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Back boiler Failure


DShK

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4 minutes ago, Bee said:

There could be a clue in the bit where it doesn't work without a full tank of water in the bow and as I understand the fire and boiler is nearly right at the front. My guess is that the system only just works. Gravity systems on narrow boats can struggle to get sufficient uphill slope to work because the damned boat slopes unhelpfully downhill to the stern. If the water tank at the bow is empty that tips the balance from working to not working. If the stove was at the back it would work wonderfully. I suggest a couple of concrete kerbstones right at the front. If the  boiler is steel it can be welded, if its cast iron its harder. For now Ii would disconnect the pipes to the boiler and just use the fire, some may suggest a firebrick at the back of the fire or filling it with sand but an empty disconnected boiler should be safe if disconnected, others might disagree but its too cold to have no heat

This is something I have tried to verify. I have loaded my bow with coal, 25KG weights and filled the tank with water. I haven't seen a 100% correlation. I would have made sure my tank was filled last night but my hose was frozen. I don't think it was that low though. I think it may contribute to the problem but not be the only factor.

 

I'm going to buy a new boiler tomorrow and replace it, in the meantime I have a little electric heater to keep me warm :)

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Oh Yuk. Corrosion. Just as an unhelpful aside I think your chimney might be steel tube. In the top pic. of the roof collar I think there is a weld line visible going down the inside,  steel tube tends to corrode quicker than cast iron or stainless so be a bit careful. I have happily used steel but it does corrode. Again, others might well know better, Glad you've got some heat, its perishing cold.

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Farecla G3 or G10 will remove the chimney crud stains.

 

The inside of your flue looks like it needs a good descaling.  Attack it with chains and wire brushes and then beat the outside all over with a fairly small hammer.

 

 

Your flue looks like it is 113mm steel CHS.  It may last as long as 10 years.  You will know it s knackered when rust pits occur about 18 inches above the stove top.

 

N

Edited by BEngo
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59 minutes ago, Bee said:

Oh Yuk. Corrosion. Just as an unhelpful aside I think your chimney might be steel tube. In the top pic. of the roof collar I think there is a weld line visible going down the inside,  steel tube tends to corrode quicker than cast iron or stainless so be a bit careful. I have happily used steel but it does corrode. Again, others might well know better, Glad you've got some heat, its perishing cold.

Roger. I think for now I will just buy a cheap chandlery thing, I want to get a properly made one sometime but not right now.

 

 

59 minutes ago, rusty69 said:

White vinegar kinda works. 

Will give this a go, thanks!

 

31 minutes ago, BEngo said:

Farecla G3 or G10 will remove the chimney crud stains.

 

The inside of your flue looks like it needs a good descaling.  Attack it with chains and wire brushes and then beat the outside all over with a fairly small hammer.

 

 

Your flue looks like it is 113mm steel CHS.  It may last as long as 10 years.  You will know it s knackered when rust pits occur about 18 inches above the stove top.

 

N

Will look into these too, thanks. I cleaned the inside of the flue with a flue brush after the photo was taken - will try those other tips too. The boat is 12 years old so I imagine the flue is as old (I am assuming we are talking about the flue rather than the chimney). With regard to rust putting, how do I see 18 inches above the stove top? I assume this is inside the flue rather than the outside? I can neither see down or up that far.

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10 hours ago, DShK said:

 

 

image.jpeg.e5aa09193ec63a1f83cbd57d0af46320.jpeg

 

Chimney is ruined. The interior skin has fallen apart and crumbles in the hand.... again this is new....

 

 

 

Not only has the cruded filled liquid stained all along the hand rails, it's stained my paint work 😢 Anyone have any suggestions how I might be able to remove it?

 

 

The staining is a common sight on the roof and down the cabin sides on boats. At night there is condensation on the inside of the external flue. If the outside fitting flue is not sealed or is a loose fitting cosmetic type of decorative chandlery flue, the condensation mixes with the flue deposits and causes the nasty looking crude and stains to run down the inside of the flue and out of the bottom and onto the roof. Coolie hats also need to be cleaned occasionally, as these too can cause drips onto the roof. The stains can become well-fixed on the surface, washing can remove some, but the paintwork my need to be cut back with a polishing compound, or even a very fine wet and dry paper. 

