Troubleshooting new build

Hi all,

This is an 8" system as per Evans/Jackson. Firebrick riser, perlite vermiculite insulation around riser. 2.5" between riser and barrel top. 8"x20" removed from barrel side and manifold formed in wire/clay. 8" conduit, set in strawless cob with granite chunks, 2" cowshit clay sand mix on that. The only changes to Evans is p channel in feed box,and tripwire in roof of burn chamber. Have also added a pizza oven on the front, but this is still blocked with sand and will remain so until we're sure the system functions without it.

Bench has two 3m straight runs with two 90 turns so total approx 28ft then 90 turn through wall to about 10' of horizontal chimney then 90° to 3m (9ft) vertical chimney with witches hat. The chimney is through a lean to attached to house and we,d hoped that the system would give us a bench in there to raise seedlings on. On recalculating that looks to be approx 48' system?

Two burns with bare pipes were fine (vertical chimney was 1m shorter) the conduit outside warmed up a bit, not 'hot' but warm to touch. Weather was not particularly cold then either.

Started adding mass and started getting back drafting, so extended vertical chimney by 1m, and capped off internal chimney from old woodburner more securely. (I was sure there was a draft, which given the complete silence after fitting the cap, allowed me a brief told you so moment)

We had a burn last weekend. Took an hour to get it going properly. We put that down to the cold wet mass. When it took off it burned fine, barrel too hot to touch, mass steaming nicely. Copper pipe in feed tube glowed orange, so approx 750°? Barrel and mass held heat for hours after. Very pleased with result

This week, added more mass to front and about 1-2 " manure/clay/sand mix.

Fired yesterday and it just would not get going. Or rather, it pulled fine, then when we added a few more sticks it started backdrafting, filling the house with smoke. Our wood isn't dry enough? The external horizontal conduit never changed from COLD to the touch. We 'think' the wet mass inside is slowing the flow down and that, added to a long cold run outside, the system is stalling. It was a lot colder today, and a friend with a traditional woodburner had her first fire and said she had a problem with down drafting.

We are going out today to buy the parts we need to connect the rocket to the existing chimney conduit. Unfortunately it's 7" diameter, but as it exists at the roof peak, perhaps it's speed of pull, will outweigh it being 1" smaller?

I didn't check the ashpit (under manifold) before yesterday's firing, but got a shock this morning when I stuck my hand in, and found it full of warm water! I bailed out 1.5L of grey looking water. Is this normal? Manifold is also lined with black deposit, which makes me think low temps. My thought is that as the fire was slow and cooler, the water that should have exited as steam, condensed back into the system.

I'll try to post picks of the build below.

I'd appreciate it if those with more knowledge could offer any advice at this stage!

Thanks
Lesley

Pics:

More pics:

The system was fine until we added the rocks and a layer of cob:

Very nice build! Cold wet mass will increase the amount of condensate. Even with the driest wood, and a completely dry RHM, the first start of the heating season when the mass is cold there will be some condensate. When pushing the limits of heat extraction with large mass bench / duct runs, the greater the amount of condensate.

I'll bet your RMH's mass hasn't fully dried, since the drying process generally takes several weeks of daily firing. So get it lit and keep it going. Use an exhaust fan at the chimney cap to force the start-up draft as needed. Once it is dried out it should run on its own. More chimney height may eventually be needed, if it continues to have a problem with back drafting, once completely dried out. But first get it dried out and the mass warmed up.

Lesley Verbrugge : O.K., No-one here is surprised with the amount of water that you have in your pipes ! Several of your fellow members have adopted the Lasagna method

of making-up the Thermal Mass, layer by layer . With lots layers of of dense/heavy rock used as fill You end up needing Much less Cob, the smallest amount of cob equals the

smallest amount of Water that must be expelled before your system is dry and working at its best !


Besides the water in the cob we must allow for the water trapped in the wood and The H2O created during the burning of the Wood gases and charcoal ! So you are adding more

water as you try to drive off the initial water used in making your cob - Thus the Lasagna method pays major benefits - but no need to change now !


Also while you are drying things out you may be surprised at the initial amount of wood you are burning ! As your system dries out it will perform better, be easier to light, and

use a lot less Wood ! Any water you can remove from your horizontal piping will also reduce fuel usage ! ** Always be sure to check that your Clean-out covers are re-installed

tightly**


If Necessary you can use a fan or hair drier to help boost the air flow through your system, While you must give your RMH lots of attention during its initial startup the feeding

of your RMH is done almost completely by ear. The initial goal is to have the combustion chamber walls glowing Bright Red within 15 minutes, This is not

happening now -but will eventually!


It is also important that you use small, very dry, fine split wood at the start. Also with Your Rocket pulling in its own air -it is warmed by the fire below and actually cools the

upper part of the sticks. This ensures that only the very bottom of the sticks are actively burning. Just as important is to make sure that when you are loading sticks into your

Feed Tube you are not accidentally pushing large chunks of Charcoal into the Burn Tunnel as this will constipate the system and cause smoke back !


I understand and totally support your goal of using your inside Vertical Chimney but would like to see more height on the chimney you are using now! While on paper I can

prove that a chimney on the windward side of the house with its opening just below the houses peak SHOULD benefit from the same lifting effect as happens with airplane

wings, this is never consistent. Conventional wisdom says your chimney must exit on the Lee or Downwind side of your house and be above the peak of the roof !


In Very rare circumstances it can be very hard to light Any Wood Stove when the wind is blowing from a contrary direction - Even if this was your problem, the fact

that your RMH will be already warm ( all that stored heat in your Thermal mass ) makes this a rarely occurring problem !


Keep you RMH as dry as possible, use very dry Fine split wood, keep the Burn Tunnel clear, look for Your fire bricks to glow red ( in a dark room), eventually you will notice

that You are using less wood and then you can play with larger chunks of wood and fewer pieces! -It may take weeks to dry your cob, depending on the amount of wet cob

you used. Vive Lasagna !


For the good of the Craft ! Big AL !

Thank you so much Byron, what you say has reassured me!

For various reasons we haven't enough time to nurse her along. So we wimped out and reconnected the woodburner chimney and she's going like a rocket.

Yesterday was a nightmare, more smoke going out the open doors, than out the chimney ) I was worried someone passing would call out the fire service! Plus, all the cobwebs turned to black, very gothic effect.

Anyway, when the system has dried out, we'll empty the oven of sand and trial that, then we'll have another go reconnecting the extra conduit and see if it works. It always was a 'maybe'.

What I have found interesting is seeing how the draw affects the end temperature. We've inserted a probe and block off the feed tube to give an end temp of around 50°C, the pitch of the roar changes too. I love it! What I'm unsure of is why, occasionally she sounds like a steam train, as in chug chug chug. Any ideas?!

We'd like to say a big thank you to everyone who has posted throughout this forum, we have learned so much from you all.

Here's a pic of the 'finished' system.

Hi big AL,

Thank you for your brilliant reply it really is appreciated.

My husband is splitting the wood to about 3/4" by 1" do you reckon he needs to go smaller?

Re the rocks, I think in retrospect we could have added a lot more, especially under the conduit. We kind of cottoned on to more rocks=less digging out the clay after that, and they are really packed into the space between the pipes.

I already understand what you are saying about feeding by ear!

Thanks once again for all the advice, you are a star!

Regards
Lesley