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Morso Squirrel flue - construction and cleaning problem


gbclive

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Last year we had the flue swept professionally.
This year, I bought a brush and rods to do it myself.
So here’s the thing.........
The 4” drain brush (all I could get today) only went about half way down, then stopped.
On closer inspection, there appears to be a sudden reduction in the internal diameter, from about 4.3” at the top through the collar to perhaps 3 inches or even a tad less from about the mid point down to the stove.
The top wider section was not too bad and is now fairly clean.
However the lower narrow section is heavily incrusted and my 4” stiff brush won’t go down past the reduction and in any case, having attacked the 1st couple of inches from the bottom with a large screwdriver, I don’t think a brush will do much.

So my first question is whether it’s possible that our flue is initially twin walled, changing to single wall for the top half?
(The external surface of the flue is uniform from top to bottom)

And secondly, I’d be very grateful for any suggestions on how best to proceed with the encrusted section.

For info, we only burn smokeless fuel, but we don’t know what previous owners used.
Thanks to this forum I understand the safety implications and have triple CO detectors as a last line of defence.

Many thanks,
Clive.

Edited by gbclive
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A common problem caused by the flue gases cooling and the gooey crap condensing and trappping the fly ash from the gases. It then sets.

Either beat the flue with hammers at the encrusted area ( from inside the boat) whilst simultaneously attacking it down the flue or get the flue realy realy hot (raging fire in Squirrel or big blowlamp on the flue at the blockage) whilst scraping away down the flue.  

Or fit a new flue.

Whichever way you need to sweep more often.

 

N

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I have owned boats with squirrels for many years and never had this kind of problem until the last couple of years? I have no idea why but facts are that having never in the past get blocked flue last winter ours became so solid with a concrete like substance the flue had to be removed and a large special drill used to chop the crud out, a cold chisel wouldn't touch it!! Is it the warm winters? or crap fuel? no one seems to know. As been stated above you need to take it to bits get the crud out and sweep it more often. I never used to even sweep mine but now every couple of weeks a 4.5 inch steel brush is rodded down with drain rods to keep it clear :(

  • Greenie 1
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If the flue pipe is straight fix a stout wire brush or chisel or trowel to a long stick and rub it up and down from the top. You can get steel wire flue brushes. Do it cold and dry.  By the sound of it you will probably get a bucketful out of it. Keep the stove door closed whilst doing it. I take it that the small half moon throat plate has been removed? I expect it has or you wouldn't really get the screwdriver up from below.

Edited by bizzard
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I think the warm winters are a possible reason too. You tend to leave the stove on tickover during the day and never really ramp it up with a good blaze as it's never cold enough outside to need it.

The flue gases then settle far lower down the flue.

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7 minutes ago, matty40s said:

I think the warm winters are a possible reason too. You tend to leave the stove on tickover during the day and never really ramp it up with a good blaze as it's never cold enough outside to need it.

The flue gases then settle far lower down the flue.

Yes those are my thoughts exactly. Only this week we noticed ours wasn't drawing properly and a torch from the top showed a near completely closed flue very near the bottom. A quick prod with a stick disloged it as it was still all soft. We havnt had anything remotely like a cold winter since the several weeks we were all frozen in back end of 2010 into 2011.

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1 minute ago, mrsmelly said:

Yes those are my thoughts exactly. Only this week we noticed ours wasn't drawing properly and a torch from the top showed a near completely closed flue very near the bottom. A quick prod with a stick disloged it as it was still all soft. We havnt had anything remotely like a cold winter since the several weeks we were all frozen in back end of 2010 into 2011.

Because I cook on the Rayburn regardless of how warm it is outside I have to open it up, so in theory it should be clean but it isnt. I now use wood to get that instant heat so in a couple of weeks when I next clean the flue all will be revealed or not as the case may be.

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A high burning rate should keep it reasonably clear. Shut down, ticking over at night doesn't hep. A person here with a big widebeam boat has a stove which is really much too small for the size of boat, she has it burning pretty fiercely most of the time, her flue doesn't get this, only light soot, and she burns Excel !.

  • Happy 1
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10 hours ago, peterboat said:

My stove flue has to be cleaned at least once a month! I use anthracite which is smokeless, if I leave it to long I get the same problem as yourself

Thanks - I’ll give the flue more frequent attention once I sort it out.

