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Even ham-handed I/T managers can do it!

August 1, 2008 3:06 PM

Well it seems that I have managed my second harvest of cucumbers this year:

http://www.terminalcore.net/gallery/weed_patch/IMG_0131

A second harvest of beans as well but I don’t have a picture handy.

The watermelon vines are _everywhere_ and are even making searching for cucumbers tough. I hope like hell this prolific vine growth signifies good watermelon growth but that remains to be seen. I’m definitely looking at a September harvest at this rate. Next year I’m definitely planting earlier.

My wife and I talked about expanding the garden out to the edge of the garage and frankly I’m all for it. I also am considering building a simple but sturdy greenhouse framework over it so that I can grow year around. I chuckle greatly at this because I’m heating the garage...and the output of the garage space heater is on the back of the garage...well inside the zone where the greenhouse would be.

I’d almost certainly have to make sure there’s nothing flammable around the “chimney” cap but that’s no big deal. If the greenhouse is well sealed against the winter weather and I put a small solar fan blowing over the...

*blink*

Well...there’s an odd idea...

Everybody remember those 70’s “freeflow” wood stoves with the pipes around them? The pipes would work on convection by taking in cool air at the bottom and heating it so it rises out the top.

The same can be done here. All it would take is two 24“ - 36” pieces of automotive “flex pipe”. You know - the kind used for making or repairing custom exhaust bends short term. I’d use 1 3/4“ to 2” in diameter pipe.

That and about an 18“ square stainless steel sheet.

Cut a hole in the stainless sheet the size of the chimney pipe and put it around it. Screw it into the wall directly. This protects the wall from the ambient heat of the pipes that we’re adding. A normal pipe ”skirt“? wouldn’t work as it doesn’t have enough surface area.

Take the first piece and wrap it from 6 o’clock to 12 o’clock around the vent pipe. Use pipe strapping and sheet metal screws to hold it on. Make sure that the bottom end of the pipe is pointing directly down towards the ground. Also make sure that one end is longer than the other - the extra length should end up on top and should extend beyond the length of the vent pipe opening by at least 6 inches. (The total pipe length will depend greatly on the size of the chimney pipe in particular.)

Take the second piece and wrap it from 6 to 12 but on the other half of the pipe. So what you get is what looks like dual exhaust that goes around the circle where a tire would be. (Anybody who has worked underneath a pickup truck knows what I mean.)

Now take the top two ends of the pipe and bend them so that they are perpendicular to the surface of the garage and - this is crucial - that they extend 6 inches or more beyond the end of the vent pipe.

So what happens here is that the space heater fires up and sends exhaust out the chimney. The chimney exhaust heats the air in the pipes causing a convection current from bottom to top. The cold air gets sucked in below where there’s no chance of exhaust contamination and heated and output into the air directly _away_ from the garage. The 6 inch limit is so that there’s no chance of the convection pipes pushing exhaust (which naturally rises upwards) into the greenhouse air.

NOTE: THIS CONVECTION CAN NOT BE FAN AUGMENTED! Or at least I don’t think it should be.

See we’re using some of the leftover heat in the exhaust to heat the air in the pipes. The problem is if we take out more than a minor amount of heat out of the exhaust then it fails to rise out of the greenhouse vent directly above the chimney. (You thought I forgot I’d have to vent that didn’t you. ;-)

Anyway exhaust gases are obviously not something we want in our food so we need to make sure those at least leave the greenhouse before they cool down enough to drop. I’m sure this exhaust could be augmented by some ductwork and a solar fan above the heater vent - kind of like a range hood in the kitchen - but if possible I’d like to keep it simpler than that.

If anybody out there has an engineering degree and can crunch some numbers for me I’d like to see them. Looking quickly at the old documents for the ancient furnace it’s at minimum a 35,000 BTU model gas-fired space heater mounted on the wall in the garage with the vent plumped directly through the wall.

Interestingly enough other than the copper used in the ground it’s a damn good furnace if old. Where people go wrong with these things is not maintaining them. For instance you _HAVE_ to blow out the combustion chamber before lighting it up for the winter season or you will almost certainly have a fire. It’s an EASY job but because it’s ”messy“ people don’t do it.

Well anyway there’s the idea. I did ask myself one other question though - if we’re putting out so much heat out of our fireplaces and furnaces why aren’t we capturing and using it? A secondary pipe - which is in effect a heat exchanger - could easily return some of the ambient heat in the home and save on heating bills.

I’m sure there’s maybe an engineering reason on newer furnaces but how many homes still have old clunkers? We can do a lot if we try...




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Comments

( 1 comment — Leave a comment )
nimitzbrood
Aug. 1st, 2008 10:17 pm (UTC)
Another way of doing this...
Convert the "mushroom cap" style chimney output to a right-angle
"stovepipe" style output.

Drill a 2 1/8" hole directly through the vertical portion of the
"stovepipe".

Push a 12" long 2" diameter exhaust pipe through the "stovepipe" so
that it sticks out 6" in front.

Attach flex pipe to the back end of the through-pipe and wind it down
around the rest of the pipe so the input is below the right-angle elbow.

Less chimney obstruction and less flex pipe needed.
( 1 comment — Leave a comment )

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