Underfloor heating, any plumbers?

[yorkie_chris]

We've got a stove which we burn coal and logs (and anything else that's free and flammable). It came with a boiler in the top of it which we intended to integrate into the proper central heating (condensing type combi boiler fed), but that looks like it's going to be a major pain in the rse. So that idea has been put on the back burner for the moment.

So, plan B. A seperate underfloor heating system just for the one room and part of the kitchen just to use the boiler and extract some of the waste heat from the flue gas.

I've got a reasonable grasp of thermodynamics, and have a fair idea of how to do it, but how would you do it?


P.S the stove has been in ages, but we removed the boiler part to avoid it burning through. It is a simple box welded up out of 1/8" plate 13" x 8" x 2" with a pipe spigot at the rear corners and a 1" hole through the middle of it. Can anyone guess at a rough heat output? And general idea of complexity and cost if we were to go with the original idea of fitting this into the main central heating circuit.

Cheers folks

[skeetly]

whats the floor of the kitchen and the room made of?
I'm guessing its a wooden floor as it'd be expensive to dig up a solid floor to put a pipe loop in and you dont like expensive.
You need a pump to drive the water round as you the stove will be higher than the floor.
If its a wooden floor you wont have a solid mass to heat up (and hold the heat) so you wont get much hot air convection from the pipe (which is what radiators do best despite their name). Easiest and cheapest way with a stove is an extra rad somewhere but it would have to be on a seperate 'open' system away from the existing 'closed' pressurised system (unless you want to pay for certificates etc etc)
A boiler will soak up some heat from the stove.
Leave doors open and let heat from stove work its way round house and put thermostatic valves on the existing rads. They will close sooner if the stove helps heat up the rooms.
Its what we do with out log burner.

IF you really are planning on digging up the floor then things are different :)

[yorkie_chris]

There is easy access underneath the sitting room and part of the kitchen, we were considering putting pipes under the wood in between the joists then putting some of that thin foil backed foam in between the joists, and also sealing up some of the numerous drafts.

[skeetly]

I've mucked about a lot with underfloor heating and it works best when you can dribble heat into something big that will soak it up and release it slowly at not much watts but over a large area. Upshot of this requirement is that its most efficient with a gas boiler (as you can modulate the firey bit easier) that is left on all the time to keep the thermal mass topped up.
Pipes under the floor just radiate the heat. This doesnt work so well as the bloody things are round albeit long :)
Wooden floors are good insulators so you wll end up with nice warm pockets between your floor joists.
Draughtproofing and insulating the floor alone would probably make a huge difference.
My moneys on kill the draughts, fit thermostatic valves to the rads (if they aren't there already) and let the mighty stove heat the air in the room when you are running it and the valves will close off the rads and the c/h boiler will use less fuel.
I'll bet it will be a more efficient use of your wood/coal/tyres/lost southerners.
:)

edit: I know this works as I have done it in our built in 1801 stone cottage.......

[yorkie_chris]

You make a fine point.

My second idea is a heat exchanger above the stove. As it stands (I think because we have no top plate, as we removed the boiler) the stove is very inefficient. Loads of draught, the stove roars like a jet engine with the draughts open and door closed, but little heat into the room. And will not drop down to a slow "simmer" to stay lit overnight.
I think it's just a poorly sealed stove coupled with a long, well insulated chimney causing this, so what about an air-air heat exchanger above the stove. There's a huge dead space above the stove in the chimney and I could weld something up in 316L stainless to suit and blow the hot air into the room.

[yorkie_chris]

N.B The reason for this sudden move to efficiency, we recently had to actually PAY for coal! And that's not a good state of affairs.

[skeetly]

Bet it would have to be pretty thick not to warp. I can see it glowing now :D

If the air cant move upwards because of a narrowed flue then its going to move faster; cue jet engine effect x 10.
Your exchanger would need to get rid of heat pretty quick :)
Normally you would control the burning rate by reducing the avilable air but thats not an option unless you seal the stove.
You could of course control it by adding small amounts of fuel often but thats a pain.

Being as you can do things metally; how about a new baffle plate inside the stove where the boiler used to live and seal the stove properly?
You can control them lovely when they are sealed.

