thinking of fitting a multifuel stove

I am thinking of fitting a multi-fuel stove, probably around 8kW.

At the moment a standard open fire place exists. It has an "ash box" beneat h the grate with vents in it that are supplied with air from the underfloor void by a tube under the hearth. The fireplace and flue depth is 9 inches and the back of the flue is only a half brick thick, but is made of blue en gineering bricks and does not seem damp at all. The flue is open - no liner of any sort. The rest of the wall is solid 9" brick. The fireplace is on an exterior wal l. Fire surround with be traditional wooden painted white. I will have a carbon monoxide detector for obvious reasons.

I have some questions. Hopefully this does not seem too lazy - perhaps a se ction could be added to the wiki eventually ...

  1. Assuming a non-balanced flue stove, where is the air drawn in ? Can the inlet be connected to a duct so that it takes air from below the floor (whi ch has air bricks !) thus avoiding need for an exterior vent in the actual room ?

  1. Is a flue liner required ? Is so what type of liner (rigid / double wall / insulated etc) ? What size ? (for say, 8 kW stove)

  2. The chimney breast is not very deep and build partly into the wall (rear of flue only half brick. Is it OK for the stove to stick out proud of the non-combustible fireplace opening (possibly further than the fire surround also) ? How high above the stop of the stove must a painted timber fire sur round and mantel be ?

  1. Do you need to fill around the liner in the flue with insulating materia l (presumably held in with a register plate) ?

  2. The half brick back to the recess will need to be insulated in some way. Is celotex covered with some type of cement fire board be OK for regs ?

  1. I will have to widen the fireplace from the 16" fire box. How much wider than the stove does the opening need to be ?

  2. Is it safe to operate the stove with the doors open for short periods of time ?

Thanks, Simon.

Reply to
sm_jamieson
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ath the grate with vents in it that are supplied with air from the underflo or void by a tube under the hearth. The fireplace and flue depth is 9 inche s and the back of the flue is only a half brick thick, but is made of blue engineering bricks and does not seem damp at all. The flue is open - no lin er of any sort.

section could be added to the wiki eventually ...

e inlet be connected to a duct so that it takes air from below the floor (w hich has air bricks !) thus avoiding need for an exterior vent in the actua l room ?

You can now get room sealed stoves where the air is drawn in a pipe that goes to the outside. Worth their weight in gold. (No cold air drawn into the room.)

ll / insulated etc) ? What size ? (for say, 8 kW stove) Yes. Refer to manufacturers instructions

ar of flue only half brick. Is it OK for the stove to stick out proud of th e non-combustible fireplace opening (possibly further than the fire surroun d also) ? How high above the stop of the stove must a painted timber fire s urround and mantel be ?

Probably best to remove everything right down to the builders opening.

ial (presumably held in with a register plate)

There is a plate top and bottom of the chimney. Double liners don't need addtional insulation.

  1. The half brick back to the recess will need to be insulated in some way. Is celotex covered with some type of cement fire board be OK for regs ?

er than the stove does the opening need to be ?

Some stoves are designed to run with doors open, some not.

All this work is supposed to be done by a trained operative these days.

Don't forget your CO alarm.

Reply to
harry

AIUI the installer needs a HETAS certificate or your home insurance is invalidated. A local guy who does such work didn't know that until he'd installed his own. He couldn't use it until he passed the exam late last year.

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He said that in his opening paragraph.

Reply to
Nick

neath the grate with vents in it that are supplied with air from the underf loor void by a tube under the hearth. The fireplace and flue depth is 9 inc hes and the back of the flue is only a half brick thick, but is made of blu e engineering bricks and does not seem damp at all. The flue is open - no l iner of any sort.

a section could be added to the wiki eventually ...

the inlet be connected to a duct so that it takes air from below the floor (which has air bricks !) thus avoiding need for an exterior vent in the act ual room ?

wall / insulated etc) ? What size ? (for say, 8 kW stove)

rear of flue only half brick. Is it OK for the stove to stick out proud of the non-combustible fireplace opening (possibly further than the fire surro und also) ? How high above the stop of the stove must a painted timber fire surround and mantel be ?

erial (presumably held in with a register plate)

ider than the stove does the opening need to be ?

As a matter of interest, what is required to safely resurrect an open fire that was last used about 40 years ago ? Is a "chimney sweep" allowed to just check the draw and make sure the chimn ey won't catch fire ? Are you supposed to have a liner and use a hetas engineer ? Anyway, I guess a liner would be a good idea as the original lime mortar mi ght be a bit leaky.

