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Turn an Upright Freezer into an Incubator

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#1 nrthlndr27



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Posted 11 February 2007 - 02:29 AM

Here's a project I just recently completed and it works awesome so I thought I would share my blueprint with anyone interested in a relatively cheap high capacity incubator.

Parts Required:
Broken Old freezer on its way to the dump (make sure it has cooling tubes running through each shelf) - $0
~20 qt plastic tub - $5
150w Aquarium heater - $20
Tubing, hose clamps, and brass fittings - $15
320 gph (11' head capacity) pond/fountain pump - $40
Alife reptile thermostat with remote temp probe - $20
Computer fan & 12 v dc adapter from trashed computer and old phone - $0

Make sure freon has been removed from compressor and cut tubing attaching compressor to internal cooling tubes. Remove compressor and extra tubing.

Cut hole in side of Freezer wall to run power cords through.

Cut holes in top of plastic tub lid to insert aquarium heater through the top, to run out power cord from pump, and holes for outgoing water and return line, and a hole to fill the reservoir with a funnel is useful also (I use this hole to insert a cooking thermometer to monitor water reservoir temp when not using for filling).

Place pump in reservoir and attach tubing to pump and the other side to cut off cooling lines. Attach return line to other cut off cooling line and route it back into the reservoir.

Install aquarium heaters (I used multiple since I had them on hand and figured it will reduce initial heating and recovery time to bring water to desired temp) into lid.

Install computer fan to circulate warm air to bottom of incubator for more uniform internal temperature.

Run all power cords out of hole. Mount thermostat on side of freezer and run temperature probe into freezer.

Fill with water and turn on. The water is going to get dark and nasty colored in a hurry since it is flushing all the crap out of the inside of the cooling tubes. I changed out the water several times and then added some anti stain/scale additive made for hottubs to the water as well as an antibacterial addititive.

The nice thing about this settup is that it provides even heating throughout the unit. I keep the reservoir temperature at about 92 degrees. This is not hot enough to affect the overall temperature of the incubator but will provide fairly rapid heating (without overheating) of the incubator when needed. When I open the door, the thermostat probe is so sensitive that it kicks the circulating pump on witin 30 seconds of opening the door. The nice thing about the setup is that the incubator temperature is controlled by the thermostat - not the aquarium heaters. All I have to do is adjust the thermostat dial to whatever temp I want and don't have to mess with the heaters.

The capacity is incredible - it will fit 9 cases of quart sized jars without having to stack, although if it was at capacity I don't know if the heat generated by spawn would cause it to overheat... Anyways, it leaves plenty of space for agar plates, liquid cultures, etc. and still plenty of room for innoculated jars.

IMO not a bad setup for about a hundred bucks.

Attached are some photos...

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#2 shadowechos



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Posted 11 February 2007 - 10:46 AM

WOW--nice setup--what are the 3 devices conected to the black tubes, on the rack in the next to last picture #15?

#3 nrthlndr27



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Posted 11 February 2007 - 11:12 AM

Aquarium heaters. One would probably work fine but I had 3 laying around so I used all of them to assure rapid (3X) heat recovery. Like I say, it's probably not needed since the 20 quart container of heated water (once brought to 92 degrees) is an adequate heat sink for any dips in temperature.

#4 Hippie3



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Posted 11 February 2007 - 01:09 PM

thx for sharing

#5 spacecake



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Posted 11 February 2007 - 01:29 PM

Good thinking aboud that ventilator !
It's deffenitly needed for such a setup...

#6 nrthlndr27



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Posted 18 February 2007 - 07:52 PM

Lesson learned...

Spend the extra 10 bucks on a direct drive pond/fountain pump. At Lowes Home Improvement they sell 320 gph magnetic drive pumps for about $40 and direct drive 330 gph by the same manufacturer for about $49.

Trashed 2 of the magnetic drive variety before switching. Luckily Lowes took them back no problem. The direct drive pumps are MUCH quieter and none of the excessive vibration of the magnetic ones.

Other than this minor setback the incubation system is working great!

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#7 Freaky


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Posted 18 February 2007 - 10:55 PM


Very nice setup, you should find another free-zer and make a fruiting chamber out of it, then you'd have a nice side by side :)

#8 nrthlndr27



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Posted 18 February 2007 - 11:12 PM

I'm actually working on a fruiting chamber prototype out of an old refridgerator. A little bit different settup but I'll post on that if it turns out decent.

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