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#1
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De-commissioning back-boilers?
Our out-dated, hard-to-control, inefficient heating system is due to be
replaced this year. Currently, we have an oil-fired Rayburn (converted from solid fuel), _and_ a back-boiler in the livingroom fireplace. The Rayburn is to be removed, and an externally mounted condensing boiler will be installed. The back boiler concerns me - it will, of course, be disconnected from the heating system, but I wish to be able to continue to use the fireplace. How does one safely decommission a back boiler? Can this be done without wrecking the fireplace? |
#2
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De-commissioning back-boilers?
On Mon, 18 Jan 2010 10:24:00 -0500, S Viemeister wrote:
Our out-dated, hard-to-control, inefficient heating system is due to be replaced this year. Currently, we have an oil-fired Rayburn (converted from solid fuel), _and_ a back-boiler in the livingroom fireplace. The Rayburn is to be removed, and an externally mounted condensing boiler will be installed. The back boiler concerns me - it will, of course, be disconnected from the heating system, but I wish to be able to continue to use the fireplace. How does one safely decommission a back boiler? Can this be done without wrecking the fireplace? Exactly the same here - ex-council, by any chance? When the CH was fitted I removed the pipes etc. (as no other part of the system was still there) but have never done the last bit (dI don't use the fire). ISTR that the back boiler should be filled with sand, but never checked on that. -- Peter. 2x4 - thick plank; 4x4 - two of 'em. |
#3
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De-commissioning back-boilers?
On Mon, 18 Jan 2010 10:24:00 -0500, S Viemeister wrote:
The back boiler concerns me - it will, of course, be disconnected from the heating system, but I wish to be able to continue to use the fireplace. How does one safely decommission a back boiler? Can this be done without wrecking the fireplace? Presumably this is an open fire with back boiler? Personally I'd keep it as a backup/auxillary heat source. Unless it is really kanckerd in which case your into replacing it anyway to keep the fireplace operational. If you want to drain the back boiler and keep the fireplace I think you have to fill the boiler with sand to prevent (slow down?) it burning through. Without the water to take the heat away the metal will get very hot... -- Cheers Dave. |
#4
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De-commissioning back-boilers?
PeterC wrote:
On Mon, 18 Jan 2010 10:24:00 -0500, S Viemeister wrote: Our out-dated, hard-to-control, inefficient heating system is due to be replaced this year. Currently, we have an oil-fired Rayburn (converted from solid fuel), _and_ a back-boiler in the livingroom fireplace. The back boiler concerns me - it will, of course, be disconnected from the heating system, but I wish to be able to continue to use the fireplace. ISTR that the back boiler should be filled with sand, but never checked on that. We simply left ours in situ and continue to use the open fire. -- R100RT Aprilia Pegaso 650 IE "The Flying Mythos" Formerly: James Captain, A10, C15, B25, Dnepr M16 solo, R80/7, R100RT (green!) www.davidhowardjeweller.co.uk |
#5
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De-commissioning back-boilers?
There is H&S document on this.
http://www.hse.gov.uk/services/local...nt/boilers.htm A backboiler behind a real fire (or box-tank behind a gas fire) works by recovering heat from flue gases, said heat then being used to pre- heat a HW tank or radiator. Decommissioning such back boilers (or either type) must be done correctly. Immediate risk - explosion Water left in the tank which can not circulate or vent will superheat - eventually rupturing or even exploding. Secondary risk - flue gases If pipes are left vented the tank will eventually corrode permitting flue gases to be transferred elsewhere, posing a serious CO risk. The proper solution is... - Remove the pipes - Fill holes occupied by pipes with fire cement - a) Fill the tank with sand & leave ventilated to the flue only - b) Remove the tank from the fireplace and refill with suitable bricks, refractory lining as necessary They are actually quite good at heating water with a gas fire. However I suspect the decommission cost is rather high even if a simple "box tank". More substantial dismantling is properly rather expensive - anyone know? Beware such backboilers exhibit a winter flood risk when the house is unoccupied. Cold air plunges down the chimney and over days can cause the tank &/or pipes to split - the resulting flood from the CW-HW tanks is either unlimited or still 800L if you have the CW isolated. I've known 3 fail in this manner, wrecking expensive wooden flooring and downstairs contents throughout (DG doors meant the water literally had nowhere to go with solid floors throughout). |
#6
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De-commissioning back-boilers?
