As I continue to use mine, let's see if I can help a little further.
Yes the big clay pot gets heated slower than if you just lit the candles and let them heat the air on it's way up to the ceiling. I have tall 10foot ceilings, that's a little high for me to get up to :-).
The pot(s) get warmed, I use 4 tea candles at a time know as it's 11F !! here
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The pot(s) stay nice and warm, this warms the air in what I believe a more evenly distributed fashion.
It is also nearer to me rather than to top of the ceiling, and when coming in from scraping ice/snow off my panels I can pretty much put my hands on them pot(s) and warm them.
To me this is very similar to the Russian style thermal mass stoves, Mother Earth wrote and explained about 2 decades ago.
I am using a mixture of pots to see where the sweet spot is ( I have all winter to play
). It also seems the metal from the bolts work to help direct the heat to the pots , but I had problems keeping the candles lit unless I dropped to fewer candles ( no air). The closed off top area is done so by my coffee cup or water jar (moister into the room) . plus is keeps the smoke off the ceiling meaning one less thing to clean later.
NOTE: Those who want to try this REMEMBER there is no free lunch, you can create enough carbon monoxide in a closed off room to be hazardous !!
Plus this is no where near efficient heating of a room. I have waste Bio-D therefore I can also use it with wicks, but it too, is a dirty smoke and much better and SAFER! mixed with sawdust and burned in my double walled stainless steel lined chimney.
This could be a life saver in the even of an ice storm and the power is totally out, but that's about it.
It is pretty, and smells great!! when cinnamon scented candles are in the mix.
The pots once warmed will continue to be warm for a short period of time depending on the air movement in the room.
If you are like Fab and I , and have left over Bio-D that's not any good for the engines, this would be a good way to make use of it, if you don't have access to sawdust and a fireplace.
There's a few U-tube vids that are total BS, in they don't really know whats what and merely do the short test, one test on there try it in a room full of tile, and said it didn't work (well DUH!) , he had a lavatory with a porcelain mass, walls with tile and no less than 3.8L of water to overcome thermal temps.
Truths I have found= the pots get hot! , it does work( but only just barely). Not efficient. Good hand, coffee/ tea/ water warmer. MY Cats don't like it.
Hope this helps
Bruce S