designing a central heating and hotwater system

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I am not sure where waists come into this. A number of contributors to this NG have bought this and found it useful, even if it has been for a one off installation. So far, you appear to be the only dissenting voice, but why would I find that surprising?
Spending 20 in the context of a cost of materials of typically between 1000 and 2000 is nothing and the information is from the recognised industry association, derived from the relevant official and informed sources.

That's a matter of opinion and expectation of performance.

.andy
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Because I know more than you.

A book like that can confuse a DIYer rather than help him.

Not so.
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The book has arrived and its not a waist of time even for a one off.
i'll have a look at the heatbanks - but IMM you need to take note that most of us on here don't need "idiot proof" installations and as for "cheaper than getting a professional in". We are damn good and confident in doing a professional job ourselves (doing it ourselves) doesn't mean that you don't want to understand how the system works or how to install it properly.
This news group is supposed to be about obtaining information to allow people to go about it themselves.
there I've said it. lol
duncan

do
connect
and
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(doing
That is so. And doing it the easiest and most effective way too. If you think you can do a professional job then fine. I have found no DIYer that has ever done what I would call a professional installation. Not one. And I seen quite a number of them. The one box solution cuts out a hell of a lot of work and design and is still cheaper than getting a pro in. Think very hard, you may be overconfident.
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IMM Wrote:

Duncan's trade, but I myself have served a 4 year Mechanica Engineering Apprenticeship and am probably far more capable of making decent joint for a water/gas system than many so called "Professionals out there! When you are working on High Pressure and Cryogenic system for years there are far more skills involved and necessary precaution to worry about. Like Duncan, the reason I post on this kind of forum is to get som understanding of the things that I am not sure about, boiler choice system design, etc and not actually doing the job.
I know by experience that if I was to employ a so called "Professional to install a system, then it is likely that he will do a shabby job an I will regret.
As I say this is "my experience" of employing people to do jobs aroun the house, whether it is fencing, double glazing or I am sure plumbing I am not for one minute suggesting that either you or anybody else fo that matter who give extremly useful information here, fall in thi bracket.
I do agree with the "One Box" solution approach, assuming as other have said that it meets the requirements and that is my dilema a present!
Interesting reading.
Thanks all
And
-- AndyHingston
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While a one box solution makes installing simpler for unskilled or cackhanded people like IMM - and will appeal to some pro installers by way of increased profits - it ties you down to the maker for the inevitable spare parts.
External components such as pumps, divertor valves and of course a storage cylinder allow you to buy the finest available - and a choice of makes at replacement time. And probably makes such replacement easier due to better accessibility.
All to often a maker will withdraw support on a product in an attempt to force new sales, before that product is truly worn out. So I'd prefer to keep this possibility to a minimum.
Installing a new system on a DIY basis is really something it is worth taking time and trouble getting absolutely right, as it should then have a long, long life.
Of course if you are tight for space, a one box solution may be the answer, but it is far from the 'one size fits all' ideal solution that our resident clown is so keen to promote for reasons best known to himself.
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wrote:

<snip drivel>
Misinformatiion not worth reading.
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Not in that book you never. It is lacking in many aspects. A poor book.
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On Fri, 18 Jul 2003 18:41:23 +0000 (UTC), "duncan"

It will give you a good appreciation of the steps in radiator and pipe sizing, radiator derating and so on plus the issues with pump selection and setting, organisation of pipes to avoid pumping over problems etc.
You can then get a lot of information from manufacturer's web sites.

It does mean that care needs to go into the sizing and branching off of pipes so that there is reasonably good balance of flow naturally. Then there are techniques with flow restrictors, blending valves etc. if you need to go further.

