'Turn Freezer into Fridge' Bodge

[Ivan]

I recently purchased some commercial mushroom spawn for some experimentation - eg oyster mushrooms can be easily grown on waste sawdust, waste paper, cardboard etc. The problem is it comes in rather large quantities (anyone interested in some low-cost mushroom spawn?!), and it needs to be stored between 0 and 5C.

I didn't think I'd get away with turfing out the contents of our domestic fridge, and the spawn can't go outside in case of freezing. So my thoughts turned to the old redundant freezer in my garage. It's well-insulated and not outside, so it will protect the spawn against freezing temperatures. The garage is often below 5C at this time of year, so it won't actually consume a lot of power to keep at 0-5C, and it's a perfect size. The only problem is that it's a freezer not a fridge. We've got an article in the Navitron downloads about converting freezers to fridges simply by intercepting the power supply, using an additional thermostat, which got me thinking. Actually, I don't have any suitable thermostats, relays etc and didn't want to waste time waiting for things to come. Then I thought of using a solar controller. I can think of several ways to do this using the TDC3 controller (eg 1)frost protection, 2)heatdump by recooling, 3)aftercooling (eg using Relay2 to cool the store if it exceeds a certain temperature), 4) thermostat function (fn14), 5) maximum store temperature, 6)minimum temperature setting for panel (eg make sure room sensor is always hotter than fridge, and then set S1min so that the compressor will only come on when the 'collector' (ie freezer storage space) exceeds S1min (set to 5C) etc).

However, I didn't have a spare TDC3, only an old BS3 controller. The BS3 isn't as flexible - it's very apparent when you're trying to do something that it wasn't designed to do) - most of the functions and/or the temperature ranges don't work at the temperatures I want (I need the freezer compressor to come on if it drops below 5C and off again before it drops to zero. The only one of the ideas listed above which will work with a BS3 is setting the maximum store temperature to 5C. However, it's important that the ambient air doesn't exceed the freezer temperature by more than the dT setting, otherwise the pump will turn on and keep going until the freezer thermostat turns it off. So to avoid this, I set the DTO and DTF temperature settings as high as possible (10C and 9C), and taped all three sensors together and put them inside the freezer with the wires running between the doorseal and the freezer body (the gap allows some ventilation - which is a good thing as the spawn needs to breathe).

I removed the plug from a short extention lead and wired the extention lead to R1 output of the controller. The freezer plugs into this extension lead, and the power feed for the controller is taken from a short lead with a plug on the end (in theory this could have been chopped off the extension lead - for simplicity). So nothing has been hard-wired to the freezer, and it can be undone in a matter of minutes.

Net effect - freezer now works as a fridge, keeping the temperature between 4C and 5C. It hardly ever runs at the moment, as the ambient temperature is lower than 5C most of the time. It definitely works though - I saw it cycling when I put the spawn in - which had been stored temporarily in an unheated room at 10C.



It might not be the cheapest way of doing this, but it's easy, quick and very reliable.

[Greenbeast]

good stuff, i bought a fridge thermostat for £11 and converted a £30 ebay chest freezer into a fridge as a prototype for doing the same to a new chest freezer, it worked fine and is now stored in the garage until needed (for christmas etc...)

i'll be purchasing a new super efficient one this year to replace our fridge freezer in the kitchen.

[Ivan]

That would work out a lot cheaper than what I did. I did consider trying to replace the existing thermostat with a cheap fridge one off ebay, but my solution was readily achievable based on what I had, and didn't require any modifications to the fridge. From what I've read, there is considerable benefit to converting an old freezer into a fridge if it replaces an old fridge - freezer insulation is a lot better than fridges, so it should use rather less energy, although a brand new fridge is probably going to be more efficient still.

My modified freezer is currently using 0.07kWh/day (ie controller power consumption only) due to cold temperatures in the garage. Of course, yours would use 0kWh, as you're not running standby power into a controller.

[Rooster]

Be very careful growing Oyster Mushrooms, the industry is littered with people suffering from lung disease.

The problem comes from both the compost and the spores which can cause disease similar to Farmers Lung often referred to as Mushroom Workers Lung or medically as hypersensitivity pneumonitis.

So you need to take proper precautions right from the start and wear decent face masks etc.

Its a problem with all mushrooms but I seem to recall that Oyster mushrooms were amongst the worst, ie high number of deaths amongst workforce.

I'm not usually a Health and Safety fanatic but people often don't realise the dangers of mushroom growing.

Here's a couple of links but just google mushroom workers lung for stacks of info ........

http://occmed.oxfordjournals.org/cgi/reprint/48/7/465.pdf

  ............... Edible oyster mushrooms, Pleurotus species, are grown all
over the world.1 A cultivation technique of P. osteatus on
artificial substrate in air-conditioned rooms rendered the
production economical throughout the year. The indoor
cultivation, however, regularly led to allergic symptoms in
workers.2"5 We present outbreaks of mushroom worker's
lung (MWL) in a modern factory of P. osteatus and
discuss the diagnosis and prevention of the disease. ...................


http://www.themushroompeople.com/showArticle.asp?id=1407

 .................. Mushroom worker's lung [MWL], (also known as mushroom compost worker's lung, compost lung, mushroom lung and mushroom picker's lung) is an allergic respiratory disease, associated with occupational exposure to a variety of substances in the mushroom and compost industries. ...............


 

[Ivan]

Rooster,

Thanks for the warning - I had heard that too. The trick is to pick them before they start dumping spores. I'm not going to be growing any huge quantity of the mushrooms, so I don't think it's going to be a major issue for me - but I'll be careful, as you rightly suggest.

I'll post some pics when they grow.