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Esmeralda01

Help with hearth design for largeish stove?

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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 :)

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I'm guessing this is the information you have seen

 

Fitting a stove in a boat

British Standard BS 8511:2010 Code of
practice for the installation of solid fuel
heating and cooking appliances in small
craft where much more detailed information
can be found. The code isn't compulsory, but
will always be referred to if an accident occurs.

 

Boat Stoves 1-page.pdf

Edited by Alan de Enfield

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I note that the installation instructions for this stove says that the "chimney must be at least 4.5 m (15 ft)"   Wouldn't that be difficult to achieve on a boat?

 

Edited by koukouvagia

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I note that the installation instructions for this stove says that the "chimney must be at least 4.5 m (15 ft)"   Wouldn't that be difficult to achieve on a boat?

 

I think that's only for normal domestic situations. Other stoves which are regularly installed on boats like the morso also quote a 14ft chimney. 

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I note that the installation instructions for this stove says that the "chimney must be at least 4.5 m (15 ft)"   Wouldn't that be difficult to achieve on a boat?

 

Tricky that. I wonder if most manufacturers say that or something like it? I think on a boat (or shed or other similar places) it might be reckoned OK so long as the chimney is above the height of nearby structures?  There are so many areas where compliance is difficult that some things just cannot work. Also I think its a big stove for a boat both physically and also its output. I wonder if, having survived this winter, you might be better off seeing if a different stove just happened along, maybe flog that one and hopefully find a smaller one?

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Tricky that. I wonder if most manufacturers say that or something like it? I think on a boat (or shed or other similar places) it might be reckoned OK so long as the chimney is above the height of nearby structures?  There are so many areas where compliance is difficult that some things just cannot work. Also I think its a big stove for a boat both physically and also its output. I wonder if, having survived this winter, you might be better off seeing if a different stove just happened along, maybe flog that one and hopefully find a smaller one?

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. 

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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. 

Then there is a problem with your installation and maybe whoever fitted out the boat did not balance your battery bank with the electrical audit.

How do you recharge the batteries ?

What is using the electric ? - Circulation pump ?

What diesel heating system do you have, how much diesel is it using ?

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Then there is a problem with your installation and maybe whoever fitted out the boat did not balance your battery bank with the electrical audit.

How do you recharge the batteries ?

What is using the electric ? - Circulation pump ?

What diesel heating system do you have, how much diesel is it using ?

The boat came as a sailaway with additions and only 3 110ah batteries which I am using for tv, laptops, lights etc, I need to add more batteries for many reasons not just the heating but I am prioritising various costs over the months. I can get it to last a good 4 hours with other electric use but not all night. 

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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. 

Ah, I sort of envisaged a narrow boat, in that case you have space for a big hearth. As for a 125mm thick hearth that is a mighty slab of concrete, the only way to do that would be to cut a hole in the floor and sit the hearth a couple of inches below the floor level, this is not a bad idea if you were to have a back boiler as you could get a bit more precious 'rise' so the system could thermosyphon. But if the stove is on legs as in the picture I really can't see the need for that thickness. There will be others on here with a better knowledge of rules etc. You will need to bolt it down somehow as well.

  • Greenie 1

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The boat came as a sailaway with additions and only 3 110ah batteries which I am using for tv, laptops, lights etc,. I can get it to last a good 4 hours with other electric use but not all night. 

When you say you can 'get it to last' what happens when it 'doesn't last' ?

How are you managing your batteries - do you charge them when the lights go out out or do you have any 'technology' to help you ?

How are you charging the batteries ? (Engine, generator, Solar, mains hook-up)

How do you know when to stop charging ?

Have you undertaken a power audit ?

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When you say you can 'get it to last' what happens when it 'doesn't last' ?

How are you managing your batteries - do you charge them when the lights go out out or do you have any 'technology' to help you ?

How are you charging the batteries ? (Engine, generator, Solar, mains hook-up)

How do you know when to stop charging ?

Have you undertaken a power audit ?

Yes at some point I will be installing a 1000ah bank with solar to match based on my power audit. Thanks for helping with my electrics but I'm really focused on the stove at the moment. :)

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Yes at some point I will be installing a 1000ah bank with solar to match based on my power audit. Thanks for helping with my electrics but I'm really focused on the stove at the moment. :)

But if you sort the power, then you can run your radiators all night.

Its your boat and your decision - good luck.

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If your stove is certified to not reach more than 100C underneath the hearth requirements are different - and much easier to meet.

Check the stove manual.

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The constructional hearth (usually concrete) is specified in building regulations to ensure that the heat of the stove is kept well away from any timber or anything else combustible. In the case of a steel boat I would have thought you could get away with a lot less thickness if there is no timber beneath the hearth e.g. a paving slab set directly on the bottom framing.

  • Greenie 1

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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. 

My boat is 50x12 and I have a. 4.7kw diesel stove, it’s more than enough for 98% if the time.  The other 2%,is when your trying to warm the boat up from cold when it’s really cold outside.  But that’s what heaters like the ebersplutters are for.  

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I was wondering - the OP mentions "radiators" but doesn't mention how they are powered (no mention od diesel, ebersplutter, noise etc). If there's a diesel powered heater, I can't understand why he's not toasty. Once running  an Eber doesn't take much power. My boat's 60 ft, but narrow - even so we have to turn the radiators down or we'd fry, so surely he should be warm enough on a wider but shorter boat.  

Summat wrong somewhere - including expectations?

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I was wondering - the OP mentions "radiators" but doesn't mention how they are powered (no mention od diesel, ebersplutter, noise etc). If there's a diesel powered heater, I can't understand why he's not toasty. Once running  an Eber doesn't take much power. My boat's 60 ft, but narrow - even so we have to turn the radiators down or we'd fry, so surely he should be warm enough on a wider but shorter boat.  

