donor oil boiler for pellet conversion?

krusty · Feb 1, 2015

Hi gang

i plan to procure a 3 pass oil boiler when I can find one for a suitable price locally. There are a whole lot of pin types available and are super cheap. What considerations are there in using a pin type over a 3 pass aside from the ability to clean it out? What would the min depth of burn chamber be? I am contemplating starting with a pin type to experiment with. The end result will be an outdoor pellet boiler for my house and small garage enclosed in a small shed/building from the elements.

krusty

flybmw02 · Feb 2, 2015

I think that is a great idea. A nice cast iron heat exchanger with the ability to clean it. keep us posted on your project.

mchasal · Feb 2, 2015

Pellergy has some information in their FAQ: http://www.pellergy.com/faq/ Though they will be specific to their burner, so you should get the depth measurement from which ever one you choose, many items will apply to any conversion.

Q. If I want to convert my existing boiler, what size boiler works best?
A. A 4-section boiler with Minimum of 100,000 btu/hr input rating and a firebox with a minimum of 12 inches of depth that is currently fired on oil or wood work best for our PB-3550 system. Smaller boilers/furnaces that provide a good sized firebox and that can allow for pellet ash buildup may be a good fit for our (smaller) PB-1525 burner system.

In general, pin type heat exchanger boilers are not a good fit for a conversion burner. These boilers do not allow for the collection of fly ash between cleanings and efficiency is poor.

Most triple pass boilers work well with our conversion burners and allow for reasonable levels of ash buildup between required cleanings.

When converting from oil to wood pellets using a Pellergy wood pellet burner, the burners are set up to fire at a maximum 65% of the rated input firing rate of the boiler on oil. Lowering the input firing rate allows for extended run times on the boiler, higher operational efficiency and system efficiency. If heat load is a concern, buffer tanks can be used for surge capacity and provide greater system efficiency.

Most cord wood and other solid fuel boilers (chip, coal, etc) can be fired with a Pellergy conversion burner system.

From that I'm thinking the problem with pin type boilers is that the fly ask collects very quickly on the pins and starts to block the passages. I suppose it would work ok until that happened, but I'm guessing the cleaning frequency required is shorter than what they would consider reasonable. I certainly wouldn't be happy having to brush out the pins every day as it takes some disassembly to get to them.

Keep in mind that the ash is just dumped in the bottom of the combustion chamber, so a door or other easy access to get to that is required.

krusty · Feb 2, 2015

My utopian goal is to build a wood gassification unit that would sit infront of the cast iron heat exchanger and the flue gasses from gassifiaction would then just flow through the cast iron heat exchanger and up and out the chimney.

I will of course keep ppl posted as cheap heat is the ideal for all of us northerners!

The other thing about fly ash and pin type heat exchangers is that I wonder how it would perform with a much shorter chimney as used in an outdoor boiler.

Stay tuned.

krusty · Mar 3, 2015

Well i was able to procure 2 Buderus boilers at a good price. They are 5 section and seem to be in good shape. The seller said there are no leaks and all things being equal I will find out this weekend. Ironically I searched high and low for reasonably priced units. Lots of folks think they are worth big $$ for something 10+ years old. Everyone is switching away from oil to NG so took longer to find something at a decent price. Anyone want to help me lift them out of my truck!?

krusty · Mar 30, 2015

This past weekend it seemed warm enough to spend some time outside working on the boiler project. I thought I had cleaned out the innards of the boiler rather well....filled up the boiler with water and slowly warmed it up. Got up to 200F without issue but man that think spewed black smoke beyond belief. Once it was shut down I opened the door to see a whole bunch more 'oil soot' come loose that was now burning. Gave it yet another cleaning inside and will procure a flue passage brush to better clean those but I think it will need a couple more firings to get the rest of the crud loosened up and out. Otherwise it just may work! Will post a video once I get it all cleaned up and functioning. Plan to work on my auger feed this weekend for it.

Bkins · Apr 4, 2015

Looks like the boiler would be pretty heavy for most trucks although you didn't say what your truck is. Not trying to be weight police it's just that it looks HEAVY, HEAVY.

Keep ousting as I'll keep reading and good luck with getting it up and running.

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