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Esmeralda01

Help with hearth design for largeish stove?

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I concur with Tonys comments re heat transmission to the hearth. We have a Morso stove -a 1416 which is about the same size as a squirel but much more aesthetically pleasing. The fitting manual gives a hearth temperature which allowed us to have two layers of 15mm Hardibacker cementitious board plus ceramic tiles on top of the plywood floor. It extends the required 150mm to the side and 300mm in front of it and is surrounded by a steel lip. Certainly the hearth does not get so hot that I can't touch it - which means that there is little chance of heat transfer to the ply floor. On the boat side and front I have 25mm calcium silicate board with an air gap to the ply lining in accordance with the guide lines for boat installations. I think that the OP is looking for this type of advice. What he needs to do is contact the manufacturer to get an indication of heat transmittance to the hearth and then consider the options.

  • Greenie 1

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I concur with Tonys comments re heat transmission to the hearth. We have a Morso stove -a 1416 which is about the same size as a squirel but much more aesthetically pleasing. The fitting manual gives a hearth temperature which allowed us to have two layers of 15mm Hardibacker cementitious board plus ceramic tiles on top of the plywood floor. It extends the required 150mm to the side and 300mm in front of it and is surrounded by a steel lip. Certainly the hearth does not get so hot that I can't touch it - which means that there is little chance of heat transfer to the ply floor. On the boat side and front I have 25mm calcium silicate board with an air gap to the ply lining in accordance with the guide lines for boat installations. I think that the OP is looking for this type of advice. What he needs to do is contact the manufacturer to get an indication of heat transmittance to the hearth and then consider the options.

Agreed but it can not be given until we know about the temperature transmitted downwards. Apart from the I think he was pointed at the best advice in the BS link.

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Thanks for your input, I have contacted the manufacturer RE heat transmission to the hearth, receiving it in writing is probably enough.

What I guess I was trying to ask from my original post was whether anyone knew if it is a  compulsory requirement of  BS EN 13240, that any stove complying with this code, must limit transmission of heat to the the hearth, such that the hearth is kept below 100 C? 

I cannot afford these codes and soliftec document just says that stoves must comply with the above?

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A lot of what is discussed is for when you want to get building control to sign off or a Hetas Approved person to self certify on houses not boats.

 

 

 

I also have questions about the size of the hearth. The manual recommends 300mm in front of the stove or 225 if the stove is not to be operated as an open fire. This means the total size of my hearth is to be about 860mm wide, and 730 deep. Seems huge compared to all the other hearths I've seen on boats. I am aware that this distance can be reduced if the hearth is installed with a high 'lip' is there any guidance on how much the size of the hearth can be reduced by with a lip and how high the lip should be?

Thanks everyone :)

 

If it was a house you need 840mm square minimum hearth istr.

 

It's not a house tho.

Edited by mark99
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Its a massive boat, 60x12, everyone I've spoken to has recommended we get about 8kw based on the internal space. I wouldn't like to rely on my radiators again especially as I cant run them all night off my batteries and they use so much diesel, we were totally freezing for a good few nights. 

Here's mine on a 57 x 12ft boat. It's a 9kW Morso Panther. 

Try to position your stove as centrally in the boat as possible.

(My flue has since been replaced with a single piece steel flue).

DSC_5948.JPG

Edited by blackrose

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Hi everyone 

I am about to install a stove on my new boat after surviving this winter with only radiators! I'm very tight on cash hence the late instillation and I'm hoping to construct the hearth myself but I want to ensure it is going to be safe not just for myself but for any potential future owner. I am struggling a bit with converting the instructions in the manual to what is appropriate in a boat setting. Hoping there are some informed people here that might be able to help. 

This is the manual for my stove. Although this manual is a newer version. My stove is 9 yrs old and the old manual has this number DIN EN 13240 . The stove also has a CE marking.  

http://www.hetas.co.uk/wp-content/mediauploads/Franco-Belge-Monaco-Installation-Operating-Instructions.pdf  

However,following the instillation instructions in the manual seems to mean we will need a constructional hearth measuring 125mm thick with a 50mm air gap, I've read in other posts that stoves with a CE marking only need a 12mm hearth. Is this correct? If not, how have people tackled the above requirement? 

I also have questions about the size of the hearth. The manual recommends 300mm in front of the stove or 225 if the stove is not to be operated as an open fire. This means the total size of my hearth is to be about 860mm wide, and 730 deep. Seems huge compared to all the other hearths I've seen on boats. I am aware that this distance can be reduced if the hearth is installed with a high 'lip' is there any guidance on how much the size of the hearth can be reduced by with a lip and how high the lip should be?

Thanks everyone :)

From page 3 of the linked manual:

Hearth

The hearth should be level and able to accommodate the weight of the stove and its chimney if the chimney is not independently supported. The weight of the stove is indicated in the brochure.

The stove should preferably be installed on a non-combustible hearth of a size and construction that is in accordance with the provisions of the current Building Regulations Approved Document J.

The clearance distances to combustible material beneath, surrounding or upon the hearth and walls adjacent to the hearth should comply with the guidance on the separation of combustible material given in Building Regulations Approved Document J and also in these stove instructions.

If the stove is to be installed on a combustible floor surface, it must be covered with a non-combustible material at least 12mm thick, in accordance with Building Regulations Approved Document J, to a distance of 30 cm in front of the stove and 15 cm to each side measuring from the door of the combustion chamber.

From Approved Document J:

27.  ... The body of the hearth may be thin insulating board, a substantial thickness of material such as concrete or some intermediate provision dependant on the weight and downward heat emission characteristics of the appliance(s) upon it

 

So:

This stove appears to stand off the floor on quite generous legs from the line drawing of the stove in the manual.

