Built a 5000 gallon boiler

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allan

Member
Jan 6, 2008
95
EUP of MI
Built another boiler (hydronic heater) with a similar design as the one I built for myself 3 years ago for my brother-in-law. This boiler is twice the size as mine. The tank is 7 foot diameter by 21 feet long. We used about 88 feet of 6-inch pipe and made the wood box 42-inch diameter by 48-inch long. The exhaust is running a bit cold as our exit temp is about 200 degrees F as it enteres the insulated flue thru the wall. At the start of the last pass it is about 280 degrees F. If I built another one, I'd use about 20 feet less pipe in the heat exchanger. we are going to monitor the pipes closely to make sure that we are not doing any damage to the steel from condensation. The boiler is very effecient, almost condensating or possibly condensating. He is heating a 30x80 garage, house, domestin HW, solarium, and attached garage. He is heating his hot water with a 50 plate heat exchanger and has it plumbed as instintanious hot water system. So far the system works great. He fires at about 140 degrees and brings the water temp up to 195 degress with a burn. Each burn consists of loading the firebox twice, one at lighting and then a refill. His wood is about 16-20 inches long and he makes two stakes in the fire box. He fires every third day right now. He is still working on insulating the tank, but has just a bit of the front to complete. He and I worked on building it about a total of 6 days from start to firing. There is about 3.5 days of stick welding and 1 day of mig welding and about 1.5 days of preping the tank. Cost to build was about 8-9K. I didn't take any pictures, I know I know, no pictures and it didn't happen. I will take some next time I'm at his place. At first I was a little disapointed by the cool exhaust temps. On initial finging with 45 degree water, it was condensating so bad that there was a steady stream out the chimney and the exhaust pipes in the lower passes had to be drained several times. If he refires at or above 130 water temp, he does not get any condensation below the exhaust fan.
 
Just an idea, but perhaps you can go back in and line some of the heat exchange piping with rock wool, refractory, or some such insulation.
 
Is there a refractory lined section to get a high temp secondary burn?
 
ewdudley said:
Just an idea, but perhaps you can go back in and line some of the heat exchange piping with rock wool, refractory, or some such insulation.
Do you mean the inside of the pipe? The ouside is in water, so that would be hard to insulate effectively.
 
I would love to have seen start to finish pics, sounds like an awesome boiler, congrats
 
Sounds like some great boilers. How do you determine the size of the firebox and secondary burn chamber? What type of ceramic insulation are you using in the secondary burn chamber?
 
started mine just Friday, water temp near freezing. Ya they sweat a little more then seams possible, mine looked like it was raining between the wet back and lower tubes. If you could sleeve a tube that might help the low exhaust temp issue, play around with velocity. You set a world record for construction.
 
Pat53 said:
I would love to have seen start to finish pics, sounds like an awesome boiler, congrats
yea I know, but I was under the gun to get the project done. Picture taking was not a high priority. I was going to one day, then forgot to get the camera. basically it looks like mine ex a little more pipe and bigger fan box, firebox and reaction chamber.
 
At what water temp are you seeing that 200* exhaust temp?

Regarding the flue gas pouring out of the exhaust; every Garn I have ever cold fired has done that until water temps get above 100-110*. The manual actually recommends having the Garn water at 100* by some form or another........
Condensation like that is a pretty clear indication that you hitting 89-90* efficiency which is cool to think about but can really wreck heat exchanger tubes in a hurry. Gas fired appliances that condense have stainless steel heat exchangers for a reason. Wood fired condensation is worse by far so condensing into mild steel or even boiler tube steel like a Garn should be avoided.

Aside from that...........I want to see that beast!!
I'm going to have to send you a pm if I ever get to the UP with enough time on my hands to take a side trip.
 
heaterman said:
At what water temp are you seeing that 200* exhaust temp?

Regarding the flue gas pouring out of the exhaust; every Garn I have ever cold fired has done that until water temps get above 100-110*. The manual actually recommends having the Garn water at 100* by some form or another........
Condensation like that is a pretty clear indication that you hitting 89-90* efficiency which is cool to think about but can really wreck heat exchanger tubes in a hurry. Gas fired appliances that condense have stainless steel heat exchangers for a reason. Wood fired condensation is worse by far so condensing into mild steel or even boiler tube steel like a Garn should be avoided.

Aside from that...........I want to see that beast!!
I'm going to have to send you a pm if I ever get to the UP with enough time on my hands to take a side trip.

Heaterman you are welcome anytime. This boiler is in Canada so bring your passport. My brother-in-law had a bad accident this year and lost his right arm. but he was right there the whole time welding with his left hand. We did have a welder weld all the pipe and another friend welded up the firebox and secondary reaction chamber.

I'm also concerned about the condensation and we are most certainly going to keep our eye on the last pass. We installed a temp gauge right at the back of the boiler about a foot into the insulated chimney. It likes to live at about 195 degrees F. At the fan box the temps about 260-280 degrees f. I recently installed a temp gauge at the same place in my boiler in the insulated chimney and my temp runs about 275 to 310. The most that I saw was 320 when I had 180 degree water. I like those temps better. If it looks like it is starting to affect the steel, then we will have to shorten a couple of runs. Both boiler steel pipe was made from A53 pipe which is rated for steam. We used 1000's of feet in our steam system at work.
 
Hmmmm..I think you really want to stay above the 250 mark in that last pass for the sake of longevity. That being said, some of it would depend on the amount of excess air, dewpoint and moisture content of the wood.
I gotta say at this point though that you are running a very efficient wood burner that is probably borderline condensing. It would be interesting to throw the Testo on that baby check the dewpoint of the combustion gas to see what is actually going on. Make sure he has dry wood in that thing or he will have trouble at those temps.
 
Anywhere close to the Sault? I would love to see that beast in action sometime!

Great job getting it finished so quickly.

Ryan
 
Medman said:
Anywhere close to the Sault? I would love to see that beast in action sometime!

Great job getting it finished so quickly.

Ryan
Yes, this boiler is near Iron Bridge, ON. Mine is very similar and it is near Sault MI. PM if you want to set something up.

Thanks Allan
 
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