Thoughts on HX movement/modification ...

[Pat53]

I've included a drawing of a Seton/GW side view showing how the HX is positioned inside the unit. Anyone who has to clean these beasts know how hard it is to get at the water tubes without taking the side and perhaps top panels off. Then you have to worry about ripping the Kaowool all to hell in the process. When I first took mine apart last year, I found the outer row of tubes in the back (vertical section) was essentially glued to the Kaowool with creosote and gunk. One of the reasons why was that there was very little room between the outside row of water tubes and the Kaowool itself. So it was easy for that small space to begin to fill in and shut off any air flow to the outside of that row of tubes, which of course means little if any heat transfer.

When I put the back panel back on, I did not replace the 2" mineral wool layer, but just added an extra 1" layer of kaowool. So instead of 3" total insulation (2" mineral wool and 1" kaowool) I just had 2" of kaowool, leaving me an additional inch of air space between the water tubes and the insulation and hopefully no clogging up and better heat transfer.

But now when I look at this HX, would it not work better if it was moved closer to the firebox? If you lowered AND moved forward the HX, would it not work more efficiently? When you look inside the unit during a burn, you see the flame path go up and then quickly over the back of the refractory and down to the stack outlet. But the HX sits very high in the firebox and also far back from the back of the refractory on the vertical section of tubes. It seems to me that if the water tubes were closer to the actual flame path it would be much more efficient?

Currently there is only about 1/2"-3/4" of room between the top/outside row of water tubes and the insulation. I would think if the HX was lowered by about 2" and moved forward about the same 2", much more of the HX would be in the flame/exhaust path.

Any thoughts on this? I plan on pulling the HX out of my unit this spring to examine it and I could modify it at that time.

thx, Pat

 

[mole]

I've included a drawing of a Seton/GW side view showing how the HX is positioned inside the unit. Anyone who has to clean these beasts know how hard it is to get at the water tubes without taking the side and perhaps top panels off. Then you have to worry about ripping the Kaowool all to hell in the process. When I first took mine apart last year, I found the outer row of tubes in the back (vertical section) was essentially glued to the Kaowool with creosote and gunk. One of the reasons why was that there was very little room between the outside row of water tubes and the Kaowool itself. So it was easy for that small space to begin to fill in and shut off any air flow to the outside of that row of tubes, which of course means little if any heat transfer.

When I put the back panel back on, I did not replace the 2" mineral wool layer, but just added an extra 1" layer of kaowool. So instead of 3" total insulation (2" mineral wool and 1" kaowool) I just had 2" of kaowool, leaving me an additional inch of air space between the water tubes and the insulation and hopefully no clogging up and better heat transfer.

But now when I look at this HX, would it not work better if it was moved closer to the firebox? If you lowered AND moved forward the HX, would it not work more efficiently? When you look inside the unit during a burn, you see the flame path go up and then quickly over the back of the refractory and down to the stack outlet. But the HX sits very high in the firebox and also far back from the back of the refractory on the vertical section of tubes. It seems to me that if the water tubes were closer to the actual flame path it would be much more efficient?

Currently there is only about 1/2"-3/4" of room between the top/outside row of water tubes and the insulation. I would think if the HX was lowered by about 2" and moved forward about the same 2", much more of the HX would be in the flame/exhaust path.

Any thoughts on this? I plan on pulling the HX out of my unit this spring to examine it and I could modify it at that time.

thx, Pat

Pat,
That's an interesting idea. The flames do seem to "short cut" over the wall beneath the tubes. In case you're curious, the typical temperature at the top of the wall (measured 1" out into the fire side) is about 1000degF with a 400-450F exhaust temp. I've measured as high as 1480F with about 550F stack temp with a rip roaring fire.