I have a story to tell here. Many years ago i bought a Much Wenlock stove with a back boiler on it. It sat filling the inglenook for years as I could never find the time to connect the bloody thing. When I got round to it I found there was so much work involved sealing the thing, removing the back boiler (was full of dry sand from the previous owner but there were too many tales of exploding boilers). making a back plate to replace the boiler, cutting and fittign a baffle plate etc. that I just went out and bought a brand new 5kw little wenlock stove.

http://www.firesonline.co.uk/acatalog/Aga_Little_Wenlock_Multi-fuel_Stove.html#aagalw

The heat is insane from it. At full tilt we have to open every door in the house as its so hot. So I run it at half speed when its cold and it tops up the c/h.
I have killed *all* the draughts and dry lined the external stone walls though; this made a huge difference.

I love stoves :)

[skeetly]

N.B The reason for this sudden move to efficiency, we recently had to actually PAY for coal! And that's not a good state of affairs.

Considering it sounds like you have a nice flue alreay in there I'd buy a new stove tbh.
Get a good one though.

That page i sent you the link form is run by our local stove emporium and they *really* know their stuff. I doubt they have any rubbish stoves in their inventory.

http://www.homeandheating.co.uk

[DarrenSV650S]

I love the heat you get from real fires. It's awesome

Sorry, nothing helpful here, just wanted to add that :)

[yorkie_chris]

Yes for temporary fix I have my mate cutting me a decent slab of steel to replace the boiler.

New stove is not an option!

[thefallenangel]

isn't there an underfloor heating kit you could buy?

I'm just firing one in here as i imagine it would be a pretty standard kit, you would just need to say the type of flooring and size of floor.

http://www.wickes.co.uk/Heating-Plumbing-+amp-Fires/Under-Tile-Warming/icat/utwundertile

[skeetly]

Yes for temporary fix I have my mate cutting me a decent slab of steel to replace the boiler.

New stove is not an option!


Fire cement it is then :D
Out of curiousity; what breed of stove is it?

[nobby]

You could give Eddie a call at Yorkshire Chimney Specialists at Huddersfield, hes pretty well clued up with solid fuel stoves and the like. Im not sure hes still trading as his web sites dissapeared, his details are here: http://www.build.co.uk/company_216159.htm

[skeetly]

isn't there an underfloor heating kit you could buy?

I'm just firing one in here as i imagine it would be a pretty standard kit, you would just need to say the type of flooring and size of floor.

http://www.wickes.co.uk/Heating-Plumbing-+amp-Fires/Under-Tile-Warming/icat/utwundertile


Hmmm. Perhaps some sort of plated boiler and use the steam to drive a generating set ?

http://www.youtube.com/watch?v=tF-0eOSqKgY&feature=PlayList&p=B383BB6DF351625E&playnext=1&playnext_from=PL&index=53

[yorkie_chris]

isn't there an underfloor heating kit you could buy?

I'm just firing one in here as i imagine it would be a pretty standard kit, you would just need to say the type of flooring and size of floor.

http://www.wickes.co.uk/Heating-Plumbing-+amp-Fires/Under-Tile-Warming/icat/utwundertile

Yeah, seen the kits but they're a fortune because they have more features than we need.

Fire cement it is then :D
Out of curiousity; what breed of stove is it?

No idea!

Parents picked it out, I think it is some cheap import. Can sort pics if you are so interested?

[skeetly]

Can sort pics if you are so interested?

Nah :)
If it had been a 'well known' type there was a slim chance I could have rooted about for some bits though...

[yorkie_chris]

Bet it would have to be pretty thick not to warp. I can see it glowing now :D

If the air cant move upwards because of a narrowed flue then its going to move faster; cue jet engine effect x 10.
Your exchanger would need to get rid of heat pretty quick :)
Normally you would control the burning rate by reducing the avilable air but thats not an option unless you seal the stove.

Well some warping you could live with so long as nothing cracks. But a fair airflow through it should keep it fairly cool.

Got to disagree with you about the narrowing the airflow bit though, surely a turbulent flow will create backpressure and reduce the amount of draught.

Have you seen the butterfly valves you can put in the flue? Ever used one?

[Rich]

So, plan B. A seperate underfloor heating system just for the one room and part of the kitchen just to use the boiler and extract some of the waste heat from the flue gas.

I've got a reasonable grasp of thermodynamics, and have a fair idea of how to do it, but how would you do it?

P.S the stove has been in ages, but we removed the boiler part to avoid it burning through. It is a simple box welded up out of 1/8" plate 13" x 8" x 2" with a pipe spigot at the rear corners and a 1" hole through the middle of it. Can anyone guess at a rough heat output? And general idea of complexity and cost if we were to go with the original idea of fitting this into the main central heating circuit.

