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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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designing a central heating and ho****er system
hi,
Any recommendations for sources of information on designing a central heating/ho****er system for please. have found sites that provide info on rating the boiler/rads but nothing on the actual design. type of heat storage etc. duncan |
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designing a central heating and ho****er system
duncan wrote in message ... hi, Any recommendations for sources of information on designing a central heating/ho****er system for please. have found sites that provide info on rating the boiler/rads but nothing on the actual design. type of heat storage etc. duncan You used to be able to buy books on the subject - or borrow them from the Library - and probably still can. If you want on-line resources, there are many - of several different types. I see there being several steps to designing a heating system from scratch. The first step is to get an understanding of the of the various types of boilers and control systems, and the pros and cons of each in order to decide on the type of system you will use. The Heating and Plumbing faq http://www.diyfaq.org.uk/plumbing/plumbingpage1.html would be a good start for this. Having established this, you need to do some calculations to establish the heat losses in each room - which will lead to establishing radiator sizes, pipe sizes and boiler size. Several radiator manufacturers (including Barlo) have programs which you can download to help you do the calcs. Finally, you have to do the detailed design - working out where to put the rads, and planning all the pipe runs - and planning the electrical bits for the control system. I'm sure that others could fill in with much more detail, but that should get you started. Roger |
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designing a central heating and ho****er system
cheers Andy
i'll go have a look at that one. I'm more than happy with the installation side soldering etc. just need the detail to get things right with for upto date specs etc. duncan "Andy Hall" wrote in message ... On Wed, 16 Jul 2003 20:43:32 +0000 (UTC), "duncan" wrote: hi, Any recommendations for sources of information on designing a central heating/ho****er system for please. have found sites that provide info on rating the boiler/rads but nothing on the actual design. type of heat storage etc. duncan I've used the Domestic Heating Design Guide, published by the Heating and Ventilating Contractors Association http://www.hvca.org.uk/publications.html It provides the data that you need for all the major aspects - calculate heat loss for the rooms - radiator sizing to account for different temperatures and operating conditions. - pipework sizing to provide adequate and correct flow - pump, pressure vessel, DHW heating options. This is not intended to be a DIY book with pretty pictures that teaches you how to solder. However, if you want that, you probably should not be contemplating a complete CH design/install. It is more of a reference that a professional might use, so it is assumed that the reader knows how to do plumbing and the other practical aspects. It does walk you through the design aspects very well as well as explaining the principles properly rather than using guestimates and rules of thumb. .andy To email, substitute .nospam with .gl |
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designing a central heating and ho****er system
"duncan" wrote in message
... hi, Any recommendations for sources of information on designing a central heating/ho****er system for please. have found sites that provide info on rating the boiler/rads but nothing on the actual design. type of heat storage etc. duncan What do you intend to do? As you are a DIYer go the combi route. Buy a high flowrate combi. Not all combi's give a trickle for hot water. They are easy to install with minium design in CH pipework and rad sizing. You connect up 5 pipes, run a power supply and a wire for a thermostat or thermostat/clock from the combi. Superb for high pressure showers. A doddle. Don't go for complicated cylinders, tanks, motorised valves, control systems, etc when there is no need to. The rad sizing can be done by using one of the many on-line rad calulators. No need to size a combi boiler as it will do 80-90% of most UK homes the CH output is so high. Any further points ask me. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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designing a central heating and ho****er system
"Andy Hall" wrote in message
... Any recommendations for sources of information on designing a central heating/ho****er system for please. have found sites that provide info on rating the boiler/rads but nothing on the actual design. type of heat storage etc. duncan What do you intend to do? As you are a DIYer go the combi route. Why? That's a bit of a put down isn't it. How is recommending the best rote for a DIYer a put down. This is uk.d-i-y. Buy a high flowrate combi. Not all combi's give a trickle for hot water. They are easy to install with minium design in CH pipework and rad sizing. You connect up 5 pipes, run a power supply and a wire for a thermostat or thermostat/clock from the combi. Superb for high pressure showers. A doddle. The radiator sizes and pipework still need to be calculated properly Use of a combi doesn't make a fundamental difference to this part of the design. Don't go for complicated cylinders, tanks, motorised valves, control systems, etc when there is no need to. Come on. It's not that difficult. A one box solution that professional experts have incorporated all the design and components is by far the best option. We don't know whether Duncan has a requirement that doesn't match a combi. That's why I said get back to me. The rad sizing can be done by using one of the many on-line rad calulators. These are useful, but are not bug free. I have seen mistakes in the U value numbers in one program and another doesn't calculate heat gains properly. They give a good ballpark figure. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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designing a central heating and ho****er system
I would disagree about the "ball park figure" being adequate to start with,
