Refrigerator reservoir

M

Mr. Marijuano

Member
I want to plop a 7-10 gallon container in my 5cu ft mini fridge and grow with the res in the fridge, plant growing through the top. Cut a hole in the top for the bucket and seal it all up so it’s not leaking cold air. The fridge is like 130 watts, and used approximately .15 kWh over the course of 8 hours at 55 degrees with nothing inside. I figure a 10 gallon dwc inside should be easy for it to handle.

Would I be better off feeding some lines through the top, into a 10 gallon chiller tank that is kept inside? I’ve seen similar discussions here, with those ideas being shot down because the person was going to run 50’ of tubing in the fridge, and air is a poor conductor. What if I throw a 10 gallon container of water inside the fridge, and run my res lines through that as a chiller? What if I throw a 10 gallon drum in there with a 50’ stainless wort chiller to run my nute solution through?

What kind of temp fluctuations can I expect in the desert heat? My tent is usually around 82-90 lights on, maybe 80 with lights off. For the next month of summer, this won’t change. I want 5 gallon buckets for each plant, but may need to step up the gallons per plant, and drop plant count if I can’t figure a safeguard against the heat.

Never grown hydro, just started indoor. Will I even have a temp issue? Shooting for 70 or below.
 
Renfro

Renfro

Well-Known Member
How much water are you going to be cooling? I don't see 130 watts cooling much at all especially in an inefficient system where air is involved in the heat transfer. One could take the evaporator coil out of the fridge itself keeping the lines intact and place the coil directly in the water in your controller. That would do the best job of heat transfer. Still though, more than 10 gallons total being chilled in a hot room and it may not keep up.
 
M

Mr. Marijuano

Member
Well I see 2 different routes to take.

Either grow a single dwc with the res inside the fridge, or cool a large res inside the fridge and run lines through that res. I could put the coils in the water as your suggested, and run it off a temp controller. I could even stick a 10 gallon container of glycol in there and put a 50’ stainless wort chiller in the glycol, running my solution through this.

If I grow a single dwc, I will go with the largest possible, maybe 7-10 gallons. If I use the fridge to cool a res and circulate through it, I plan for 3 5gal buckets plus the res in the fridge.

I’m currently running the fridge around 65 degrees on a temp controller and tracking power consumption. Peaks around 200 watts but settles around 90 watts when cooling. IIRC, we are at 0.2 kWh over 8 hours. Obviously it will cool more when there is a “heat load,” but this looks promising. Going to set it around 58 degrees and track it over a day. It is in my garage which goes well over 100 every day, so the conditions are over what my plants would experience in the worst conditions of my tent.

Any thoughts about an ice probe/Peltier cooler and it’s power consumption?
 
A

Atomizer

Well-Known Member
I`ve used a chest freezer as a root chamber but that was aero not dwc. I`d go for the single dwc bucket installed in the top of the fridge, once the water is cool the fridge just needs to maintain it. I dont see the fridge having enough capacity to deal with the heat returning from remote dwc buckets. The freezer i use has an internal volume is 170L/45gal, thermostat (stc-1000) is set for 21C, differential set for 0.3C. The compressor kicks in at 21.3C and runs for 6 minutes which drops the internal temp to 21C After the compressor shuts down, the thermal flywheel effect carries on cooling. The internal temp levels out at 19.3C which takes another15 minutes. With the room temp ramped up to 35C, the freezer is on for 6 minutes and off for 103 minutes. Power consumption 235w per day, less than 10w an hour to maintain 2C root chamber temp swing. Chest freezers have better insulation due to running much lower temps typically down to minus 25C. .
 
M

Mr. Marijuano

Member
Atomizer said:
I`ve used a chest freezer as a root chamber but that was aero not dwc. I`d go for the single dwc bucket installed in the top of the fridge, once the water is cool the fridge just needs to maintain it. I dont see the fridge having enough capacity to deal with the heat returning from remote dwc buckets. The freezer i use has an internal volume is 170L/45gal, thermostat (stc-1000) is set for 21C, differential set for 0.3C. The compressor kicks in at 21.3C and runs for 6 minutes which drops the internal temp to 21C After the compressor shuts down, the thermal flywheel effect carries on cooling. The internal temp levels out at 19.3C which takes another15 minutes. With the room temp ramped up to 35C, the freezer is on for 6 minutes and off for 103 minutes. Power consumption 235w per day, less than 10w an hour to maintain 2C root chamber temp swing. Chest freezers have better insulation due to running much lower temps typically down to minus 25C. .
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I would love to use a freezer for this trial, but it just won’t fit in the room I have. I wanted to try this setup outdoor, but it’s just too damn hot to even bother with it right now. Going to hit 110f this weekend. Glad I called off my work trip. F that.