On 18 Jan, 15:24, S Viemeister wrote:
Our out-dated, hard-to-control, inefficient heating system is due to be replaced this year. *Currently, we have an oil-fired Rayburn (converted from solid fuel), _and_ a back-boiler in the livingroom fireplace. The Rayburn is to be removed, and an externally mounted condensing boiler will be installed. The back boiler concerns me - it will, of course, be disconnected from the heating system, but I wish to be able to continue to use the fireplace. *How does one safely decommission a back boiler? *Can this be done without wrecking the fireplace? Disconnect the pipes and plug the holes. Drill a couple of small vent holes at bottom front (you may get some residual water out). Use the fire as normal. At some stage it will burn through the front panel of the back boiler at which point you can use fire cement to effect a repair until such time as you wish to rip it all out and install a refractory fire back |
#7
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De-commissioning back-boilers?
On 18 Jan, 17:12, "js.b1" wrote:
Beware such backboilers exhibit a winter flood risk when the house is unoccupied. Cold air plunges down the chimney and over days can cause the tank &/or pipes to split - the resulting flood from the CW-HW tanks is either unlimited or still 800L if you have the CW isolated. I've known 3 fail in this manner, wrecking expensive wooden flooring and downstairs contents throughout (DG doors meant the water literally had nowhere to go with solid floors throughout). Thanks for that. I was aware of the explosion risk ; the freeze & flood hazard had never occurred to me. A link to an HSE document on the fatal explosion is below. http://www.hse.gov.uk/press/2009/coisw61109.htm |
#8
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De-commissioning back-boilers?
S Viemeister wrote:
Our out-dated, hard-to-control, inefficient heating system is due to be replaced this year. Currently, we have an oil-fired Rayburn (converted from solid fuel), _and_ a back-boiler in the livingroom fireplace. The Rayburn is to be removed, and an externally mounted condensing boiler will be installed. The back boiler concerns me - it will, of course, be disconnected from the heating system, but I wish to be able to continue to use the fireplace. How does one safely decommission a back boiler? Can this be done without wrecking the fireplace? It seems that our short term solution will likely be to drain/disconnect/remove the piping, making sure that combustion products can't find their way into the house, and drill holes into the boiler body. I've seen mention of filling the boiler with sand - but am not sure how feasible this is - or why it should be done. The fireplace only gets occasional use, but eventually we'll need to remove all of the back boiler bits. |
#9
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De-commissioning back-boilers?
On 20 Jan, 00:37, S Viemeister wrote:
I've seen mention of filling the boiler with sand - but am not sure how feasible this is - or why it should be done. Heatsink. If you don't do it, the cast iron back boiler gets to about 400C, cracks and collapses, possibly bringing down some of the fireplace. |
#10
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De-commissioning back-boilers?
Andy Dingley wrote:
On 20 Jan, 00:37, S Viemeister wrote: I've seen mention of filling the boiler with sand - but am not sure how feasible this is - or why it should be done. Heatsink. If you don't do it, the cast iron back boiler gets to about 400C, cracks and collapses, possibly bringing down some of the fireplace. That makes sense. Would it be a reasonable idea to make a decent-sized hole in the upper part of the water jacket (for the sand), along with one or two smaller ones along the bottom front (for water release)? |
#11
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De-commissioning back-boilers?
On 20 Jan, 11:35, Andy Dingley wrote:
On 20 Jan, 00:37, S Viemeister wrote: I've seen mention of filling the boiler with sand - but am not sure how feasible this is - or why it should be done. Heatsink. *If you don't do it, the cast iron back boiler gets to about 400C, *cracks and collapses, possibly bringing down some of the fireplace. Never come across cast iron firebacks then? Its probably not cast iron anyway but mild steel. |
#12
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De-commissioning back-boilers?
On 20 Jan, 14:46, cynic wrote:
Never come across cast iron firebacks then? Yes. They're bedded in mortar, which has a similar heatsinking effect. If they're not, they can crack too. Besides which, firebacks are cast in thicker sections than back boilers. Its probably not cast iron anyway but mild steel. No, mild steel rusts through too quickly. There's advice linked from the HSE site on a recommended process for decomissioning. I think this was linked from here recently too. Mostly (AFAIR) it involved a drilled hole moderately high up, then slowly pouring dried sand down a pipe. |
#13
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De-commissioning back-boilers?
