FRP Tank Manufacturers

I am aware that what are called “condensing furnaces” (liquid fuels such as LP or oil) which are very high efficiency (94-96%) suffer from problems of condensation in the flue system that tend to force builders to resort to stainless steel for those components.

Due to this issue of condensation I will probably add a few things to my design such as a small incline of the flue pipe (about 1/4″ per foot) to a drain plug to allow drainage. If the flue gasses get below 100 C then condensation will start to occure.

One of the things that may be eating the aluminum is Sodium/Potatssium Hydroxide (lye) from the ash of the burn. Hydroxides will react with aluminum and generate hydrogen. Eats the alunimum right up quick. Acids generally do not effect aluminum much at all, since this promotes the development of a protective coat of oxide (the basis of “anodizing” is reacting aluminum with a weak nitric acid solution with a current passed though the alumium item to the other electrod in the bath).

Also, with regard to increasing thermal mass in a hydronic storage unit, adding medium sized, rounded pebbles will double or triple the mass without increasing volumn. The water is then acting as a heat exchange fluid and the pebbles (which are 5-7x more thermal mass per volumn) act as the mass.

That’s what I have to add.

Don’t underestimate the insulation around the internal heat riser in my design. It’s a ceramic fibre blanket which has 4-5 times the R-value per inch compared to fire brick that is more commonly used in rocket mass heater installations. So the 1″ of insulation in my design is thermally equivalent to 4-5″ of fire brick. You may be right that if the space around the chimney were smaller, it might develop a stronger draft, and the exhaust might give up more heat to the stove, but my main source of draft is the chimney of the fireplace next to the rocket stove, and the exhaust is plenty cool.

Good luck in your design.

I also noticed in your picture that you have minimal insulation around the heat riser. This allows a much larger space inside of the containment barrel. In most rocket stove instructions I’ve seen, this space is kept to a minimum so that more heat is transmitted through the containment barrel and further speeds up the flame going into the heat riser.

All of that said-I have been doodling out designs of this nature for a while and was really pleased to see someone else working in the same direction. I am inspired to go outside and cut up the water heater I have been saving for this very purpose. I think that one of my variations will be to put a flange on the burn tube so that I can bolt it to the containment barrel as it will make experimenting or changing out the guts much easier. Thanks for you posting, I just stumbled across it a little while ago and am looking forward to reading through more of the posts. Jim

I am planning on heating a small space and have no interest in any thermal mass. Also, it’s a fairly small space so I don’t really think I need anything like a water heater or 55 gallon drum, those may be to large. Looking around, it seems that a 30 gallon drum may be just the size I am needing. I am planning on 4″ square tube for the ‘J’ and 4″ round tube for the exhaust. With that being said, here are my questions:

1) How long should the feed tube be? You mentioned you are able to feed a 6″ 2×4 with no problems so I figure it should be at least 6″ but, is there an ideal length?

2) How long is the horizontal tube, from the feed tube to the interior exhaust tube. I have not been able to find any information regarding that.

3) How critical, if at all, is the exhaust port placement? Looking at your pictures it looks like you have it near the bottom, a little ways off to the side. Based on what I have read so far, it seems that higher would be bad, but does it matter where on the bottom it goes?

For anyone that cares, I am hoping to find a 30 gallon drum with a lever lock lid thing (I don’t know the real name, I hope you can understand what I am talking about). If I do find one, I will turn it upside down so when it is time to clean out the inside all I have to do is open the ‘lid’ and any crap will fall out. I am also hoping to add a sliding cover to the open end of the feed tube so I can ‘tune’ the burn.

I think that covers it. Thank you for the information and your time.

I also started thinking about the possibility of a rocket stove where the flame in the burn tube came from
propane or natural gas instead of wood. Wonder if you could get the side ways burn and proper draft and still capture the efficient radient heat from a small gas flame?

Your results may vary from mine as you have a larger combustion chamber.

If u could help me with these questions I would be grateful.
1. Do you need the extended length of dryer duct or is that just for more radient heat output?
2. I plan to paint barrel with high temp black paint. It looks like you did the same on your water heater.
My barrel is painted I assume I will need to remove the old paint before applying the high temp paint?
3. How did you build and insulate your chimney? I was going to use 4″ stove pipe (inner wall), vermiculte/clay insulation fill and 8″ furnace ducting (outer wall) Do you think that will work to trap enough heat in the chimney for the re-burn.
4. Is it necessary to insulate around the horizontal steel burn tube? It looks like you did not do that.
5. Since your stove is close to the wall I was wondering is the pink material at the end of your fireplace a regular wall or insulation material?
6. My stove will not be close to a wall, but 6 inches of the bottom will extend over the brick and I plan to build legs on the barrel and get it about 12 inches from the laminate floor. Will that be too close to the floor?

thanks for your help.

But I wonder if the “mass bench unit” could not be used in conjunction with a normal say gas or oil furnace or boiler chimney pipe connection to increase the effeciency. by say adding a blower type exhaust heat exchanger to blow the hot air through a thermal mass type bench set up say in a basement.

Or even some type of coiled copper pipe for thermal heat storage kind of like an indirect tank only it the heat is stored in the thermal mass instead of a water tank!

Anyway very good article young man! Good to see something different and in a different point of view!

@ terry,
I think you would do fine with 4″ to 6″ intake. Other than the combustion chamber, the body of the stove will be cooler than most wood stoves. However, I still recommend lots of space between the stove and anything flammable, especially if you will leave the stove unattended.

My question is how often do you have to add fuel to the system? I am wondering how incovenient it would be to have to trek outside in winter, not that we have tough winters in Buffalo NY mind you!