Cheers folks

The size of your boiler is approx the same size as ones we fit to the Charnwood LA20i which gives out 2.3KW so at a rough guess i'd say about 2KW at best for yours. It seems an odd way of mounting the boiler above the flames as it has a greater chance of burning through and warping up there. Normally they are surrounding the fire bed or at the back of it.

Personally i'd either hook the boiler up to a seperate cylinder connecting it into the HW, or i'd run the upstairs rads off of it (depending on how many and size). To save cutting the rads upstairs out of the combi system you could buy a few cheap rads and hook them up on seperate sides of the rooms up stairs. That way you have the choice of using the Gas or Solid fuel to heat your rooms.

If you keep the boiler running just the upstairs you'll get away without a pump where as if you try to run anything downstairs you'll need one to get any decent heat.

Some of the suggestions i've made are perhaps best explained with a diagram. So if you want any further info drop me a pm.

Rich

[yorkie_chris]

I understand, cheers.

Does the cylinder perform any function other than as an energy store?

[skeetly]

Well some warping you could live with so long as nothing cracks. But a fair airflow through it should keep it fairly cool.

Got to disagree with you about the narrowing the airflow bit though, surely a turbulent flow will create backpressure and reduce the amount of draught.

Have you seen the butterfly valves you can put in the flue? Ever used one?

I've got a customer's holiday home with one of them dampers. Just finished a fortnights work there too. If you'd asked me last week ii could have tried it out with the doors open.....
With out being able to do the maths (but remembering some bits of physics) I think the available fuel and air is going to add up to quite a bit of airflow. I think you'd need to really strangle the flue (hee hee throttle) to stop it from going mad.
I'd say it was a very fine balance and I predict a lot of mucking about before you get it right :)
I'd love to hear about the progress though......

[yorkie_chris]

The size of your boiler is approx the same size as ones we fit to the Charnwood LA20i which gives out 2.3KW so at a rough guess i'd say about 2KW at best for yours. It seems an odd way of mounting the boiler above the flames as it has a greater chance of burning through and warping up there.

I thought the same when I first saw it, this is why we removed it.
Then again, it's not going to warp or burn if full of water.

[Rich]

I understand, cheers.

Does the cylinder perform any function other than as an energy store?

You would get away without it if you just wanted to run radiators off of it, just make sure you have a decent size header tank to take the expansion and excess heat that it'll kick out.

Oh and i've just realised you've got a combi, you'd have to run seperate HW supplys to the sinks/basins to get it to work so knock that idea on the head. It's do able though and a good use of the heat, but alot of messing about. D'oh

[punyXpress]

I thought the same when I first saw it, this is why we removed it.
Then again, it's not going to warp or burn if full of water.

Only if the water's circulating.
If not, BOOM !
Re price of coal:
Has Missyc jibbed at going down the pit again?

[Rich]

I thought the same when I first saw it, this is why we removed it.
Then again, it's not going to warp or burn if full of water.

I've seen 1/4" steel boilers split from heavy use, mainly down to crap in the system preventing a good flow but it is possible.

Alot of the newer solid fuel boilers have thermostats controling the airflow to the fire therefore controling the fire bed preventing it getting too hot and burning too much fuel. Thats the only problem I can see with yours is its control. If you don't put enough rads on taking heat away from the boiler the system could just end up like one big kettle no good to anyone and a potential danger.

[yorkie_chris]

I would fit a blow-off valve as matter of course anyway if we do use it. The slight problem being I don't know this boiler has been pressure tested so don't know what to set a blowoff valve at!

Pressure buildup on the open system idea wouldn't be too much of an issue as any steam could bubble out of the expansion tank.

[Bluefish]

I would fit a blow-off valve as matter of course anyway if we do use it. The slight problem being I don't know this boiler has been pressure tested so don't know what to set a blowoff valve at!

Pressure buildup on the open system idea wouldn't be too much of an issue as any steam could bubble out of the expansion tank.


just don't use a plastic tank, lol.

[yorkie_chris]

You don't see many of those in the scrapyard :-P

[skeetly]

I would fit a blow-off valve as matter of course anyway if we do use it. The slight problem being I don't know this boiler has been pressure tested so don't know what to set a blowoff valve at!