This is the big advantage of a cylinder. You can make it adequately sized to be sure that you will always have a plentiful supply, regardless of the draw rate.
For example, I have a cylinder with multiple tappings on the top which will take 22mm pipework. It is fed from the roof tank in 28mm pipe. The effect is that I can run two baths at full tilt or a bath and a shower or two showers at 25 litres/minute each.
You can go for very large combi boilers and get a flow rate of up to about 20 litres per minute with a 35 degree temperature rise. For a lot of the year when the mains water is warmish - say 15 degrees and above, you will be able to mix the heated water with quite a lot of cold - e.g. in a shower mixer.
However, if you are concerned about the worst case, that would be in the winter when the water supply can be well below 10. If you consider that the user temperature in a shower is around 40 degrees, you can see that almost all of the boiler hot water will be needed and little opportunity to add cold. Therefore you end up with 20 litres per minute between two showers - i.e. 10 each. Then it becomes a matter of opinion as to what you find acceptable. Personally I feel that 15 litres/min in a power shower with adjustment between hard jets and drench mode is about the minimum - others say less or more. If you already have a shower in place, try measuring the flow rate with a bucket and stop watch to get a feel of what you are getting.

The well known site on these is DPS. www.heatweb.com although the cylinder manufacturers are making them as well.
The main advantages that you can get out of one of these are that
- the primary circuit can remain vented so that the bulk water in the cylinder is not pressurised. Sealed cylinder pressurised systems require a BBA or IoP approved installer to fit them
- The cylinder can store water at higher temperatures than if it is used for hot water. It can be at 80 degrees rather than 60, so a third more energy is stored in the same space. The mains cold water is fed through a plate heat exchanger external to the unit and then the primary water from the tank is pumped through the exchanger when there is demand to heat the water. This type of exchanger is highly effective on heat transfer and so if the water supply is up to it, much greater flow rates than with a combi can be achieved.
As the store is being used, the boiler will be adding heat back in, although typically at a lower rate than you are using it. To give a simple example, you might be drawing hot water at a rate such that 60kW is required to heat it to the extent required. If the boiler is able to deliver 30kW into the cylinder, then the net rate of use is 30kW. Therefore the amount of hot water that you can get at the 60kW rate is twice as much if the boiler is adding heat in, using this example. Once the stored energy runs out, the flow rate would have to be halved to maintain the same temperature rise. Make sense?
The same additive effect occurs in a conventional cylinder of course - the difference being that the amount of energy stored is 25% less.
If you are going the condensing boiler route, it won't be as efficient with a thermal store as it can be with a conventional cylinder because the operating temperature is higher. It's also better to run the radiators separately from the primary circuit than from the store.

A fast recovery type. Vendors of these include Albion and Telford among others. These have various arrangements to increase the surface area of the coil - e.g. more turns, multiple pipes, etc. The point is to increase the transfer rate of heat so that the water is heated more rapidly, and if you have hot water priority arrangement that the boiler is not taken from heating the house for too long.

There should be plenty of those. Thrills and spills for all the family :-)

.andy
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Need to size with a combi as it never runs out of hot water.

Most store water at 75C these days.

You know little of HVAC.

If the rads are run for the store backup electricity can be incorporated. High wattage immersion cols are available.

The system should a DHW priority system when using these.
No need to go tank/cylinder as a combi or heat bank will be far better all around.
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Provided that the requirements in terms of flow and temperature rise are within its capabilities.

We've had that discussion.

Seemingly I know more than you do and do present even handed and more complete explanations.

That depends on the requirement and circumstances.

.andy
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Which it should depending on model.

It wasn't a discussion, it was me attempting to educate you on the topic. I failed.

In your dreams.
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wrote:

Then you go heat bank if a combi is not adequate.

I
You are rank amateur with limited knowledge of the subject. Duhhh!!! LOL!!

You are foolish that is certain.
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What are your requirements? baths, showers, size of house, etc?
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Now this is revolutionary. Asking the customer about his needs.
Maybe you could get a job in sales or the diplomatic service yet. Foreign legion perhaps??
.andy
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Is there a full moon?
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duncan Wrote:

So, have you completed your design
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