Simon.

Reply to
sm_jamieson

Through various adjustable vents. Normally in the doors to under the grate and at the top to provide an "air wash" down the glass in the doors to try and keep them clean. There is no ducted air inlet on most stoves.

Sounds like your existing open fire is a "Baxi Burnall". We had one and when the hearth was installed for the stove the air feed that went into the ash box space was extended with a swept 110 mm waste bend to a hole in the slate hearth. This is positioned to rear of the stove, allows "enough" ventilation and can't be seen.

Really depends on the state of the existing chimney. I'd say yes as stove shoves out flue gases some what hotter than an open fire and a cold chimney may cause excessive condensation of tar and may lead to a chimney fire. Size will be dictated by the stove, the installation instructions will tell you what it needs. The most common size is 6".

Ours does:

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Be aware they get damn hot. Keeping young children away and not falling against it when on is recomended. B-) Also be aware of the proximity of soft furnishings.

Building regs have something to say about how close stuff can be and the size/thickness of the hearth etc.

I would, even if the maker suggests that it's not required. We have a twin wall 7" liner. Pretty sure it's not insulated right to the top (I only saw two emoty bags of vermiculite...). The liner maker said it doesn't need insulation but the bottom of the flue has to be cleared of a bucket full of crispy crumbly burnt tar once a month running the stove 7 hrs/day on seasoned hardwood.

I should think so. Isn't celotex fire approved?

Look at the building regs for minimum clearances.

Yes, though most stove makers don't recomend it. Knackers effciency and lowers the flue gas temperatures.

Reply to
Dave Liquorice

the grate with vents in it that are supplied with air from the underfloor void by a tube under the hearth. The fireplace and flue depth is 9 inches and the back of the flue is only a half brick thick, but is made of blue engineering bricks and does not seem damp at all. The flue is open - no liner of any sort.

section could be added to the wiki eventually ...

inlet be connected to a duct so that it takes air from below the floor (which has air bricks !) thus avoiding need for an exterior vent in the actual room ?

youi d9onmt need anything more than the underfloor vents to meet COMBUSTION requirements. You may still need trickle vents to comply with ORDINARY ventilation as the regs say the air has to be from above a certain level

insulated etc) ? What size ? (for say, 8 kW stove)

Yes. If the house is pre 1970 (IIRC) a flexible l;nert may be allowable, otherwise duble layer insulated stainless sectioned liner. This is the most expensive bit. In any case its advisable to prevent soot build up - the flue inner heats quickly and doesn't soot uop nearly as fast.

flue only half brick. Is it OK for the stove to stick out proud of the non-combustible fireplace opening (possibly further than the fire surround also) ?

yes, but a non combustible hearth must be provided. There are minimum dimesnions in te regs. Look them up.

mantel be ?

I would advise ar least 9". the stove itself can, under exceptional circumstances reach 200C plus. Under fault it may even go to red heat, if its not got a water jacket and back boiler. needless to say you would not normally run it like that, but if you do put very dry thin wood like crates on... I have seen stoves and pipes a dull red..

(presumably held in with a register plate) ?

Not if its a double insulated flue: but for a flexible liner, yes you should, and thats the problem. Pouring the insulant down from the to doesn't locatete flue centrally,necessarily.,

celotex covered with some type of cement fire board be OK for regs ?

Don't bother with the celotex. its not fireproof anyway- it will charr. One or two layer of cement fire board will be all you need. Ive used thata s a protecting plate for puimbing /blowlamp work. Its amazingly effective stuff. But if it's blockwork id simply render it..

than the stove does the opening need to be ?

Wide enough to stack logs each side :-)

if the ventilation is adequate yes. But we never do .,..

Reply to
The Natural Philosopher

I found a few on the internet. Not sure if that is compatible with the air wash design that I believe keeps the glass clean. Also I was hoping to get a clean burn stove so I can burn logs in a smokeless zone. The bloke up the road gets away with it but the maximum fine is 1000 quid.

It says BAXI PATENT FIRE on that ties up. Fair enough to a vent that is close enough to avoid draughts in the room

Thats interesting - is the flue exiting out of the rear ? I didn't realise that could be done. I was expecting to need a dog leg flue to take the flue close enough to the back wall.

Our first child is due in October ! A very good fire guard will be vital.

How do you do that ? Some type of brush up the flue ?

