be to choose a system that matches the requirements and not preclude either solution. Combis have their attractions, as do storage systems, but there is no one size fits all solution. I have had both setups in this house, and both have pros and cons. Yes either system can be "perfect" in an ideal world, but it is very difficult to achieve perfection in the real world with real budgets. Exotic solutions exist for combis and storages systems (and systems that are a mixture of both). It seems rather too easy for the proponents of one particular technology to talk about the exotica as if it is routinely fitted mainstream stuff. For most users the generalisations (flow rate, space, performance etc) are mostly true, even though there are exceptions to the "rules".
--
Cheers,

John.

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True. But things like the space a conventional storage system takes up are easily understood by most. And most can again easily work out if saving that space is worth it to them.
Thing is there are countless examples of firms recommending replacing these with a combi regardless of the needs of the household. And we have such a person posting here regularly. Very few will be starting with a blank canvass where the considerable extra cost of a storage system will matter. But if they already have one the costs of bringing it up to date are not large when replacing a boiler at the same time.
--
*Pride is what we have. Vanity is what others have.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

Boy he got it!! They take up more space and people can see that.
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wrote:

The problem is people like George Wimpey seem to fit storage systems to very small flats. God only knows why as I guess they are more expensive as well as taking up additional space. Certainly no better than Combi systems I have used. And there appear to be more things to go wrong (microprocessor PCB + spaghetti wiring)
Also if the storage system needs replacing I wonder how heavy it is and how you get it out of a top floor flat without taking the roof of and hiring a crane.
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snipped-for-privacy@yahoo.co.uk wrote:

Could be any number of reasons I guess... but I would be surprised if they are deliberately pushing their total costs up without good (to them) reasons.
It may come down to the case that a conventional system will require less user education - so they will get fewer complaints from the people who can't understand how to get a bath of hot water out of a combi.
Water pressure variability issues can be more of a problem in high rise and multi unit properties. I expect that gas supply infrastructure may also come into it.
Quite a number of new builds seem to be opting for unvented storage systems as well.

The differences in total system complexity are not that great - just the components may be distributed further apart on a storage system.

Which bit of the system did you have in mind?
--
Cheers,

John.

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The whole assembly of the thermal store. Believe it weighs >=50kg but is bulky. Certainly wouldn't fancy moving it up 4 flights of stairs.

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snipped-for-privacy@yahoo.co.uk wrote:

A conventional hot water cylinder is paper thin, and nowhere near 50kg. A straight forward single man lift.
Header tanks are typically plastic and even lighter.
--
Cheers,

John.

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wrote:

A Gledhill thermal store complete with pumps, heat exchanger, casing, very thick insulation, etc, is not light. I have seen these in flats, which is overkill when a well specced quality combi can deliver the same DHW and heating.
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