Just replaced my boiler

[Scott Mills]

Fair enough, but you are also paying to keep a (presumably large) amount of water hot continuously, for good heat exchange that tank must be at about

70oC+ which is rather hot to maintained all the time.

I say its personal choice and depends on your circumstances.

Combi works for me: *hot* water whenever I want, and as there is only 2 of us we don't notice the heating cutting out when the shower is on. A large heat storage would be more preferable if my hot water demands during 'heating hours' was excessive. However, I'd say both solutions are far superior to a standard stored water system which in my experience simply causes arguments - albeit they are more expensive

.

[IMM]

It gives a high flowrate for a bath then a lower infinitely continuous flowrate that gives hot water for ever.

[IMM]

Many cast iron boilers have fans too. The Neataheat was hardly simple.

[Lurch]

On Tue, 6 Jul 2004 19:38:55 +0100, "IMM" strung together this:

That's probably why I didn't bother as the bath is hardly ever used but the shower is, and the 35HE is more than adequate for that.

[IMM]

Mr Pole, you didn't bother because you didn't know about it.

[Dave S]

Provided your mains pressure is high, then high pressure HW from a combi is exactly what you *can* expect. You are confusing pressure and flow rate. In winter, the incoming mains water is colder and the flow rate therefore has to be reduced through the combi boiler to achieve the same temperature HW. Therefore, in winter, flow rates will be lower than in summer for the same output temp.

In general, combi boilers are characterised by mains pressure, lowish flow rate HW. The pressure is dependent on your mains pressure and the flow rate is dependent on the power of the boiler.

*or* a combi boiler on good mains pressure.

I believe an explanation of pressure and flow which I wrote a few years back still resides somewhere in the FAQ.

cheers Dave

[IMM]

That he is.

With some combi's that is the case. Stored water combi's have constant temperature and flow rates. High flowrate combi's can overcome any problems in flow.

Not so. See above.

In some models yes, in others, not the case.

[Andy Hall]

No, there's an initial reasonable rate while the store is being used, then the rate drops to that which the power input can support.

No, that is only true until the store runs out.

When the store is empty, it depends directly on the power

.andy

To email, substitute .nospam with .gl

[IMM]

I said "constant temperature and flow rates".

Two stage, which a number of combi's support.

A 22 litre/min jobbie will be fine, that is clear.

Two stage, as it has been mentioned.

[Dave Plowman (News)]

Until the store runs out.

[Dave Plowman (News)]

Anyone ever wondered why IMM hates storage systems - except when they're part of the boiler, and therefore too small to be of much use?

Perhaps it's something to do with the way he works pipes...

[Andy Hall]

It would involve understanding first form physics and the ability to multiply. We wouldn't want IMM multiplying, now would we.... ;-)

.andy

To email, substitute .nospam with .gl

[Ed Sirett]

It does depend on your standpoint. The Netaheat and Profile (similar in many ways), are typical of middling complexity units with electronics but no software.

[IMM]

Here is lune who advocates not servicing a boiler for 10 years speaking.

.........and another lune says....

Andy do you understand your How Things Work book yet?

[IMM]

Still not simple. The simplest modern boilers tend to have everything run through the pcb and a diagnostics check. Then check will tell you what component is faulty and the operation is done by the pcb. All you need know is the operational functionality.

[Dave Plowman (News)]

Loon, actually. Not that I'd expect you to understand that.

Perhaps you'd tell us just how often you service boilers. The authorities might be interested given that you're not CORGI registered.

But if you're just referring to your own, just how often do you service it - ie strip it down for a thorough clean etc?

[Dave Plowman (News)]

Given that PCB failure is all too common, what diagnoses the faulty PCB?

[Dave S]

ok. I should have qualified that statement - I was talking about a basic combi such as the Ferolli Modena I installed in my last house.

Once the store has been emptied, the principle I described above applies.

They can certainly *reduce* problems with flow. Whether they overcome problems depends upon one's requirements.

ok - I'll rephrase the first sentence: In general, basic, low spec combi boilers are characterised by mains pressure, lowish flow rate HW. Higher spec combi boilers increase the long term flow rate (by increasing the power of the boiler) and increase further the short term flow rate (by having a storage tank built in). Once the storage tank is emptied, the flow rate is dependent on the power of the boiler. Depending on personal circumstances and personal preference, that may or may not be a problem.

Dave

[IMM]

That is the problem. Most assess combi's by the worst case example, which is very wrong. Many combi's installed are under specified in flowrate terms. the models are there, but the idiots fitting them don't fit them due to ignorance.

Saying combi's can't cope is like saying don't fit a system boiler as they don't heat the house, because the man next door fitted a 30,000 BTU/hr model when he needed 100,000 BTU/hr.

Combi's can serve the vast majority, that is 90% plus, of British homes without any problems at all, providing the mains pressure can cope. Just simply just fit the model to suit.

How is the Modena? I have had some good feedback from them.

That is true, but the store of water is adequate for average use. The store is rarely exhaust in most homes.

Or the combi used.

That is better. You should have also said that a stored water combi very rarely runs out of high flow water. You make it sound as it running out of high flow hot water is a common occurrence. It is not. The re-charge times on these models is also exceptional.

[Dave Plowman (News)]

Most consider a combi to be a cheap replacement for a storage system. When it's discovered that to get the same flow/temperature under most domestic conditions actually can cost more, the 'advantages' become somewhat less...