I always have stray pieces of kaowool falling onto the tubes from overhead. It must be messing up the air flow above the tubes somewhat since the gap is so small. It would be nice to lower the Hx enough to be able to clean the tubes without disturbing it (or raise the insulation). I don't have any issues with the back cover though. I take the back cover off about once a month to dust the tubes. No buildup. I don't have any piping behind the boiler (besides the return pipe), so I can do the whole job in 2-2 1/2 hours. If you end up modifying it please let us know how it works out!
JR






I'm not concerned enough to actually do something about it though. If you try something, please let us knnow how it works!

 

[Pat53]

Hi Mole, when you say the "top of the wall", do you mean the top ledge of the back refractory piece?

There is no doubt that the portion of the tubes that is near the "bend" are way out of the exhaust flow. I wonder what the difference in temp "at the top of the wall" and the back corner (bend area) would be? I would bet its substantial.

It just seems to me that by getting those water tubes more directly into the flue gas stream would increase heat transfer significantly? Also, when you look at the square tube manifolds, they each have about 3" of "dead space" on the ends. I wonder if cutting those down closer to the outermost tube would help at all. Probably not a big deal tho.

BTW, how were you able to measure the heat inside your firebox "at the top of the wall"? I'd like to check mine.

thx, Pat

 

[2.beans]

does the flame really do the same thing with the door shut?

 

[Pat53]

does the flame really do the same thing with the door shut?

No, the flame will swirl around more in the firebox with the door open. I would think with the door closed it makes a faster exit out of the firebox?

Pat

 

[sparke]

Cleaning the hex is my only real complaint when it comes to these style boilers. I am looking to make a radical change in Hx design this summer. I mentioned one of my ideas to Jesse, but I have not heard back from him. Basically I am trying to figure/design a hex that is inverted from what we have existing. Another words, make the exhaust travel through pipes like a down draft gasification boiler hex. This way all we would have to do is run a brush through the tubes now and again. No taking the unit apart, no more looking like I just escaped a collapsed coal mine!

 

[sparke]

Oh, my thoughts on lowering the Hx are; I think it is unnecessary. My refractory can be glowing orange and as long as hx is clean the exhaust temps are still only 250-400*. That tells me the Hx is extracting a whole helluva lotta heat : ) I think the only way to extract more heat would be to add more surface area to the Hx...

 

[PassionForFire&Water]

My 5-cents on this is not to touch the heat exchanger.
It is doing it's job to extract the heat out of the flue gasses, under the condition of course that the flue gas path is unobstructed.
To improve your heat to the water you can do something like in the attached self-explaining picture. Much easier as a DIY-project.
This way you will capture much more radiant heat that is otherwise lost, because there is no water jacket.
DO NOT FORGET THE SAFETY ACCESSORIES WHEN YOU DO IT !!

Now, by doing this you will probably bring the firebox temp down, so this can open an other can of worms .... .
You can maybe start with a copper absorber on just 1 side and see what you get.

 

[mole]

Hi Mole, when you say the "top of the wall", do you mean the top ledge of the back refractory piece?

There is no doubt that the portion of the tubes that is near the "bend" are way out of the exhaust flow. I wonder what the difference in temp "at the top of the wall" and the back corner (bend area) would be? I would bet its substantial.

It just seems to me that by getting those water tubes more directly into the flue gas stream would increase heat transfer significantly? Also, when you look at the square tube manifolds, they each have about 3" of "dead space" on the ends. I wonder if cutting those down closer to the outermost tube would help at all. Probably not a big deal tho.

BTW, how were you able to measure the heat inside your firebox "at the top of the wall"? I'd like to check mine.

thx, Pat

Pat,
Yeah, exactly - the ledge of the back refractory piece, with the thermocouple horizontal with the top of the refractory piece, protruding about 1" out over the fire.. About a year ago when I had the back skin off for routine cleaning I added the thermocouple and ran the wire out between the top and bottem back cover pieces. I placed a cheap 1" thick refractory brick over the wire to hold it in place. It was a ceramic thermocouple. Unfortunately I broke it about a month ago, while wiping the ash off of it. It sort of crumbled in my hand. If you can describe specifically where on the bend you want the temperature measurements, I can try to get them. I don't have another ceramic thermcouple but I can probably hook somethin else up that will last for a shorter time. I'm due for a cleaning this weekend anyway. Maybe I can set something up.

