I'm using a conventional 'wrap around' wood stove boiler as a heat exchanger on top of a 5" BB rocket riser to help heat my hot water and provide central heating. The boiler is rated at 45,000 btu/hr and this output, it appears, can be achieved if you keep the firebox well stoked with decent dry hardwood mixed with a little softwood.
The BB also heats a single skin brick bell.
When I get the chance, I'll post details of my build and how the system performs.
If the firebox was left uninsulated the high temperatures needed to help promote clean combustion would be hard to achieve.
Additionally, the firebox (if made from steel) would degrade very quickly under the prolonged exposure to high heat. There are quite a few threads on the forums showing catastrophic failure of metal components in rocket stoves.
Nick Kendall wrote:I am new to this but really like the idea you have using old stove as batch box had anyone else done this? I would like to try this but would insulate the riser as well
Yes. I've used a Charnwood Country 4 as the basis of a BB Rocket.
It's quite heavily modified though... To follow as closely as possible the dimensions on the Batchrocket Resources site, I had to cut off the rear of the stove and extend the depth of the firebox. The whole of the original stove is heavily insulated with insulating firebricks and superwool - there is no metal from the original stove (apart from the cast iron door) that is in contact with the fire. It's a 5" sidewinder system that I use to heat water and a brick bell. It works really well and is into its second winter with only a few issues.
I think your idea should work, but I would put a 'proper' insulated chimney on the exhaust side to ensure you have enough draw for the whole system.
I would also include an area at the base of the chimney exhaust flue where you could light a priming fire to get everything pulling in the right direction, especially when the system hadn't been used for a while.
Travis, I was worried about the flash steam possibilities too. That is why, when my system was piped up by our plumber, I made provision to easily retro fit a pump on the hot water flow from the boiler if needed.
My relatively small boiler has a capacity of only 28 litres or so. In nearly two winters of operation there has been no evidence of flash steam generation or 'kettling' - the simple thermo-syphoning system has worked unassisted.
I have a generator (we're out in the wilds of Wales and we sometimes loose power in stormy weather) but the electrically powered central heating pump only operates on the radiator circuit after the water from the BB has been injected into the hot water system. If the power fails, the thermo syphom from the BB keeps working, circulates hot water and prevents an overheat situation.
There's some interesting comments being posted on here.
Just to re-iterate what I've mentioned before -
I have linked a combined Batch Box rocket mass heater/water into an existing 'conventional' oil fired central heating hydronics system, and it works...
The BB rocket is located inside the house and provides mass heating storage for the room it's located in (and to some extent, adjoining rooms) as well as hot water.
The boiler I use with the BB is rated at 45,000btu/hr.
The boiler is located around 10" above my 5" heat riser and it doesn't flash steam.
The boiler thermo-syphons into the central heating system (via a 'Neutralizer' multiport device) without a pump.
The whole water system side is open vented - in the event of a power failure there is no pressure build up and excess heat is soaked up by a gravity fed 'heat leak' radiator.
Mine is not an ideal system. If I had the finances and the time I would build perhaps an 8" BB Rocket to drive a large boiler that would thermo-syphon via large diameter piping to a 2,000 litre (or larger) highly insulated thermal store. The BB Boiler would be on an independant open vented water coil loop that would only require a small volume of water. The water in the thermal store would store this heat and domestic hot water and the central heating would be fed from this indirectly - that is, these systems would be in their own enclosed pipe loops. The water in the store would just exchange the heat into them. (Tim Barker has done something similar with a domestic hot water/shower rocket)
It's nothing new. A lot of mainland European countries already use this type of arrangement and have done successfully for many years. The difference until now is that most of the existing systems use pellet or wood gassification boilers to heat the stores which are very expensive and relatively complicated. They rely on a lot of electronics, sensors, forced air fans, etc to ensure they function and the combustion is correct.
What I love about the BB Rocket is its simplicity and its ability to keep working in the event of a power outage. It doesn't need sensors, fans or valves - just dry wood and a bit of manual attention now and then. I really think that a BB rocket would be in it's element in this application. The large volume of water in the thermal store is ideal to 'smooth out' the btu output from a BB and store that heat for many hours. Maybe one day...
I'm not really answering your question William, but I'll explain how I've linked my Batch Box rocket water heater to an existing oil fired central heating system (hydronic) over here in the UK.
The BB heats a Clearview wrap around boiler from a normal box stove. It's rated at 45,000btu/hr. I've located the boiler around 10" above and to one side of the 5" heat risers exit. It's a 4 port boiler but only 2 ports are connected (lower left - cold water in, upper right - hot water out) The flow of water is caused by a simple thermo-syphon that then connects to a 'Neutralizer' Neutralizer - a multi-port beast that allows several heat sources to work together without interacting with each other. It therefore allows us to use either the BB, the oil CH boiler or both together. Thankfully I'm really only using the BB for most of the time, but it's handy to have the oil CH backup for when were away from the house.
I have a high limit stat and a low limit stat fitted to the feed and return pipes from the BB boiler and the whole combined system is open vented - ie: unpressurised. I made provision to fit a pump onto the hot feed from the boiler in case the BB boiled the water in the boiler, causing it to flash steam, but we have had no issues like that so far after two winters use. Certainly, in our case a simple thermo-syphon transfers the heat from the BB boiler without using a pump. We have used 1" copper pipes to connect things up.
