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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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#1
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Wood burner with back boiler
Any advice on using the back boiler in a wood burner to augment an
existing expensive to run oil fired Rayburn heating system? Has anyone done this? What would be the best solution? |
#2
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Wood burner with back boiler
Hi
On Thu, 9 Mar 2006 06:35:45 +0000 (UTC), HandyMart wrote: Any advice on using the back boiler in a wood burner to augment an existing expensive to run oil fired Rayburn heating system? Has anyone done this? What would be the best solution? It's another of those 'it all depends' situations..... g Firstly - what sort of woodburner do you have - and what sort of heat ourput is claimed to the back boiler. Bear in mind that you'l only get the claimed outpur with the woodburner going 'flat out' - which may make it uncomfortably hot in the room which contains the woodburner. AFAIK, there are two systems for 'coupling' boilers together. The problem to to make sure that the 'cooler' of the two boilers doesn't end up looking like a radiator, and taking heat from the other boiler, rather than contributing heat to the system. One system is a metal tank that sits underneath your existing hot water cylinder - full details here.... http://www.dunsleyheat.co.uk/linkupsys.htm and a discussion about its use here http://www.newbuilder.co.uk/forum/in...zie_1129020452 The other system was a cube, about 1ft per side, which contained a bunch of motorised valves - and acted as a kind of 'changeover switch' between the two heating systems - controlled by thermostats. Can't find a reference to it at the moment.... sorry Both systems will involve a fair bit of re-plumbing to retro-fit.... If your central heating system is pumped (likely) then don't forget that your woodburner will need a gravity-fed radiator 'somewhere' that can dump heat in the event of a mains electricity failure. We lost the mains back in January - by the time we'd got back from walking the dogs the 'heat dump' radiator was far too hot to touch, the system had boiled over, and there was a very 'hot' smell about the place. Luckily, I've got one of those 12v to 240v inverters - so we were able to run that from the car until the mains came back. ISTR that Dunsley were very helpful when I contacted them.... A Google on 'Dunsley neutraliser boiler' will give you hours of reading pleasure g Good luck ! Adrian Suffolk UK http://www.brentnall.plus.com/bungalow.htm ======return email munged================= take out the papers and the trash to reply |
#3
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Wood burner with back boiler
Many thanks Adrian, some good starters here. Martin Adrian Brentnall wrote: Hi On Thu, 9 Mar 2006 06:35:45 +0000 (UTC), HandyMart wrote: Any advice on using the back boiler in a wood burner to augment an existing expensive to run oil fired Rayburn heating system? Has anyone done this? What would be the best solution? It's another of those 'it all depends' situations..... g |
#4
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Wood burner with back boiler
HI Martin
On Fri, 10 Mar 2006 07:40:20 +0000 (UTC), HandyMart wrote: Many thanks Adrian, some good starters here. No problem - if you need to chat about the project then feel free... Adrian adrianatambquality.co.uk Martin Adrian Brentnall wrote: Hi On Thu, 9 Mar 2006 06:35:45 +0000 (UTC), HandyMart wrote: Any advice on using the back boiler in a wood burner to augment an existing expensive to run oil fired Rayburn heating system? Has anyone done this? What would be the best solution? It's another of those 'it all depends' situations..... g ======return email munged================= take out the papers and the trash to reply |
#5
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Wood burner with back boiler
On Thu, 9 Mar 2006 06:35:45 +0000 (UTC), HandyMart
wrote: Any advice on using the back boiler in a wood burner to augment an existing expensive to run oil fired Rayburn heating system? Has anyone done this? What would be the best solution? Have a look at a Dunsley Baxter Neutraliser. Rick |
#6
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Wood burner with back boiler
Your back boiler takes the heat out ot your fire and you end up with a dead fire that you have to sit over to get warm. At the same time your radiators that are taking the heat from it are only lukewarm and never really have any serious heat output. Keep your oil fired system as is for heating the rads if you want real heat in them. It would be essential to have your wood burner standing in the room rather than recessed in a fire place. If its in the fireplace you lose a lot of the heat while vice versa. |
#8
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Wood burner with back boiler
speaking from experience Dave you would be bunging wood in every half
hour and still getting little heat if you have a back boiler in it. To answer the other matter, if the stove is placed within the chimney place rather than outside it, a lot of the heat just goes up the chimney. If the fireplace is sheeted over with tin flush with the wall, with a hole for the flue so that the whole stove is actually standing in the room, then all the heat is radiated within the room. another common mistake many people make is to light the fire on a grate and clear out the ash every day. I burn wood on a bed of ash and only clear it out when it rises above the front plate, that is about 4 inches. It has to be cleared out about every three weeks and burns better on a bed of ashes which hardens. There is an art to using wood burning stoves and they are a terrific fire place. |
#9
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Wood burner with back boiler
It must be something to do with 'Noelog's' stove that he loses heat to
the back boiler- my experience matches that of Adrian that driving the stove up to it's capacity output overheats the room it's in. I've got a Dunsley Neutraliser to marry an oil CH system and the wood burner. An interesting plumbing exercise as it's like some octopus with 9 pipes going to it. One thing that you do need to look at it is a black box that switches off/down the oil burner if the wood stove is hot. And do remember that you need to have a lot of wood continuously and the equipment to process it. If you want anymore info and experience I'm more than happy to pass it on. Rob |
#10
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Wood burner with back boiler
I'm only speaking from my own experience. Thats why I dumped it.