On 20 Jan, 14:57, Andy Dingley wrote:
On 20 Jan, 14:46, cynic wrote: Never come across cast iron firebacks then? Yes. They're bedded in mortar, which has a similar heatsinking effect. If they're not, they can crack too. Quite the opposite to heat sinking, the refractory retains the heat so the cast iron attains a higher temperature. Solid fuel (coke) boiler firebars and fireplace grates are also made of cast iron and attain red heat (1000C) on occasion. When in a hole stop digging! Besides which, firebacks are cast in thicker sections than back boilers. Its probably not cast iron anyway but mild steel. No, mild steel rusts through too quickly. I should tell Dunsley and other companies who make wrap round high output solid fuel back boilers from 4 mm mild steel with long service life. I am sure they will be fascinated by your information. There's advice linked from the HSE site on a recommended process for decomissioning. I think this was linked from here recently too. Mostly (AFAIR) it involved a drilled hole moderately high up, then slowly pouring dried sand down a pipe. |
#14
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De-commissioning back-boilers?
"Onetap" wrote in message ... On 18 Jan, 17:12, "js.b1" wrote: A link to an HSE document on the fatal explosion is below. http://www.hse.gov.uk/press/2009/coisw61109.htm The decommissioning leaflet linked from the above page: http://www.hse.gov.uk/services/local...nt/boilers.htm The illustration of a back boiler installation shows that is not acting as structural support for any of the chimney brickwork. Is that what I'm likely to find in this 1950's house enabling the boiler to be taken out without risk of some of the chimney liner brickwork coming down, or at least needing support ? Roger R |
#15
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De-commissioning back-boilers?
On Jan 20, 9:26*pm, "Roger R"
wrote: The illustration of a back boiler installation shows that is not acting as structural support for any of the chimney brickwork. From my mother's 1950s (ok 1947-1951) the chimneys are all U-shaped self-supporting (and supporting joists of rooms above with walls & ceilings additionally). Lintel may be angle iron, but I suspect it may be concrete. Very small windows (a foot) use what looks like cast in place concrete 8in high, larger windows use a smooth grey cement lintel equally oversized into the room & span, both on slate padstones. Note however the mortar may be utter crap so beware cracking particularly if the lintel is above the fireplace opening which is not unusual (big open fire reduced for gas fire either by builder or later on). Is that what I'm likely to find in this 1950's house enabling the boiler to be taken out without risk of some of the chimney liner brickwork coming down, or at least needing support ? People here are referring to cast-iron backboiler, if yours merely heats the HW tank you may find it is a simple box made of copper. I assume copper going by the green verdigras all over it. Drilling a big hole in the top of the front face and tubing very fine sand in should be effective. When it has water in the temperature and thus thermal expansion distance is limited. Without water the temperature can become grossly elevated and thus thermal expansion distance is much less limited - it could exert significant forces. By filling it with sand you restrict the temperature it can heat to, thus limit its thermal expansion distance - and provide a degree of heat storage. Sand filling matches the temperature, and better matches the thermal expansion, of the surrounding brickwork. If you find blue tiles they are a refractory lining and quite common in that period. Coal is pretty nasty (acidic) and 1950s mortar pretty crap really even without coal's onslaught. Wood was often burnt with chimney fires treated with wild abandon as first attempts at central heating. Watch out for gas poker taps hidden behind kitchen units, they are invariably still live :-) I am also dubious that some gas fires are supplied by what were originally pipes sized for gas pokers and due to distance combined with small bore have historically been "passed over" re pressure drop limits :-) With backboilers of that era you will probably find the pipes into the chimney are not well sealed - they should be sealed with fire cement but rarely are, it's often polyfilla collecting together various previous cracked attempts into a wallpaperable but non-sealed ensemble. |
#16
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De-commissioning back-boilers?