If you run several batches a day it can provide most of our heating and hot water requirements on all but the coldest of days. Plus of course the heat from the bell and the glass door easily heat the room the BB is located in.
On my J tube rocket in my workshop I use a 5mm thick steel plate as an adjustable 'closure cover' for the feed tube. It's fitted with a heat resistant handle (from an old box stove door) that doesn't get hot.
The plate itself does get quite warm after a while but, as a bonus, it acts like a small radiator and gives off extra heat to the room. It hasn't really degraded or warped yet after several years of use.
Hi Fox - I've studied ppotty's videos for a while and his latest one seems to work well with a proper glass door.
My 6" workshop J-Tube Rocket has a large feed 'area'. I lined the walls with vermiculite board to make a sort of low 'firebox'. It works really well but I have to use a steel blanking plate to cover some of this 'firebox' or else I would get smokeback. The amount of air that I admit to the fire depends on the amount of fuel and state of the burn. It's also handy for closing down the J when the fire has gone out, so retaining the heat in the mass of my brick bell.
An added bonus of this arrangement is that the steel plate acts as a small radiator and gives off a lot of heat. It is fitted with a cool touch handle so it can be adjusted without having to wear gloves.
Hi Linda. It may be worth obtaining a moisture meter. In the UK you can get one for around £20. Split a piece of your fuel and check the level on a freshly exposed section of the wood. Ideally your wood should have a moisture content of 20% or less.
If your wood isn't dry enough, try to get hold of some clean, unpainted and non-treated pallets. Cut them into small sections and make sure they are dry (they should 'ring' when hit together, not 'thud' )
Fire up the beast and once the 'dragon' is up to temperature, if your stove stops smoking your original fuel may well not have been dry enough. If the smoke persists then lets look at some other possible issues.
Jeroen - as a temporary fix for this years winter, you could try dry-stacking masonry bricks (or similar) around the sides of the metal stove to at least give you a certain amount of mass storage for the excess heat coming from the stove.
I've tried that on a couple of our wood 'box' stoves and it does help a little
I would always go for an insulated chimney if you can. As has been mentioned, it factors in a degree of safety in most types of weather conditions. You may well get days where the stove will not be safe to light with an uninsulated flue system.
Over here in the UK, Insulated SS pipe is available at a reasonable price Insulated Flue Systems - I realise it's the 'other side of the pond...' but there's probably an equivalent product available near you or via an on-line supplier.
Staci Kopcha wrote: Oh lordy, though, do we have pallet wood- my husband has a fine collection! Some are broken down, but those I am not sure of Heat treated or chemical treated- is that okay?
Don't use chemically treated pallets. Heat treated ones are OK.
We recently had a delivery of over 70, 10 feet long pallets that were used for transporting roofing sheets - they are heat treated only. I've saved the long lengths of planking for future construction work but the rest are providing lots of great kindling and 'rocket wood'.
The system was commissioned last winter and it works very well. It's an open vented system that is connected to a standard oil fired CH system via a 'neutraliser'. It provides hot water for heating radiators and domestic use.
When I get time I'll post an article on its construction and operation on the forums.
On a few of the steel bodied stoves we have, I've replaced the steel plate 'fireplates' with insulating vermiculite firebricks.
This inevitably reduces the size of the inside of the firebox but the stoves performance is improved immensely. Burns are now much hotter and cleaner.
We used to have insulating firebricks on the base of our ESSE woodfired cookstove firebox but they also supplied you with a steel plate to protect these from abrasion from the logs. All other woodstoves we've ever owned relied on a bed of wood ash on the floor of the firebox to act as insulation and protection.
It depends a lot on your particular set-up, but as a rule of thumb it is usually preferable to have as few bends as possible in your flue pipe. If you have to have them, the 15 degree would be better than the 30 degree option.
Jesse Baker wrote: I know a source of 2” soapstone slabs if I can get them I’ll build my bell bench/raised bed from stacked soapstone so it won’t take long to dry.
I'm very envious of you Jesse... Soapstone is a fabulous storer of heat. I obtained some chunky blocks of it several years ago and used to place them on the top of our box stoves to act as thermal storage. They worked very well, still being warm many hours after the fire in the stoves had gone out.
Over here in Wales (UK) I've lit my Batch Box water/mass heater and my workshop 'J' tube several times already. We live in an old stone farmhouse that feels cold when the air is damp and we've had some very chilly evenings recently.
I've had to warm the chimney on my BB with a small pre-fire at the chimney base. I tried a fire one evening when there was no wind but heavy rain and the BB stalled and filled the room with smoke...! Once the draught was established it worked fine
I've used the 'shell' of a Charnwood Country 4 woodstove as the basis for my own 5" Batch Box rocket Mass/Water heater and it works very well. I basically cut off the rear of the stove body and extended and lined the firebox to match the dimensions on Peters excellent resource site.
I posted some details when requested advice on heating water with the unit.
I'm interested to hear if anyone has any comparisons regarding particulate emissions of a 'standard' wood stove and a batch box or 'J' tube rocket. We have a mixture of these in our property and I'm hoping the rockets are performing better on all fronts