[Cob] cob/earth oven also heating hot tub intake?

[Amanda Peck]

More short on space than lazy?

There are some problems I can see:

a) How is the hot water going to get into the tub?  Easiest in some ways 
would be thermosyphon but that means that the tub is going to have to be 
higher than the oven.  That way it would circulate on its own.  Might have 
some temperature regulation problems there as well.

Water pressure is easy, but maybe not that easy to regulate the heat in the 
tub.

A separate hot water pump might well be the best option.  Let me know if you 
find one (I'm looking, but not very hard so far, for one--non-electric--to 
run hot water into a large container--20-30 gallons or so--in the attic so 
hot showers and baths are available without whole system water pressure--and 
without toting  emptying 5-gallon buckets of water!).  It could recirculate 
and be turned off as necessary.

b) copper pipes, sweated or soldered.  Need lead-free solder if you solder, 
need to have the melting temperature of everything WELL ABOVE the possible 
maximum temperature of the fire (not just the whole oven?).  There might 
also be some problems with expansion and contraction of your tubing.

c) are you going to want to be able to hot tub without baking, or vice 
versa?  I think that recycling heat sounds like a good idea.  And hot tubs 
are a great idea.  Although so far I've been thinking about Becky Bee's cob 
version for myself.

I could see some sort of moderately complicated damper system to run the 
smoke from the oven's chimney under the hot tub, or not, with another option 
to just build a fire under the tub?  A two-story structure--oven at the 
bottom with tub on top--or just off to the back on the bank or rock ledge up 
there.  If there's no handy bank or rock ledge, there's going to be a lot of 
heavy building--no little thatch roof over the oven, especially if one 
wanted the option to build a fire under the tub.
..........
Tys wrote (snipped)

I would like to build a cob baking oven and run copper piping through it,
probably in the middle of the 'fire box' area (so it'd look like a rack in
the middle of the oven) and this copper pipe would have water flowing
through it that would be attached to the intake/outtake of a hot tub. I'm
sure most of you know about wood fired hot tubs with the stove as a separate
unit (not a submersible).   The questions arise:

1. Could the cob oven handle the temperature differences possibly created by
the water flowing through it?

2. Would having a 'rack' of tubes (I imagine a zig zag pattern) going
through the middle of the oven mess up the fire? The baking?

3. Am I just being too darn lazy?



Cheers,

Tys



--------------------------------------------
Tys Sniffen
415.606.7746
Efficiency Consultant:  <http://www.ideamountain.com/> www.ideamountain.com




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