Pressure buildup on the open system idea wouldn't be too much of an issue as any steam could bubble out of the expansion tank.

Er. You really really dont want it as a pressurised system.
Open has been fine for a long time for this sort of thing :)
If you going to refit the tank just make sure that you have the outlet at the top and the inlet at the bottom. That way the hot water will convect away to be replaced by the cold. You need a rad big enough to be a heat sink but if the tanks is 2kw then choosing a rad size is not hard from the manufacturers specs. if the rad is below the tank you need a pump to drag the hot down into it.
I bet you will have spent not far off the cost of a new stove by the time you're finished though..................

[yorkie_chris]

There was never the intention to pressurise it :-)

There's no way to fit the boiler so convection will circulate water, it fits horizontally over the top of the fire so inlet and outflow are level.


If we were to put flexible tubing under the wooden floor, how much heat does that type of tubing dissipate per length?

[skeetly]

There was never the intention to pressurise it :-)

There's no way to fit the boiler so convection will circulate water, it fits horizontally over the top of the fire so inlet and outflow are level.


You wont need a blow off valve but you will need a pump.


If we were to put flexible tubing under the wooden floor, how much heat does that type of tubing dissipate per length?

No idea. Phone up a a manufacturers tech help line?
Hepworth, speedfit (john guest).

[Luckypants]

Chris, what you describe wanting to do is what I have in my house, although it's been designed in. My stove has a built in boiler (Charnwood CW50B) and is linked into a traditional cylinder / CH system by means of a Dunsley Neutraliser. So I have some understanding how these things work, because I have made improvements over the years and have planned several others. My next house will use a similar system, if I get my way.

The advice so far is good, especially the bit about controlling the fire and the hot water produced. It is imperative that excess heat in the fire's boiler is dumped somewhere AND also that the fire can be controlled to prevent boiling in the boiler, if the boiler has enough steam it will explode VERY badly - my father in law was a plumber and always relates the horror story of one that exploded.

Most of the solutions to adding a stove to a heating system rely on some clever gizmo such as my neutraliser, a Heating Innovations H2 panel, thermal store or other such expensive trickery. These tend to be designed to work with traditional systems, not much use with a combi. My idea would be introduce heated water from your stove on the return to your boiler. This has the effect of reducing the frequency the combi fires to keep the radiators hot, thus saving gas. If you have TRVs on almost every radiator it may be enough to keep the house at a stable temperature once warm. NOTE you must leave at least one rad uncontrolled to act as a heat dump if the fire is burning but all TRVs have closed!

However, I understand that combi boiler radiator systems are pressurised and I'm not sure that any of the solutions to achieve getting the hot water into the return would suitable or safe. I guess you need someone who knows about combi's to answer that.

[skeetly]

When we have done ufh there is usually a 'mixing' manifold that mixes in some of the returning (gone cold) water in with the hot water going into the loop. Theres a thermostat to gauge this. It helps to get th most from the fuel used.
A 'simple pump the hot water round a loop' type system that you envisage might result in the circulating water getting too hot for the plaggy pipe to handle.....
This would be a failure :)

[skeetly]

Dunsley Neutraliser.

He speaks the truth. We just fitted one of these to combine a rayburns output with a giant oil fired boiler for a mansion sized house.

Power is nothing without control.................

[Luckypants]

Well to be honest a nuetraliser is old hat, but when retro fitting it can be slotted in quite easily.

Good point about melting the placky pipe Mark! :D

[skeetly]

Well to be honest a nuetraliser is old hat, but when retro fitting it can be slotted in quite easily.

Good point about melting the placky pipe Mark! :D

As old hat as it may seem it works a treat :)
You can still buy them too.......300 quid.

[Luckypants]

Sorry, didn't mean it didn't work. I have more ambitious plans for my next multi-source heating system is all.

[skeetly]

Sorry, didn't mean it didn't work. I have more ambitious plans for my next multi-source heating system is all.

Do tell! :)

[Luckypants]

Do tell! :)

I think we have hijacked Yorkie's thread enough, PM / MSN me :D

[yorkie_chris]

Hmmm.
SV thermostat housing? Chop a radiator in half and weld it up so it will fit between joists, when the thermostat pops it will heat the radiator not the pipe coils.*

But, with an open system it will never get over 100c anyway (with the tank in the loft I reckon that is a 7m head so only about 68kPa, negligible effect on boiling point). So, depending on what the manufacturer says I think the tubing should be able to handle the max temperature OK.

