Combi boilers

SWMBO has just given me my project for next spring - revamp the bathroom, she has already selected the suite she wants. Now me and the kids have showers (over the bath at the mo) but she prefers a bath so I want a fitted shower cubicle The only place I can fit a separate shower is in the corner where the airing cupboard is with the hot water tank. I have nowhere else I can put the tank so I was thinking of a combi boiler system for the rads and hot water. I am sure lots of you have experience of these but I have a few questions.
At present I have a 20 year old Wickes boiler 45k btu(works fine apart from replacing the pilot stat every few years) on a Y plan system, this is hung on the wall in the kitchen, would a combi be a fairly straight forward replacement.
The present shower over the bath is a pumped system, can the pump be dispensed with when using a combi (understand combi's use mains pressure, mine is ok but with hard water)
The loft tank only feeds the hot water cylinder and the power shower, all cold taps, appliances and WC's are mains fed
Combi(condensing) boilers used to have a bad reputation for failing, has this improved on recent models?
Any recommendations
Bazza
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If you still want to have the bath you'll find the time it takes for the average combi to fill it very much longer than with a decent storage system (especially in cold weather where the incoming mains water is very cold) as a combi can't heat the same volume of water at the same temperature instantly as a storage system can dispense.
If you look at the spec of a combi it will give the water flow at a certain temperature. You can measure your present flow (and temperature) to the bath to compare. And since you already have all the parts in place for a decent storage system which presumably works pretty well, beware of prats like Drivel who will be along shortly to tell you a combi is the answer to world peace. ;-)
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

Not this pillock again!! There are high flow combis around. This man should eff off.
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There are indeed. At a high cost. And both the gas and water main might need replacing to supply them.

Isn't about time you went away again? You're still obviously not well in the head.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

This man should eff off.
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Dave Plowman (News) wrote:

Waiting for the bath to fill is not really a big problem as we mostly take showers, it's just that I would "really" like to have a separate shower and the only way is for the tank to go, have already told the wife that the boiler is old and could fail at anytime and with the new regs the airing cupboard is not an option anymore ;-)
I have no other problems with the system but as I will be totally gutting the bathroom anyway I may as well go the whole hog. I await to hear what the good doctor has to say, I do keep an open mind
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wrote:

See my post on this.
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wrote:

There's two characteristics of a combi system I'd flag up. Firstly the time for hot water to arrive at the bathroom basin can be frustrating and unlike storage can't be shortened by increasing flow. You're bound to notice this because your existing storage is adjacent to the bathroom. Made worse if backfeeding from the new combi position over existing 22mm pipework. The other issue is that you will now have a single point failure for DHW and CH. You need to have contingency plan. Perhaps a maintenance contract, but that's another issue...
Jim A
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Is the time taken to get hot water to the tap due to the run of the pipes or the heating time of the combi? the combi would be mounted in the kitchen directly below the bathroom. I have an immersion heater but never had to use it, if the boiler has failed I have always managed to fix it the same day, admittedly it is old with not much gubbins, are combi's much more complicated?
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Its due to the volume of water in the pipes and the limited flow rate of the combi. The water heats as near as dammit instantly at the combi but changes in flow rate at a remote tap take time to be reflected in the temperature delivered at the tap, unlike storage systems where the temperature is independent of flow rate. Sorry didn't mention that earlier. Some top of the range combis have a limited reservoir of hot water but never installed one so no idea if that helps.
BTW not dead set against combis but best to understand their characteristics.
Jim A
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Do not generalise. There are combis that can do 3 bathrooms. Many are just brilliant.
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Yes they are - but them so are most modern boilers. You can say goodbye to your near total reliability with simple fixes if anything goes wrong.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

Take no notice of this idiot.
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The Atmos is very simple. You tend to get what you pay for in combis.
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wrote:

Some combis have a small integral water vessel to prevent this.
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Right - if you need the space and realise the limitations of a combi (or rather your wife does) it could well be the way to go.

The best advice is to ignore totally what he says as he knows the value of nothing and would love to spend other's money on his 'quaint' ideas. But plenty others will give you good advice based on your actual requirements.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

Take not notice of this idiot. Combis have no limitations as there is a model out there that will give fast delivery and high flowrate delivery too.
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Of course you've conveniently omitted the cost of such a thing - as usual. That's the trouble with just quoting adverts.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

Please eff off as you are vacant in the head.
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On Mon, 12 Nov 2007 14:25:16 GMT someone who may be Bazza

Have you warned SWMBO that a combination boiler is likely to take two to three times as long to fill the bath? Is SWMBO happy with this?

Do you really want to have one in the bathroom? Would it not be better/possible to put one elsewhere and cut the bathroom queue?
The sort of combination boilers one tends to see in houses are fine for one or two people, but any more than that and their limitations tend to show up.
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David Hansen, Edinburgh
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