the odds are you will end up with a boiler and radiators which are too small. Bigger IMO works best for heating systems, this applies to boiler and radiators. Of more importance, where are the 10 year maintenance and running costs factored in on a combi system without soft water. How do these costs compare with a traditional conventional vented boiler, even allowing for a tank replacement every 10 years? Thinking about it, are there any boilers of any type with a 10 year warranty even with soft water? In the past, my boiler life achievements were in excess of 20 years, have these days gone forever? Regards Capitol IMM wrote in message ... "Andy Hall" wrote in message .. . Any recommendations for sources of information on designing a central heating/ho****er system for please. have found sites that provide info on rating the boiler/rads but nothing on the actual design. type of heat storage etc. duncan snip Buy a high flowrate combi. Not all combi's give a trickle for hot water. They are easy to install with minium design in CH pipework and rad sizing. You connect up 5 pipes, run a power supply and a wire for a thermostat or thermostat/clock from the combi. Superb for high pressure showers. A doddle. The radiator sizes and pipework still need to be calculated properly Use of a combi doesn't make a fundamental difference to this part of the design. Don't go for complicated cylinders, tanks, motorised valves, control systems, etc when there is no need to. Come on. It's not that difficult. A one box solution that professional experts have incorporated all the design and components is by far the best option. We don't know whether Duncan has a requirement that doesn't match a combi. That's why I said get back to me. The rad sizing can be done by using one of the many on-line rad calulators. These are useful, but are not bug free. I have seen mistakes in the U value numbers in one program and another doesn't calculate heat gains properly. They give a good ballpark figure. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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designing a central heating and ho****er system
"Capitol" wrote in message ... I would disagree about the "ball park figure" being adequate to start with, Ballpark is fine. There are a few on-line calculators. It is best to use a few. Ad 5 to 10 % extra if you like. the odds are you will end up with a boiler and radiators which are too small. The smallest of comi's will do the CH on a "very" large house. The boiler sizing is not a problem if it is not a big house. Of more importance, where are the 10 year maintenance and running costs factored in on a combi system without soft water. Always have a de-scaler on a combi, or on "any" system in hard water. How do these costs compare with a traditional conventional vented boiler, even allowing for a tank replacement every 10 years? Thinking about it, are there any boilers of any type with a 10 year warranty even with soft water? In the past, my boiler life achievements were in excess of 20 years, have these days gone forever? Firstly, a combi is a system boiler with a water section. Many share the same components. Secondly, a combi has most of the "system" in one box. Only the rads and a wall stat are ouside the box. So when you start comparing breakdowns and longevity compare like with like. On a cylinder/tank set up include any problems with the F&E tank, the cold water storage tanks, the cylinder, the 3-way zone valve, the cylinder stat, the programmer, all the associated pipework, etc. Then you will find that a combi is no less reliable, and get a good make of combi, probably far more reliable overall. Got it? I had a Potterton Neatheat for over 20 years. The boiler was very reliable in itself because there was not much in it. In that time I went through 3 pumps, a zone valve, a zone valve motor, a cylinder, cylinder stat, room stat and a programmer. On the boiler a relay, flue fan and a pressure differential switch. Overall the "system" was not that reliable. I am certain a good Vaillant would have given far less trouble over 20 years. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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designing a central heating and ho****er system
"IMM" wrote
| Don't go for complicated cylinders, tanks, motorised valves, | control systems, etc when there is no need to. | Come on. It's not that difficult. | A one box solution that professional experts have incorporated | all the design and components is by far the best option. giggles Microsoft runs away Owain |
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designing a central heating and ho****er system
On Thu, 17 Jul 2003 21:13:08 +0100, "IMM" wrote:
"Andy Hall" wrote in message .. . Any recommendations for sources of information on designing a central heating/ho****er system for please. have found sites that provide info on rating the boiler/rads but nothing on the actual design. type of heat storage etc. duncan What do you intend to do? As you are a DIYer go the combi route. Why? That's a bit of a put down isn't it. How is recommending the best rote for a DIYer a put down. This is uk.d-i-y. Because you are suggesting that a single box combi solution is the most appropriate for a DIYer on the basis that it is apparently simple. The reality, of course is that there are a whole load of issues such as incoming water mains pressure and flow, appropriate sizing of pipework, flow restrictors and a whole raft of other issues to deal with to make it work properly. You don't know what the usage requirements are so how can you be so sure that this is the right solution. Why not a thermal store, or have you gone off those this week? Buy a high flowrate combi. Not all combi's give a trickle for hot water. They are easy to install with minium design in CH pipework and rad sizing. You connect up 5 pipes, run a power supply and a wire for a thermostat or thermostat/clock from the combi. Superb for high pressure showers. A doddle. The radiator sizes and pipework still need to be calculated properly Use of a combi doesn't make a fundamental difference to this part of the design. Don't go for complicated cylinders, tanks, motorised valves, control systems, etc when there is no need to. Come on. It's not that difficult. A one box solution that professional experts have incorporated all the design and components is by far the best option. You know full well that there is more to it than that. We don't know whether Duncan has a requirement that doesn't match a combi. That's why I said get back to me. The rad sizing can be done by using one of the many on-line rad calulators. These are useful, but are not bug free. I have seen mistakes in the U value numbers in one program and another doesn't calculate heat gains properly. They give a good ballpark figure. I have seen U values in at least one that are out by a factor of 3:1 on a material that mattered. This led to a 2:1 discrepancy with calculating by hand using the Building Regs numbers. The latter was correct. That is not to say that the programs arenot useful, but just using them blindly without understanding the maths that they are doing is a recipe for problems. On an investment of this size in money and time, it makes more sense to sit down for a couple of hours with a piece of paper and a calculator and to check properly. