Millet - thanks!! Will be digesting your words for awhile, cuz a soil-based thermostat that runs the entire config never crossed my mind. I was thinking only about air temps. So this is a new league now - with the kind of control you propose. Again - digesting your kind comments and counsel. Will follow up with anyone, as I progress. Thanks (to all).

Laaz - yes - your concern is both merited and compelling, and quite valid and applicable immediately. Your point is why I'm looking very, very hard at precision-dimensioned, thin-walled, plastic containers that sit inside each trash can (discussion with Dale). As this was assembling itself before my eyes this past weekend, I could never bear the thought of exposing naked copper coils directly to media, and plastic bag liners have never given me the flexibility I want. So - somehow - some way - thin walled plastic containers (that fit very snug) will be the future of this....

Thanks, all.

Hmmm... Vince do you think the heat will transfer through the thin plastic container without major loss ? Keep us posted on this when you have it set up, I would really like to know the outcome.

This could be something I could set up on my back deck with some type of foliage cover for my lemons & limes...

Laaz - i really appreciate your dialog on this one - becuase it's the biggest thing on my mind with this design right now (other than the brand new level of control Millet proposes - and all implications). Last year (Winter), i used soil heating cables wrapped around 17-gallon rubbermaid containers, that are probably 4 times thicker (or more) than thin-walled plastic containers. Inside the stucco planter, and with cover boards, these cables somehow kept my entire citrus crop above 64F degrees - through the thick plastic walls.

Given the documented raw power of protected copper coils (which were also at 80F degrees when night temps were 41F degrees), and much thinner plastic walls for the nesting containers (that will lift right out), and with sealing the top of the gap between the two - I think heat transfer will be very efficient. Who knows? Sand betweeen containers and around the pipe/coils? hmmm. "holey" nesting containers, perhaps? i've ruled out nothing, and your point is on my mind in a big way. I even have PDF specifications for this Brute trash can (!!). LOL! http://www.usplastic.com/catalog/product.asp?catalog%5Fname=USPlastic&category%5Fname=24896&product%5Fid=2712

SonomaCitrus - that is exactly the type of device I was thinking of. Thank you. (!!) I never knew they existed. How wonderful to have beer brewers!! . Nor did I know such a devices might cost $99, which is more than the cost of everything else shown thus far. But that's exactly the kind of device needed to keep this think low maintenance. I'm not one for enjoying manual plug-ins every single day, and a simple timer doesn't account for weather changes. Thanks!! Nice to meet you. -v

p.s. I'll just edit this post since I'm the last one to post, and curious how editing works. Here is cost breakdown (to me) for this specific contraption, at this point in completion:

-- 1/2" (OD) flexible Copper tubing - 30 feet @ $1.xx per foot = $31.00 (US)
-- 10-gallon Brute trash cans - three at 12.92/ea = $38.76
-- 1/2 (ID) Plastic pipe and clamps = $5 (??)
-- Maxi-jet 1200 pump = $20
-- 5-gal bucket with lid = $4.35
-- Aquarium heater (150W off ebay) = $6
-- Space blankets - two @ 3.95/ea = $7.90
-- Total (gross - but without shipping/sales tax) = $113.01 (US/SoCal)
-- Total (actual to me) = less than $70, given in-house supplies from home-made hydroponics contraptions. -v

Vince, You sure put a lot of time & work in your project & I hope it works out good - sounds like it will. Although, it's too big of a project for me. You got me thinking of a heated cable I put on my roof to prevent ice dams! It comes in lenghts of 100 ft & I think 150 -200 ft. I got the 100 ' for about 50 -$60.00 --uses 500 watts. It has no thermostat but, I would put it on a timer to go on at night (except for warmer nights). I wired it to a switch inside w/ a red lite when power is on (to remind me to shut off) . It runs V shaped along bottom edge of roof & then along top of gutter & down into downspout . Would this be about the same as those soil warming cables?? Am going to experiment & get my ladder up to wrap some 4 mil plastic around the cable & see if it melts. It may get too hot (?).
I also like Laaz's idea of old waterbed heaters! They have a thermostat but are small & only good for seedling trays (am looking for them!).
You guys have some GREAT ideas here! Thanks
Patty...
BTW..My sunroom was at 45* this am (may be to 35-40 next few months)& is 54* now. Soil temp is almost 50*. .. Is that too cold?

