Re: Less than 50% rads should have TRV's ???

[Tony Bryer]

Condensing boilers are high efficiency boilers that waste almost

> no heat out of the flue. They are environmentally friendly, but > only work in the condensing mode when the working conditions are > correct - less than 50% of the radiators must be fitted with > thermostatic radiator valves, for example. They also have a > shorter than average lifespan and can be very expensive to buy. > > Is this correct? Ive recently had a Condensing boiler fitted (to > replace a 15yr combi) - and all but 1 of my rads have TRV's...

These days condensing boilers are much the same price as regular boilers (obviously better makes tend to cost more) and the well-designed ones should be just as reliable. The stuff about not having TRVs is rubbish. They are more efficient when in condensing mode (water returning to the boiler at about 55C or lower) but the efficiency gradually reduces above this and in non-condensing mode is still higher than a conventional boiler. To maximise efficiency, set the temperature on the boiler to be as low as necessary to give the required heating output.

Which boiler did you get?

[Jim Alexander]

Unless you have stored DHW in which you need to set the flow temperature high enough to avoid Legionnaires disease.

Jim A

[PeTe33]

presumably that would only be of relevance in a vented HW storage tank?

[Aidan]

On Dec 5, 7:58 pm, "Pet @

;=AC)" <

No. Vented, unvented, combi.

All manner of bugs will go forth and multiply in your water, given suitable conditions. Tepid water, about blood temperature, suits them nicely.

[Andrew Gabriel]

I cannot find a single case of Legionnaires disease which was caught from a domestic water system in the UK (or anywhere else come to that). It would appear to be a disease which, for whatever reason, is only found in (or maybe only infectious in) commercial/institutional environments.

[The Natural Philosopher]

Thats why solar heating is so 'organic' :-)

[Guy King]

The message from "Jim Alexander" contains these words:

Out of interest, how many people die of legionnaires in the UK in a year?

[Jim Alexander]

I should have put my point differently. There is a standard which I have seen/heard of and which I am of course furiously searching for which specifies a minimum storage termperature of 60deg. Maybe/maybe not a sort of "Part P" of which I ignore the process but not the standards. However ignoring the minimum storage temperature would involve ignoring a standard. As regards your question maybe Google is your friend but the answer is irrelvant to the underlying point regarding condensing boilers.

Jim A

[mark]

In message , Jim Alexander writes

Ah! Hence your question about the Vaillant. It has a special setting for raising the cylinder to a temperature that kills bugs.

[Jim Alexander]

Thanks for that Mark. I missed that when I read through the VRC 400 download. From the manuals I thought your VRC 400/Ecotec combo could deliver separate temperature control of hot water and heating circuit flow. Still think that from the manual but when I emailed Vaillant the question they said .... NO. With the Legionaires function they are almost there. Not totally convinced by the Vaillant response. I'm expecting somone to suggest a condensing combi but no thanks.

Jim A

[Merryterry]

Legionella is present in many water supplies including domestic. There are many cases of death through legionella in UK water supplies. Also many cases of non-fatal Legionnares

Try

[Andrew Gabriel]

Where is the evidence it is present in domestic water supplies? If it is present in domestic water supplies, does anyone know why it's apparently not infectious in domestic water supplies?

[David Hansen]

On 06 Dec 2006 19:39:20 GMT someone who may be [e-mail] (Andrew Gabriel) wrote this:-

Many tests.

This has been explained several times in several threads.

The little nasties are not particularly dangerous in low concentrations. At the temperature of cold water they are largely inactive. At high temperature they are killed off. Between these two temperatures is ideal breeding conditions and they multiply rapidly. In large concentrations they are dangerous, particularly to susceptible people.

[David Hansen]

On 7 Dec 2006 09:32:20 -0800 someone who may be " [e-mail]" wrote this:-

Is the house insulated as much as possible? Cavity walls and loft in particular, assuming they can be insulated.

[Andrew Gabriel]

So why is it not infectious?

Sorry David, I've never seen this explained here. I wasn't even aware that there are (apparently) no cases of Legionnaires disease which were caught from domestic water systems, until I went looking for the stats.

Are you perhaps claiming these conditions never occur in domestic water systems but do in commercial/institutional water systems? If so, then sorry but I don't believe this is the case, or a valid explanation.

The only possible explanation I can come up with might be that Legionnaires disease is only diagnosed if there are multiple cases, and for an infected domestic water system there probably wouldn't be, and the infection might be more loosely identified as some type of pneumonia. This is however a complete shot in the dark.

[David Hansen]

On 08 Dec 2006 19:32:28 GMT someone who may be [e-mail] (Andrew Gabriel) wrote this:-

It is rather more complicated than a simplistic infectious/not infectious question. It is only when the concentrations of the little nasties rise to high levels and a susceptible person does something that leads to them being breathed in that they become a danger. Otherwise, like many other things, they are nothing to worry about greatly. They have existed for a long time and will continue existing.

No. If I was claiming that then I would have said so.

It should be fairly obvious that a hot water cylinder that is not heated hot enough will be an ideal breeding ground for the little nasties. That is why there are recommendations on storage temperatures and heating times. There is a concern that solar water heating outwith the summer could produce ideal breeding conditions, though that will not be the case with the supplementary heating that is likely to be used at these times.

There is also a question over badly designed and installed cold water storage tanks. Again there are recommendations on this.

There is also a question over showers, spray taps and the like. Again there are recommendations on this.

This is not something to panic about, the roads pose far more dangers, but it is something to be aware of and manage. Part of that management is to be aware that places where there are concentrations of susceptible people are places to be particularly careful with system design and maintenance.

[Jim Alexander]

Thank you. But what I hoped for was a debate about how to achieve the "recommended" storage temperature in a condensing boiler where heating flow/return temperature has been optimised at a lower temperature. Given the silence I suspect that the answer is even less well understood than the legionaires issue.

Jim A

[David Hansen]

On Mon, 11 Dec 2006 10:51:24 GMT someone who may be "Jim Alexander" wrote this:-

A lower return water temperature is what is optimised. Radiators should be made larger so that more heat will be given off, thus lowering the return water temperature.

Unless one has an unusual setup the temperature specified on the cylinder thermostat should be ac hived.

[Jim Alexander]

Well yes, but in a boiler retrofit the radiator size is a constant, the return temperature can only be lowered by either or both lowering the flow temperature or reducing the flow velocity, both of which conspire to defeat the original design output.

How if the flow temperature and/or the flow velocity has been reduced to an average flow temperature less than cylinder thermostat setting?

Jim A

[tony sayer]

In article , Guy King writes

A mate of mine had it around a couple of years ago. Damm near did him in but he was from good old hardy Lancashire stock;?

Or perhaps the good lord didn't want to put up with him too soon;)