 

I had all the work to do that you're going to be doing. I actually stopped using Excel and the cheaper brands of smokeless, because I think, perhaps incorrectly, that those had a lot of sulphur in them and would, with condensation, produce an acid. Not good for the flue. The flue had rotted far too quickly from being new. However, when it came time to find a welder to fabricate the new flue, I had some trouble finding one. When I eventually did find one, I had two flues made and still have the spare flue. I did not have a double skin flue on the Morso; it's a single-skin 4" bore. So far, sticking to a 'decent' fuel has worked out. I like Supertherm. Newburn was ok, too. 

 

I fit a narrower bore tube inside the external end of the main flue, to direct condensation and deposits back down the inside of the flue, avoiding it escaping onto the roof. 

 

You will need to make a template for the flue shape. Using strips of 6mm ply, 4" in width should be ok, and cut into sections, glue or screw together, to make the shape that most resembles the original. It is then possible to try it against the top of the stove and roof outlet. If you're confident about it, this can be handed to a welder, or you could produce a drawing.

 

 

 

Edited by Higgs
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Narrowing of the pipes is resistance to flow. This cannot be helped when connecting radiators, but in my opinion, there should be an unrestricted circuit of 28mm pipe from the top outlet of the backboiler to the bottom inlet, with radiators dropped in-between from T junctions. 

 

 

Edited by Higgs
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11 hours ago, Bee said:

There could be a clue in the bit where it doesn't work without a full tank of water in the bow and as I understand the fire and boiler is nearly right at the front. My guess is that the system only just works. Gravity systems on narrow boats can struggle to get sufficient uphill slope to work because the damned boat slopes unhelpfully downhill to the stern. If the water tank at the bow is empty that tips the balance from working to not working. If the stove was at the back it would work wonderfully. I suggest a couple of concrete kerbstones right at the front. If the  boiler is steel it can be welded, if its cast iron its harder. For now Ii would disconnect the pipes to the boiler and just use the fire, some may suggest a firebrick at the back of the fire or filling it with sand but an empty disconnected boiler should be safe if disconnected, others might disagree but its too cold to have no heat

 

If the stove has a backboiler/thermocycling it sounds like another good reason stoves in narrowboats shouldn't be installed by the bow doors. Yet so many are.

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7 minutes ago, Higgs said:

 

Could some of that be down to not using antifreeze as an inhibitor in the system. ??

 

 

 

 

Could be but not necessarily. I had a radiator leak a couple of winters ago on a small square rad I'd fitted in the bathroom 15 years previously. I sort of plugged it with some product I bought and chucked in until spring and then I changed the rad. Last winter I discovered the new rad was blocked at the top even though my system is always full of inhibitor. Whether that crap came from the new rad itself because I'd failed to flush it out before installation or had migrated from another part of the system I don't know, but the antifreeze/inhibitor itself hadn't prevented the build up of crap over the years. 

 

I've drained and replaced the mixture dozens of times over the years but the tap at the bottom of the system only lets the smaller particles out.

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4 minutes ago, blackrose said:

 

 

Could be but not necessarily. I had a radiator leak a couple of winters ago on a small square rad I'd fitted in the bathroom 15 years previously. I sort of plugged it with some product I bought and chucked in until spring and then I changed the rad. Last winter I discovered the new rad was blocked at the top even though my system is always full of inhibitor. Whether that crap came from the new rad itself because I'd failed to flush it out before installation or had migrated from another part of the system I don't know, but the antifreeze/inhibitor itself hadn't prevented the build up of crap over the years. 

 

I've drained and replaced the mixture dozens of times over the years but the tap at the bottom of the system only lets the smaller particles out.

 

It makes me wonder whether a pump fitted on the side via a stop valve might be in order to occasionally speed through the flow to clear debris.

 

 

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10 hours ago, DShK said:

). With regard to rust putting, how do I see 18 inches above the stove top? I assume this is inside the flue rather than the outside? I can neither see down or up that far.

The flue will rust from the inside out.  One day yo will see little orange brown spots on the outside of the flue. That tells you if has rusted through from the inside, and is in need of urgent renewal, as flue gases will soon be leaking into the boat.