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Is everyone on this thread referring to burning coal-based solid fuel?  I burn only wood, and don't have this problem much on the boat, although I used to at home when burning wood that wasn't dry enough - the sweeps brush just wouldn't get through, so I rigged up an end consisting of nails driven at right angles which got most of it off.  On the boat it's much simpler, using a length of square section steel (a piece of my old market stall) to rummage around from the top.

I'm surprised that the worst of the crud in the OP's flue is in the lower insulated section though - it usually condenses in cooler parts of a flue. But it could be that the condensate in the wider upper part ran down and accumulated at the constriction.

Edited by Mac of Cygnet
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OK, thanks everyone - as always lots of helpful advise and information.

I will definately clean the flue MUCH more regularly from now on!

I’ve removed the deflector / baffle plate whilst cleaning, however I’m aware of the Morso advise not to have it fitted if the flue is less than 4.5m so pondering this. Would the draw be better or worse without it?

No sign of a half moon plate - I can see a circular view of the grate when looking down.

Todays plan is to buy a broom pole, and attach a sturdy wire brush to it, with a thin rope attached and kept tight from the throat to help get some lateral pressure.

I’m also contemplating somehow rigging up a suitable hole cutter on a long shaft? I have a range of sizes.

Also I might try burning some of the flue clear powder in the hope of softening the crud.

I’ll report back <_<

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My cleaning device is a bunch of chains. Usually bits I've saved from mine and other peoples' discarded button fenders, or similar. The basic idea is that you attach cord to both sides of the bunch, long enough to reach the length of the flue. Once the chain bunch is in the flue, you use a seesaw action, pulling and dropping the cord, which flails the inside. It does shift the crap.

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More info:

It appears that we have an unusual flue installation.

For some reason the internal insulation with its lining has been cut away or discontinued from half way up. This has resulted in a distinct internal ledge half way up at the top the insulated section. The professional boat flue cleaner did not make any comment last year, but I remember him using a homemade chain flail attached to a cordless drill. 4 x sink plug chain attached to a wooden disk.

I get the feeling that over many years, some brushing may have stopped at this lip - there is definitely a drastic increase in crud from the ledge or lip down to the throat within the more narrow insulated section.

So why would the installer have done this and is the inner skin that retains the insulation normally robust enough to withstand drastic treatments such as chain flails or nails in a bit of 2” x 2” ?

Of course it might not be an original Morso flue. Outside dimension is uniform at about 4.5”.

Thanks,

Clive.

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If your OD is 4.5", then the ID of the insulated part is only going to be about 3 - 3.5", which is really not very much.  I wouldn't be happy with such an arrangement, especially with a ledge halfway up to provide somewhere for the crud to accumulate.  In fact, I would either be looking to get a new flue, or take that one off and try to remove the lined bit which is giving the trouble.

To answer your question about the baffle plate - it has the effect of slowing down the flow of smoke and gases, allowing more time for heat transfer.  Without it, your stove will be a little less efficient, but will draw better.  I had to take out the one I had made for my Carabo, as the stove smoked me out every time I lit it.

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17 minutes ago, Mac of Cygnet said:

If your OD is 4.5", then the ID of the insulated part is only going to be about 3 - 3.5", which is really not very much.  I wouldn't be happy with such an arrangement, especially with a ledge halfway up to provide somewhere for the crud to accumulate.  In fact, I would either be looking to get a new flue, or take that one off and try to remove the lined bit which is giving the trouble.

To answer your question about the baffle plate - it has the effect of slowing down the flow of smoke and gases, allowing more time for heat transfer.  Without it, your stove will be a little less efficient, but will draw better.  I had to take out the one I had made for my Carabo, as the stove smoked me out every time I lit it.

Thanks - that does make a lot of sense.

But as the stove was drawing well over the last 3 winters, until very recently, I’m going to try and clean the flue robustly, and also remove the baffle plate.

I’m hoping that the draw will then be improved. If it’s OK I’ll know to keep a close eye on it including the dodgy ledge and clean it very often. This will be much easier with no baffle plate to remove each time.

If not I will bite the bullet and comply with one of your two suggestions.

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