Draw much better, but temps way too low...

Hi, I posted here about a year ago, was blasted by a mad drive by response and retreated to my cave to rebuild and re purpose my RMH. I did this two more times, and on my third, I've tweaked and tweaked and am getting far better results than previous.

I have a relatively small space, so originally shrunk everything down to 4" pipes. I had a lot of problems and wasn't drawing well, so sized up to a 6" system following dimensions as laid out in Rocket Mass Heaters, by Ianto Evans & Leslie Jackson.

Presently my place is cozy, though by no means has any really cold weather crept in. It's fairly mild where I am in N. Ireland, between -10*f at coldest (for about a week or two) and warmest gets to 70-80*f in summer. Right now it's sitting around 45*-55*f which is a likely average. I'm in a roundhouse/yurt insulated with hemp-lime plaster and sheep wool insulation.

I have a couple hard turns in the MH side, and have done my best to remove any 90*, I do think my flow is not bottlenecking too bad anywhere. In general she's pulling a good draw with little or no heat in the morning in the system, when I go to fire up. But, I'm get a lot of ash buildup in the burn chamber and have emptied it three times in this build already, (since about early september) filling about a half gallon space each time.

I don't believe I'm getting secondary burn at the top of the riser. My temps at the top of the riser get to about 350-400*, which is half of what I've seen people describing in other threads. WOW! what a major difference that is!

So, I am looking for ideas as to my main issues.
-too much ash
-low burn temp

I only get blow back into the building if a storm is raging & it's very windy. I plan to resolve that soonish with an "h" cap I'll build, when I did this with the 4" system it worked a charm.

Here are some pics:

Too much mass, not enough insulation in the feed and burn tunel.

Randy : " Max'' is definitely looking in the right direction, this is a major culprit, as long as you are looking into the guts of your RMH, take a good L@@K
at the Transitional zone this can have a CSA as big as 3Xs the other places with easy sweeping curves gradually tapering down to the size of the Duct-
work in your Thermal mass ! For the Good of the Craft! Big AL

Satamax Antone wrote:Too much mass, not enough insulation in the feed and burn tunel.

Wouldn't this change the burn as it heated up? Meaning that once the burn tunnel was hot, and all that mass was hot it seems this would change the quality of the burn, wouldn't it?

How should I insulate a chamber that is 4" thick in places? I used about 4" around my riser flu of vermiculite, is that a bad choice of insulation type?

Thanks for your insights.

Rebuild feed and burn tunel out of insulating firebricks, with 3" or 4" of perlite or vermiculite around, then you can cob the outsides. Everytime i've tried, and there's several others who have tried too, puting mass in the feed and burn tunel gives this result.

Satamax Antone wrote:Rebuild feed and burn tunel out of insulating firebricks, with 3" or 4" of perlite or vermiculite around, then you can cob the outsides. Everytime i've tried, and there's several others who have tried too, puting mass in the feed and burn tunel gives this result.

Ok, Satamax... will do... thanks for the feedback. It will be a little while before I can, as I'm in daily use of the system at present, but will give my feedback on the results once I do! Thanks again.