"js.b1" wrote in message ... On Jan 20, 9:26 pm, "Roger R" wrote: The illustration of a back boiler installation shows that is not acting as structural support for any of the chimney brickwork. :From my mother's 1950s (ok 1947-1951) the chimneys are all U-shaped :self-supporting (and supporting joists of rooms above with walls & :ceilings additionally). Lintel may be angle iron, but I suspect it may :be concrete. Very small windows (a foot) use what looks like cast in lace concrete 8in high, larger windows use a smooth grey cement :lintel equally oversized into the room & span, both on slate adstones. Note however the mortar may be utter crap so beware :cracking particularly if the lintel is above the fireplace opening :which is not unusual All original, and with concrete lintles for window openings so probably ditto for fireplace. Lime based weak mortar with sand and lime (white) internal bricks. Is that what I'm likely to find in this 1950's house enabling the boiler to be taken out without risk of some of the chimney liner brickwork coming down, or at least needing support ? :People here are referring to cast-iron backboiler, if yours merely :heats the HW tank you may find it is a simple box made of copper. I :assume copper going by the green verdigras all over it. Perhaps you are confusing me with someone else - I havn't posted any picture. The back boiler is indeed only for the hot water tank, but is a cast iron type with a removable panel above a coarsly ribbed lower part. Below this ribbed tank is a gap allowing the hot gasses to pass under and around the back. The hot gasses are diverted by means of a sliding plate out of sight on top of the unit. The brand name on the front face is 'Redfyre'. Photo available later. Roger R |
#17
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De-commissioning back-boilers?
On 20 Jan, 20:00, cynic wrote:
Yes. They're bedded in mortar, which has a similar heatsinking effect. If they're not, they can crack too. Quite the opposite to heat sinking, the refractory retains the heat so the cast iron attains a higher temperature. Rubbish. Whilst it's going to "retain the heat", all that's going to do is to keep it warmer in the morning, after the fire has gone out. Peak temperature when lit for a piece of thin cast iron is going to be higher for a plate with an air gap insulation behind it, compared to masonry in reasonable contact. It's about the dynamic equilibrium of heat flow in vs. out when burning (i.e. conduction), not about heat storage (i.e. heat capcity). Solid fuel (coke) boiler firebars and fireplace grates are also made of cast iron and attain red heat (1000C) on occasion. Firebars are made of two different metals: some are a simple grey cast iron, others an austenitic stainless. Parkrays and similar use a mix, with the better steel in the middle where it's hotter. If you put them in the wrong place under a coke fire, the plain grey iron doesn't last at all long. Mostly though, firebars are just that: bars. The reason they're installed as separate bars is to stop cracking and warping like this. The bars are free to move (compared to a one piece grate) so that they don't crack (they'd warp first) and any slight warping is absorbed in the rattle space around them. Although solid one-piece grates were used for a long time, they didn't work for the higher temperatures when we switched from coal on open grates to coke in enclosed box stoves. Also, "red heat" is around 600 to 800 C. 1000 C is a pale yellow. Although you can achieve orange heats within the coals of a domestic fire, you won't get the ironwork to 1000 C. |
#18
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De-commissioning back-boilers?
We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Andy Dingley saying something like: Its probably not cast iron anyway but mild steel. No, mild steel rusts through too quickly. Not if it's 6mm thick to start with. I have a rescued BB that's 20 years old and still plenty thick. I intend to re-use it and expect it to last for many years yet. |
#19
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De-commissioning back-boilers?
On Monday, January 18, 2010 at 3:58:56 PM UTC, Jeweller wrote:
PeterC wrote: On Mon, 18 Jan 2010 10:24:00 -0500, S Viemeister wrote: Our out-dated, hard-to-control, inefficient heating system is due to be replaced this year. Currently, we have an oil-fired Rayburn (converted from solid fuel), _and_ a back-boiler in the livingroom fireplace. The back boiler concerns me - it will, of course, be disconnected from the heating system, but I wish to be able to continue to use the fireplace. ISTR that the back boiler should be filled with sand, but never checked on that. We simply left ours in situ and continue to use the open fire. -- R100RT Aprilia Pegaso 650 IE "The Flying Mythos" Formerly: James Captain, A10, C15, B25, Dnepr M16 solo, R80/7, R100RT (green!) www.davidhowardjeweller.co.uk I would advise looking at what the HSE guide lines are ! they recommend removal of back boiler rather than venting although this is an option. having worked in the industry some 16 yrs, my safety concerns are fumes and smoke usually find their way up the redundant channels and pipes ! Stick to HSE guidlines would be my advise. |
#21
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De-commissioning back-boilers?
