Steve Edwards

Yeah, thanks Bill, I did forget to convert between voltages.

Daniel,

Not sure what you mean by "can drift something" but if you mean "drive" or "power" then here's my guestimate at it - but I'm new to these kind of calculations so you might want to get these checked out by someone with more experience with battery banks...

47kWh/day is 1958.333Watts continuous. At 240v that's 8.160Amps continuous load. Assuming an inverter efficiency of 80% that's about a 10.2Amp draw on the batteries. So a 916Ah bank should last for around 90 hours without recharge.

Corrections to the above welcome - I want to learn how you folks calculate this!

Hello Perry,

I'm not sure I understand what you mean when you say "using the same method as a rocket heater" but, in general, this isn't a new idea; check out Jean Pain on Wikipedia and Youtube for more.

I haven't yet used this method to heat my house but I am currently using a smallish heap (about 7 cubic meters with 100 meters of burried hose) to heat water for both outdoor use (it's nice to have a hot water supply out in the garden when the weather is cold) and for washing dishes in the house - currently getting about 40 litres of water in the region of 60 degrees Celsius from our heap before we need to let it stand and recharge for a few minutes and this lasts for about 3 weeks before the heap temperature starts to quickly decrease. My somewhat limited practical experience of this system is showing me that there are issues with keeping my heap at optimal temps that are mainly to do with keeping it well aerated and moist.

Hi Michael,

I guess the gas flow through the flues will stop once the temp inside drops below what's needed to keep things moving and I suspect (though don't know) that a drop below this critical temp will tend to lessen or mitigate an on-going all-out leakage of heat from the stack without the need for a damper. However, I have seen some builds on Youtube where folks do close off the entry to the feed-tube when not in use. I'd imagine this doesn't need to be a perfect seal and would stop the leakage of a lot of heat. Probably a whole lot cheaper than adding a damper too.

Edited to add: Just saw your location. Ok, with you being in Alaska perhaps the external temp. is so low that you'll never hit the point where the stack stops pulling till the heat has been robbed from the bench. In which case I'd think a well sealed cover over the feed tube would probably be enough.

BTW, you might find this article comparing bells and flues interesting: http://blog.dragonheaters.com/wood-heat-storage-flues-vs-bells/.

Sandy,

I like this design and would like to try building something with a bell next (something like this or the 4" Castle build) - so a few questions if I may...

1) Approx how many fire bricks were needed in this build and could I use cheaper reclaimed house brick (I'm in the UK) for the lower half or 3/4 of the heat storage bell?

2) What is the white gasket being used between the drums - ceramic fibre?

3) Does the foot of the heat storage bell need any insulation where it contacts the floor or are the lowest bricks & exit air temp low enough just to foot it directly onto something like a concrete slab?

4) Those barrel caps are a cast refractory material right? If so, what material did you use and how robust is it to repeated heat stress? I'm new to refractory materials (well, other than clay in cob ) and I guess I'm worried about what might happen if either of the caps were to fail and this were in an indoor situation; are there any mitigation steps that might be taken with an indoor installation?

Many thanks in advance!