If the flue gasses are cooler, stuff is more likely to condense in the flue so having the flue insulated might be a good idea. But who doesn't want a crackling log now and then ?

Thanks, Simon.

Reply to
sm_jamieson

neath the grate with vents in it that are supplied with air from the underf loor void by a tube under the hearth. The fireplace and flue depth is 9 inc hes and the back of the flue is only a half brick thick, but is made of blu e engineering bricks and does not seem damp at all. The flue is open - no l iner of any sort.

a section could be added to the wiki eventually ...

the inlet be connected to a duct so that it takes air from below the floor (which has air bricks !) thus avoiding need for an exterior vent in the act ual room ?

wall / insulated etc) ? What size ? (for say, 8 kW stove)

A flexible liner and insulation poured down the chimney might be cheaper ? A suppose the flexi is ribbed which would trap tar, etc.

rear of flue only half brick. Is it OK for the stove to stick out proud of the non-combustible fireplace opening (possibly further than the fire surro und also) ?

und and mantel be ?

erial (presumably held in with a register plate) ?

Noted about the flue not centralising.

way. Is celotex covered with some type of cement fire board be OK for regs ?

Its brickwork. The celotex was about insulating the wall since its only hal f brick at the back of the builder opening / flue. Without any it would be a very obvious cold bridge.

ider than the stove does the opening need to be ?

I guess I'll take it back to the builders opening and see what I've got.

Thanks again ! Simon.

Reply to
sm_jamieson

/ insulated etc) ? What size ? (for say, 8 kW stove)

common misconception, in practice the cost of a flexible liner is not that much

- a few hundred quid (in parts).

IOW the smaller cross section of the liner keep gases moving fast enough to get them out the chimney before the "tarry nasties" condense on the (warmer than std flue anyway) inner liner walls...

of flue only half brick. Is it OK for the stove to stick out proud of the non-combustible fireplace opening (possibly further than the fire surround also) ?

it will warm the room quicker if it projects (out from the chimney breast say). Think of it as a solid fuel powered convector heater (with secondary radiation)

Least optimal is a stove "tucked away" in a cramped hearth "where the fire used to be" - they need circulation air/space to work at their best.

(presumably held in with a register plate) ?

agreed, the cost is trivial compared to the access issues (tower scaffold, cherry picker, wobbly ladder)

eh ??

p?

but that's hardly critical is it?

than the stove does the opening need to be ?

but not so tight that the convection airflow is stifled. If it projects into the room then that's probly "n/a" anyway?

what? define "adequate"?

Jim K

Reply to
Jim K

wall / insulated etc) ? What size ? (for say, 8 kW stove)

much - a few hundred quid (in parts).

Presumably something like this would be fine:

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get them out the chimney before the "tarry nasties" condense on the (warmer than std flue anyway) inner liner walls...

(rear of flue only half brick. Is it OK for the stove to stick out proud of the non-combustible fireplace opening (possibly further than the fire surround also) ?

say). Think of it as a solid fuel powered convector heater (with secondary radiation)

used to be" - they need circulation air/space to work at their best.

material (presumably held in with a register plate) ?

cherry picker, wobbly ladder)

Surely a couple of guys on roof ladders ? They don't use scaffolding or a cherry picker to fit a new TV aerial.

wider than the stove does the opening need to be ?

the room then that's probly "n/a" anyway?

Must be able to calculate it. What about a CO sensor rigged up to a motorized vent / window ? So that if you fall asleep with the door open its not fatal ! 'Twould be a nice DIY project.

Simon.

Reply to
sm_jamieson

cherry picker, wobbly ladder)

rather them than me especially if its a gable end stack...

erm... 10m of flue liner is a *little* more awkward than a 2kg TV aerial ...

Jim K

Reply to
Jim K

And a bit more delicate. It's quite easy to kink as you feed it up the side of the building and over down into the chimney. If it does kink the chances are the stresses on the join between the strips will pull them apart, back into strip.

Ask the chap who installed our liner, twice... Well two tries, the first wasn't very succesfull. B-)

Reply to
Dave Liquorice

There are room sealed stoves or ones with ducted air but they aren't "the norm".

Fairly sure most stoves can top or rear exit.

That was the plan for that stove but there wasn't enough clearance on the rear corner of that big stone lintel (it's 6" thick) to get the dog leg in. TBH with the amount of crap that builds up in the bottom of the flue I'm glad it has the bottom of the T on the rear of the stove to collect in.

