Blower instead of CleanOuts?

[bryan]

Working on my first RMH that is going to go into my yurt. Going with a fairly standard design except that I am going to do a separating wall where the burn chamber is under the 'wall'. So the feed will be outside and the heat riser inside.

The main thing I am not sure of is where cleanouts are required. My vent lines will be all in a bench and exiting close to the floor before turning up and going maybe 8 ft up to a chimney cap. Was wondering if I put in a removable elbow outside if I would be able to just use a strong blower to force a lot of air thru the system to blow the ash all the way thru (either borrow a leaf blower from work, or I have one of those powerful tube fans for construction work). Is the ash generally very light, or does it get a lot of condensate in it and so ends up being clumps?

If blowing it out wouldn't work, where are the required cleanout spots? Just after the barrel or at every turn, or what?

Thanks in advance!

Bryan

[Donkey]

Oct 27, 2010 11:28:12 GMT -8 bryan said:

Working on my first RMH that is going to go into my yurt. Going with a fairly standard design except that I am going to do a separating wall where the burn chamber is under the 'wall'. So the feed will be outside and the heat riser inside.

Careful that the burn tunnel isn't too long. No more than half the length of the heat riser.

The main thing I am not sure of is where cleanouts are required. My vent lines will be all in a bench and exiting close to the floor before turning up and going maybe 8 ft up to a chimney cap. Was wondering if I put in a removable elbow outside if I would be able to just use a strong blower to force a lot of air thru the system to blow the ash all the way thru (either borrow a leaf blower from work, or I have one of those powerful tube fans for construction work). Is the ash generally very light, or does it get a lot of condensate in it and so ends up being clumps?

Kinda depends on how long the runs are and if exhaust temp gets below condensate level.. I'd assume there will be condensate.
The ash DOES tend to be fine and light otherwise.

If blowing it out wouldn't work, where are the required cleanout spots? Just after the barrel or at every turn, or what?

Pretty much at every turn. Ideally, you want to be able to get down each leg of the pipe and under the barrel/heat riser area.

Thanks in advance!

Bryan

Cheers!

[bryan]

Thanks for the info and the lightening fast response (was a little worried it would be weeks before anyone replied).

Worked a bit more on the layout to keep the burn tunnel short and going to do a sort of sloping wall on the back side of the barrel. Making it out of cement board and adding on some junk yard tiles (why do they have millions of white tiles at salvage yards!?) just in case the fire ever goes the wrong way.

I've seen references to making the duct work the same effective diameter as the burn tunnel and heat riser which makes sense to keep from having restrictions. But was wondering why not make the duct work bigger than 'system size'? Would be less restriction, larger surface area to transfer heat and slower gas flow so longer time for the gas to shed heat to the bench. Also I am limited on space so doubt I can get more than 15 feet of line inside the bench, so wanted to get it to transfer heat as best as possible. Any downsides to this?

Bryan

[canyon]

With the challenge of short runs through the bench you can install turbulators in the horizontal run and get better heat exchange (lower your exit stack temp)

[Donkey]

Oct 30, 2010 10:27:29 GMT -8 bryan said:

I've seen references to making the duct work the same effective diameter as the burn tunnel and heat riser which makes sense to keep from having restrictions. But was wondering why not make the duct work bigger than 'system size'? Would be less restriction, larger surface area to transfer heat and slower gas flow so longer time for the gas to shed heat to the bench. Also I am limited on space so doubt I can get more than 15 feet of line inside the bench, so wanted to get it to transfer heat as best as possible. Any downsides to this?
Bryan

With your short run, that could work quite well.
You could build your bench more like a bell stove, with a LARGE void in it for this effect. Essentially it would be hollow.

For long runs this could be a dangerous practice, as wide spots in flow can ALSO produce high pressure areas which can back up the works.