If you think that you have a box of cold water being pumped through the heart of your fire most of the time it takes the heart of the fire away. perhaps if the room is small you may not notice too much. I now have a lovely big wood burning stove and it heats quite a big room comfortably even on the coldest day of winter. Now if I had a box of cold water being pumped through it continuously I would probably have lukewarm rads everywhere and a poor fire. Of course there are variable factors like piling on firewood and adding coal, stopping draughts etc but for consistency the wood fire without a boiler is best by far. Then Handy Mart would have to spend a lot of money putting in a new cylinder with two loops and make the boiler. It would be a waste of a lot of money and he would curse the day he put it in. |
#11
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Wood burner with back boiler
On 11 Mar 2006 16:04:52 -0800, wrote:
speaking from experience Dave you would be bunging wood in every half hour and still getting little heat if you have a back boiler in it. I suspect that you are expecting too much from the back boiler, to supply 15kW of heat you are going to be bunging wood in fairly often, the energy has to come from somewhere. You also mention pumped rather than gravity, I can see that overcooling the fire as well. I'll be putting in a wood burner at some stage here with a boiler but I don't expect it to heat the whole house (our 38kW oil jobbie struggles when it's -5C and blowing a gale) but it should be able to keep the chill out and will be completely passive, no pumps or motorised valves. To answer the other matter, if the stove is placed within the chimney place rather than outside it, a lot of the heat just goes up the chimney. Ah an open based chimney, that seems like a bad installation to me. A properly installed wood burner really needs an insulated flue to stop the gases condensing inside the chimney. This implies that the base of the chimney is "sealed" from the room. another common mistake many people make is to light the fire on a grate and clear out the ash every day. I burn wood on a bed of ash and only clear it out when it rises above the front plate, Agreed wood burns best on a bed of ash. Coal on the other hand doesn't. I've just cleaned out our open fireplace after burning the cut up remains of two old sofas. Lots of heavy wire staples, castor sockets, screws etc left on the grate enabling a nice bed of ash to build up. Fire burned great on that, doesn't now. B-( -- Cheers Dave. pam is missing e-mail |
#12
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Wood burner with back boiler
Adrian Brentnall wrote: HI Martin On Fri, 10 Mar 2006 07:40:20 +0000 (UTC), HandyMart wrote: Many thanks Adrian, some good starters here. No problem - if you need to chat about the project then feel free... Adrian adrianatambquality.co.uk Thanks Adrian. It is possible the project may simplify to replacing the DHW cylinder with a twin coil one and only using the wood burner to heat the water via the second coil. This still gives rise to some questions: Would a heat dump radiator be required or advised? Would a simple gravity system work OK? Should I have a separate header tank or could the existing one for the oil fired system be used? What are the considerations when selecting a twin coil cylinder? Martin |
#13
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Wood burner with back boiler
HI Martin
On Mon, 13 Mar 2006 18:45:52 +0000 (UTC), HandyMart wrote: Adrian Brentnall wrote: HI Martin On Fri, 10 Mar 2006 07:40:20 +0000 (UTC), HandyMart wrote: Many thanks Adrian, some good starters here. No problem - if you need to chat about the project then feel free... Adrian adrianatambquality.co.uk Thanks Adrian. It is possible the project may simplify to replacing the DHW cylinder with a twin coil one and only using the wood burner to heat the water via the second coil. Only trouble there is that you'll quickly get to the point where your DHW is 'hot enough' - and then what are you going to do with the 'surplus' heat....? ((On our system, with a fairly crude control, the first 30 mins to 1 hour after the stove coming up to 'pump on' temperature (about 45C) has the boiler output directed to DHW heating, via a stat on the tank. After that, the circulating water runs through the radiator circuit.)) What's the rated output of the boiler ? This still gives rise to some questions: Would a heat dump radiator be required