Thumper Club Forum
Club House => Chatter => Topic started by: guest27 on June 15, 2008, 01:33:14 PM
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HI All
Nowt to do with thumpers...
Had the boiler repaired again yester day and the plumber asked whether we had thought about replacing the boiler rather than having it fixed all the time. First off he is not punting for work.... He is a good guy if somewhat busy.
We have an old Ideal Mexico (100,000 btu), which I guess is not the most efficient of boilers, heating a large detached house.
If we were to look at thins what should we be thinking of? A quick chat with Tony suggested a good quality conbi boiler - but having a look about I can see that there are combis and combis, and condensing boilers and others etc etc.
I know a number of you have more knowledge of all of this than I have - what sort of questions should I be asking in relation to finding a good outcome - hot house, hot water, low bills, low CO2 print (or tending to all of those)
Ta
R
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Rog, one of my plans is to replace our boiler with a combi which can take pre-heated water. The idea is to have solar collectors (on the garage) pre-heat the water in a tank before passing into the boiler which would 'top up' the temperature. From memory you need a water tank which can withstand mains pressure and so they are not cheap. Doesnt answer your question but might be worth considering when choosing a boiler.
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I had to replace our combi 18 months ago in the middle of a cold snap. We were told that condensers were pretty much the way to go nowadays. It cost £1600 to have a BAXI one fitted by a CORGI registered fitter. We heard all manner of stories about how we could have got one for less but on closer inspection the money we paid was about right really. You will save money by getting a new one. A poorly boiler just wastes energy. And you just know the one you have will fail you just when you are in from afreezing ride and all you want is a hot bath. Those three days without a a decent hot water supply were murder. We ended up with a "wheelie-bin"-type contraption in the bathroom to give us hot bath water.
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Glad there are also some other strange people on here too - I was wondering if I could fit a mains pressure stainless tank before the boiler to preheat water in solar panels...
Brilliant minds
Saw a thing called the tadpole the other day - a tank that 'removes' the gas from water before it goes into the boiler - anyone know anything of these?
R
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rog, if youre fitting a new boiler, thenit will have to be a condensing boiler, you dont really have any choice in it!, from experience, i would say fit a worcester bosch, theyre probably the best of the bunch, and whilst you may have to pay a bit more to fit them, they pay for themselves in the long run with their reliability. i have seldom had to go back to a worcester that ive fitted, theyre the last word in reliability, and when we move to our new house in a few weeks, i'll be fitting one there. the solar hybrids idea is nothing new. basically you fit a set of solar panels on the roof, and feed these to a mains pressure hot water system9also known as an unvented hot water system) the panels will heat the water in the tank, this then feeds down to the boiler, and goes in the cold inlet side of the boiler. the idea being that if the water is hot enough, the boiler senses this and just lets the water through, but if the water isnt hot enough, the boiler kicks in and boosts it up to the required temp. its a major investment though, as the combi, cylinder and panels are all expensive items on their own. if your house is an old one, it is always worth looking into topping up your insulation, as the amount you can save by propperly insulating can easily exceed the amount you save by fitting a new boiler. current regs iirc call for between 9 and 12 inches of insulation in a loft!!
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With regard to the solar heated input....I use a standard copper cylinder (which comes with urethane insulation) it is ok for mains pressure (this may depend on your local pressure, it's pretty low here, and this cylinder is in the garage, so it's not a disaster if it leaks! :D), the solar panels run into the indirect loop of the cylinder, thus i can run a mixture of fernox and antifreeze through them without contaminating the rest of the system...the indirect loop has a pump, controlled by a temp sensor, such that when the panel temp exceeds the tank temp the pump runs. and as previously stated, the output of this cylinder feeds the main system, the boiler only coming on if the main system needs hotter water than is being supplied by the auxilliary input tank (such as at night and cloudy days).
I'm currently using home made panels (old steel single panel radiators, painted matt black, in an insulated box with a tripple wall clear plastic/poly top) these work tolerably well, but nowhere near as well as the evacuated tube systems now available, but at £400 per panel (well, thats the best price i can find) i'm not in a position to go down that route yet, mind you, if oil keeps going up, i may have to.
