Millet has done extensive research on soil and ambient air temperatures and effects on citrus. He cites articles in another thread here. While I'm trying to ramp up my grasp of his research, points, and pointers, I have instead spent more time investigating *how* to warm soil (the mechanical), as opposed to the botanical. And this has led to much discussion with Millet, Joe, Benny, Laaz, and others in recent past.

To summarize, this is a list of more common soil warming methods thus far (with which we are mostly familiar):

a. Heating mats
b. Heating cables
c. Christmas tree lights
d. Copper pipes with circulating warmed water (warmed with aquarium heater)
e. Submerging a plant's container in a tub with aquarium heater and warm water (*). in bath style.

I encountered item e above in the GW greenhouse forum. It seems people have been reading our warming threads. They're sure discussing heating cables in the greenhouse forum like I've never seen them do before - ever.

Anyway, my own interest this year is copper pipes with citrus, and heating cables and aquarium heater with outdoor hydroponics. Hopefully I can have my copper coil prototype running before December.



I have attached "revision 6" of the diagram I had posted in the GW Citrus forum. This conveys how my anticipated design has changed somewhat. The change from revision 5 is subtle, but such changes might make a big difference in the success of my first prototype. More later, I hope. I was rough on my citrus trees this past Summer, with yet another transplant, but I have yet to lose my first citrus tree. Next year should be better for my plants, though this year great for ideas. [img][/img]

I know already from past and kind input from JoeReal and Millet that bringing cooler (freshly circulated) water back in to the top of the reservoir could be a concern. That is - since warm water rises, then why bring the cooler water back right on top of the warmest water in the reservoir?

So my current configuration was not my first choice, but I figure with these factors, my first prototype will work around this issue for these reasons:

-- relatively active water circulation (from two pumps)
-- aquarium heaters need ambitious circulation to even work
-- the coolest water coming in from top must run past the aquarium heater to get back to bottom
-- if I pump from the bottom, this might facilitate a quicker warming of the entire body of water (but who knows?)
-- if the actual prototype doesn't address such matters sufficiently, I'll consider adapting something. The copper coils inside each 10-gallon container won't be changing, even if I change the reservoir configuration.
-- furthermore - I'm trying to get gravity to work for me in this - not against me. Bringing circulated water back to the reservoir from the bottom is truly an obstacle. Take a length of hollow pipe and blow through it. Then submerge the end in some water that's at least a foot deep, and try blowing again. The weight of water in reservoir makes it harder to get good flow - whether with air or water. Anyway, these are my latest thoughts thus far. Thanks.

So - I just wanted to acknowledge good points from JoeReal and Millet that may not be reflected in my pending prototype. Thanks.

Thanks Vince keep us posted on any updates.

I remember you from my CO2 testing on (GardenWeb) Your the only one that kept me going. Glad to see you here Dale

Laaz - thanks. This forum was a fantastic idea. Thanks. I don't forget your points either, in that enormous (previous) thread on this topic - rubber hoses instead of plastic hoses for spacer tubes, winter canopy protection, and further observations. So some of your ideas aren't in my diagram either, but we already know there are countless variations. I can only explore one (or perhaps two - as I have a second design already in mind). This diagram presumes large (10-gallon) soil containers. Making things smaller (in future) will open up a lot of design options (for me). Hopefully actual pics will follow soon.

Dale - I remember that thread pretty well. Everyone taught me a lot, and you were exploring a lot of design factors that really inspired me also, in alternate creative ways. LOL. This forum is gonna be fun (already is). Thanks for the welcomes, guys. Great to see you. Can't wait to meet more folks too.

What size heater is being considered for the prototype? Had you planned on using only one, or perhaps a number of them to create a more consistent temperature throughout the reservoir? At what sort of flow rate will the pumps be operating (can we estimate how much time the water will have to be heated?)?

I really like the idea... keep up the good work

~Derek

Vince, I think Derek could be a great help in your design opperation with his engineering knowledge. When do you think you will begin construction? - Millet

Thanksgiving weekend is when I start cutting copper (the official begin of construction phase). I agree on the wisdom of collective design, and I'd love to know if Derek perceives a more efficient waterflow design (with less drag) than my part-time ponderings for two moons have generated. Please let me know (anyone), publicly or privately. Many thanks. -v

As promised, here’s a preliminary verdict – the system works (!!). And no leaks (!!). The first prototype (phase 1) worked overnight in its first dry run (a wet dry run), on a cold and blustery night with Santa Ana winds. The winds blew off my space blanket tarp, but why have it another way? I’m talking nearly a 40F degree difference between ambient air temps and water temps in the reservoir/copper pipes last night. So - testing with media is next, but I *had* to report something this weekend.



These are the components, methods and conclusions of phase 1 (the first overnight dry run, without plants or media):

-- reservoir (5 gallon black bucket – with cover),
-- one water pump (Maxi-jet 1200), and one water circuit
-- three copper-coiled containers on the left hand side
-- aquarium heater (150 Watt, set at 31C/ ),
-- no plants and no media in the containers (yet).
-- The total water circuit (for three 10-gallon modules) is 37 feet (about 30 feet copper tubing, and 7 feet plastic tubing pieces).

