new owb!!

[AIM]

I had to get a hold of a friend of mine that sells concrete admixtures about this. He is well versed in the science and chemistry involved in concrete.
He said that copper will not corrode in straight concrete. By straight concrete he means stone, sand and portland. No fly ash, or other cinder type admixtures that are acidic. Chlorides and other similar admixtures that are and have been very common in concrete mixes will also corrode copper.
In a nutshell. He says that "concrete" will not corrode copper.
"admixtures" is what corrodes copper.

Phase 2 of our conversation.
Any piping that is subject to a high degree of expansion and contraction and is in DIRECT contact with concrete is susceptible to failures due to wear. Concrete is an abrasive material that does not expand and contract like copper will. In time this dissimilar expansion and contraction can literally wear holes in the piping.

Phase 3 of our conversation.
My friend had doubts about the concretes ability to withstand the temperatures that it would be subject to. Even though the piping would have a cooling effect on the concrete there are certainly bound to be "hotspots" that would exceed it's ability. Even the fire resistant gun safes that are lined with crete will be just a crumbly pile after a big fire.
(I wonder if this is why these units are not insulated)

Even with these doubts that my friend had I still think this is a cool idea. I wish the website that the guy has would show more detail on what and how he is making them.

 

[Elim]

Thanks for the info AIM. I am interested in these as well. I am glad there are many minds looking/thinking about this.

 

[tex]

I know that he claims using a "special" aggregate in the concrete to withstand the heat, but I don't know about any of the corrosion or abrasion concerns. That all makes perfect sense that it could happen. For the sake of argument, even if the copper sprung a leak would it really matter? The concrete would keep it contained. Over time I suppose the water would follow along the pipe to where it exits out of the concrete, but that seems like it could be caulked.

This is all very good info from everyone. If I was going to build a similar unit, what do you guys think about wrapping the copper first before the concrete is poured. Something like heat shrink tube would add a layer of protection between the copper and "crete", and allow for expansion/contraction. Just a thought.

 

[Elim]

I know that he claims using a "special" aggregate in the concrete to withstand the heat, but I don't know about any of the corrosion or abrasion concerns. That all makes perfect sense that it could happen. For the sake of argument, even if the copper sprung a leak would it really matter? The concrete would keep it contained. Over time I suppose the water would follow along the pipe to where it exits out of the concrete, but that seems like it could be caulked.

This is all very good info from everyone. If I was going to build a similar unit, what do you guys think about wrapping the copper first before the concrete is poured. Something like heat shrink tube would add a layer of protection between the copper and "crete", and allow for expansion/contraction. Just a thought.

I was thinking about lining it with rubber. Something like tire inner tubes maybe? That would give a little room for expanding, and contracting, and not corrode the copper. I wonder if he would take some recommendations for possibly improving his product?

 

[cassandrasdaddy]

here

http://www.copper.org/applications/plumbing/techcorner/problem_embedding_copper_concrete.html

 

[tex]

Elim,
Give him a call. For all I know, he may already wrap the copper. If not, he should be open to suggestions if he has any smarts.

cassandrasdaddy,
Thanks for the cool link! That settles a lot of questions.

 

[Slick]

Our huge industrial double pass boiler at work has a concrete lined door that is blasted with a flame all day long, it's actually curved to turn the flame and send it on it's second pass, it's some kind of insulating or flame resistant concrete. We had to have it repoured once, we used to turn the boiler off at night which was bad for the heating/cooling reasons, now we leave it on low flame all night. I could see the concrete taking the heat, not sure about the copper not cracking over time though.

 

[AIM]

I was telling a buddy of mine about this. He has been intending to build a boiler for a few years now. he just couldn't decide just how he wanted to design it. It seems he liked this idea enough that it prompted him to do some research.

His design is sort of an offshoot of this concrete boiler.

Metal burn chamber
1/2" copper line wrapped around and around.
Entire unit suspended within a larger metal box and filled with agriculture lime.

His biggest concern was the concrete not holding up to the heat and temperature variables. His first idea was to fill the box with sand but learned that sand is a poor thermal conductor.

His research indicated that lime is a great thermal conductor.

Another thing about the concrete unit that he didn't like is the innability to modify or repair the unit. I guess he's right about that one.... Once it's poured. your done....

With his design. If you ever need to modify or repair something. You simply unbolt the outer box. Clear the lime away and do whatever you need.

 

[Butch(OH)]

Along with the premature steel/weld failures from OWB users, there are just as many who have been using them for 15-20 yrs. It comes down to how you fire them, proper use of the mfr. recommended water treatment chemicals, and the type of water you have. And, anyone can wind up with a lemon, regardless....

