26 October, 2009

How I Got A Free Coolroom That Runs For Free

You wanted a way to keep some of your food in a coolroom to preserve it better and save energy?  But can't afford a coolroom and want one for practically free and practically free of running costs?  You know what?  I just may be able to help you...

Let me stress that this isn't for everyone.  You may have concerns, or perhaps you don't have the space for a coolroom such as the one I'm about to describe.  So let me lay out what you need:
  • You need an old chest freezer in which the compressor has died, but which still has an intact evaporator.  (If the chest freezer was trashed for leaks in the coils, forget it.  It will have to hold water...)
  • You need either an evaporative cooler that you use daily during summer, or a buried low pressure drip irrigation system on a timer (or that you use for an hour or two every day,) and preferably, one that runs on recycled grey water and rainwater, not on your town water mains supply.
  • You need a spot outside which is conveniently handy to the kitchen, has day-round shade, and big enough to put your chest freezer.
If you pass those requirements, then carry on...

I got a local friendly refrigeration technician to donate me a chest freezer that he was only going to have to take to the recyclers anyway, and asked him to de-gas it and identify the copper lines that went to the evaporator coil. (That's the one which is around the actual icebox and is the bit that cools the interior.)  He not only identified it for me, he also kindly took out the compressor and neatly cut the copper tubes for me.  That cost me a carton of the local brewery's finest, but hey! - I got a soon-to-be-very-useful coolroom out of it!  (In fact, I got *two* for this price, I just haven't set up the second one yet.)

Now find the place where the feed to your buried drip irrigation system passes closest to your chosen location.  (In my case, the front veranda fulfills all of these requirements.)  Because I wanted to to be as environmentally conscious as possible (and where I am gets hellaciously hot in summer and is on bottomless sand where the water just seeps away to China within minutes of watering) I've made a load of compost and dug that into my vegetable garden beds, then added a low-pressure drip irrigation system and topped that off with leftover hay and straw from the rabbit cages. I feed this system from a grey-water recovery system that settles the grey water in a small tank on the ground and then pumps it up a few meters to the head tank.  That gives enough flow for my garden, and it's all pretty much free water.

Anyhow - that water in the head tank stays fairly cool due to its large volume (200 liters) and location in the shade of some mature trees.  And if you use a similar system (or perhaps a water bore with pressure reducer) or your irrigation system has a pressure reducer on it, then that's what you use.  Find the line after the timer, solenoid, and pressure reducer, and cut the line.  Put two right angle connectors on, and run two new hoses (preferably buried so it will stay cool) to your freezer.

Attach them to the copper tubes your technician pointed out, and then run your irrigation system and check for leaks around your new connections (and also under the freezer in case there *was* some leak in the evaporator coil) and check that running the water for an hour or so does indeed cool the inside of the freezer significantly.

That's it.  There's not much to say about this.  It may develop a leak due to corrosion one day - but old unloved chest freezers are a dime a dozen, and I'll have extended its lifespan by however many years it lasts.  It works extremely well, because the cooling arrangements in a freezer are designed to transfer as much heat out of the icebox as possible.  Be that into a refrigerant gas or water, doesn't matter.

So that is it - I've left the side panel off so you can see that the compressor is gone, and one of the hoses is attached to the copper down there.  Unfortunately for me, the leak in this freezer was on the other copper pipe and I had to open up some of the lagging to get to it.

Adapting from the thinnish copper tubing to your reticulation system is up to each individual situation.  That's why there isn't a huge instructable, just all these vague holistic suggestions...  I got clear tubing and adaptors at my local hardware, and just fitted it as best I could. It's important that you make sure there are no leaks!

Also of course, using that clear tubing ensures I'll never be tempted to put full water mains pressure on the system.  It was a deliberate choice, because once you attach something like this to water mains, there's every possibility that you'll cost yourself a fortune in water, and of course also there's a huge environmental cost to town water, so why not use whatever you can recycle locally?

You'll also see that there is a second set of condenser tubes in there which I've just left - they don't go anywhere near the icebox itself and aren't needed.  Also you'll see how I had to open up a section of the back of this freezer to get above the leaking section of copper tubing for one side of my water circuit, normally this would also come out in the compressor compartment.  

It keeps a remarkably cool temperature inside, provided you run your water during the heat of the day.  That's why I suggested a drip irrigation system, because these are best run around the hottest time - being buried, it doesn't damage the plants and in fact provides them with the water at the time they need it most - when the sun is driving their sap around at maximum rate.  And that's also the time your coolroom will need the most help resisting the outside heat.  It's a win/win situation...

My next project will involve my evaporative cooler and the second freezer.  See, the water in an evaporative cooler gets quite cooled by going around the cooling pads, and then sits there doing nothing else except go around again.  So instead of pumping it to the cooling pads direct, I intend to redirect it through the second freezer first.  I should get almost refrigerator-like cooling inside it, and since I'm running the evap cooler daily anyway, it will again be essentially for free.  In winter, one will need only run the water pump, and cold air and breeze will supply what little cooling this second coolroom will need.  And those small pumps cost less than a lightbulb to run...   In fact, this project may well involve some 12V pumps and my lighting solar panel...

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