designing a central heating and hotwater system

[IMM]

Nahhhhh. You are not getting there.

The whole is being ripped apart anyhow.

[IMM]

Because I know more than you.

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

Not so.

[Andy Hall]

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

To email, substitute .nospam with .gl

[IMM]

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.

[IMM]

What are your requirements? baths, showers, size of house, etc?

[Capitol]

Sadly not true, as our friend has found out the hard way!

Combis with descalers in hard water areas, don't generally seem to give 10 years service. All my friends with new boilers are getting less than 10 years life from their modern boilers.

Where are the manufacturers offering a 10year warranty?

I would regard that as being totally unreliable, only one pump at most would be necessary on a reliable system.

Regards Capitol

>

[IMM]

Please read again. The smallest combi is approx 80,000 Btu/hr, which is big enough for a largish 4/5 bedroomed house. Most houses in the Uk are a lot smaller than that. The average sized combi is approx 95,000 btu/hr. They must have a large house or one with no insulation.

Why are they being scrapped? In many cases they are being replaced because the replacement cost is so low compared to fixing. Also the newer combi's work better, and give better flowrates, than a 10 year older. A combi can be bought for approx £350 in trade places, and £400 off-the-shelf in B&Q. A

13 litre/min can be bought in Wickes with all the trimmings. Combi prices have tumbled. They are so cost effective it is worth putting in two in a 2 bath house, with one doing upstairs heating and the other doing down.

Many give 5 years on the heat exchangers. I think Vaillant give 3 or 5 years on the whole combi. Many give 2 year guarantees.

But average for a tank/cylinder setup over 20 years!!!

Over 20 years? I would say 2 pumps. I have seen few pumps go beyond 10 years.

[Andy Hall]

Predictably, you have ducked the issue when put on the spot.......

You don't know that. .andy

To email, substitute .nospam with .gl

[Andy Hall]

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

To email, substitute .nospam with .gl

[duncan]

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

[IMM]

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.

[IMM]

Ducking nothing. Nahhhhh. You are not getting there.

If a whole system is being fitted the whole house will be disrupted.

[IMM]

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

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

You are foolish that is certain.

[IMM]

Is there a full moon?

[IMM]

Not in that book you never. It is lacking in many aspects. A poor book.

[Capitol]

It's taken me some time to check the figures quoted above. The range of common condensing combi boilers is 75Kbtu/hr to 156Kbtu/hr. The central heating output of these units however varies from 53Kbtu/hr to 156Kbtu/hr. Small units cannot be relied upon to cope with a 4 bedroomed house in winter. The figures are from the architectural digest, so I have no reason to doubt them. The house is modern with insulation to the relevant standard. Looking at the heat exchanger materials, with some manufacturers using copper and aluminium, I'd be very surprised if the average life expectancy would ever exceed 10 years for these units. I guess that is why better manufacturers use stainless steel. The figures for water delivery at 35C rise are in the region of 10L/min for most of the units. 17 minutes to fill the bath! I still think that an ion exchange water softener is essential in hard water areas.

Regards Capitol

[IMM]

The CH output is generally lower than the hot water output to reduce boiler cycling as in 90% plus of cases the boiler, for CH purpose, is too large. In most cases the CHG output can be raised to hot water output. Very few combi's fitted are 53,000 btu/hr. The average is way above that. Go to B&Q and you will see a 80-85,000 btu/hr off-the-shelf BIASI combi, for £400.

The super small ones of 53,000 btus, no. But I have never actually come across one of these and they are not the normal units you will see on sale. An average run of the mill combi that is fitted in most homes? It will cope with power to spare.

Neither have I, but they are so vague as to be useless giving only the highs and the lows The average combi fitted in UK homes will cope with a 4 bed house.

How modern? Insulation regs have risen recently and progressively risen since the regs first insisted on insulation in 1974. Many people would consider an insulationless 1973 house modern. What is the CH rating of the house in btu/hr?

On what experience/figurers do you base this assumption? A copper/alum' heat exchanger will last 20 years plus if the installation is fitted right and serviced right too. A boiler with the burner pressure far too high may not last that long (poor servicing). Modulating burners have helped improve longevity. Electronic controls on some boilers (combi and system) will lock out if the burner pressures are way out. BTW, in most cases the same heat exchangers are in the system boilers. Makers use the same exchangers and add a water section to make a combi. Many condensing boilers have the same exchangers as combi's and system boilers and add a smaller condensing exchanger. They keep their production lines and component counts down.

Stainless is becoming more common and 5 year guarantees are given, even with the Hepworth cheapie from Travis Perkins. Yet, the reason why many combi's are scrapped is not that the heat exchanger has burnt out. It is because of other factors, the biggest is ignorance of the combi operation by "plumbers". In many cases it is that the repair cost is not far off a new combi as they have tumbled in price, with many being below the price of many system boilers. Also a new combi will invariably have a better flow rate, be physically smaller and probably a faster response rate with pre-heat exchangers or built-in water store vessels.

And your point? 10l/min is the rate for the cheap end of combi's. Flowrates far in excess of this are available, even up to two bathroom jobs (well 1.5 and 2 with a push). A Worcester HighFlow will fill bah in 5 mins, as will many other high flow combi's. 17 minutes to fill a bath? Even if the temp coming out is at bath temp of 45C that is 10 minutes fillup, as 100 litres is the average bath capacity. After all you are on about "most" here, and most baths will be 100 litres. If the combi is delivering hot water at above 45C then 7 to 8 mins fill up time. Then get a 18-19 litres/min combi and the fill up time is 4-5 mins. Wickes even sell a 13 L/min off-the-shelf combi for £525. At these prices you can afford to buy two combi's and have one do upstairs and one down for natural zoning and split the bathrooms. Highly cost effective.

And the pumpless high pressure showers in all combi's are for free.

Don't go on old wives tales and ignorant "plumbers", who are very good at drains and gutters. Go to heating engineers.

Many combi's are designed for ease of design and installation, true DIY. For e.g., the Ariston Microgenus even has a built-in filing loop and pressure differential valve, among other failsafe goodies. These are combi's are designed for people with a limited knowledge of heating and are the models DIYers should aim for.

Not so. A phosphor descaler will do. They are very effective in eliminating scale, or at least 98% of it. Any scale left around is easily removed by normal washing.

[AndyHingston]

I am not sure abou 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

[Dave Plowman (News)]

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.

[IMM]

Misinformatiion not worth reading.