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Hot climate growing pains!


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Old 06-13-2014, 11:39 AM
MontyJ MontyJ is offline
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Question Hot climate growing pains!

Hola to All!

Yes, I am in Mexico, the Sonoran desert to be more specific. and it is hot here, of course. And I need some advice on how to proceed (or not!) with my drip bucket system during the (very) hot summer months!

My current outdoor, non-shaded setup is:

- 14 std 5 gal drip buckets with various combinations of 3.75" and 6" net pots in the lids.

- All buckets are wrapped with "Panda film" to block light and reflect some sunlight to reduce heat. Lids covered as well except for net pots.

- 30 gal nutrient reservoir (Igloo Quick&Cool Camping cooler) with air bubbler and 1,000 liter/hour submersible pump. I also have a smaller pump in the return line to boost return flow over normal gravity return.

- Plants are mostly tomatoes, with one butternut squash and one cucumber plant as a test of using the same nutrient levels for growth.

- Current feeding cycle is:

Daytime = 20 minutes on every hour
Nighttime = 15 minutes on every hour

- Daytime air temp is now in the 90's during the day, dropping to the 70's at night

The Problem: Nutrient temps

I have tried various Peltier cooling devices, and even converted a mini-fridge to a chiller, running 50' of thin-walled hard plastic 1/2" feed tubing in a bucket of water in the fridge. The fridge simply cannot keep up with the heat load produced by the buckets, reservoir, connecting hoses, etc. I can get only get about a 5 deg C drop in the ambient temp of the nutrients.

Inside the buckets I have measured up to 104 deg F during the hottest part of the day, which of course is not 'ideal' for any plants! Dropping the nutrient temp down to around 90 deg F is about the best this current setup can do.

Calculations indicate I would need about 18,000 BTU's (1.5 ton a/c) to properly cool the water down to 70 deg F or so. I simply cannot afford that for something I would only use 3-4 months a year.

Temps have been this high for almost a month now, and I am astounded that the tomatoes (cherry, salad, and regular) are still producing great fruit, tho the regular tomatoes are just now starting to ripen. The cherry and salad varieties are producing pretty good at this point.

So my question is: Can I further mod the chiller unit for better efficiency?

So far, I have not removed the ice compartment "box" or moved the thermostat. I have removed all air deflectors, etc. and put in as many water bottles as the unit can hold.

Would it really help to remove the freezer box itself?

Should I move the thermostat into the large bucket with the looped tubing and water?

Even small, incremental improvements in things may help, but I am thinking the plants are going to simply give up soon if I don't make some improvement. And the really hot months of Jul and Aug are yet to hit, LoL.

TIA,

Monty

[Edit] By "thermostat" above, I really meant the 'sensor' for the thermostat!


Last edited by MontyJ; 06-13-2014 at 11:43 AM.
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  #2  
Old 06-18-2014, 10:50 PM
Stan Stan is offline
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Are you running your air stone 24 hours a day? If yes this will make the reservoir water temps just as high as the temps outside. If you let it run on the same schedule as the water pump the temps won't get that high. I have noticed an easy 15 degree difference by doing this when it's in the 90's.

Last edited by Stan; 06-18-2014 at 10:53 PM.
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Old 06-18-2014, 11:16 PM
MontyJ MontyJ is offline
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Quote:
Originally Posted by Stan View Post
Are you running your air stone 24 hours a day? If yes this will make the reservoir water temps just as high as the temps outside. If you let it run on the same schedule as the water pump the temps won't get that high. I have noticed an easy 15 degree difference by doing this when it's in the 90's.
Yes, I do have it on all the time. I knew it had to be injecting hot air, but rather assumed it would be a better tradeoff to leave it on all the time. I guess I just thought the nutes would lose all oxygenation and it would take time to build it back up again.

I will certainly give that a try! Thanks for the tip!''
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Old 06-19-2014, 02:02 AM
GpsFrontier GpsFrontier is offline
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Hello MontyJ,
I have a different experience with using air pumps and their relation to water temps than stan. You can run your own tests, and your experience may vary from either of ours. For me I have two water culture systems running outside in 102 to 110 temps right now, and both remain cool. I do add ice to them daily, but not because of the air pumps. Regardless If I had the air pumps running or not, the water temps would get high without adding ice to bring the temps back down.

I know theatrically it stands to reason that pumping warm air bubbles into cool water should warm it up. But I haven't found it to work that way in the tests I've done. Years back I thought using this principal I could cool a nutrient solution by pumping cool air through the air pump. I took the air pump and placed it in the freezer, and closed the door with the plug and air line running out. I took a container with about one gallon of water in it and took the water temp before the test. Then placed the air stone in the container and plugged it in. I let it run like that for over an hour and tested the water temp. The water temp was exactly the same after, as it was to start with. There was no temp change at all.

Also just to let you know, the saturation point of dissolved oxygen levels in water is directly related to temperature. The higher the temperature, the lower the dissolved oxygen level. Thus the quicker it will be depleted by the plants.
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  #5  
Old 06-19-2014, 11:24 AM
MontyJ MontyJ is offline
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My 'common sense' was telling me that with the huge heat load from the buckets, tubing, and unshielded reservoir, etc, the load from the bubbler was miniscule, so I did not worry about it.

But, I have learned that my 'common sense' does not always serve me correctly, so am willing to listen and learn!

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