mole

 

[Pat53]

Thanks mole, but don't worry about the thermocouples. I'm reasonably sure that positioning the HX more directly into the flue gas path would increase efficiency somewhat. I'm also entertaining building a new HX design that Randy brought up a few weeks ago, which would be a single pipe "snake-like" HX made out of 1 1/4" material using 90 degree U bends. It would probably be about $800 to make based on my preliminary cost estimate... ouch ! In any event I think I'm going to try moving the HX lower and slightly forward just for the hell of it and see what happens for next season. But it sure would be interesting to try the other HX design too ... LOL

Pat

 

[Pat53]

My 5-cents on this is not to touch the heat exchanger.
It is doing it's job to extract the heat out of the flue gasses, under the condition of course that the flue gas path is unobstructed.
To improve your heat to the water you can do something like in the attached self-explaining picture. Much easier as a DIY-project.
This way you will capture much more radiant heat that is otherwise lost, because there is no water jacket.
DO NOT FORGET THE SAFETY ACCESSORIES WHEN YOU DO IT !!

Now, by doing this you will probably bring the firebox temp down, so this can open an other can of worms .... .
You can maybe start with a copper absorber on just 1 side and see what you get.

What is that thing, never seen anything like it?

Pat

 

[bigburner]

snake type HX will require large gpm or it will make steam, unless you can keep the diameter large enough. And if you do it wrong enough you might even get 100 to 1,000 degrees super heat at least at that point you won't need a pump. I remember reading this before and I don't think a mono tube HX is the best choice. surface area is what you are looking for, hard to achieve with a snake. I would almost need to be hydro formed to get the coil tight enough. The thing that's wrong with the steon HX is maybe tube diameter, but also the inlet/out let should be piped out opposite ends of the manifold for equal pressure drop. Other then that I thing the over design is good, off course I would reconfigure the whole cabinet issue, with a flue bypass

 

[Pat53]

snake type HX will require large gpm or it will make steam, unless you can keep the diameter large enough. And if you do it wrong enough you might even get 100 to 1,000 degrees super heat at least at that point you won't need a pump. I remember reading this before and I don't think a mono tube HX is the best choice. surface area is what you are looking for, hard to achieve with a snake. I would almost need to be hydro formed to get the coil tight enough. The thing that's wrong with the steon HX is maybe tube diameter, but also the inlet/out let should be piped out opposite ends of the manifold for equal pressure drop. Other then that I thing the over design is good, off course I would reconfigure the whole cabinet issue, with a flue bypass

BB, this is what I was kinda thinking about. All 1 1/4" black pipe. What do you think?

Pat

 

[PassionForFire&Water]

snake type HX will require large gpm or it will make steam, unless you can keep the diameter large enough. And if you do it wrong enough you might even get 100 to 1,000 degrees super heat at least at that point you won't need a pump. I remember reading this before and I don't think a mono tube HX is the best choice. surface area is what you are looking for, hard to achieve with a snake. I would almost need to be hydro formed to get the coil tight enough. The thing that's wrong with the steon HX is maybe tube diameter, but also the inlet/out let should be piped out opposite ends of the manifold for equal pressure drop. Other then that I thing the over design is good, off course I would reconfigure the whole cabinet issue, with a flue bypass

BB, this is what I was kinda thinking about. All 1 1/4" black pipe. What do you think?

Pat

Hi Pat53,
Just try to understand what you are trying to accomplish?
Your first posting with drawing looks radical different than your last drawing.
Or do you want to add the last drawing (HX) on the inside or outside of your first drawing?

Efficiency wise it will not gain you a lot if you stick with 1.25" steel black pipe on the outside or inside for that matter, because the emmitted radiant heat will miss largely the carbon steel pipe, unless again you build a water jacket. If you want to do it in steel your only option is to build a water jacket around the firebox.
In the boiler industry it is not for nothing that they try to limit the so called jacket loss.