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 ..andy To email, substitute .nospam with .gl |
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designing a central heating and ho****er system
"Andy Hall" wrote in message ... On Thu, 17 Jul 2003 21:13:08 +0100, "IMM" wrote: "Andy Hall" wrote in message .. . Any recommendations for sources of information on designing a central heating/ho****er system for please. have found sites that provide info on rating the boiler/rads but nothing on the actual design. type of heat storage etc. duncan What do you intend to do? As you are a DIYer go the combi route. Why? That's a bit of a put down isn't it. How is recommending the best rote for a DIYer a put down. This is uk.d-i-y. Because you are suggesting that a single box combi solution is the most appropriate for a DIYer on the basis that it is apparently simple. You are getting there. It is simple. And..will most likely fit the bill. The reality, of course is that there are a whole load of issues such as incoming water mains pressure That is why I said get back to me. You don't know what the usage requirements That is why I said get back to me. Don't go for complicated cylinders, tanks, motorised valves, control systems, etc when there is no need to. Come on. It's not that difficult. A one box solution that professional experts have incorporated all the design and components is by far the best option. You know full well that there is more to it than that. Not much more. So no need to complicate matters and best buy the ideal, simple, one-box, off-the-shelf solution. Clever people these boiler engineers. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 06/06/2003 |
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designing a central heating and ho****er system
On Fri, 18 Jul 2003 00:30:58 +0100, "IMM" wrote:
Because you are suggesting that a single box combi solution is the most appropriate for a DIYer on the basis that it is apparently simple. You are getting there. It is simple. And..will most likely fit the bill. But doesn't answer the question which was asked, which was how to go about designing the complete system. That certainly is not a case of trotting along to B&Q, buying a combi boiler, a few radiators and plumbing bits and sticking it all together and hoping. Radiator and pipework sizing need to be done properly whichever solution is chosen. For a combi boiler of sensible capacity to be useful, it is often necessary to upgrade the gas supply from the meter - this may be non trivial. The water main may need to be upgraded, also non-trivial. If there is existing internal pipework for hot and cold water, it is likely to need modification and re-routing in order for the relative flows to work reasonably well. Flow restrictors may need to be fitted, etc. etc. A conventional boiler and system may be more suitable since it is likely that none of the above issues will need to be addressed. If somebody is capable of working out radiator, boiler and pipe sizing correctly and of doing the required plumbing work properly (which would need to be done whatever the system) then fitting of a pump, motorised valves and cylinder and tank are not a stretch of ability or intellect. It is also a more scalable solution in terms of meeting a range of requirements. A one box solution that professional experts have incorporated all the design and components is by far the best option. You know full well that there is more to it than that. Not much more. So no need to complicate matters and best buy the ideal, simple, one-box, off-the-shelf solution. Clever people these boiler engineers. Clever enough not to assume that one size and one technology fits all. ..andy To email, substitute .nospam with .gl |
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designing a central heating and ho****er system
"Andy Hall" wrote in message ... On Fri, 18 Jul 2003 00:30:58 +0100, "IMM" wrote: Because you are suggesting that a single box combi solution is the most appropriate for a DIYer on the basis that it is apparently simple. You are getting there. It is simple. And..will most likely fit the bill. But doesn't answer the question which was asked, which was how to go about designing the complete system. It does answer the Q. Most of the design is inside the box, done by experts. The only design is the rad sizing and the pipe run. Not difficult. That certainly is not a case of trotting along to B&Q, buying a combi boiler, a few radiators and plumbing bits and sticking it all together and hoping. Not hoping. It is not far off what you say. Just a combi with the correct flowrate and size the rads and buy them. Radiator and pipework sizing need to be done properly whichever solution is chosen. That is why I said get back to me. For a combi boiler of sensible capacity to be useful, it is often necessary to upgrade the gas supply from the meter - this may be non trivial. One pipe run is trivial, when looking at the whole system. The water main may need to be upgraded, also non-trivial. It may not need an upgrade. If there is existing internal pipework for hot and cold water, it is likely to need modification and re-routing in order for the relative flows to work reasonably well. Flow restrictors may need to be fitted, etc. etc. It may only require a small modification. Flow restrictors on all taps are easy and cheap to fit. A conventional boiler and system may be more suitable Maybe, but unlikely. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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designing a central heating system - wow
