Advice please on stove

[Lisa009]

Hi new here firstly Merry Christmas to all.

 

I wondered if anyone could give me some advice please.  

 

We have a hamlet hardy stove with a twin wall flue all fitted properly by a professional who is on holiday now so cant call we have had no problems for about a year now every time the flue cools down after the stove being on there is a loud cracking noise which does sound like metal on metal which is driving me mad it is so loud it makes me jump.  

 

We have checked and thoroughly cleaned the flue chimney and stove etc checked the fire bricks, throat plate welds etc it is all good no cracks or smoke anywhere it should not be have also re cemented all the joins to make sure no gaps and cant work out what is causing it the only thing that has changed since the installation is solar is on the roof now and noticed it after that but maybe pure coincidence as the solar is not close enough to the chimney.

 

Could it simply be expansion ?  Or has anyone come across this 

 

Thanks 

[Dr Bob]

What exactly do you mean by 'every time it cools down'?

Does the noise only happen when you shut the stove down completely or is it when it cools a bit after being very hot? You don't actually say when you started hearing the noise. What time of year. Most expansion/ contraction noises on boats (all boats) happen in warmer months when the sun is out...but that is not when the stove is lit.

Does the noise happen at the same time everyday or is it closely linked to the fire temperature?

Is it one noise or does it sound multiple cracks over a short time period?

We have a double skinned flue but don't hear any noises on heat up or cool down. Maybe it's the internal liner moving which is difficult to see. Is you CO alarm reading zero?

[matty40s]

It could be he has used cement in the roof collar rather than rope and silicon as well as the top of the stove.

This stops the flue expanding and contracting smoothly. There may well be a small noise when it is heating up, but the crack may be more noticeable when cooling if the top cement cools first and traps the flue.

[Lisa009]

Hi thanks for coming back to me this has only started happening in the last 6 weeks and happens when it is cooling down every time and it's getting worse.

 

I was just looking up the installation guidance and am very worried that this person cut corners now as he is now uncontactable all the time.

 

I think I need to sort this out myself now as starting to think it is unsafe.

 

From what I can see there is a flue spigot out of the top of the stove with only cement where should the rope go under that or is it visible am thinking I need to take it apart  ?

 

On top of the spigot is an adapter for an sflu double skinned flue and it sits on there with a bracket holding it to the wall 

 

Thanks very much 

 

 

 

[Yellowback]

Pictures?

[Lisa009]

Will be taking it apart when everyone else is up to see more hopefully 

[Lisa009]

8 hours ago, Dr Bob said:

What exactly do you mean by 'every time it cools down'?

Does the noise only happen when you shut the stove down completely or is it when it cools a bit after being very hot? You don't actually say when you started hearing the noise. What time of year. Most expansion/ contraction noises on boats (all boats) happen in warmer months when the sun is out...but that is not when the stove is lit.

Does the noise happen at the same time everyday or is it closely linked to the fire temperature?

Is it one noise or does it sound multiple cracks over a short time period?

We have a double skinned flue but don't hear any noises on heat up or cool down. Maybe it's the internal liner moving which is difficult to see. Is you CO alarm reading zero?

Hi the noise happens when cooling down and the fire is almost out no co alarm reading at all have checked but think it is coming from the top of the stove where the 4 inch meets the 5 inch twin wall.  Between them is an adapter from 4 to 5 inch flue.  Excuse my lack of technical terms.  This never used to happen only the last 6 weeks.

[Tony Brooks]

a single loud crack is not uncommon when hot metal contracts as has been said. I agree the flue collar on the outside of the boat needs inspecting (chimney off) to see how the flue has been sealed to the collar. If it is firs cement I would dig it all out until I could see the rope that should be under the to seal and replace it with high temperature silicon. if you do find fire cement then the installer may have used it on the underside of the collar and on the stove end of the flue but as long as the flu can expend upwards the lower end should not mater noise wise.  FWIW my single wall flue would rise a mm or so above the rood collar when it was hot so any rust that is trying to grip the flue may make such a noise. If fire cement has been used it may be a good idea to deal with the underside of the roof collar as well.

 

Any joint that tries to grip the mating surfaces is likely to cause the noise.

 

Car exhausts will also make that kind of noise when they cool down so it should not be unexpected on a flue. As its a  twin wall flue I would expect internal metal distance pieces between the two skins unless the makers are relying upon the insulation to hold the two skins apart. If there are metal distance pieces the weld on one might have failed but as you don't detect any CO I would not worry about it.

 

It would be a good idea to have a close look at the stove to to collar joint just in case the securing bolts have failed and it can move slightly. Look for rust dust around the joint. however I suspect the stove is too new for that to be likely.

[Bee]

Taking it all apart could be a real pain. The whole lot might have to be taken apart from the top down and you will end up with a heap of sooty parts and still no obvious answer. Could easily be the cast iron or steel pieces of the stove itself. We have a bread machine that does that and quite loud too, not just little clicks and ticks. I would check the top of the stove again around the chimney outlet, this can get really hot and if it is a tight fit somewhere then that could be the cause but the cure could be making it a loose fit and that might not be a good idea either. Sorry, not much help.