Now, if you would use copper, what is one of the best conductive materials available to human, about 8 times better than carbon steel and 25 times better then stainless steel.
With a copper sheet, you get the large area you need to capture the radiant heat the unit (refractory) is emmiting.
You silver-solder the 3/8" or 1/2" copper tube to the copper sheet. Silver is an even better conductor then copper.
Now the water that is flowing in the copper pipe will get heated by the conduction of the copper.
The water will suck the heat out of the copper tube by means of conduction and the copper tube will suck heat out of the copper sheet.
You creating Delta T's, and that what you need.
No Delta T no heat flow

As long as the water flows tru the tube, you will not form steam.
Even if there is no flow in the copper tube the water will just boil off via your T&P valve set at around 200F, because you dont' have a lot of volume there is no safety issue.
Also, this diameter copper tube can have 400 psi at 400 or 500F
You need to play around with the safety diveices and controls, like for any boiler. I learned a lot on this on this forum.

If the copper would absorb the heat this fast you and me would be "rich men"

What I suggest however for your boiler desing is that you integrate a thin wall stainless steel secundary air ladder that will burn off and clean-up a lot of the unburned combustion gasses before it hits the top heat exchanfer per your first desing. This will probably also solve your problem of your existing HX clogging up.

By introducing only primairy combustion air in the bottom you will consume all the Oxygen in the fire, so above your fire there is no or not enough O2 for a comlete scundary combustion.
Hence a lot of energy goes lost up the stack because of incomplete combustion.

I'm not sure if your design is a natural draft or forced draft system, but I would try to keep the primary air colder (not pre-heated) so that it density is heavier and then this combsution air will react slower and will give the chemical reactions more time to take place. Some tme ago there was a posting on a sec air combustion air ladder configuration.

Hope this explains the physics behind the problem a little bit.

More questions, more answers.

 

[Pat53]

snake type HX will require large gpm or it will make steam, unless you can keep the diameter large enough. And if you do it wrong enough you might even get 100 to 1,000 degrees super heat at least at that point you won't need a pump. I remember reading this before and I don't think a mono tube HX is the best choice. surface area is what you are looking for, hard to achieve with a snake. I would almost need to be hydro formed to get the coil tight enough. The thing that's wrong with the steon HX is maybe tube diameter, but also the inlet/out let should be piped out opposite ends of the manifold for equal pressure drop. Other then that I thing the over design is good, off course I would reconfigure the whole cabinet issue, with a flue bypass

BB, this is what I was kinda thinking about. All 1 1/4" black pipe. What do you think?

Pat

Hi Pat53,
Just try to understand what you are trying to accomplish?
Your first posting with drawing looks radical different than your last drawing.
Or do you want to add the last drawing (HX) on the inside or outside of your first drawing?

Efficiency wise it will not gain you a lot if you stick with 1.25" steel black pipe on the outside or inside for that matter, because the emmitted radiant heat will miss largely the carbon steel pipe, unless again you build a water jacket. If you want to do it in steel your only option is to build a water jacket around the firebox.
In the boiler industry it is not for nothing that they try to limit the so called jacket loss.

Now, if you would use copper, what is one of the best conductive materials available to human, about 8 times better than carbon steel and 25 times better then stainless steel.
With a copper sheet, you get the large area you need to capture the radiant heat the unit (refractory) is emmiting.
You silver-solder the 3/8" or 1/2" copper tube to the copper sheet. Silver is an even better conductor then copper.
Now the water that is flowing in the copper pipe will get heated by the conduction of the copper.
The water will suck the heat out of the copper tube by means of conduction and the copper tube will suck heat out of the copper sheet.
You creating Delta T's, and that what you need.
No Delta T no heat flow

As long as the water flows tru the tube, you will not form steam.
Even if there is no flow in the copper tube the water will just boil off via your T&P valve set at around 200F, because you dont' have a lot of volume there is no safety issue.
Also, this diameter copper tube can have 400 psi at 400 or 500F
You need to play around with the safety diveices and controls, like for any boiler. I learned a lot on this on this forum.