Hey guys
What a response. Its funny that not matter how you pose a question on here about heating/ho****er it always ends with combis in the red corner and conventional systems in the green corner, fighting it out. LOL I feel that I'm a well confident DIYer having now nearly completed the whole house extension myself. Wouldn't choose a combi for its convenience unless it fits the bill. Andy - I've sent away for that book so will take a few evenings reading that. With combis its even more important to get the piping sizes correct and design right to prevent hot water not feeding enough sources (kitchen, shower etc.) It is still bothering me that having two showers in use in the morning is still gonna be a problem with a combi. Plus the missus likes a bath and not sure that she has the patients to wait for it. Thermal stores - any suggestions on them please. What sort of cylinder should I go for if i go down the convential route? duncan well at least i'll have all weekend to read the response lol "duncan" wrote in message ... hi, Any recommendations for sources of information on designing a central heating/ho****er system for please. have found sites that provide info on rating the boiler/rads but nothing on the actual design. type of heat storage etc. duncan |
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designing a central heating and ho****er system
On Fri, 18 Jul 2003 10:22:16 +0100, "IMM" wrote:
"Andy Hall" wrote in message .. . On Fri, 18 Jul 2003 00:30:58 +0100, "IMM" wrote: Because you are suggesting that a single box combi solution is the most appropriate for a DIYer on the basis that it is apparently simple. You are getting there. It is simple. And..will most likely fit the bill. But doesn't answer the question which was asked, which was how to go about designing the complete system. It does answer the Q. Most of the design is inside the box, done by experts. Sorry I don't buy that. From the high level functional point of view, the combi is simply bringing into the box the pump and an alternative means of providing the hot water. Granted, it does reduce the component count vs. a cylinder system. However, from a *design* perspective, there is little or nothing involved in provisioning a vented cylinder, motorised valve(s) and pump. One is going to choose a suitably sized cylinder for the application, hopefully of a fast recovery type. The only design decision there is to try to make sure that the boiler is adequately sized to provide enough heat to recover the cylinder in a sensible time. This will imply a certain flow rate and pipe size for the primary connections to the cylinder - normally 22mm. Motorised valves are completely standard, so no design decision there. If the boiler is not a system one and does not have an internal pump then in a proper design, one would normally work out the required flow and head in order to select the right pump type and setting. However, with electronically controlled pumps such as the Grundfos Alpha this is largely taken care of anyway. The only design is the rad sizing and the pipe run. Not difficult. No it isn't, but that is where most of the *design* work is - not in the boiler. That certainly is not a case of trotting along to B&Q, buying a combi boiler, a few radiators and plumbing bits and sticking it all together and hoping. Not hoping. It is not far off what you say. Just a combi with the correct flowrate and size the rads and buy them. .... and checking the provisioning of services, adequacy of plumbing and so on. Radiator and pipework sizing need to be done properly whichever solution is chosen. That is why I said get back to me. For a combi boiler of sensible capacity to be useful, it is often necessary to upgrade the gas supply from the meter - this may be non trivial. One pipe run is trivial, when looking at the whole system. That depends on where it has to run The water main may need to be upgraded, also non-trivial. It may not need an upgrade. Agreed. I am simply pointing out that it may do and that can be difficult and expensive, which in turn may be a decision factor in what to do. It is better to point this out up front so that it can be checked, rather than glossing over and potentially having a nasty surprise. If there is existing internal pipework for hot and cold water, it is likely to need modification and re-routing in order for the relative flows to work reasonably well. Flow restrictors may need to be fitted, etc. etc. It may only require a small modification. Flow restrictors on all taps are easy and cheap to fit. Fine, but it should all be taken into account. A conventional boiler and system may be more suitable Maybe, but unlikely. We have no data to say one way or the other. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 ..andy To email, substitute .nospam with .gl |
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designing a central heating and ho****er system
"Andy Hall" wrote in message ... It does answer the Q. Most of the design is inside the box, done by experts. Sorry I don't buy that. After I had hopes for you too, and you say that. From the high level functional point of view, the combi is simply bringing into the box the pump and an alternative means of providing the hot water. Granted, it does reduce the component count vs. a cylinder system. You are getting there. Or are you? It vastly reduces the design aspect too. However, from a *design* perspective, there is little or nothing involved in provisioning a vented cylinder, motorised valve(s) and pump. There is, especially for a novice. The only design is the rad sizing and the pipe run. Not difficult. No it isn't, It is easy enough, and about the only complex part in fitting a combi. One pipe run is trivial, when looking at the whole system. That depends on where it has to run It is not a Middle East oil pipeline. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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designing a central heating and ho****er system