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Steve
What sort of temp does the rad-solar panels acheive in the water - is it worth the effort of making? Do they warm any on winters days?
All
Any thought about the boilers with a Stirling Engine in the flue - seem to remember a lot of fanfare about them and then nothing. Are they as good at that! lol
Thanks for the input and keep it coming please.
R
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With regard to the solar heated input....I use a standard copper cylinder (which comes with urethane insulation) it is ok for mains pressure (this may depend on your local pressure, it's pretty low here, and this cylinder is in the garage, so it's not a disaster if it leaks! :D), the solar panels run into the indirect loop of the cylinder, thus i can run a mixture of fernox and antifreeze through them without contaminating the rest of the system...the indirect loop has a pump, controlled by a temp sensor, such that when the panel temp exceeds the tank temp the pump runs. and as previously stated, the output of this cylinder feeds the main system, the boiler only coming on if the main system needs hotter water than is being supplied by the auxilliary input tank (such as at night and cloudy days).
I'm currently using home made panels (old steel single panel radiators, painted matt black, in an insulated box with a tripple wall clear plastic/poly top) these work tolerably well, but nowhere near as well as the evacuated tube systems now available, but at £400 per panel (well, thats the best price i can find) i'm not in a position to go down that route yet, mind you, if oil keeps going up, i may have to.
no, you need to use a mains pressure cylinder, theyre usually stainless steel, and come with an expansion vessel on top, as the heated wqater needs to have somewhere to expand into, they also need to be fitted with any number of non return valves and pressure relief valves and also temp relief valves. in sohort, no, you cant use your existing cylinder. i cant begin to say how many water byelaws you will be contravening, not least the risk of a tank full of potentially boiling hot water bursting inside a house or garage.
however, theres a slightly more budget way of getting in on solar, try looking up a panel called "solartwin" this can be piped into existing systems, and connected directly into the hot water cylinder, and on the direct side too, not the indirect. the panel is devised in order to allow it to freeze up in winter, and then thaw out and still work ok. fially, the solar twin has a small photovoltaic panel built into it, this powers a pump that circulates the water from tank to panel, as its photovoltaic, it only works when the sun shines, so you dont waste heat at night by pumping your hot water round a solar panel on a dark roof. this system means you dont need to modify an existing cylinder fed hot water system too much to get the benefits of solar.
the payback time of a full solar system may be around 20+ years, but as energy prices rise, it makes more sense. i may well be fittng a solar panel when we move house, but im in the plumbing trade, so im not subject to the usual crippling installation costs.
i think anyone interested in this technology who wants to see how to do it on the cheap would find a trip to CAT (centre for alternative technologys) in wales well worth their while. they even run residential courses on how to build you own panels.
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Thanks for that John R
I have the CAT DIY book on solar panels and may follow that route - but as you say as fuel prices rise....
Whilst I have to pay installation costs we have a very good local plumber - callout and fixing the pilot tube on the old boiler £10 - cannot argue... mind you have to be happy to leave the house open as he is liable to turn up at 2 in the morning on his way home from another job.
Will only work for GC this - but he was here late one night - fixing the same problem which is why we are thinking of looking at another boiler rather than throwing money at this - and he got too low on our drive and backed his van over the bank on the edge - spent a couple of hours around midnight on Friday looking for sober mates with 4X4s to come and pull him off. But at least he remembers where we are.
Will talk this load over with SWMBO
Similar thoughs - have a book on green buildings here and it mentions hydrothermic floors - not the std type with the pipes a few inches below the surface but running solar heated water through a 6' thick block of sand / concrete etc to heat it up over the summer to leak heat over the winter. Now it strikes me digging a 6" hole under my house is liable to see the whole lot fall into the hole. Any thoughts on how to insulate the area around the house so the heat does not conduct away with out having to dig a big hole - so I will not fill the hole with terracotta sand (the best for heating*) but we are on very rocky sub so not too bad.