If the copper would absorb the heat this fast you and me would be "rich men"

What I suggest however for your boiler desing is that you integrate a thin wall stainless steel secundary air ladder that will burn off and clean-up a lot of the unburned combustion gasses before it hits the top heat exchanfer per your first desing. This will probably also solve your problem of your existing HX clogging up.

By introducing only primairy combustion air in the bottom you will consume all the Oxygen in the fire, so above your fire there is no or not enough O2 for a comlete scundary combustion.
Hence a lot of energy goes lost up the stack because of incomplete combustion.

I'm not sure if your design is a natural draft or forced draft system, but I would try to keep the primary air colder (not pre-heated) so that it density is heavier and then this combsution air will react slower and will give the chemical reactions more time to take place. Some tme ago there was a posting on a sec air combustion air ladder configuration.

Hope this explains the physics behind the problem a little bit.

More questions, more answers.

Hi Marc, I'm really not all that dissatisfied with my current set-up, but always looking at alternatives to increase efficiency, i.e. heat transfer.
That copper "thing" is interesting. Is that a real device or just some kind of drawing?
How would that copper sheet hold up to an overheat situation? I would imagine it would kind of "melt", would it not? Mole had mentioned that he has had firebox temps of almost 1500F on a really hot burn. Silver melts at 1750F and copper at about 1975F. Not much room for error there?

My HX is actually staying a lot cleaner this year now that I've added storage (hotter burns and less idling), plus using some better seasoned wood this year. My flue gases are not obstructed, but the HX is definitely not in the direct path of those flue gases, just kind of along side them I guess you could say.

As far as trying to modify the unit itself, I won't be doing any of that, way out of my league... LOL The combustion air is preheated for the Seton, it is natural draft that comes in thru SS tubes in the back and passes thru the flue gas exhaust just before it exits the boiler, really no way to change that. According to Fred Seton, the warmer air increases efficiency?

I appreciate your input, that copper plate is interesting.

thx, Pat

 

[PassionForFire&Water]

Hi Marc, I'm really not all that dissatisfied with my current set-up, but always looking at alternatives to increase efficiency, i.e. heat transfer.
That copper "thing" is interesting. Is that a real device or just some kind of drawing?
How would that copper sheet hold up to an overheat situation? I would imagine it would kind of "melt", would it not? Mole had mentioned that he has had firebox temps of almost 1500F on a really hot burn. Silver melts at 1750F and copper at about 1975F. Not much room for error there?

My HX is actually staying a lot cleaner this year now that I've added storage (hotter burns and less idling), plus using some better seasoned wood this year. My flue gases are not obstructed, but the HX is definitely not in the direct path of those flue gases, just kind of along side them I guess you could say.

As far as trying to modify the unit itself, I won't be doing any of that, way out of my league... LOL The combustion air is preheated for the Seton, it is natural draft that comes in thru SS tubes in the back and passes thru the flue gas exhaust just before it exits the boiler, really no way to change that. According to Fred Seton, the warmer air increases efficiency?

I appreciate your input, that copper plate is interesting.

thx, Pat
-----------------------------------------------------------------------------------------

Hi Pat,
i was kind of under the impression that you made this wood boiler your self.
Also your signature says "selfmade" Seton.
So I was thinking that you were trying to figure out some ways to make improvements.
That's why I gave you some input on how I would make improvements to a wood boiler setup like yours.
Sorry, for not getting this right.

The picture I attached is something i came across 6 to 12 months ago on the Internet.
It is definitely something European, most likely German or Scandinavian.
I did some testing myself, but used "cheap" aluminum transfer plates for 1/2" PEX radiant heating.
It works for aluminum, although aluminum has only 60% of the conductivity copper has.