"Alan James" wrote in message ... "IMM" wrote in message ... Superb for high pressure showers. I agree, but the wait for hot water at the WHB with a combi is still a pain when you are in a hurry to get to work. More old wives tales! Some combis have pre-hearted heat exchangers and some with small pre-heated hot water vessels to give pronto hot water at taps. Don't go for complicated cylinders, tanks, motorised valves, control systems, etc when there is no need to. Well there may be no need but then unvented DHW performance does come at a price which most people who have tried it thinks its well worth. Are you on about cylinders? --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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designing a central heating system - wow
"duncan" wrote in message ... Andy - I've sent away for that book so will take a few evenings reading that. A waist of time for a DIYer doing a one-off. With combis its even more important to get the piping sizes correct and design right to prevent hot water not feeding enough sources (kitchen, shower etc.) The hot and cold water pipes must be sized right, but that is ballpark It is still bothering me that having two showers in use in the morning is still gonna be a problem with a combi. Plus the missus likes a bath and not sure that she has the patients to wait for it. More old wives tales again. There are high flow combi's around that will do two showers and fill a bath pronto. Thermal stores - any suggestions on them please. Go Heat bank not a thermal store. There is a difference http://www.heatweb.com "Integrated" heat banks are available that are pretty idiot proof. They come complete with all controls, pumps, etc. You mount your boiler, connect up the boiler flow and return pipes to the heat bank, connect up the flow and return of the rad circuit from the heat bank, supply power to the heat bank control box, run a wire to the room stat, run a wire to the boiler and connect up the cold mains and hot water draw-off pipes. Simple, and a state of the art solution. More expensive, but as you are doing it yourself a hell of a lot cheaper than getting a professional in. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
#18
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designing a central heating system - wow
On Fri, 18 Jul 2003 18:41:23 +0000 (UTC), "duncan"
wrote: Hey guys What a response. Its funny that not matter how you pose a question on here about heating/ho****er it always ends with combis in the red corner and conventional systems in the green corner, fighting it out. LOL I feel that I'm a well confident DIYer having now nearly completed the whole house extension myself. Wouldn't choose a combi for its convenience unless it fits the bill. Andy - I've sent away for that book so will take a few evenings reading that. 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. With combis its even more important to get the piping sizes correct and design right to prevent hot water not feeding enough sources (kitchen, shower etc.) 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. It is still bothering me that having two showers in use in the morning is still gonna be a problem with a combi. Plus the missus likes a bath and not sure that she has the patients to wait for it. 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. Thermal stores - any suggestions on them please. 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. What sort of cylinder should I go for if i go down the convential route? 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. duncan well at least i'll have all weekend to read the response lol There should be plenty of those. Thrills and spills for all the family :-) "duncan" wrote in message ... hi, Any recommendations for sources of information on designing a central heating/ho****er system for please. have found sites that provide info on rating the boiler/rads but nothing on the actual design. type of heat storage etc. duncan ..andy To email, substitute .nospam with .gl |
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On Fri, 18 Jul 2003 22:41:47 +0100, "IMM" wrote:
"Andy Hall" wrote in message .. . It does answer the Q. Most of the design is inside the box, done by experts. Sorry I don't buy that. After I had hopes for you too, and you say that. From the high level functional point of view, the combi is simply bringing into the box the pump and an alternative means of providing the hot water. Granted, it does reduce the component count vs. a cylinder system. You are getting there. Or are you? It vastly reduces the design aspect too. Please explain precisely how it reduces the *design* NOT the implementation aspects. However, from a *design* perspective, there is little or nothing involved in provisioning a vented cylinder, motorised valve(s) and pump. There is, especially for a novice. This is a put down. Please explain what is difficult about these aspects. The only design is the rad sizing and the pipe run. Not difficult. No it isn't, It is easy enough, and about the only complex part in fitting a combi. Do you have some exact design rules? Please quote an example and give the basis of calculation such that it can be adapted to different situations. One pipe run is trivial, when looking at the whole system. That depends on where it has to run It is not a Middle East oil pipeline. It might as well be if it involves ripping out the floor or wrecking the decorations of a kitchen. ..andy To email, substitute .nospam with .gl |
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designing a central heating system - wow
"Andy Hall" wrote in message
... 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. Need to size with a combi as it never runs out of hot water. Thermal stores - any suggestions on them please. 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. Most store water at 75C these days. 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. You know little of HVAC. It's also better to run the radiators separately from the primary circuit than from the store. If the rads are run for the store backup electricity can be incorporated. High wattage immersion cols are available. What sort of cylinder should I go for if i go down the convential route? 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. 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. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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On Fri, 18 Jul 2003 23:06:50 +0100, "IMM" wrote:
"duncan" wrote in message ... Andy - I've sent away for that book so will take a few evenings reading that. A waist of time for a DIYer doing a one-off. 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. With combis its even more important to get the piping sizes correct and design right to prevent hot water not feeding enough sources (kitchen, shower etc.) The hot and cold water pipes must be sized right, but that is ballpark It is still bothering me that having two showers in use in the morning is still gonna be a problem with a combi. Plus the missus likes a bath and not sure that she has the patients to wait for it. More old wives tales again. There are high flow combi's around that will do two showers and fill a bath pronto. That's a matter of opinion and expectation of performance. Thermal stores - any suggestions on them please. Go Heat bank not a thermal store. There is a difference http://www.heatweb.com "Integrated" heat banks are available that are pretty idiot proof. They come complete with all controls, pumps, etc. You mount your boiler, connect up the boiler flow and return pipes to the heat bank, connect up the flow and return of the rad circuit from the heat bank, supply power to the heat bank control box, run a wire to the room stat, run a wire to the boiler and connect up the cold mains and hot water draw-off pipes. Simple, and a state of the art solution. More expensive, but as you are doing it yourself a hell of a lot cheaper than getting a professional in. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 ..andy To email, substitute .nospam with .gl |
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designing a central heating and ho****er system
"Andy Hall" wrote in message ... On Fri, 18 Jul 2003 22:41:47 +0100, "IMM" wrote: "Andy Hall" wrote in message .. . It does answer the Q. Most of the design is inside the box, done by experts. Sorry I don't buy that. After I had hopes for you too, and you say that. From the high level functional point of view, the combi is simply bringing into the box the pump and an alternative means of providing the hot water. Granted, it does reduce the component count vs. a cylinder system. You are getting there. Or are you? It vastly reduces the design aspect too. Please explain precisely how it reduces the *design* NOT the implementation aspects. Nahhhhh. You are not getting there. One pipe run is trivial, when looking at the whole system. That depends on where it has to run It is not a Middle East oil pipeline. It might as well be if it involves ripping out the floor or wrecking the decorations of a kitchen. The whole is being ripped apart anyhow. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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"Andy Hall" wrote in message ... On Fri, 18 Jul 2003 23:06:50 +0100, "IMM" wrote: "duncan" wrote in message ... Andy - I've sent away for that book so will take a few evenings reading that. A waist of time for a DIYer doing a one-off. 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? Because I know more than you. 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. A book like that can confuse a DIYer rather than help him. It is still bothering me that having two showers in use in the morning is still gonna be a problem with a combi. Plus the missus likes a bath and not sure that she has the patients to wait for it. More old wives tales again. There are high flow combi's around that will do two showers and fill a bath pronto. That's a matter of opinion and expectation of performance. Not so. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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On Fri, 18 Jul 2003 23:26:04 +0100, "IMM" wrote:
"Andy Hall" wrote in message .. . 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. Need to size with a combi as it never runs out of hot water. Provided that the requirements in terms of flow and temperature rise are within its capabilities. - 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. Most store water at 75C these days. We've had that discussion. 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. You know little of HVAC. Seemingly I know more than you do and do present even handed and more complete explanations. It's also better to run the radiators separately from the primary circuit than from the store. If the rads are run for the store backup electricity can be incorporated. High wattage immersion cols are available. What sort of cylinder should I go for if i go down the convential route? 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. 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. That depends on the requirement and circumstances. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 ..andy To email, substitute .nospam with .gl |
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"Andy Hall" wrote in message ... On Fri, 18 Jul 2003 23:26:04 +0100, "IMM" wrote: "Andy Hall" wrote in message .. . 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. Need to size with a combi as it never runs out of hot water. Provided that the requirements in terms of flow and temperature rise are within its capabilities. Which it should depending on model. - 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. Most store water at 75C these days. We've had that discussion. It wasn't a discussion, it was me attempting to educate you on the topic. I failed. 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. You know little of HVAC. Seemingly I know more than you do and do present even handed and more complete explanations. In your dreams. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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"duncan" wrote in message ... Hey guys What a response. What are your requirements? baths, showers, size of house, etc? --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 06/06/2003 |
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designing a central heating and ho****er system