[Lisa009]

13 minutes ago, Tony Brooks said:

a single loud crack is not uncommon when hot metal contracts as has been said. I agree the flue collar on the outside of the boat needs inspecting (chimney off) to see how the flue has been sealed to the collar. If it is firs cement I would dig it all out until I could see the rope that should be under the to seal and replace it with high temperature silicon. if you do find fire cement then the installer may have used it on the underside of the collar and on the stove end of the flue but as long as the flu can expend upwards the lower end should not mater noise wise.  FWIW my single wall flue would rise a mm or so above the rood collar when it was hot so any rust that is trying to grip the flue may make such a noise. If fire cement has been used it may be a good idea to deal with the underside of the roof collar as well.

 

Any joint that tries to grip the mating surfaces is likely to cause the noise.

 

Car exhausts will also make that kind of noise when they cool down so it should not be unexpected on a flue. As its a  twin wall flue I would expect internal metal distance pieces between the two skins unless the makers are relying upon the insulation to hold the two skins apart. If there are metal distance pieces the weld on one might have failed but as you don't detect any CO I would not worry about it.

 

It would be a good idea to have a close look at the stove to to collar joint just in case the securing bolts have failed and it can move slightly. Look for rust dust around the joint. however I suspect the stove is too new for that to be likely.

Hi thanks Tony forgive my ignorance where should the rope be is it supposed to be under under the cement where the 4 inch flue bit that sits on top of the stove  is ?  What I am worried about is the person may not of bothered or forgot  to put rope in and dont recall rope being used anywhere but the glass.

 

What I was thinking of doing is getting some fire rope from toolstation if they are open and sealant ? Taking the whole thing apart and checking then resealing however I have just taken the ceiling decorative plate off to look through the ceiling out to the chimney there is no marks singes or anything like that perfectly clean however there is nothing there but a gap so wondering whether there should of been fire board there or ceramic wool or just a gap? 

 

Any help is much appreciated it is freezing and scared to put it on until checked thoroughly 

 

Thanks 

[Lisa009]

Also while I am on the subject does anyone know the max kw stove that is safe for a boat as am thinking of getting another one anyway so may well use this problem to do that have seen a few but they are above 5 kw and around 7 kw

[Alan de Enfield]

Just now, Lisa009 said:

Also while I am on the subject does anyone know the max kw stove that is safe for a boat as am thinking of getting another one anyway so may well use this problem to do that have seen a few but they are above 5 kw and around 7 kw

It will depend on your boat size (beam and length) and the quality of your insulation, and, the size and design of your windows.

 

We could get far too hot with a 2kw in a 30 foot NB, (did an experiment and once the room temperature got to 50+ degrees and we couldn't breathe I gave up with the experiment). Similarly in a 45 Foot NB with a 5KW stove it was easy to get too hot.

Our current 14 foot widebeam has an 8KW and again it can easily get too hot.

 

If you are prepared to 'manage' the stove by shutting it down and opening it back up, or opening and closing doors and windows then pretty much any stove will do, but, 5KW seems to be the 'norm' for pretty much all NB's

[Lisa009]

11 minutes ago, Alan de Enfield said:

It will depend on your boat size (beam and length) and the quality of your insulation, and, the size and design of your windows.

 

We could get far too hot with a 2kw in a 30 foot NB, (did an experiment and once the room temperature got to 50+ degrees and we couldn't breathe I gave up with the experiment). Similarly in a 45 Foot NB with a 5KW stove it was easy to get too hot.

Our current 14 foot widebeam has an 8KW and again it can easily get too hot.

 

If you are prepared to 'manage' the stove by shutting it down and opening it back up, or opening and closing doors and windows then pretty much any stove will do, but, 5KW seems to be the 'norm' for pretty much all NB's

Hi we have a 60 x 12 boat we always have windows doors open when the stove is on for ventilation we have double insulation saw a stove I liked that someone is selling but thought it would be too hot although with the current stove on it is not really warm it does not heat that much we have a hardy s4 arada 

 

Think I might get the current one  sorted first anyway and worry about upgrade later  as it is too cold and need heat now 

 

Thanks though for the info

[Lisa009]

41 minutes ago, Lisa009 said:

Hi thanks Tony forgive my ignorance where should the rope be is it supposed to be under under the cement where the 4 inch flue bit that sits on top of the stove  is ?  What I am worried about is the person may not of bothered or forgot  to put rope in and dont recall rope being used anywhere but the glass.

 

What I was thinking of doing is getting some fire rope from toolstation if they are open and sealant ? Taking the whole thing apart and checking then resealing however I have just taken the ceiling decorative plate off to look through the ceiling out to the chimney there is no marks singes or anything like that perfectly clean however there is nothing there but a gap so wondering whether there should of been fire board there or ceramic wool or just a gap? 