R
* it is all to do with the wave length of the radiation and thus why water filled steel rads need to be hotter for a given level of comfort to cast iron ones - or better still terracotta blocks...
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John of course is right.....but i'm not hampered by making my living from plumbing......and i wouldn't ponce about with anyone elses setup, if it bu55ers up, then I shall have to do the job properly, maybe get john in:-)
with regard to the home made panels....they put out heat in any sunlight, winter or summer.....but not much in just bright daylight. unlike the new vacuated black tube type....which chuck out heat in any weather.
but at least mine prove the system works...and when i can afford the pukka ones I will get some.
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im not touting for work steve! i work for a large energy management company doing industrial/commercial heating and plumbing maintainance, so im not really after any more work, i gave up on foriegners as we called them some years back. like you said, its your system so your problem. just dont tell the insurance company or the neighbours!! id reccomend a pressure vessel though, they arent dear, in fact if you were closer, ive one you could have. its just a safety thing really, when water wants to expand, theres not a lot you can do to stop it!!
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this is an interesting forum, ok, its setup by a panel manufacturer, but the stuff in it is pretty generic, and its pretty new, but, its got some handy installation diagrams showing pipe layouts etc and is handy for anyone who may want to figure out how to lay out a system.
http://www.solarsavings.co.uk/forum/viewtopic.php?f=11&t=7
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Similar thoughs - have a book on green buildings here and it mentions hydrothermic floors - not the std type with the pipes a few inches below the surface but running solar heated water through a 6' thick block of sand / concrete etc to heat it up over the summer to leak heat over the winter. Now it strikes me digging a 6" hole under my house is liable to see the whole lot fall into the hole. Any thoughts on how to insulate the area around the house so the heat does not conduct away with out having to dig a big hole - so I will not fill the hole with terracotta sand (the best for heating*) but we are on very rocky sub so not too bad.
this may interest you, not quite what you want, but its handy info if you dont want to dig under the house!!!!
http://www.nrel.gov/docs/fy04osti/36277.pdf
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Thanks for the offer john.....no i wasn't after you doing a 'foriegner' (the same name for it in my job as well :) )
well, the guy who bought my SRX #3 is a plumber (strangely...called John....) and he has pressure vessels and all that stuff.
As i have just fitted a new header tank in the loft....i may use that as the supply for the secondary tank and the indirect loop as well, not ideal, lots more pipes etc, ther's so many ways to organise it, especially as i'm not pushed for space.....probably going to go through many many arrangements before i get it right :-)
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John, again, thank you very much.
R
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The majority of boilers are much of a muchness and different plumbers will have their favourites. I know some plumbers swear by boilers I wouldn't touch. Saying that I'd make sure it has a stainless heat exchanger whatever make it is, the condensate is corrosive and it's reckoned they last longer.
Combi boilers are not necessarily the best boilers for all, plumbers love them because they are quick and easy to fit. They give mains pressure hot water, good for showers, but at reduced flow due to passing through boiler slow enough to be heated.. This causes problems if you have more than one tap on at a time, even a washing machine with cold fill only will cause pressure to go up and down. Flats or households with only two or three people in them they may be OK for, but more than that, especially if you have a second bathroom, I wouldn't recommend them. One big advantage is you only heat the water you use. From a family point of view if you have a cylinder with the immersion you have a backup should the boiler fail.
As luck would have it I went to a presentation last week about air source heat pumps see http://www.trianco.co.uk/activair.cfm. I have to say myself and most of the plumbers there were greatly impressed, from a cost, performance and installation point of view they are great. Much cheaper than solar, works rain or shine and is compact. Had a demo of the unit going and while we were there it heated about five gallons of water to over 40c in maybe two hours, not bad from cold. You can download a pdf of the brochure from the site. Yes they are trying to sell the product, but some stuff sells itself, worth a look.