Here is where I stand with this mini-fridge: (BTW, I got this thing for $8 because the lady tore the cord off and couldn’t reconnect it. Offered to wire it up for $10 and let her keep it, but she already had a new one. Score for me.)

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25.33 hours in and only 0.42kwh used. My rate is 28c/kWh, so less than 14 cents a day set at 66*f. It is currently 98 in my garage where this is, and has been over 90 degrees for the past 10 hours or so. I am feeling very confident about it’s performance with no load. At the very least, I feel it would perform awesome if the ref coils were in a glycol bath within the refrigerator, and my solution running through a 50’ wort chiller.

It peaks around 220 watts, settles around 100 and slowly drops to 90ish.

F40AB666-5D10-4032-9BB1-45F4FE2A1227.jpeg

Is there any way to better estimate cooling power and temp swings? I am terrible at math, so not even sure if there is some common formula the hydro guys use to estimate, other than the crappy calculators online.
 
SCJedi

SCJedi

Well-Known Member
Why do that at all? Just wind a copper coil around a 5gallon bucket and chill that in the freezer/fridge. Or better yet, break down and buy a normal water chiller
 
5BY5LEC

5BY5LEC

Well-Known Member
Depending on how much your time is worth....your going to spend a lot of time building/testing/fine tuning that vs buying a chiller for 300 bucks.
I would say that if you cannot afford one, sterilize it first and then run bennies. See if you even need one.
 
M

Mr. Marijuano

Member
5BY5LEC said:
Depending on how much your time is worth....your going to spend a lot of time building/testing/fine tuning that vs buying a chiller for 300 bucks.
I would say that if you cannot afford one, sterilize it first and then run bennies. See if you even need one.
Click to expand...
That’s the problem I’ve been facing with all these diy grow projects. Sometimes I need to tweak things for my environment or situation and a custom build would do me well, however the hours of research, design, sourcing parts, building, testing, and fine-tuning is just too much sometimes. There just aren’t enough hours in the day between work, family, and growing.

My main thing is efficiency. There is no doubt in my mind that I will need some source of efficient chilling until maybe September. The cost of a chiller has never been an issue, I just yearn for efficiency. I don’t want to drop $400 on a chiller that is going to run 24/7 @200 watts or whatever they are.

What kind of performance can I expect from your average 1/10 or 1/4 hp chiller? I’ve seen the charts, but how often and to what degree will the water temp rise in a punishingly hot environment with insulated buckets/res? I know it’s a bit of a guess, but what might I expect? How many kWh per day/week/month in such a hot environment? If I can just buy a chiller that will barely turn on that can chill a couple buckets, I’ll 100% go that route, but I was under the assumption that running air at the temp we’re talking about would raise my temps quickly, causing the chiller to run all the time at whatever it’s rated wattage is.

I’m not a commercial grower, and don’t produce a lot for myself. I am cheap as hell, and only made the indoor plunge because I love gardening (been outdoors for many cycles), but first and foremost, this is an INVESTMENT for me. I want to do what makes the most financial sense, when taking into considerations all of my factors.

Sorry if I’m just an over-complicated piece of shit; that’s why I became an inspector.
 
M

Mr. Marijuano

Member
SCJedi said:
Why do that at all? Just wind a copper coil around a 5gallon bucket and chill that in the freezer/fridge. Or better yet, break down and buy a normal water chiller
Click to expand...
That was one of my considerations in an earlier post. Just cool a large “heatsink” in the fridge, and run my solution through a stainless wort coil when needed.

I think I can fit a 7 gallon bucket in there pretty good.
 
M

Mr. Marijuano

Member
Renfro said:
Then buy a chiller. It will be the most efficient. Cobbling a setup out of a refrigerator is the least efficient way to go.
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I was under the assumption that modified refrigeration setups were more efficient due to their size/cooling power in comparison to a chiller. Why would someone tear down a perfectly good beer fridge to make a chiller that sucks ass?

You can’t DIY a more efficient chiller using a refrigerator? It’s essentially a chiller inside an insulated box. Maybe I’m just a pleb.
 