IMM wrote in message ... "Capitol" wrote in message ... I would disagree about the "ball park figure" being adequate to start with, Ballpark is fine. There are a few on-line calculators. It is best to use a few. Ad 5 to 10 % extra if you like. the odds are you will end up with a boiler and radiators which are too small. The smallest of comi's will do the CH on a "very" large house. The boiler sizing is not a problem if it is not a big house. Sadly not true, as our friend has found out the hard way! Of more importance, where are the 10 year maintenance and running costs factored in on a combi system without soft water. Always have a de-scaler on a combi, or on "any" system in hard water. 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. How do these costs compare with a traditional conventional vented boiler, even allowing for a tank replacement every 10 years? Thinking about it, are there any boilers of any type with a 10 year warranty even with soft water? In the past, my boiler life achievements were in excess of 20 years, have these days gone forever? Firstly, a combi is a system boiler with a water section. Many share the same components. Secondly, a combi has most of the "system" in one box. Only the rads and a wall stat are ouside the box. So when you start comparing breakdowns and longevity compare like with like. On a cylinder/tank set up include any problems with the F&E tank, the cold water storage tanks, the cylinder, the 3-way zone valve, the cylinder stat, the programmer, all the associated pipework, etc. Then you will find that a combi is no less reliable, and get a good make of combi, probably far more reliable overall. Got it? Where are the manufacturers offering a 10year warranty? I had a Potterton Neatheat for over 20 years. The boiler was very reliable in itself because there was not much in it. In that time I went through 3 pumps, a zone valve, a zone valve motor, a cylinder, cylinder stat, room stat and a programmer. On the boiler a relay, flue fan and a pressure differential switch. Overall the "system" was not that reliable. I am certain a good Vaillant would have given far less trouble over 20 years. I would regard that as being totally unreliable, only one pump at most would be necessary on a reliable system. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 Regards Capitol |
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designing a central heating and ho****er system
"Capitol" wrote in message ... IMM wrote in message ... "Capitol" wrote in message ... I would disagree about the "ball park figure" being adequate to start with, Ballpark is fine. There are a few on-line calculators. It is best to use a few. Ad 5 to 10 % extra if you like. the odds are you will end up with a boiler and radiators which are too small. The smallest of comi's will do the CH on a "very" large house. The boiler sizing is not a problem if it is not a big house. Sadly not true, as our friend has found out the hard way! 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. Of more importance, where are the 10 year maintenance and running costs factored in on a combi system without soft water. Always have a de-scaler on a combi, or on "any" system in hard water. 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. 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. Where are the manufacturers offering a 10year warranty? 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. I had a Potterton Neatheat for over 20 years. The boiler was very reliable in itself because there was not much in it. In that time I went through 3 pumps, a zone valve, a zone valve motor, a cylinder, cylinder stat, room stat and a programmer. On the boiler a relay, flue fan and a pressure differential switch. Overall the "system" was not that reliable. I am certain a good Vaillant would have given far less trouble over 20 years. I would regard that as being totally unreliable, But average for a tank/cylinder setup over 20 years!!! only one pump at most would be necessary on a reliable system. Over 20 years? I would say 2 pumps. I have seen few pumps go beyond 10 years. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 06/06/2003 |
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On Fri, 18 Jul 2003 23:28:50 +0100, "IMM" wrote:
Please explain precisely how it reduces the *design* NOT the implementation aspects. Nahhhhh. You are not getting there. Predictably, you have ducked the issue when put on the spot....... It might as well be if it involves ripping out the floor or wrecking the decorations of a kitchen. The whole is being ripped apart anyhow. You don't know that. ..andy To email, substitute .nospam with .gl |
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designing a central heating system - wow
On Sat, 19 Jul 2003 00:03:29 +0100, "IMM" wrote:
"duncan" wrote in message ... Hey guys What a response. What are your requirements? baths, showers, size of house, etc? 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 |
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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 "IMM" wrote in message ... "duncan" wrote in message ... Andy - I've sent away for that book so will take a few evenings reading that. A waist of time for a DIYer doing a one-off. With combis its even more important to get the piping sizes correct and design right to prevent hot water not feeding enough sources (kitchen, shower etc.) The hot and cold water pipes must be sized right, but that is ballpark It is still bothering me that having two showers in use in the morning is still gonna be a problem with a combi. Plus the missus likes a bath and not sure that she has the patients to wait for it. More old wives tales again. There are high flow combi's around that will do two showers and fill a bath pronto. Thermal stores - any suggestions on them please. Go Heat bank not a thermal store. There is a difference http://www.heatweb.com "Integrated" heat banks are available that are pretty idiot proof. They come complete with all controls, pumps, etc. You mount your boiler, connect up the boiler flow and return pipes to the heat bank, connect up the flow and return of the rad circuit from the heat bank, supply power to the heat bank control box, run a wire to the room stat, run a wire to the boiler and connect up the cold mains and hot water draw-off pipes. Simple, and a state of the art solution. More expensive, but as you are doing it yourself a hell of a lot cheaper than getting a professional in. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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"duncan" wrote in message ... 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. 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. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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"Andy Hall" wrote in message ... Please explain precisely how it reduces the *design* NOT the implementation aspects. Nahhhhh. You are not getting there. Predictably, you have ducked the issue when put on the spot....... Ducking nothing. Nahhhhh. You are not getting there. It might as well be if it involves ripping out the floor or wrecking the decorations of a kitchen. The whole is being ripped apart anyhow. If a whole system is being fitted the whole house will be disrupted. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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designing a central heating system - wow