 

N

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1 hour ago, Higgs said:

Narrowing of the pipes is resistance to flow. This cannot be helped when connecting radiators, but in my opinion, there should be an unrestricted circuit of 28mm pipe from the top outlet of the backboiler to the bottom inlet, with radiators dropped in-between from T junctions. 

 

 

Done that way I usually use 22mm pipe, 15mm drops, and have no problems with flow.

Putting them all in series is asking for problems with flow. And using a pump is madness, uses electricity and if the pump stops you have a runaway boiler, steam everywhere and dangerous.

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Just now, Tracy D'arth said:

Done that way I usually use 22mm pipe, 15mm drops, and have no problems with flow.

Putting them all in series is asking for problems with flow. And using a pump is madness, uses electricity and if the pump stops you have a runaway boiler, steam everywhere and dangerous.

 

My system originally came with a pump to the side, connected with a 15mm and could be isolated. Not interfering with main pipe flow. However, inline I wouldn't have. 

 

 

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The last installation i did I cut a hole in the floor and sat the stove and the tray it sat on directly on a crossmember, it lowered it a couple of inches but with these systems you are fighting for every inch of uphill slope you can get. When it all works it is the best possible system (I think) and it is simple and trouble free but its all about getting an uphill rise in a boat that perversely sits downhill at the back.

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27 minutes ago, Bee said:

The last installation i did I cut a hole in the floor and sat the stove and the tray it sat on directly on a crossmember, it lowered it a couple of inches but with these systems you are fighting for every inch of uphill slope you can get. When it all works it is the best possible system (I think) and it is simple and trouble free but its all about getting an uphill rise in a boat that perversely sits downhill at the back.

Unless of course you have a reverse layout with the living area at the back. It make the idea of a reverse layout almost palatable 🤔

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1 hour ago, Higgs said:

 

My system originally came with a pump to the side, connected with a 15mm and could be isolated. Not interfering with main pipe flow. However, inline I wouldn't have. 

 

 

I do have an inline pump.  It is a centrifugal type Johnson with mag drive so it cannot leak, installed in the return line.  It offers very little resistance to flow and is normally off.  It is controlled by a pipe stat with override and is handy when starting up.  A short burst of pump once the fire has warmed up some awater assists the thermal circulation to get going after which, at bearable levels of fire, the system operates without.

 

The key to getting good thermal circulation is something I read many years ago in a plumbers guide to gravity circulated central heating design.  (Remember all those  big cast iron pipes in churches and schools etc?)  That advised getting the biggest vertical rise possible immediately after the boiler and then falling all the way back to the boiler  The 'push' the vertical pipe creates is quite significant, and it is more effective than a long slanting rise.

 

I think the OP might find it beneficial to take the radiators off and give them a good flush with either a hose, or better, a pressure washer. Then take the rad  valves off the pipes and check the pipework for sludge.  If sludgy some Fernox system cleaner (or similar)  would be a good idea.  Not the best of times to be doing it though!

 

N

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Some good info here guys, thank you.

 

I realised I didn't engage my brain when I said my system was all in series. My radiators are in fact in parrel with the main circuit. I can turn them off and bypass them.

 

I did use some system cleaner but there was definitely still sludge in the system. I think I will run a bunch more through just the bottom pipe before I install the new boiler, and try and get it as clean as possible. I may take a radiator off if easy enough, and see how that is looking. it's kind of annoying that the pipework is all soldered joints, there is no way to dissasemble and check these things.

 

A minor question - The threads that connected the pipework to the boiler had some kind of sealant on. Is this recommended? Is there a special type I should use or is any old sealant okay? (I have literally never had a chance to do plumbing work in my life!)

 

I will be going to the chandlery today to get some new parts, will update everyone with progress. Thanks again for the support.

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1 hour ago, Bee said:

The last installation i did I cut a hole in the floor and sat the stove and the tray it sat on directly on a crossmember, it lowered it a couple of inches but with these systems you are fighting for every inch of uphill slope you can get. When it all works it is the best possible system (I think) and it is simple and trouble free but its all about getting an uphill rise in a boat that perversely sits downhill at the back.

 

How big was the stove? I don't understand why you couldn't get uphill slope from the backboiler outlet up to under gunwale height? I've got a big 9kW double door Morso Panther and there was at least a foot of room to get a slope uphill to the top run.

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