In message , Andrew
writes On 21/01/2019 13:46, wrote: On Monday, January 18, 2010 at 3:58:56 PM UTC, Jeweller wrote: You obviously didn't and are 8 years too late. Shall we make that 9, this year? :-) -- Graeme |
#22
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De-commissioning back-boilers?
Blimey this thread has a checked history over many years, but we when we
moved in here did not even realise there was a back boiler in the fireplace, it was only later on when we needed a new hot water cylinder that the plumber found it which had been disconnected and stop ends put on the pipe it was still full of water and had not leaked after over 30 years. He of course stuck a hose on a tap at the bottom and drained it. It was amazing that we had not had a flood in those 30 years or so. Maybe they made things a little better back in the 1930s! Brian -- ----- -- This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please Note this Signature is meaningless.! wrote in message ... On Monday, January 18, 2010 at 3:58:56 PM UTC, Jeweller wrote: PeterC wrote: On Mon, 18 Jan 2010 10:24:00 -0500, S Viemeister wrote: Our out-dated, hard-to-control, inefficient heating system is due to be replaced this year. Currently, we have an oil-fired Rayburn (converted from solid fuel), _and_ a back-boiler in the livingroom fireplace. The back boiler concerns me - it will, of course, be disconnected from the heating system, but I wish to be able to continue to use the fireplace. ISTR that the back boiler should be filled with sand, but never checked on that. We simply left ours in situ and continue to use the open fire. -- R100RT Aprilia Pegaso 650 IE "The Flying Mythos" Formerly: James Captain, A10, C15, B25, Dnepr M16 solo, R80/7, R100RT (green!) www.davidhowardjeweller.co.uk I would advise looking at what the HSE guide lines are ! they recommend removal of back boiler rather than venting although this is an option. having worked in the industry some 16 yrs, my safety concerns are fumes and smoke usually find their way up the redundant channels and pipes ! Stick to HSE guidlines would be my advise. |
#23
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De-commissioning back-boilers?
Brian Gaff wrote:
Blimey this thread has a checked history over many years, but we when we moved in here did not even realise there was a back boiler in the fireplace, it was only later on when we needed a new hot water cylinder that the plumber found it which had been disconnected and stop ends put on the pipe it was still full of water and had not leaked after over 30 years. He of course stuck a hose on a tap at the bottom and drained it. It was amazing that we had not had a flood in those 30 years or so. Maybe they made things a little better back in the 1930s! Brian If that is as exactly how you described it then whoever undertook the original disconnection did exactly what should not be done. A drained back boiler is just a lump of Iron or occasionally copper which will get very hot which may or may not matter depending on what surrounds it, one full of water and capped becomes a sealed pressure vessel and if it or bits of capped pipe connected to it rupture under pressure then the results can be nasty, low end is a split and you get a puddle for a while, high end is a sudden explosive failure which could well be strong enough to cause a lot of damage especially if it blows the contents of the burning grate into the room over everything including occupants. Ideally a disconnected back boiler and piping should be filled with sand though if it is left uncapped pressure should not build up. GH |
#24
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De-commissioning back-boilers?
On 1/22/2019 5:44 AM, Marland wrote:
Brian Gaff wrote: Blimey this thread has a checked history over many years, but we when we moved in here did not even realise there was a back boiler in the fireplace, it was only later on when we needed a new hot water cylinder that the plumber found it which had been disconnected and stop ends put on the pipe it was still full of water and had not leaked after over 30 years. He of course stuck a hose on a tap at the bottom and drained it. It was amazing that we had not had a flood in those 30 years or so. Maybe they made things a little better back in the 1930s! If that is as exactly how you described it then whoever undertook the original disconnection did exactly what should not be done. A drained back boiler is just a lump of Iron or occasionally copper which will get very hot which may or may not matter depending on what surrounds it, one full of water and capped becomes a sealed pressure vessel and if it or bits of capped pipe connected to it rupture under pressure then the results can be nasty, low end is a split and you get a puddle for a while, high end is a sudden explosive failure which could well be strong enough to cause a lot of damage especially if it blows the contents of the burning grate into the room over everything including occupants. Ideally a disconnected back boiler and piping should be filled with sand though if it is left uncapped pressure should not build up. Mine was left uncapped, drained, had a number of holes drilled into it, and was filled with sand. And the new combi has saved a fortune in heating costs. |
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