Life will never be the same... A fire guard to keep 'em away or falling against it but let them learn, under guidance, what "hot don't touch" means. By that I don't mean letting them touch and get burnt but to get close and feel the heat.

Sorry unclear description, bottom of the flue in the T piece mentioned above. It falls down from above and collects. We do get the whole flue swept at the start of the season but not much comes down.

Crackling logs, tend to spit and/or explode, sending glowing red hot embers considerable distance... You'll see that the building regs have a larger distance for the hearth in front of a stove than at the sides or rear. And burn marks in the carpet in front of any stove that has been in use for a couple of year, even without leaving the doors open.

Reply to
Dave Liquorice

I guess you won't find that nice stone opening we did. That was hidden behind this hideous monstrosity:

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This range style fire place:

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Was completely hidden behind a plain flat platerboard/stud lining. Note the other fire opening above it at 1st floor level.

Oh I forgot to mention earlier 8 kW is quite a large stove unless you have a large room to go with it or it has a boiler.

Have you done a rough heatloss calculation for the room? If it's a normal sort of lounge size 8 kW is probably twice the amount of heat required and you can't turn stoves up and down quickly like a gas or electric fire. Our stove is 10 kW but it has a boiler and the split is 7 kW to water and 3 kW to room. The room becomes very toasty even with the door left open. Heat loss calcs said about 3 kW required.

Reply to
Dave Liquorice

/ insulated etc) ? What size ? (for say, 8 kW stove)

much - a few hundred quid (in parts).

what about *double layer insulated stainless sectioned liner. This is the most expensive bit.* applies in anyway to a cheap flexible liner??

centrally,necessarily.,

Well yes actually it is, as our local fireman said when he attended the last chimney fire in a wood stove and flexible liner equipped house "liner was touching the brickwork, mortar we think had gone, dust and trash in the roof space in the crack caught fire, timbers nearby caught, and up she went'

I was the fire officer at one of my companies and spent several hours talking to firemen about things that cause fires. My sister in laws house burnt down. I am friends with the local volunteer fireman. I neither take these things lightly nor for granted.

I regard a flexible liner in an old chimney with suspect mortar joints as frankly dangerous. Maybe only one in a thousand will catch fire, but the loss of your entire property which is never fully covered by insurance in terms of irreplaceable mementoes and the like is something I think spending a grand for a proper flue is worth doing to prevent.

And FFS get a proper newsreader that doesn't inject 4 carriage returns for every line you type or quote.

Reply to
The Natural Philosopher

10KW heats my entire 6 bedroom house.

But it takes a LONG time. Rate of rise in the sitting room with an open fire pushing out about 10KW above the central heating is around 1 degree C per hour..

..but the kitchen with a 600W AGA in it almost never needs CH at all.

the bedroom with an 8KW IIRC wood stove is better, as there is not much masonry in it - mostly timber framed apart from the chimney stack - and there isn't a big concrete floor either.

we probably damp that down to about 2KW and that gets the room warm by about 5C in an hour. The stove and chimney area are often still warm in the morning when we wake up, and sometimes enough embers to get going again are still there as well.

Reply to
The Natural Philosopher

wall / insulated etc) ? What size ? (for say, 8 kW stove)

much - a few hundred quid (in parts).

your full stop groups both kinds together.

centrally,necessarily.,

"we think"..... if it was *that* critical & *that* common a problem you'd think it would have made it into the Bldg Regs in the last 40 years? everything else has....

tea boy too?

that's sad. And the cause was thought to be............??

then again you do live in a house made 99% of sticks....

yet it is an approved method in the Bldg Regs...

and how would you retrofit a "proper flue" into an old chimney then??

Jim K

Reply to
Jim K

Oh I've probably overspec'd by miles then, since this is not a primary source of heating. I'd just make sure the radiator TRV is working !

Simon.

Reply to
sm_jamieson

"How do you do that ? Some type of brush up the flue ? ".

If it can be arranged, and you are using a back, rather than top, exit from the stove, do a soot trap at the bottom of the flu that leads to an external trap for soot removal. Rob

Reply to
robgraham

Have a look at the Clearview range. Airwash, clean burn and under floor air duct.

You still get black glass if you shut them down completely overnight.

I think you need 12" of non combustible hearth in front of the fire opening.

Building Control can sign off a d-i-y installation.

I would insulate the flue unless you can use the twin wall that Harry mentioned.

Our 12kW version uses a garden barrow full of wood in 24 hours so don't expect to save money over gas CH.

Reply to
Tim Lamb

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