The barest minimum you can get away with would be 1/2" thick of something non-combustible under the stove.

I strongly recommend you go thicker than that, so something like a sheet of fireboard (NOT waterproof tile-backer board please!) tiled in something like quarry tiles would be fine for this stove, as long as it extends 300mm (about a foot) in front and 150mm (6") to either side of the stove opening and has the correct clearance behind and to the sides of the stove body, which are all 150mm (6") for this stove.

So the minimum size hearth for this stove will be

Depth:  883 mm (150mm behind + 433mm stove depth + 300mm in front) 

Width:  861 mm (150mm side + 561mm stove width + 150mm side)

TL;DR

You need a hearth a foot wider than this stove and 18" deeper than this stove.

It's one of the reasons the Morso Squirrel is popular on boats: That only requires 100mm (4") clearance behind and to both sides and the extra few inches matter on a boat installation.

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I used a pair of paving slabs for my smaller stove, one on top of the other, and then tiled to     try to ensure little heat got conducted to the floor. If I was fitting a larger stove I think that I would cut the floor out, shutter it up and cast a  solid concreter slab on top of any non-combustible ballast.

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Musing: Would a clean highly-polished stainless steel plate suspended an inch off the floor under the stove help to keep the floor cool?  Obviously this wouldn't satisfy any regulations as they would correctly point out that you would need to polish it twice daily and that was unlikely to happen. But would it have an effect?

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12 minutes ago, system 4-50 said:

Musing: Would a clean highly-polished stainless steel plate suspended an inch off the floor under the stove help to keep the floor cool?  Obviously this wouldn't satisfy any regulations as they would correctly point out that you would need to polish it twice daily and that was unlikely to happen. But would it have an effect?

Yes.

Most of the short legged stoves that pass the relevant standards for less than 100ºC underneath the stove use this technique.

It's not stainless steel usually, and it tends to be an inch under the stove rather than from the hearth, but there is a suspended metal plate with generous air gaps underneath the stove.

  • Happy 1

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What concerns me with any boat is the fixing of the stove to the hull, worse case scenario the boat is rammed and tips up, OK if not lit, but lots of folks run 24/7.

Should one rely on the flue which is fixed to the bulkhead or the mass of the stove to hold the stove in place. 

PS I would have thought that silicate board would be the preferrred insulator, though it needs to be tiled etc.

Edited by LadyG

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20 minutes ago, LadyG said:

What concerns me with any boat is the fixing of the stove to the hull, worse case scenario the boat is rammed and tips up, OK if not lit, but lots of folks run 24/7.

Should one rely on the flue which is fixed to the bulkhead or the mass of the stove to hold the stove in place. 

PS I would have thought that silicate board would be the preferrred insulator, though it needs to be tiled etc.

BSS Failure if not secured..

Quote..

Are non-portable appliances properly secured against accidental or unintended movement? Check for the presence and condition of securing systems on all non-portable appliances. Where practicable, apply light manual force to check the security of all non-portable appliances. Where a manual check is not practicable, such as with solid fuel and oil-fired stoves, check the condition of securing systems.

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BSS inspector gave our sf stove an almighty shove to prove that the securing screws weren’t, um, secure. BSS fail until I’d addressed that. 

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14 minutes ago, WotEver said:

BSS inspector gave our sf stove an almighty shove to prove that the securing screws weren’t, um, secure. BSS fail until I’d addressed that. 

The OP is probably not worried about building his boat to RCD standards, but not having the SF Stove 'bolted down' is also an RCD 'non-compliance'.

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22 hours ago, Esmeralda01 said:

Thanks for your input, I have contacted the manufacturer RE heat transmission to the hearth, receiving it in writing is probably enough.

What I guess I was trying to ask from my original post was whether anyone knew if it is a  compulsory requirement of  BS EN 13240, that any stove complying with this code, must limit transmission of heat to the the hearth, such that the hearth is kept below 100 C? 

I cannot afford these codes and soliftec document just says that stoves must comply with the above?

Re bit in red above - I wish I had a gramophone record I could play to say this! You can afford to read "these codes"! Just go to Manchester City Library website and find their link to their online reference library. Search for British Standards. A link to British Stds online (BSOL) will come up. Use that, MCL pay the BSOL licence (bless them!). Free for you and you don't even have to be an MCL member. Once in BSOL search using the std no (eg 13240 and perhaps, another time, 8511 -the CoP for "Stoves in Boats" of which the Soliftec sketch is a precis). You will then get the titles of stds having this number, listed. Choose the one you're interested in and click the little icon on the far right (quick view). Eventually the full text of the std will appear as a read only .pdf. You'll find 13240 very technical but 8511 is quite practical and readable and IMHO gives all the answers!

Morso and Aarrow were represented at a high level in the drafting of 8511 back in 2010 and I believe all their 13240 compliant stoves meet the <100°C to the hearth requirement but it's good that you've asked the mfr in your case, it's what I did and so I can use the not less than 12mm non combustible hearth under my stove. Other hearth arrangements are given in 8511 and it now accepts that a 125mm constructional hearth is probably the least popular solution for a boat!!!

Richard

edit to add;-

Actually I couldn't remember what stove you said you were looking at originally so I've just re read your OP. As "The Biscuits" has already pointed out, your manual already says that the stove can use a 12mm non combustible hearth so therefore it doesn't raise hearth temp by more than 100°C in the 13240 test.   

 

      

Edited by rjasmith

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