Paul
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Rog, one of my plans is to replace our boiler with a combi which can take pre-heated water. The idea is to have solar collectors (on the garage) pre-heat the water in a tank before passing into the boiler which would 'top up' the temperature. From memory you need a water tank which can withstand mains pressure and so they are not cheap. Doesnt answer your question but might be worth considering when choosing a boiler.
Steve, a reasonably simple way to do this would be to use a cylinder in reverse, use the solar to heat the cylinder and run the mains water through the coil, the coil should be rated to at least 3 bar on a normal cylinder as this is what sealed heating systems are rated to. I you get a high recovery cylinder the heat transfer should be pretty good, not as efficient as using a mains cylinder but significantly cheaper. All combis will take a pre-heated source mains fed and depending on design pump fed.
Paul
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paul, whilst all combi's work in pretty much the same way, I have to say that I don't find them all the same. there are some which stand above the rest in terms of build quality and reliability. i'm not going to list them here, but combi's like bikes, aren't all equal, though they all do roughly the same thing. also its worth mentioning that NOT all combi's will take a pre heated cold feed. the solution for those that wont is to use a thermostatic mixer valve on the hot feed AFTER the combi.
air source heat pumps, like ground source ones are touted as the future technology to watch, but im not convinced, they still require a reasonably large quantity of electricity to run them, despite their obvious efficiency advantages over gas heating, and the heat pump technology is pretty specialised stuff to maintain, you think plumbers are expensive, try calling an a/c guy out, that will really make you wince! i think its too young a technology to throw money at just yet. its getting there, but its still not quite up to the mark. i went to the worcester technology centre last year, and they were just running load tests on their greenskies ashp unit, and whilst it looked promising, its still not quite powerful enough.
finally, theres the water byelaws to take into account. if youre planning to run a cylinder in reverse like you say, then you will still need to be aware of the regulations governing unvented hot water systems, which is in fact what you will be making, and the possible legal pitfalls of such an installation. im not saying don't do it, but im just pointing out that the supply of water is quite strictly governed in the uk for a reason, and if you choose to break the rules, at least be aware of what they are. 'it was only in my own house so affects no one else' isnt an excuse that would stand up in court.
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Ive found this thread quite interesting
also its worth mentioning that NOT all combi's will take a pre heated cold feed. the solution for those that wont is to use a thermostatic mixer valve on the hot feed AFTER the combi.
Is there anyway of telling the difference ?
finally, theres the water byelaws to take into account. if youre planning to run a cylinder in reverse like you say, then you will still need to be aware of the regulations governing unvented hot water systems, which is in fact what you will be making, and the possible legal pitfalls of such an installation.
Do the correct cylinders have some form of pressure relief to ensure the pre-heated water does not overheat and presurise the mains supply ?
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I've mailed Johnr about the combis, because I'm unaware as to a reason why some combis would not take preheated water.
With regards to cylinder you can fit a twin coil cylinder, with the cylinder being open vent. If you look at the product sales brochure 12kw system diagram you could just swap the underfloor heating section for the mains supply to the combi. With a SolarTwin panel system you could just use a single coil cylinder because the water is heated in a vented cylinder and you would use the coil to run the mains water as previous. I'm looking at this method for my parents place in France. All the previous methods would get round the unvented hot water regulations, which apply to stored hot water under pressure pointed out by Johnr.
Paul
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Seems some manufacturers do advise against preheating water, so the only thing is is to sort out a couple of boilers and talk to the manufacturers.
One major thing Johnr did point out to me is there are lots of places with higher than 3bar mains pressure which would stress a standard cylinder, therefore you'd need to pressure test your mains and use a pressure reducing valve to bring it down to around 2 1/2bar. It's worth mentioning you need a minimum of 1/2bar, though I'd recommend at least 1 bar.
I personally do not think a non-return valve is needed as the temperatures using a cylinder as described would not cause that much expansion. The unvented cylinder have temperature and pressure relief and these cylinders can only be fitted by a suitably qualified person.
One thing to remember is that with HIPS around now if you want to sell your house it will need a report which shows energy efficiency and correct installation.
