Solar water heating and combi boilers

I have been investigating installing a solar water heating system that I wanted by use to provide pre-heated water to my combi ("the warmer the water feed, the less gas used to heat it" principle). I have spoken with a number of suppliers of Solar thermal systems and some say its possible whilst others say it will damage the combi. What is the "truth" here?
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On Sun, 14 May 2006 10:13:41 +0100 someone who may be "Keith D"

The truth is that it depends on the combination boiler. Some will cope with heated water at the inlet others will not.
Depending on the answer to the obvious question there are then a range of options, depending on the house layout, hot water demand, condition of the boiler and determination.
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David Hansen, Edinburgh
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I can't understand why you want to do that. Water from the solar system is warm or hot enough for most tasks on most days. If it needs a boost you can provide that from your programmer.
That's our experience, not theory.
Mary

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Mary Fisher wrote:

How would you achieve this "boost" without a hot water cylinder?
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You do have a cylinder. It's not a problem :-) The OP didn't say that he didn't have one.

Mary
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On Sun, 14 May 2006 16:46:39 +0100, Mary Fisher wrote:

He said he has a combi which means that he doesn't have a cylinder. So it is a problem :-)
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No it doesn't!
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Mary Fisher wrote:

OK then, it means he *probably* does not have a cylinder. Better?
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Whatever
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On Sun, 14 May 2006 16:43:29 GMT someone who may be John Stumbles
I know people that do. The combination boiler provides hot water to the kitchen, while a cylinder provides decent amounts of hot water for showers and baths.
Other than small houses with compact services, a variety of sources of hot water are often the best approach.
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David Hansen, Edinburgh
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On Sun, 14 May 2006 10:13:41 +0100, Keith D wrote:

Solar and combis are an awkward combination. It's do-able but probably expensive.
But before going further may I ask: 1: is your house already draught-proofed and insulated to the highest standards 2: does your heating system already have thermostatic radiator valves, a programmable thermostats and - if the house is not absolutely tiny - separate heating zones 3: is your combi already a high-efficiency condensing type?
If the answer to any of these questions is No then improving the relevant area(s) is likely to make more sense both economically and ecologically than spending £1000s on a solar water heating system.
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On Sun, 14 May 2006 14:23:09 GMT someone who may be John Stumbles

Cavity wall and loft insulation, to the greatest extent possible are certainly important, as well as cost-effective draught-proofing. Important for reducing heating costs.
However, none of these affect hot water production to any extent. What matters is the layout of the house and the services within it. Insulation of the hot water pipes is certainly a good move in many circumstances.

Important for reducing heating costs.

If it is not I would ask questions about how old it is. Replacing a relatively new boiler is not sound financially or environmentally.

Economically solar water heating is still a long term investment, at current fuel prices. However, the price of sunshine is not going to increase, unlike other fuels. There are also other advantages, such as being able to largely turn the boiler off in summer and thus (probably) prolonging its life. If it is the sort of combination boiler that has a small hot water cylinder this will also save some gas.
Environmentally solar water heating is an excellent investment.
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David Hansen, Edinburgh
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I agree. I wish we'd done it years ago.
Mary

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On Mon, 15 May 2006 12:21:18 +0100, David Hansen

Actually it is a long term non-investment as in most cases, and all commercially installed and maintained systems, it will never even break even.

There is no evidence that this is the case at all, and in all probability it will almost certainly reduce its life as seals and bearings in pumps and valves really dislike being unused for months on end and corrosion will also worsen.

In propaganda.
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Peter Parry.
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On Mon, 15 May 2006 23:36:55 +0100 someone who may be Peter Parry

At current prices DIY systems are long term investments. Systems where one pays someone to install it are probably not going to break even at current prices, but note the name of this newsgroup and that the price of sunshine is not going to increase, unlike other fuels.

Incorrect.
Pumps should indeed be turned over occasionally. However, that has no bearing on the life of the boiler.

No bearing on the life of the boiler either.

Corrosion where?

Incorrect. As I pointed out and you snipped, it can save more gas than people think.
You can keep trying with your incorrect assertions for as long as you like. However, because somebody may believe you, they will be rebutted whenever necessary.
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David Hansen, Edinburgh
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On Tue, 16 May 2006 08:36:11 +0100, David Hansen

If it proves popular what's the betting ownership of it will get taxed (indeed the mechanism for doing so has already been put in place by Nulabor) :-).

I'd be interested in seeing any. The only mentions I have found are unsubstantiated statements usually made by peddlers of solar fittings.

Both have bearing on the life of the "conventional" system and hence the economics of solar water heating. In many boilers the pumps and control valves are integrated within the boiler.

The boiler casing. It is a fairly common cause of terminal failure of room sealed boilers.

I snipped the bits about saving energy (which I agree is a far more sensible starting point and applicable no matter what system is used) but didn't see anything about how solar heating can save more gas than people think.

So will unsubstantiated and incorrect claims for solar water heating making economic sense. People may buy it for other reasons not all of which may be altogether objective and that is their free choice. What is wrong is to claim it makes _economic_ sense when quite plainly in the vast majority of cases it doesn't (which of course is exactly why the proponents of it always studiously avoid using figures).
For example the oft quoted solution of the solar powered motor pumped panels on the direct side of the water system makes great claims about the economic sense of doing this (saving the few watts an electric pump takes) but makes little or no mention of the fact that for most people living east of a line drawn roughly from Lincoln to Bristol you also need to install an ion exchange water softener otherwise the panel will quickly be ruined because of scale from the hard water.
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Peter Parry.
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wrote this:-

You haven't given any evidence of your claims.
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Mary Fisher wrote:

Well, let us get some...
How much did your solar system cost in total?
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John.

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No, dear, he's supposed to be providing the 'evidence'.

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John Rumm wrote:

I will let him do that, but my question still stands if you don't mind me asking?
What did your system cost to have installed? And what does it consist of?
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John.

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