It is similar to solar hot water collectors.
I did put mine on the outside of a prototype wood boiler, left and right side.
My outside metal skin temp of a non-water jacket model was around 385F on full burn, but the unit was insulated at the inside with vermiculite boards
Got around 8,000 BTU/hr per side for an Aluminum/copper tube collector setup.
For copper, My guess is that this would be around 30% to 40% better.

There is another guy in Germany or Austria, Toby Haffner, he put solar hot water type collectors inside masonary heaters.
Check this link, there are some beatifull pictures: http://www.toby.at/toby-hafner-system/kachelofen/index.html
Very interesting stuff, .... thinking outside of box, or inside the firebox in this case.

Your concern about overheating is very true, but this can be solved with the appropriate controls.
We are 2011, controls should not be a big issue any longer.
It's all there, just a matter of putting the right electronics togetter.

 

[Pat53]

Hi Marc, yes, I did build my Seton, but it is the same as what Fred Seton makes. I would think the only place these panels could be safely used would be on the outside of the refractory walls, between there and the insulation. I would think storage would be a must also. I wonder how many "extra" BTU's could be attained with these panels for the same amount of energy used to extract it?

thx, Pat

 

[Pat53]

Another follow-up . When I removed the HX this fall I also modified it a bit. I moved it forward AND down about 1 1/2". The HX is now more directly in the exhaust flow. I had a ripping fire going for over 4 hours and no problems of any kind.

One of the best reasons for modifying the HX will be when it comes to cleaning it. There is now about 2" of air space above the tubes which will make them much easier to clean without ripping the kaowool. And the outside row of tubes on the vertical section are now about 1 1/2" inside the kaowool and will not only be easier to clean, but should be much better at absorbing heat than they were before. they were virtually right up against the insulation in the back. The 4"X4" headers on both ends of the tubes are now fully exposed to air flow and heat. Before the modification, one side of the headers was right up against the kaowool. I also cut off about 1" on the ends of the headers that just seemed to be dead space.

I have to believe that this modification will help somewhat with heat transfer?

Pat

 

[mole]

Another follow-up . When I removed the HX this fall I also modified it a bit. I moved it forward AND down about 1 1/2". The HX is now more directly in the exhaust flow. I had a ripping fire going for over 4 hours and no problems of any kind.

One of the best reasons for modifying the HX will be when it comes to cleaning it. There is now about 2" of air space above the tubes which will make them much easier to clean without ripping the kaowool. And the outside row of tubes on the vertical section are now about 1 1/2" inside the kaowool and will not only be easier to clean, but should be much better at absorbing heat than they were before. they were virtually right up against the insulation in the back. The 4"X4" headers on both ends of the tubes are now fully exposed to air flow and heat. Before the modification, one side of the headers was right up against the kaowool. I also cut off about 1" on the ends of the headers that just seemed to be dead space.

I have to believe that this modification will help somewhat with heat transfer?

Pat

Pat,
Thanks for the update on the modifications. I'm glad it worked out well. Will you have any way to measure how the modifications change efficiency? Congratulations on finding and fixing the pluggage too! That's got to be a big relief!!

 

[Pat53]

Another follow-up . When I removed the HX this fall I also modified it a bit. I moved it forward AND down about 1 1/2". The HX is now more directly in the exhaust flow. I had a ripping fire going for over 4 hours and no problems of any kind.

One of the best reasons for modifying the HX will be when it comes to cleaning it. There is now about 2" of air space above the tubes which will make them much easier to clean without ripping the kaowool. And the outside row of tubes on the vertical section are now about 1 1/2" inside the kaowool and will not only be easier to clean, but should be much better at absorbing heat than they were before. they were virtually right up against the insulation in the back. The 4"X4" headers on both ends of the tubes are now fully exposed to air flow and heat. Before the modification, one side of the headers was right up against the kaowool. I also cut off about 1" on the ends of the headers that just seemed to be dead space.

I have to believe that this modification will help somewhat with heat transfer?