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I set all modules on 2x4 lumber outdoors on patio (concrete), and covered the entire contraption with a space blanket tarp (80% heat retention) but it was loose fitting and blew off in winds last night.

9:00 PM – turned everything on.
Ambient air temp = 50F (10C)
Reservoir Water Temp at bottom = 65F (18.3C)
Thermometer 1 (air at bottom of first container to left of reservoir) = 64.2F (17.9C)
Thermometer 2 (air at top of container, under sealed lid of far left container) = 63.0F (17.2C)

10:00 PM – aquarium heater and pump on for one hour
Ambient air temp = 42.4 (5.7C)
Reservoir water temp = 72F (22.2C)
Thermometer 1 = 63.1F (17.3C)
Thermometer 2 = 61.2F ((16.2C)

11:00 PM – aquarium heater and pump on for two hours
Ambient air temp = 41.7F (5.4C)
Water Temp = 81F (27.2C) -- Nearly a 40F-degree difference in water temp vs ambient air temps!!! Wow!!!
Thermometer 1 = 63.9F/
Thermometer 2 = 62.1F/

Conclusions?

(a) Once I put this contraption in my stucco planter, with media and trees, and insulation and such, I will still need warmth retention (cover boards) over the containers at night.

(b) Once the containers are filled with media (mix-sized CHC), I think the respective temps in these containers are going to jump dramatically.

(c) If nightly temps get really cold, I can always do like Derek suggested, and add a second aquarium heater to reservoir. But all figures reported here are with one heater.

(d) For 10-gallon containers in serial configuration, the temperature dropoff with each container might be noticeable. Then again – I don’t know. I haven’t tried this with media yet.

(e) Maybe I can find some kind of switch that automatically turns everything on at 70F or below. Hmmmm. Double hmmm. Where does one find a plug-in, extension cord type temperature-activated switch? New research project (sigh).

(f) Will this method compete with heating mats or cables for warming efficiency? There is no question that this method takes more work to set up, and basic skill with hand tools. But I’ve never seen raw power like this from heating cables.

(g) Contingencies? Copper-coil warming has the edge over anything – hands down. It’s much easier to throw a second aquarium heater into a reservoir than it is to re-configuring mats or cables.

I didn’t intend this design process to stretch for 2.5 months, but I never envisioned it failing. You guys never wavered either. Thank you. Please email or post any questions. Otherwise, my three year old niece wants another “cooking lesson” from her Uncle Vince today. -Vince

onewebfoot That's COOL!! Pretty impressive. Keep us updated Dale

Thanks, Dale. There remain only two unaddressed matters at this point (with one pump - or two - either way). What will media temps be when containers are filled? For reasons confirmed by JoeReal and Benny in past, I believe media temperature will be much higher than "air" temperature was for initial readings, as moist media transmits warmth very effective.

Also - anybody staring at those pics has probably thought what I have already - what if this setup were used with smaller containers that sit inside each trash can? thin-walled plastic containers that can be lifted out on moments notice? i'm already working on that. Thanks, Dale!. -v

onewebfoot (thin-walled plastic containers that can be lifted out on moments notice).. Thats a great Idea. Dale

Very impressive Vince !

Vience, first I can certainly see you are mechanically talented. The quality of your word is clean and well done. In section (e) where you mention "some kind of a switch" to turn the heat on and off, can't you use a thermocouple type of thermostate simular to hot water heaters to adjust the temperature in the reservoir? Mabe Benny. Joe or Laaz can help in this area. You mention 70F soil temperature. I think 64 would be plenty warm enough. If you should notice leaf drop (WLD) then a higher soil temperature of 70F would be helpful. Check on the internet to see the mean soil temperature in the major citrus growing reagons of Florida, California and Texas, both winter and especially summer adverages. This will give you a guide. What root zone temperature you want for your trees depends on what your intentions for growth are. Higher temperatures for constant foliage growth, or a lower temperature for tree maintenance. I would tend for temperature that would give my tree some foliage growth year around. You can rely on air temperatures to give the foliage enough cool temperatures for good flowering. I would check the mean soil temperatures for areas in Florida and California that best grow certain citrus varieties. Say areas best for grapefruit, areas best for oranges or mandarins. I bet Dr. Malcom Manners could be an invaluable help in this area. He would have the greatest knowledge. I think you could feel free to ask his assistance, should he not read this thread. Your first container possibly might have a consistantly higher soil temperature than the last container in the series, so you could grow a variety that requires higher heat, and in the coolest container a variety that likes cooler soil temperatures. Great work indeed!! Keep good records on such things as the timing of growth flushes, blooming time, tree growth, and problems, at different medium root temperatures. ect. ect. ect. A lot of valuable information on CONTAINER GROWING can be learned. Remember, knowledge on what turns out to be harmful, is just as valuable as knowledge on the benifits. Nice work, thanks for sharing this with us. PLEASE let us know what is going on step by step. Take care - Millet

Here’s another thought. With the size of your containers (Full size trash cans) when it becomes time to change the soil it seems it will be a very difficult job. Citrus roots by nature grow shallow and spread quickly. They will in no time entangle themselves in the heating coils. Have you thought about how you will remove the trees to change the soil media without damaging the roots severely ?