"Andy Hall" wrote in message ... On Fri, 18 Jul 2003 23:47:38 +0100, "IMM" wrote: Need to size with a combi as it never runs out of hot water. Provided that the requirements in terms of flow and temperature rise are within its capabilities. Which it should depending on model. .. and whether the model is up to the requirement. At some point, and this is within the range of households with larger requirements, one goes beyond the ability of combi boilers to provide adequate results. Then you go heat bank if a combi is not adequate. We've had that discussion. It wasn't a discussion, it was me attempting to educate you on the topic. I failed. To educate requires that you be educated yourself first, and based on your track record, that seems highly dubious. You are rank amateur with limited knowledge of the subject. Duhhh!!! LOL!! You know little of HVAC. Seemingly I know more than you do and do present even handed and more complete explanations. In your dreams. certainly not in yours..... You are foolish that is certain. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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"Andy Hall" wrote in message ... On Sat, 19 Jul 2003 00:03:29 +0100, "IMM" wrote: "duncan" wrote in message ... Hey guys What a response. What are your requirements? baths, showers, size of house, etc? 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?? Is there a full moon? --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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"duncan" wrote in message
... The book has arrived and its not a waist of time even for a one off. i'll have a look at the heatbanks Not in that book you never. It is lacking in many aspects. A poor book. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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IMM wrote in message ... "Capitol" wrote in message ... IMM wrote in message ... "Capitol" wrote in message ... I would disagree about the "ball park figure" being adequate to start with, Ballpark is fine. There are a few on-line calculators. It is best to use a few. Ad 5 to 10 % extra if you like. the odds are you will end up with a boiler and radiators which are too small. The smallest of comi's will do the CH on a "very" large house. The boiler sizing is not a problem if it is not a big house. Sadly not true, as our friend has found out the hard way! 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. 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 |
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"Capitol" wrote in message
... The smallest of comi's will do the CH on a "very" large house. The boiler sizing is not a problem if it is not a big house. Sadly not true, as our friend has found out the hard way! 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. 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. 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. Small units cannot be relied upon to cope with a 4 bedroomed house in winter. 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. The figures are from the architectural digest, so I have no reason to doubt them. 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. The house is modern with insulation to the relevant standard. 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? 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. 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. I guess that is why better manufacturers use stainless steel. 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. 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! 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. I still think that an ion exchange water softener is essential in hard water areas. 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. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003 |
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Like Duncan, the reason I post on this kind of forum is to get some 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 and I will regret. As I say this is "my experience" of employing people to do jobs around 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 for that matter who give extremly useful information here, fall in this bracket. I do agree with the "One Box" solution approach, assuming as others have said that it meets the requirements and that is my dilema at present! Interesting reading. Thanks all Andy |
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AndyHingston wrote:
Duncan's trade, but I myself have served a 4 year Mechanical Engineering Apprenticeship and am probably far more capable of making a decent joint for a water/gas system than many so called "Professionals" I am 100% in agreement with you Andy. Being an ex Time served Agricultural engineer. With the advice of a plumber friend I ripped out a Gravity fed single pipe Parkray back boiler C/H system and replaced with fully pumped gas Back boiler with "living flame" fire front. Just got a friendly corgi chap to come in and connect gas meter to my pipework. 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 and I will regret. Ohhh tell me about it. Current project had a "qualified" plumber do plumbing that has subsequently been ripped out and done "professionally" by yours truly and advice taken from this friendly bunch. As I say this is "my experience" of employing people to do jobs around the house, whether it is fencing, double glazing or I am sure plumbing. There seems to be a far higher percentage of qualified persons that bodge or do a "make do" job because "time is money" whereas the DIY'er isn't working on a £150+ / day rate and would rather take time to do a job to his/her accepted quality of workmanship. Pete -- http://gymratz.co.uk - Best Gym Equipment & Bodybuilding Supplements UK. http://trade-price-supplements.co.uk - TRADE PRICED SUPPLEMENTS for ALL! http://fitness-equipment-uk.com - UK's No.1 Fitness Equipment Suppliers. http://gymratz.co.uk/hot-seat.htm - Live web-cam! (sometimes) |
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