Hi Patty. Yes - a lot of work, but not bad over 2 months. The results were better than (I) expected - but again - there are quicker/cheaper solutions that do indeed work well.....I just have this thing for water-oriented designs. My final questions will wrap up soon. Thanks, Patty. Please say more. Would love to read about *any* other warming method. i will probably be quiet for awhile, given events of late. Very nice to meet you. -v

Patty, you ask " if 50F soil temp is to low"...it depends. If you want your citrus trees to have any growth what so ever over the winter months, then yes, 50F soiltemperature is to low. 55.4F is "absolute zero" for citrus roots to function. At temperatures at or below 55 your trees will have absolutely no growth at all until the soil temperatures increases. For good growth during the winter try for 64F. - The expo was fun. -Take Care - Millet

Thanks Millet, I read your posting on getting ready for spring & moved 2 plants w/ blossoms to the warmer L room window & out of colder room. At least for 2 weeks. Had a great time in SC..you are a true friend.

Vince, nice to meet you too! Saw you on GW several times. When you said here "copper water designs" ( or similar?) you hit me in the head w/ a hammer. I saw your coiled copper & my eyes got as big as quarters. I made sculptured sprinklers & fountains out of copper for about 7 yrs.-- all diff. designs, drilled each hole by hand to go exactly where I wanted it to go etc. so the spray pattern was also a sculpture in itself. I feel like I created a monster cuz everyone copied me & my designs, & there was a "sprinkler war" going on here LOL. They all claimed to be "originaters"! I did more soldering than a plumber does in 2 lifetimes LOL. So, I learned alot about copper --self taught, old fashioned trial & error & a lot of reading. Ooops, getting off topic now
What does anyone think of the roof de-icer cable? How similar is it to the soil warming cables ? Any one know Thanks...Geez, it's so nice to be here & talk to NICE people who KNOW things!
Patty

Patty - you're scaring me with talk of hammers. But you fascinate with talk of copper fountains. Perhaps we could take a fountain collaboration offline, as I was thinking about fountains last night.

I can't speak to warming methods other than "soil heating cables" or this new copper coil contraption. Would love to see comments from anyone about any method. As for originators - adapting copper pipes to a soil warming application in a near-hydroponics style was and is completely original. There's a 2.5-month history of this concept, from my computer keyboard, but copper in general could be adapted in countless ways - and people have already taken copper pipes into their personal think tanks, and I hope to see what they come up with. But...my design's incomplete without my thin-walled plastic containers (which I'm researching). I share Laaz's concern about future repots. -v

thank you, farslayr. (!!) I found the thread, and the thermostat discussions start with "lovethosepalms" post of June 13, i think. I will look into this. Thank you. For others, here's the thread: http://forums.gardenweb.com/forums/load/palms/msg0600234715984.html

(I had to edit - the previous link posted was for something else entirely from another browser session)

Also ... it's minor epiphany time - again - in another way. Instead of "thin-walled plastic containers" that sit inside each Brute trash can, how about stand-up, robust, plastic "field bags" that stand inside each Brute can instead? I've been corresponding with greenfire. Field bags are much cheaper than even budget plastic containers. http://www.greenfire.net (brose to find "field bags", but they have a lot of different containers also. I might protect naked copper pipes further with a thin sheet of plastic between pipe/coil and field bag. Thus, with your home-made thermostat/relay device, and field bags, this specific model of coil warming might be complete and field ready. thanks, all. now will truly try to be quiet for awhile.

Vince, get a patent or copyright. Patents are VERY expensive & copyrights only cost $10-20.00 I still have some forms I can mail you. It's easy too. Just attach a detailed drawing/pics of your design & fill out form & mail to Washington DC.

Anyone know why the time here says 5 hours past my time here?