*My stepdad's a sparky, he says the first use of underfloor heating he saw was a guy bolting a pair of normal radiators underneath the floor!


The problem is, what happens if the pumps switching is delayed, there can be very little convective movement because the stove is above the cooling coils.

I don't think an explosion is possible under steady state, because the system is not sealed. But, a large amount of steam could be generated when the pump is switched on when the stove is hot and has formed a steam bubble in the boiler. This I don't like.

[yorkie_chris]

I think we have hijacked Yorkie's thread enough, PM / MSN me :D

Nah chat away! Engineering geek here :cool:

[yorkie_chris]

A 'simple pump the hot water round a loop' type system that you envisage might result in the circulating water getting too hot for the plaggy pipe to handle.....
This would be a failure :)

True. But I think we will use somewhere around 150m of pipe on 4 or 5 different circuits.

That's quite a lot for the size of boiler from what rich says, in fact, is this even going to put out an appreciable amount of heat? Or am I going to end up with a perfectly engineered, double fail-safed system which will barely warm up its working fluid lol.

[skeetly]

Hmmm.
SV thermostat housing? Chop a radiator in half and weld it up so it will fit between joists, when the thermostat pops it will heat the radiator not the pipe coils.*


Sv rad is designed to have air forced through it so wont work so well...


But, with an open system it will never get over 100c anyway (with the tank in the loft I reckon that is a 7m head so only about 68kPa, negligible effect on boiling point). So, depending on what the manufacturer says I think the tubing should be able to handle the max temperature OK.


A long as the heat dissipates fast enough, it will be a long length of pipe with bends with a poor pump doing its best; might need 2 pumps ;)



*My stepdad's a sparky, he says the first use of underfloor heating he saw was a guy bolting a pair of normal radiators underneath the floor!


Normal Rads do most of their work by convecting so this wouldnt work very well



The problem is, what happens if the pumps switching is delayed, there can be very little convective movement because the stove is above the cooling coils.

I don't think an explosion is possible under steady state, because the system is not sealed. But, a large amount of steam could be generated when the pump is switched on when the stove is hot and has formed a steam bubble in the boiler. This I don't like.

If you put the stat in the right palce and adjust it right the pump will kick in pretty quick. Most boilers should be able to 'kettle' a bit before killing you anyway...
If they arent some cheap chinese impor...oh wait.

[skeetly]

True. But I think we will use somewhere around 150m of pipe on 4 or 5 different circuits.

That's quite a lot for the size of boiler from what rich says, in fact, is this even going to put out an appreciable amount of heat? Or am I going to end up with a perfectly engineered, double fail-safed system which will barely warm up its working fluid lol.

That can happen too :)

[yorkie_chris]

I could hydrostatically test the boiler, but that won't tell me a thing unless I destroy it and make another. But that won't tell me a thing because mine will be made differently 'cos I can't guarantee materials, so I'll have to destroy that and make another!

But, we can put the thermostat right behind the boiler so it will get the temperature quickly.


What I did think of was some fair sized body of water in between the fire and pump. So if a delay caused a temperature "surge" it would be well diluted before reaching anything sensitive.

[yorkie_chris]

Here is the big safety question.

This system is open to the atmosphere via a pipe looped over at the top pointing down into the expansion tank, it's also got a pipe to the bottom of the expansion tank.

What could possibly cause this to go bang short of both of the feeds to the boiler becoming sealed off?

Flash steam if the boiler is allowed to get glowing white then gets cold water dumped into it? Would that go bang or just shoot steam-clean my loft?

[skeetly]

But, we can put the thermostat right behind the boiler so it will get the temperature quickly.




On the boiler would be best ;)

[skeetly]

Here is the big safety question.

This system is open to the atmosphere via a pipe looped over at the top pointing down into the expansion tank, it's also got a pipe to the bottom of the expansion tank.

What could possibly cause this to go bang short of both of the feeds to the boiler becoming sealed off?

Flash steam if the boiler is allowed to get glowing white then gets cold water dumped into it? Would that go bang or just shoot steam-clean my loft?

