John Harrison

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since Jun 10, 2016
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Recent posts by John Harrison

The brick bell on my 5" RMH gets warm right down to floor level when heated for some time. The top is appreciably hotter but the whole bell is providing useful heat.

I'm sure a 'thin' bell (essentially a hollow wall) would be very effective.
2 months ago
Hi Kelly

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.
2 months ago
I agree with Thomas. A Batch Box with a tight fitting door would be a good solution.

The added bonus is the amount of heat that the glass on a BB door puts out. It quickly warms the space while the main mass of the bell/bench/whatever gets up to temperature.
2 months ago
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.
3 months ago
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...

3 months ago
Is there a reason why you're planning to build the rocket boiler outdoors?
3 months ago
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.
3 months ago
Hi Dan

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.
3 months ago
I used Linseed oil on my Batch Box brick bell and it has worked very well.
3 months ago