I agree and would add that there are those around who can tear up anvils. There are also people with no morals building and selling P.O.S. units. There also seems to be local conditions (water) that cause some more problems than others and an OWB is probably not a good choice. What I realy dont understand is the mind set that allows one to spend 10K or more for heating only to let it rot away inleu of spending $20 and 2 hours once a year to service it and put it to bed for the summer? but what the hey it keeps people that build heaters and the scrap yard guys in jobs I guess

 

[mtfallsmikey]

Well, if a person were going to construct one out of concrete/concrete block,why not constuct the firebox with firebrick/mortar?

 

[WoodchopWood]

"I asked the same question about heat loss. My understanding is that you'll never have snow build up on top of the unit, but due to the ceramic effect of the concrete on the wood burning, you can use a smaller fire for the same amout of heat. That equals less wood at the end of the season. The builder says he just basically smolders the fire all day, and can heat with only one loading per day."

This is crazy talk. There is no efficiency or engineering in this design, it's simply a big concrete fire box. Build a secondary burn chamber and it might begin to make sense. With the pending laws set to discourage smoking outdoor boilers looming large, burning wood efficiently and cleanly has to be the goal of any boiler design or the product will be excluded from use. Might make a great bunker in that case.

 

[Kingsley]

Where is Heiss from? State?
It has my curiosity peaked.
Marty

 

[rex]

Where is Heiss from? State?
It has my curiosity peaked.
Marty

i belive somewere near grand rapids MI.....

http://heissheaters.com/

 

[tex]

He's just North East of Grand Rapids, MI. He was in the process of moving from Cedar Springs to Greenville when I talked to him. I think there are some folks in WI using these if you wanted to check it out Kingsley.

 

[tex]

I've been stewing over this design for awhile now. How about using standard 1" galvanized pipe instead of copper. It seems like it will hold up to a lot more punishment. I know others have built units with standard pipe heat exchangers. Would the galvanized still last 30ish years like it does in your house plumbing before it scales up too bad? Could it be treated not to scale up like the boiler boys do? I'm still considering building something, and am just throwing out ideas. Galvanized would be a lot cheaper than copper also.

 

[fwaid]

As a newbie to this site I was reading this thread and am curious about where to see pictures of this concrete OWB or a website. Anyone know? I've been using a OWB from FreeHeatMachine for two winters now and, although I am saving money from my calculations, I'm disappointed about how much wood I burn. Being in Western NY it does get pretty cold but I'd like to get more efficiency from the OWB. My OWB is 105 ft from the house and I both pre-heat domestic hot water and also heat the house. I do know I have less than 3 degree (F) drop from boiler exit to house. However, I burn over 33 face cord over 7 months, keep the house temp at 60F and it struggles to do that. I'm thinking maybe another, larger, heat exchanger at the indoor oil-fired boiler would solve my immediate temp problem and re-insulating the OWB may increase the efficiency and reduce wood consumption. Any thoughts?

 

[Marc]

Yes, the pipe will erode in time if it is embedded in the concrete without protection. The vintage in-floor radiant systems were done like that, concrete is acidic. Plus, copper expands/contracts.





Does not apply...see previous. At the end of the day, dunno if I'd buy one or not...

Generally speaking concrete is very alkili. It's why rebar in concrete doesn't corrode, the high pH allows for passivation.

 

[tex]

Generally speaking concrete is very alkili. It's why rebar in concrete doesn't corrode, the high pH allows for passivation.

So, with that said, galvanized pipe wouldn't corrode either. Right?

 

[gwiley]

I think that one of the reasons metal pipe in concrete fails is due to the abrasion caused by expanding/contracting on temperature changes. Copper pipe tends to be much thinner and softer and so I would expect it to be more vulnerable.

 

[H-Ranch]

As a newbie to this site I was reading this thread and am curious about where to see pictures of this concrete OWB or a website. Anyone know? I've been using a OWB from FreeHeatMachine for two winters now and, although I am saving money from my calculations, I'm disappointed about how much wood I burn. Being in Western NY it does get pretty cold but I'd like to get more efficiency from the OWB. My OWB is 105 ft from the house and I both pre-heat domestic hot water and also heat the house. I do know I have less than 3 degree (F) drop from boiler exit to house. However, I burn over 33 face cord over 7 months, keep the house temp at 60F and it struggles to do that. I'm thinking maybe another, larger, heat exchanger at the indoor oil-fired boiler would solve my immediate temp problem and re-insulating the OWB may increase the efficiency and reduce wood consumption. Any thoughts?

You might want to start a new thread with some more details about your particular situation - square footage of the house, estimated insulation quality of house, type/size of heat exchanger in the house, type of wood burned, how long wood was seasoned, and any other details that might be important. I think that will give the best chance for getting replies from people with experience similar to yours. Insulation is cheap and is probably worth doing more around it - I don't know any details on your specific model though. I have heard of guys burning more than 11 full cords for sure.