or advised? It's somewhere for the 'spare heat' to go - after you've got the DHW tank as hot as you want it.... Would a simple gravity system work OK? If you do that you'll maybe find it difficult to 'turn off' the circuit....? Should I have a separate header tank or could the existing one for the oil fired system be used? You might want to work on the two systems independantly...? Could use one tank and a stop-cock on the feed to each system..? maybe..? What are the considerations when selecting a twin coil cylinder? Don't know. For our system I just specced the largest possible tank to fit into the space available - and the manufacturers made the tank up for me with 2x copper coils.... Solar goes to the lower coil, woodburner goes to the upper coil. Hope this helps Adrian Suffolk UK www.inspired-glass.co.uk/bungalow.htm ======return email munged================= take out the papers and the trash to reply |
#14
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Wood burner with back boiler
On Mon, 13 Mar 2006 20:45:14 +0000, Adrian Brentnall wrote:
Only trouble there is that you'll quickly get to the point where your DHW is 'hot enough' - and then what are you going to do with the 'surplus' heat....? Agreed, even a small wood burner is quite capable of boiling a cylinder of water in a few hours. Would a heat dump radiator be required or advised? It's somewhere for the 'spare heat' to go - after you've got the DHW tank as hot as you want it.... Aye, one thing you don't want is you boiler boiling, you must be able to get rid of the heat and it must be fail safe. ie the heat must still be capable of being dissipated when mains power has failed and backup power systems have run flat or out of fuel. When the power goes is when you really need the wood burner to be on to provide heat for the house. Having to shut it down to stop it exploding strikes me as just plain silly. IMHO the only way to reliably achieve this fail safe mode is with a gravity loop. If you do that you'll maybe find it difficult to 'turn off' the circuit....? Should I have a separate header tank or could the existing one for the oil fired system be used? You might want to work on the two systems independantly...? Isolation valves that can be locked open on the wood burners gravity loop would enable the different primary loops to be isoloated for maintenance if required. A Dunsley Naturaliser is the way to go but from my investigations of the device it is nothing more than a sealed empty box where all the loop feeds and returns (oil boiler, wood burner, cylinder and CH) come together. -- Cheers Dave. pam is missing e-mail |
#15
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Wood burner with back boiler
On Mon, 13 Mar 2006 23:43:29 +0000, AJH wrote:
IMHO the only way to reliably achieve this fail safe mode is with a gravity loop. I think it's also the only legal way to go with a batch loaded wood burner. FECK, are the bar stewards putting "comon sense" regulations on wood burners now. -- Cheers Dave. pam is missing e-mail |
#16
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Wood burner with back boiler
I think it's also the only legal way to go with a batch loaded wood burner. FECK, are the bar stewards putting "comon sense" regulations on wood burners now. Part J isn't it? As I drove to work I realised I was in error, I have been "familiarised" with a domestic, batch loaded, pressurised, wood burning system with a CE mark. I know it cannot legally have been installed and self certified but I did not see, or ask to see, the building control officer's certificate ( and I wouldn't know what one looked like if I were shown one). I'm happy it was fairly safe as it had the thermal inertia of two tonnes of water to absorb any runaway. AJH The proposed wood burner is of the "chuck it in one at a time" variety and would not be pressurized. Batch loaded is something else I think and I suspect it's the pressurized aspect that gives rise to regulatory controls? Martin |
#17
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Wood burner with back boiler
On Thu, 16 Mar 2006 23:26:27 +0000, AJH wrote:
Either way it is probably non trivial to get a pressurized water system approved for a wood burner in single domestic premises. Agreed, I wouldn't be surprised if a pressurised primary fell under all the regulations pertaining to boilers as in steam engine... -- Cheers Dave. pam is missing e-mail |
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