 

Any help is much appreciated it is freezing and scared to put it on until checked thoroughly 

 

Thanks 

Hi Tony am I right that the 4 to 5 inch adapter for the twin wall should have fire rope or is it the collar from the stove that needs it or both and is victas heat resistant sealant good enough on top of the rope just working out a plan thanks again 

[Tony Brooks]

13 minutes ago, Lisa009 said:

Hi Tony am I right that the 4 to 5 inch adapter for the twin wall should have fire rope or is it the collar from the stove that needs it or both and is victas heat resistant sealant good enough on top or just working out a plan thanks again 

 

I can't answer that. I would hope a flue size adaptor would just be a good fit plus a smear of silicon but the boss on top of the stove is probably different (remember your photo shows very little detail). Personally I would not fit twin wall flue on my boat so I don't have a clue about your exact setup.

 

Typically, but not specific to your setup, the hole in the stove boss/collar and the roof collar is maybe 10 mm too large for the flue (in your case the inner flue) so the flue can if required fit at a slight angle to vertical. This gap is then packed with glass fibre rope leaving maybe a 10 mm recess that you fill with heat resistant silicon. The rope pervents rust in the collars or on the flue gripping the two surfaces and the silicon is flexible enough when set to allow for the flue to expand and contract.

 

As I buy my heat resistant silicon for the likes of  Screwfix/Toolstation i have no idea what Victas heat resistant sealant is. If it sets solid like cement than I would no use it. I use a product called Plumbaflue but the purists here may suggest its heat rating is not high enough but @bizzard says he conducted tests on a shovel in his stove and ordinary silicon was as heat resistant as the high temperature stuff.  I know a friend who used heat proof sealant he bought from a chandlers and ended up with black liquid running down the flue for weeks. I suspect that might have been a Victas product but don't know for sure.

 

Now you have the ceiling ring down have a good look at where the flue enters the roof collar (unless the double skin prevents you seeing anything). If you can see it you should be able to tell if its just a gap and maybe see the rope, silicon, a cement like product. If the latter that may be the problem as described by someone else above.

 

Ideally you should have no combustible material within 6" (I think but check the advisory BS 8511 to be sure) of the flue. When i installed mine I removed the "plastic" roof insulation and pushed Rockwool/glass fibre roof insulation in to fill the gap. Often off cust of such insulation can be found in skips where roof or loft work is being done.

[Mad Harold]

It's too cold at the moment to mess around with your heating.

Might be better to wait for warmer weather.If there is no monoxide leaking,it may be better to leave it alone for the present.

I think your noise could be caused by different expansion and contraction rates of different metals.

[Tracy D'arth]

Slacken the bracket holding it to the wall a bit, it could just be that.

[Alan de Enfield]

8 minutes ago, Mad Harold said:

It's too cold at the moment to mess around with your heating.

Sort of agree - get it all part and something breaks and you end up with a big hole in the roof and still no heating.

 

If on a mooring get a couple of 1Kw (or maybe 2 or 3x  400/800 watt from Aldi, Poundstretcher etc) electric heaters.

Instant heat

 

During the Winter I leave 2x 375 watt heaters connected (on timers) and it costs £1 a day in 'leccy.

[Mad Harold]

15 minutes ago, Tracy D'arth said:

Slacken the bracket holding it to the wall a bit, it could just be that.

Yes,it could be.

It could also be rust flakes trapped somewhere stopping the natural contraction of the metals untill the last moment,and then a sudden contraction.

You might try tapping gently all around the flue with the sole of your shoe (take your foot out first) and see if that has any effect.

 

[Tony Brooks]

1 hour ago, Tracy D'arth said:

Slacken the bracket holding it to the wall a bit, it could just be that.

Good call.

[BWM]

Whatever the cause of the noise, don't be overly concerned about using the stove as is. If the flue is kept clear with regular sweeping and you have a C/O alarm any minor cracks in fire cement will not be a danger - many range type stoves have loosely fitting top plates with no seals and are fitted in an 8'×7 cabin.

[Yellowback]

Looking at the picture, how would you get any rope in there?

[Lisa009]

Hi we have taken the flue off the the adapter for the twin wall just came off with a slight pull all the cement had disintegrated we are just cleaning it up now ready to re seal we think that was loose there are no cracks anywhere inside  we are also putting exhaust insulation tape around the top near the roof can anyone remind me where the rope should go on the collar to the stove where the cement is in the picture  ??  Thanks everyone 

[Ex Brummie]

Dig out the fire cement and replace it with a ring of ceramic rope, the same diameter as the width of the ledge. The internal pipe of the flue should sit on this, and the pipe through the roof collar should be free to expand. Another ring of fire rope around the top of the flue will stop it rusting to the collar.

[Tony Brooks]

It would normally go between the  flue and that collar on the stove. If you look you will see a shelf or some little shelves for the flue or and and addapter to sit on. That normally leaves a gap between the collar and flue. You pack the fire rope or even Glass fibre exhaust bandage between the two but leaving a gap/recess at the top to fill with sealant/high temperature silicon.