Choosing a condensing boiler

[Fuoleum]

I want to get a new boiler that will give me as much hot water a

possible. I have been advised that Vailant have aluminium hea exchangers (except at the very top of the range) and so should b avoided.

Other boilers that made my short-list based purely on the amount o l/min at a 35 C temp rise are (in order of flow rate) Worcester, Bax (Joint top these two, but the Baxi is several hundred pounds cheaper) Glow Worm (I saw in one of these threads that these have a stainles stell heat exchanger?), Ferroli (I've been advised that these ar super-reliable, but the flow rate is 1.5l/min lower than the top two).

Is there anything to decide on other than cost and flow rates, o should I immediately rule out some, or add-in others based on factor that I know nothing about?

Thanks

Ala

-- Fuoleum

[RedOnRed]

I think you'll find that Worcester Bosch's have aluminium heat exchangers too. So seeing as Vailant and WB have two of the best reputations, it may be worth disregarding the aluminium factor.

[Dave Plowman (News)]

To get a decent flow rate out of a combi, apart from having an expensive combi, you *might* have to upgrade both the incoming water and gas mains.

If you have the space, a storage system will guarantee decent flow rates for a normal house and family.

[Doctor Evil]

Modern aluminium heat exchangers are coasted in silicon, unlike the rubbish of old.

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[Doctor Evil]

.......he has a big think and spurts out......

The gas was uprated for natural gas 30 years ago....not in the caber manual.

...the caber have confused him as the storage system is lousy on showers and takes up space everywhere......just like the cabers piled up in his living room....

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[Dave Plowman (News)]

They put in new gas mains to houses on that change? What a fool. Or did you mean something else? It's difficult to tell with one so illiterate.

One of these days you'll learn by reading. There's not a combi available at a sensible price that can match the flow of a decent storage system.

Of course you probably don't wash, living in a trailer.

[Doctor Evil]

....from a hard morning stacking his cabers in the living room.......he is startled into life.....spurting henceforth....

...an amazing observation by him...people do learn by reading......

....of course total and utter garbage spouted out.

.......more confusion....the Pickies do wash occasionally to show off their gold bracelets.....I wonder if he washes his cabers.......they must kook good all clean besides the sideboard.

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[John Stumbles]

Slightly misleading on the gas there Dave: if you replace a typical non-combi rated at maybe 15kW with a typical combi rated at 24-28kW you may have to uprate the gas supply, but you'd have to do that if you replaced the 15k boiler with a higher output non-combi: it's just that combis tend to be more powerful than non-combis.

And allow electric backup via an immersion heater. However in a lot of places (not just modern rabbit hutches: Victorian working class housing too) space is at a premium and the saving in space of a combi compared to a boiler plus cylinder (plus water storage tank) outweighs the benefit of the higher flow rate. Of course one can sometimes put the tank and cylinder in the attic but that's expensive (in terms of time if your DIY, actual £££ if you pay someone else to do it).

Also, having mains pressure hot water is an advantage over gravity fed where the occupants want a shower (as people do increasing these days. Again, one can put in a mains pressure stored water system but that also is expensive.

Just because you-know-who seems to be punting for combis (albeit in pairs) doesn't actually make them a bad thing :-)

[Doctor Evil]

Totally inaccurate are the words you should use.

You can have electric backup with a combi. They are cheap enough to have another backup combi too. I have seen them for around £360. But may as well have two installed properly with one doing downstairs and one upstairs CH and the DHW outlets joined for the bath.

Some truth there, but an inaccuracy in that a combi doesn't mean a lower flow rate. You get the right combi or fit two small combi's which is highly cost effective and give a combined high flowrate.

And still gives a piss poor shower.

Very true.

A brilliant thing and a God send to countless millions all over the world. But try telling that to people who polish cabers.

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[Dave Plowman (News)]

Ok then - you're the one that knows all the specs by heart. Give the make and model that will provide high - ie over 20 litres a minute flow at 60C differential?

Crikey. He can't even spell his own race...

[Dave Plowman (News)]

Well, yes. But you'd not normally need to increase the size of a non combi

- assuming the old system worked ok. And there's always enough 'spare' to heat up the water storage.

Indeed. If space is a premium, then you may well have to forgo the best.;-)

But many systems already have these - and the likes of IMM recommends ripping them out.

I've got an Aqualisa fed off the storage system in 22mm, and it's a brilliant shower. Plenty of flow to wash you clean.

Of course not. But since he has the one answer to all, it's worth giving the other side. Or more to the point ask about how much space the OP has and whether they use baths a lot.