Renfro

Renfro

Well-Known Member
A water chiller is designed to chill water. A refrigerator is designed to chill air and thus the contents. A chiller has a very efficient heat exchanger built into the system that will be hard if not impossible to beat even if you place the evap coil directly into the nutrient solution (block of ice). You also have a much cleaner install instead of a mangled fridge lol. A chiller can be placed outside the tent so the heat from the condenser coil doesn't warm up the grow space.
 
Renfro

Renfro

Well-Known Member
You can get 1/10th HP chillers and up. Depends on the amount of water you need to chill and how much you need to cool it. Here is a nice little chiller for a small system that only uses 264 watts when it's cooling and how much it has to actually run will depend on the heat load and system capacity.

https://growershouse.com/activeaqua-chiller-refrigeration-unit-1-10-hp

The titanium heat exchanger will not corrode or mess with your nutrients. Always size your pump to the chiller, for example this 1/10 HP chiller recommends a flow rate through the heat exchanger of 400–1060 GPH / 1500-4000 L/hour. You can use the return line from the chiller as a waterfall to oxygenate the nutrient solution. Chill the water in your controller and then recirculate that to and from the plant sites.
 
M

Mr. Marijuano

Member
Renfro said:
A water chiller is designed to chill water. A refrigerator is designed to chill air and thus the contents. A chiller has a very efficient heat exchanger built into the system that will be hard if not impossible to beat even if you place the evap coil directly into the nutrient solution (block of ice). You also have a much cleaner install instead of a mangled fridge lol. A chiller can be placed outside the tent so the heat from the condenser coil doesn't warm up the grow space.
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Well, my tents intake from the room, so eh LOL.

Stuck this in the corner of the garage to test. Will check back in an hour, but I’m wondering if the temp will stay as steady if 65 instead of 81. It isn’t collecting heat quickly, so I wonder if it will shed it at an equal rate.

Again, not a scientist or physicist.
A19BE4CA-3DF8-412F-8170-1042EF7E9412.jpeg
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A

Atomizer

Well-Known Member
If the dwc bucket is inside the fridge it wont be picking up heat from the room like uninsulated dwc buckets and pipework runs. Work out the total surface area of bucket and pipework exposed to the room temp and multiply that by the temperature difference. If you have the headroom, a fridge with a dwc bucket set in the top/lid will be more energy efficient and prolly quieter too. No circulation pump required (saving a few more watts), no insulation or external plumbing to buy or fit. Fridges and freezers are designed to be energy efficient. The insulation is injected not wrapped around a taped up ;) The condensor heat doesnt equate to much, its easily handled by the ventilation system.
 
5BY5LEC

5BY5LEC

Well-Known Member
Mr. Marijuano said:
That’s the problem I’ve been facing with all these diy grow projects. Sometimes I need to tweak things for my environment or situation and a custom build would do me well, however the hours of research, design, sourcing parts, building, testing, and fine-tuning is just too much sometimes. There just aren’t enough hours in the day between work, family, and growing.

My main thing is efficiency. There is no doubt in my mind that I will need some source of efficient chilling until maybe September. The cost of a chiller has never been an issue, I just yearn for efficiency. I don’t want to drop $400 on a chiller that is going to run 24/7 @200 watts or whatever they are.

What kind of performance can I expect from your average 1/10 or 1/4 hp chiller? I’ve seen the charts, but how often and to what degree will the water temp rise in a punishingly hot environment with insulated buckets/res? I know it’s a bit of a guess, but what might I expect? How many kWh per day/week/month in such a hot environment? If I can just buy a chiller that will barely turn on that can chill a couple buckets, I’ll 100% go that route, but I was under the assumption that running air at the temp we’re talking about would raise my temps quickly, causing the chiller to run all the time at whatever it’s rated wattage is.

I’m not a commercial grower, and don’t produce a lot for myself. I am cheap as hell, and only made the indoor plunge because I love gardening (been outdoors for many cycles), but first and foremost, this is an INVESTMENT for me. I want to do what makes the most financial sense, when taking into considerations all of my factors.

Sorry if I’m just an over-complicated piece of shit; that’s why I became an inspector.
Click to expand...
LOL if nothing else that means you have attention to detail.
I have 20 gallons and an ecoplus 1/4 horse. It turns on for about 5 minutes every 2 or 3 hours.
It's rated for 3a @110. That's not much power at all. 330 watts.
 
5BY5LEC

5BY5LEC

Well-Known Member
Renfro has a good idea too. If you use your chilled water return line as a waterfall you could get rid of your airstones and air pump.
This would be super, super efficient.
 
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