Combi-boiler or stored?



No problem. I have a similar size house to you. 3 bed, 1 bath.
I have a Worcester Bosch Greenstar 28HE in the loft feeding a DPS Pandora heat bank, also in the loft. No additional cold tanks at all. Hot water is mains pressure, with a flow rate of 40 litres per minute @ 60C.
Basically, both a system like this and a combi are going to provide absolutely superb showers, as they both provide mains pressure and the shower head or valve will limit flow rate to below the capacity of the boiler.
The main differences between the systems will be on bath filling performance or on having multiple showers. If you have/do neither regularly, then the combi will save you money.
Note that if you install in the loft, there may be additional costs, most of which didn't apply to me because they were already present.
1. Loft must be boarded. 2. Loft must have lighting. 3. Loft must have mounted loft ladder (can fold away). 4. Hatch must have guard rails. 5. You need a slightly more expensive vertical flue. 6. You need longer pipe and electrical control runs.
Christian.
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Of course I should have mentioned that cost is a factor.
Those thermal stores look a great idea but they look pricey.
I suppose a combi is the cheapest option, but I have a feeling it won't be up to the job, simultaneous use, bath filling. I only have 3 bed semi - but for resale and our own use, perhaps combi isn't the way to go.
I guess if I go for anthing other than combi and consdidering I'm doing the whole system, except rads & pipework, I should not replace with old hat tank & cylinder. I suppose I can get a decent regular boiler for not much, is condensing worth it?
What are those German boiler manufacturers alluded to?
What sort of cost am I looking at for boiler, heat store, controllers?
--
Mike W



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For good quality components, you're talking between 1500-2000, including all controls, zone valves, condensing boiler, heat bank, programmer, programmable room stat. It could be done cheaper, if you intend to use less regarded brands, however the above will get you something decent, like a Worcester Bosch Greenstar and DPS heatbank.
Basically a stored energy mains pressure hot water system will cost you twice that of an equivalent quality instantaneous combi in parts, although the time spent fitting will have less of a difference and hot water performance will be in a different league.
Christian.
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Of course many don't start from scratch and may already have a storage system much of which can be re-used.
--
*Fax is stronger than fiction *

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

Maybe I'm overlooking something but it seems the prices are almost comparable
worcester bosch 40kw combi 1350
worcester bosch 28 HE system boiler & pandora heat bank 1500
I know you can get a cheaper combi - but to try and reduce performance problem...
This at present is leaning me towards the latter
-- Mike W
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wrote:

you
An alpha CB50 is approx 1K. One box , on the wall. and performance is all you need.
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Correction. All *you* may need. Not the same thing - by a long chalk.
--
*Strip mining prevents forest fires.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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My comparison was more with a standard flow rate combi, and remembering that external controls are required for the installation of the storage system, such as a couple of zone valves, programmer etc.
Certainly, if you start talking about 40kW combis, then the figures start to close in on each other.
Christian.
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that
to
Discounted heating do it at 1,297.20 Including VAT
The bottom line after installation is a difference far greater than 200.
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Yes, you have about 100 quids worth of external controls not required by the combi. Plus about half a day's work additional to that required to install the combi.
The additional work:
1. Installing zone valves and associated wiring (see below, as this can be predone)
2. Additional pipework runs if cylinder not colocated with boiler (this can run both ways, depending on the current DHW layout and the proposed locations)
3. Physical installation of cylinder.
The heat bank itself is actually considerably easier to install than a conventional gravity cylinder. Plumbing wise, it needs just a mains in (also running to a garden tap and hose for topping up), hot water out, primary flow and primary return.
They are also available with all controls (zone valves + programmer) preinstalled, so you just connect it to the boiler, mains, hot water outlet and the radiators. That was no good for me, as I was having an S-Plan-Plus system with the zone valves remote to the boiler/cylinder location, so their preassembled options weren't appropriate.
Christian.
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200.
the
can
(also
outlet
their
Not to mention pipes, fittings and valves and pipe insulation, etc. All adds up. I would guess 600 more bottom line.
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You need to shop around more. A few elbows and Ts aren't going to cost that. Nor is there any guarantee that more pipework is needed than the combi. Indeed, the cylinder is often more conveniently placed to break into the DHW system than the boiler, so requires fewer additional runs.
Christian.
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On Wed, 22 Sep 2004 10:18:30 +0100, "Christian McArdle"

In fact it's far more likely to be able to drop in in place of the existing cylinder if one wanted to do that, or easily in the loft position, simply because the boiler is typically in the kitchen, the cylinder on the first floor and tank (space) in the loft.
.andy
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wrote:

All
that.
DHW
Who wants a boiler in the kitchen? Why not have the dishwasher in the bathroom as well.
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It was an observation as to where they typically are.
Of course it's possible to move the boiler elsewhere, but this is additional pipework and cost.
.andy
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wrote:

combi.
the
And more space and less noise.
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wrote:

If you are looking at short term sale then it doesn't matter because most buyers won't know the difference - especially if you sell in the spring to autumn when the water is warm.

Definitely. I have made savings of between 25 and 30% compared with my previous conventional boiler.

Worcester Bosch, Vaillant, Viessmann, MAN,......

For the lot, something in the 1500-2000 range if you want decent ones.
.andy
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The Alpha CB50 will do you fine. The flowrate is excellent and will fill a bath quicko and give excellent showers. Take no notice of amateur know-it-alls, a large flow combi is ideal for you. If I was you that is what I would go for.
It is also a very cost effective way to go, also saving valuable space in your semi.
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Look at: http://www.alpha-boilers.co.uk/products/CB50.html
The Worcester Bosch Greenstar 40kW condensing combi is good too.
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The marketing literature is full of claims which do not look nearly so good when the technical data is checked.
- The flow rate is specified as 18lpm but this is only until the 57 litre store is empty. This equates to a total of 90 litres mixed with cold water for a bath (which is not enough) After that it will be 11lpm because the output to water is 28kW.
- The marketing information claims that the vessel is fully recovered in 3.5 minutes. The data sheet says to 70% of capacity and with the boiler already running.

Quite.
Except that this isn't one.

.andy
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