It should be fine. Sometimes the boiler can 'kettle' (small steam bubbles) if you cant dump heat from the system fast enough. You need to make sure the pipe going back to the header tank is long enough and wide enough so that you dont start getting hot water expanding into the header tank.
There was a fatal accident a while back when this happened with an immersion heater system ffs. Plastic header just got so hot it folded over and dumped gallons of boiling water through the ceiling onto some poor woman while she slept :(

You do have 7m of head though so you should be OK.
It all comes back to controlling the heat source though...

[yorkie_chris]

That is dodgy! But should not be possible with a steel tank.

It is controlling the heat source which is problem. I am looking at design of dunsley yorkshire stove and thinking how basic ours is! Draft control on ours is just a flap on the back of the ash box which does not seal well. I am thinking I may weld this up, and weld a 3" pipe onto it with a ball valve. That way could even duct in cold air from somewhere.

[skeetly]

That is dodgy! But should not be possible with a steel tank.

It is controlling the heat source which is problem. I am looking at design of dunsley yorkshire stove and thinking how basic ours is! Draft control on ours is just a flap on the back of the ash box which does not seal well. I am thinking I may weld this up, and weld a 3" pipe onto it with a ball valve. That way could even duct in cold air from somewhere.

Ours is a 3" metal disc on a thread so you can 'spin' it in and out.
a 1/16th gap to keep the thing over night and 3/8th to have it roaring.
Thats how fine the control is. Tiny leaks make a massive difference

[yorkie_chris]

Is yours tightly sealed enough to actually go out if the vent is closed fully then?

[skeetly]

yup will kill it dead. Seems strange I know when it has a 6" hole in the top but it does work

Get the fire cement out and chase the joints, you might be surprised

[Luckypants]

Ours is a 3" metal disc on a thread so you can 'spin' it in and out.
a 1/16th gap to keep the thing over night and 3/8th to have it roaring.
Thats how fine the control is. Tiny leaks make a massive difference

got to agree with Skeetly there, the air control on mine is thermostatic, but the amount of movement on a 2" disc is 5mm from fully open to fully closed. if not properly sealed the fire never 'slumbers'.

[yorkie_chris]

Ours will not, with the door shut and the draught "fully closed" it still roars like mad.

I don't think the ash box is actually sealed onto the base of the stove. Bloody folks buying cheap shoite.http://alltopmovies.com/wp-content/uploads/2009/08/tim-enchanter-monty-python.jpg "I warned ye!"

[skeetly]

Big leak somewhere then. You should be able to find it if you get it roaring...

[skeetly]

Big leak somewhere then. You should be able to find it if you get it roaring...

Relatively speaking that is, could be quite a small opening or lots of them.........

[Luckypants]

Does the fire 'roar' with only coal on it even with everything closed? If it does then that suggests a leak underneath as coal fires need air from below to burn well.

[yorkie_chris]

Roars with anything on it if you close the door.

I think it is the tray underneath for the ash box as well as the flap at the back which is supposed to close the airflow off.

[Luckypants]

definitely has a leak below. I'll demonstrate on mine the effect of leaving the ash pan door open, it will kettle within a few minutes and I have no doubt there would be explosive steam after 10 or 20 minutes.

You will have to control the rate of burn before fitting a boiler.

[phil24_7]

I have killed *all* the draughts and dry lined the external stone walls though; this made a huge difference.



What dry lining did you use and what steps did you take to remove the draughts?

[skeetly]

What dry lining did you use and what steps did you take to remove the draughts?

Cottage got gutted when I bought it. New wooden windows and doors with proper compressible seals. New floors (gutted I didn't put ufh in them :( )
Originally I left the walls unlined but stone walls have the same insulating value as an inch of polystyrene so Ilined them with insulated plasterboard and it's been much better :) New extension each end helped as well....
You need to make sure that your walls aren't damp and that you have a vapour barrier to stop any moisture withing the house condensing on the walls behind the boards or you will have hassle.
Easy. For a builder....... ;)

[yorkie_chris]

Update, we figured the underfloor thing was going to be a right pain in the rse, so forgot about it.

Finally replaced where the boiler lived in the fire with a chunk of inch plate (f*** me that took some cutting wit oxy-acet!), TIG'd up the ash-box where whatever arfa-jobbin swine had just tacked it up, and got rid of the letterbox-flap, instead rivetted a bit of 1/8" plate to the back of box covering the opening entirely, TIG'd a 1 3/4" elbow to that, bit of pipe and put a disc inside as a butterfly valve.

Works a treat, burnt about half a bucket of coal in last 5 hours and it's warm as toast in ere.