[Doctor Evil]

.......my God he is trying to think again....read it......

........60C differential.......yes that is what he said...... so, 5C coming in and he wants 65C out of the taps. Why? may you ask....do cabers required 65C water to keep them clean? ...clearly the rambling thoughts of a deranged mind.....

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[Nick Mason]

OK before we start I also have LIMITED SPACE as this is a 70's 3 bed semi and I CANNOT in ANY WAY fit TWO COMBI's

OK lets begin.

Remember I CANNOT in ANY WAY fit TWO COMBI's

I want to run a bath at 12-15 litres a minute with an incoming water supply at 5-10 deg C mainly so I don't forget the bath is running, go off and read 8 chapters of war and peace, eventually have the bath overflow sometime in the next decade and flood the house.

I don't like lukewarm baths so anything like a "35 deg rise combi" is useless, If I want to bathe in fluids around 40 deg C I will piss in a bucket.

Sometimes when eating Cadbury's flake I like my baths quite hot and full to the top so lets settle on 10 deg C in, 60 deg C out, 12-15 litres a minute. A mere 50 deg C rise.

I take showers using a pump assisted shower once in a blue moon as I prefer to wallow in my own muck in a civilised bath listening to the radio.

Remember I CANNOT in ANY WAY fit TWO COMBI's

Now, come up with a solution in 50 words or less that is available in the UK using:

a) a single combi boiler mountable within a 700mm x 500mm x 400mm location

b) any boiler that need not be a combi ;-) fitting the size requirements above but using a huge airing cupboard hogging storage tank but offering huge amounts of water storage so man, wife and two children can all have a separate bath using hot water on same evening

Remember I CANNOT in ANY WAY fit TWO COMBI's

[Doctor Evil]

The Potterton Powermax, Ideal Istor and Gledhill Gulstream will all fit in your airing cupboard and the flue will terminate through the loft using long lengths.

Go to appliances 2000 range.

If your airing cuboard is that big then two combi's can be fitted on the back wall and flued through the roofspace to the outside. Highly cost effective. Also the W-B Highflow (under counter standard washing machine sized) will fit in your airing cupboard as will the The Alpha CB50.

All these will supply a bath zippo.

Or you can fit any of these in the loft out of the way.

Easy when you know how.

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[Nick Mason]

Despite my original post saying "Remember I CANNOT in ANY WAY fit TWO COMBI's" I note you said "If your airing cuboard is that big then two combi's can be fitted"

NO I AM NOT INTERESTED IN TWO COMBI'S

NO I AM NOT INTERESTED IN TWO COMBI'S

OK now we have that out of you please inform us this

What is the premium you pay for a single combi solution compared to an equivalent non combi solution and a nice bulky copper hot water tank?

[Doctor Evil]

You said you have a large airing cubord. Two combi's can go in there.

You should do as this will benefit you in performance, economy and redundancy (you always have a boiler up if one goes down). You should not say you are not interested in something when you clearly do not understand. You are asking for advise. I am giving you professional advise FREE.

Premium? You pay less for a combi solution and have high pressure showers thrown in for nothing. No pumps or the likes.

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[Nick Mason]

No it was a normal airing cupboard in a 70's 3 bed semi that accommodate a hot water cylinder and leaves enough space to air some washing.

Is the failure rate of these super combi's so poor that I need two of them.

Should I duplicate my copper pipework and radiators as well?

How about a duplicate gas supply preferably from another continent?

Professional?

OK since you can't be arsed a single non combi boiler and hot water tank meeting the above requirements is approx 750-800 quid (condensing WB 29HE)

One of the solutions you offered (the Potterton in its lowest output form) is 1300+ quid

It's a premium in anyones language (except yours)

And if I need two of the buggers?........well, i'll have to put the corgi's to sleep.

[Dave Plowman (News)]

I'll try and answer that. Since IMM is a total wanker who only ever quotes adverts - and best possible scenarios from them as well. And knows nothing about living in a house with a family since he lives on his own in a trailer.

To fill a bath quickly, you need something like 20-25 litres per minute with the hot at 60C+, and the cold at the same sort of flow - at say about a temperature of about 5 C.

This will fill a good sized bath in the time it takes to get undressed and sort out the towels, etc. ;-)

And by the time you've had that bath, the average boiler will have replenished the storage cylinder if it's a fast recovery type.

I'm awaiting skilled - ie not IMM or drivel - opinions on which combi can match this, and the cost.

Of course, if you haven't got the space for a storage cylinder then there's no argument - you'll just have to put up with what you can get.