Pat

Pat,
Thanks for the update on the modifications. I'm glad it worked out well. Will you have any way to measure how the modifications change efficiency? Congratulations on finding and fixing the pluggage too! That's got to be a big relief!!

Hi Mole, not really sure, but more than likely yes. I did another burn yesterday and went from 112F to 194F in 3.5 hours in the 500 gallon storage tank. But I have to believe that this modification will absolutely improve efficiency. Every bit of tubing and the 4' X 4" headers are now fully exposed to airflow. I'm getting about a 25F delta T on the medium setting on the circulator and over 30F on the slow seting with a good hot burn going (450-500F stack temp).

And yes, it is a huge relief to not listen to that banging and pounding coming from the HX on a hot fire. Runs smooth and quiet now, like it should. I have no idea why just those 2 tubes were partially plugged, but that must have been what the problem was. The other tubes were basically clear. If I remember correctly, last year it would take about 4 hours to go from about 130F to 195F, but that is also when the house was calling for more heat, right now the demand is small. But even so, I think the modification will prove to have been a good one. It is going to make it much easier to clean the tubes for sure.

Pat

 

[Pat53]

Since I'm about 1/2 way thru the burning season I decided to take the back panel off the Seton and clean the tubes. I was pleasantly surprised to see very little buildup on them. I really believe by lowering and moving forward the HX I'm getting better heat transfer and less buildup on the tubes. The horizontal tubes are much easier to clean now also, and less chance of snagging the kaowool while doing so. Oh, and the kettling problem I used to have has not returned, even with 500F stack temps at times.

Pat

 

[Singed Eyebrows]

Thanks mole, but don't worry about the thermocouples. I'm reasonably sure that positioning the HX more directly into the flue gas path would increase efficiency somewhat. I'm also entertaining building a new HX design that Randy brought up a few weeks ago, which would be a single pipe "snake-like" HX made out of 1 1/4" material using 90 degree U bends. It would probably be about $800 to make based on my preliminary cost estimate... ouch ! In any event I think I'm going to try moving the HX lower and slightly forward just for the hell of it and see what happens for next season. But it sure would be interesting to try the other HX design too ... LOL

Pat

1 1/4" was an off the cuff estimate. You would need to carefully calculate the gpm flowing through the exchanger & the available heat. Steam cleaners have a very long relatively small diameter pipe that is fed by a low gpm piston pump, none of which will be present in your boiler. So opinions that you will have a wood fired steam cleaner are less than accurate, Randy

 

[Singed Eyebrows]

Thanks mole, but don't worry about the thermocouples. I'm reasonably sure that positioning the HX more directly into the flue gas path would increase efficiency somewhat. I'm also entertaining building a new HX design that Randy brought up a few weeks ago, which would be a single pipe "snake-like" HX made out of 1 1/4" material using 90 degree U bends. It would probably be about $800 to make based on my preliminary cost estimate... ouch ! In any event I think I'm going to try moving the HX lower and slightly forward just for the hell of it and see what happens for next season. But it sure would be interesting to try the other HX design too ... LOL

Pat

Pat, The original problem was banging/kettleing in the exchanger. If this is gone I would leave the exchanger alone. The increased efficiency you talk about would probably not be near enough to offset the $800? exchanger cost. I thought you would build it yourself for about 40 bucks. I believe I also mentioned about variable flow through the exchanger as you dont have a constant btu heat source. In order to do a real decent job I think you would need to use a variable speed pump & some kind of controller to run it based on water temp. I would only undertake this as a last resort, if the banging is severe, Randy

 

[Pat53]

Hi Randy, I still have the same HX, I did not build the "snake" one I had mentioned. what I did was to change the position of the existing HX so that it is more in the exhaust stream.

Pat

 

[Singed Eyebrows]

Hi Randy, I still have the same HX, I did not build the "snake" one I had mentioned. what I did was to change the position of the existing HX so that it is more in the exhaust stream.

Pat

Pat, Yes, I understand that. I was just trying to be sure you didn't throw a ton of money at your boiler with very little to gain, if the banging had stopped, Randy