Paul
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We should be OK as to pressure as we had the connection to the mains checked not long back - making sure there was no lead pipe in there,- the water board man went a little pale when he saw where our water was coming from. As far as he could tell it was connected (via a reducing valve) to the 14" main that serves our village and half of Port Talbot. The tap was leaking - which is their tap - he just said we would wait until it failed...
Mind the rusted steel pipes would probably fail if the pressure was too high.
What this has to do with thumpers I do not know.
R
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What this has to do with thumpers I do not know.
R
Nothing, which is one of the reasons I like it here, someone goes off on a tangent and people just go with it, bit like chinese whispers.
Paul
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If you heard my neighbours ball valve hammering every time they draw water, you'd know what this thread has to do with thumpers! :D
Our water supply used to be a cast iron 2" pipe supplying water to cattle troughs and 5 households. When tested we had over 2000ppm of Fe and if the cattle drank water the washing machine wouldn't fill! :( We renewed the main ourselves and the pipe was that full of silt and corrosion that you could only make out the diameter of a straw in a 6" length and maybe see daylight. :( Needless to say 18 months after replacing the pipe, Scottish Water came and connected us to Perth town water which is abstracted from the Tay 5 miles away and pressure is way over 3 bar.
This thread has been good, because I have been 'contemplating' various alternatives to mains gas 22 years old cast iron boiler for 2 years now. However, plumbers have advised us to stick with what we have (Ideal Mexico) until it blows up, as you have to recoup the cost of the new set up.
Probably go for an open vented mains gas condensing boiler, into a twin coil stainless mains pressure Maxi cylinder with either solar or wood boiler input into the other coil. You get hot water at mains pressure, which is useful in a wee house like ours, with poor header tank height. Can't get my head round how to do the central heating bit as well, need diagrams ???
Need more insulation in the loft afore going down this route, only about 6" at best up there and would it be better to get the 40 year old wiring renewed afore laying fresh insulation, and treating the woodworm, as its 25 years since that was done? :-\ All suggestions, comments welcome!!! ;D
Alternatively, go out and ride the bikes, as a motorcyclist "Never knows!" ::)
Boppin', Bill
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http://www.google.co.uk/imgres?imgurl=http://www.causewayheating.co.uk/images/whichboiler3.gif&imgrefurl=http://www.causewayheating.co.uk/whichboiler.cfm&h=324&w=302&sz=14&tbnid=saNPriqkvv4J::&tbnh=118&tbnw=110&prev=/images%3Fq%3Dopen%2Bvented%2Bcentral%2Bheating%2Bdiagram&hl=en&sa=X&oi=image_result&resnum=3&ct=image&cd=1
Bill, above gives you diagrams for 4 different systems, obviously you will have an extra coil on the cylinder. I'm curious, especially given your poor header tank height why you are opting for open vent. On the boiler heating and hot water coil a sealed system would be more efficient and with faster warm up times. There's no reason not to have the wood or solar coil vented if you wanted, dependant on the system you put in. You would then have a traditional heating system on one side and just the extra coil to provide alternative heat. You're only other problem would be which controls to use to decide on which heat source you're using for the cylinder and to control temperature and times for each.
You will need to do wiring and woodworm treatment first and put in as much insulation as you can get/afford. I think in Scandinavian countries they have 18" and more, granted they are colder there, but everything you lose you pay for.
With regards to water hammer, besides the ballvalve it could be the stopcock hammering and can sometimes be relieved by slightly opening or closing the valve, I replaced mine to solve the problem. Funny enough even my neighbour using the mains water would cause it to hammer, as we have a shared mains.
Paul
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Good evening Paul,
Thank you for the URL and info, much appreciated. More pondering! ;)
My regards, Bill.
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just an update on this ancient thread. ive just bought myself a new solar panel and water cylinder alongside a new combi boiler, and am in the process of fitting it into my new house near blackpool. when its done, anyone who wants to see how it all works is welcome to come and look, or ask what they like.