Summat wrong somewhere - including expectations?

Mentions using "so much diesel and batteries" so presume has a heater of Ebersplutter or other make of similar.    I think the main problem is not if it's a 5kw or 8kw stove as both would be okay, but distributing the heat around the boat.

Edited by Robbo

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Mentions using "so much diesel and batteries" so presume has a heater of Ebersplutter or other make of similar.    I think the main problem is not if it's a 5kw or 8kw stove as both would be okay, but distributing the heat around the boat.

Just so -  fitting a large fire isn't going to solve the circulation problems; the next question is bound to be how to circulate the heat and that can't be solved by fans (of any ilk) and a back boiler for his large stove may not be available, plus jiggering around with the existing radiators and its circulation challenges to link the two

Still we haven't been asked about that, mebe best to keep quiet, or if the OP is reading this lot - go back and look a the whole problem before fitting a large stove and then finding out that its heat doesn't reach everywhere that its needed. 

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..........or if the OP is reading this lot - go back and look a the whole problem before fitting a large stove and then finding out that its heat doesn't reach everywhere that its needed. 

That's pretty much where I was coming from when I posted "Then there is a problem with your installation" way back up the thread.

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Thanks for your advise. We have a Webasto diesel powered heater that powers our central heating, whilst it is sufficiently warm when it has been on for a while, it uses a surprising amount of electricity and diesel, it would be very expensive and we would require a large battery bank to keep it running 24/7 which it really needs to be when very cold (I'm also pretty sure these type of heaters aren't meant to be used in this way). I am also very aware that our battery bank is currently insufficient for our needs and we are in the process of replacing, which will mean we can keep the heating on longer.

We have bought the stove (which is the correct size for the size of room we have) for a number of reasons:

  • As it can be left on for longer periods of time and throughout the night without destroying our batteries.
  • to help with humidity/ condensation on the boat 
  • It will give us a lot of heat in the main room at least, where as, unless the radiators have been on all day, it is still a bit chilly on very cold days.
  • because we wanted one for aesthetics and feel etc.

We have one large main room and an open corridor to the bedroom, we will be circulating the heat from the stove with fans as best as anyone on any boat can.

What we really need help on is how to  install a safe hearth.

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Thanks for your advise. We have a Webasto diesel powered heater that powers our central heating, whilst it is sufficiently warm when it has been on for a while, it uses a surprising amount of electricity and diesel, it would be very expensive and we would require a large battery bank to keep it running 24/7 which it really needs to be when very cold (I'm also pretty sure these type of heaters aren't meant to be used in this way). I am also very aware that our battery bank is currently insufficient for our needs and we are in the process of replacing, which will mean we can keep the heating on longer.

We have bought the stove (which is the correct size for the size of room we have) for a number of reasons:

  • As it can be left on for longer periods of time and throughout the night without destroying our batteries.
  • to help with humidity/ condensation on the boat 
  • It will give us a lot of heat in the main room at least, where as, unless the radiators have been on all day, it is still a bit chilly on very cold days.
  • because we wanted one for aesthetics and feel etc.

We have one large main room and an open corridor to the bedroom, we will be circulating the heat from the stove with fans as best as anyone on any boat can.

What we really need help on is how to  install a safe hearth.

A Webasto is designed to be left-on for long periods, switching it on and off causes coking up and untold problems. Leave it on and let the thermostat control the temperature.

I realise that money is tight but it may be a good investment to get someone to look at your whole system - eg you may have battery capacity problems because you have reduced capacity from undercharging - your 3x 110ah batteries may now be as low as (say) 50Ah.

A Webasto will use only 1-2 amps when running - (so if running for 12 hours per day its just around 18 AH per day) if your batteries cannot support this then you have much wider issues.

You may not be bothering about electrics at the moment but maintaining correctly charged batteries is key to many aspects of boating.

Your heater should use (roughly) 100ml of diesel per hour per Kw, so a 5kw heater will use 0.5 litres per hour, or about 35p per hour to run. but it will not be running continuously say, 12 hours or £4.20 per day.

Your solid fuel consumption will (probably) be about 2 1/2 days per 20kg bag at around £10 per bag so about £4 per day.

Add in the £1000s to install your fire correctly and it will pay you to sort out your Webasto system

Edited by Alan de Enfield

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A Webasto will use only 1-2 amps when running - (so if running for 12 hours per day its just around 18 AH per day) if your batteries cannot support this then you have much wider issues.

^^^^ This

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Ugh, so this is another one of those threads where everyone weighs in with advice on everything but the actual question. It's so hit and miss on this forum, a shame because it could be really good. 

Edited by Cpickle

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Ugh, so this is another one of those threads where everyone weighs in with advice on everything but the actual question. It's so hit and miss on this forum, a shame because it could be really good. 

And the answer you gave the OP was?

I think few people have easy access to all the documents required to give the OP a definitive answer although some may have a general idea. The OP could not tell us how the stove is rated re the heat transmitted to the hearth and when I looked at the link I could see no mention of this. As The Biscuits pointed out this has profound implications for the thickness of the non-combustible hearth.  I did not answer because I could not find this info and others pointed to the relevant advisory BS.

What did happen is that the question indicated all was probably not well with the boat systems so the OP was advised of it. Now, perhaps you believe that we should not try to resolve issues arising from questions but I would rather try to help the questioner avoid problems. After all the OP can choose to explain or ignore.

If you do not find the way the forum operates then simply do not read it and more to the point do not post any questions.

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