@Drover , just had a good look at some of your original mod photos and thought about your thermostat for controlling fan operation for cooling the back of 3 way fridges. However, I am sure that over the years since you first started on fridge mods, you have improved your knowledge as much as I have. The thermo seemed to be placed on the tubing which has all the bumps and lumps on it and BEFORE the pipe dips down and enters the condenser (that part with all the fins!!), but perhaps it is the camera angle?
For those that don't know, when the solution of ammonia and water is heated and boils, the vapours of boiling water and super heated ammonia gas rise up the tube and go through a series of uphill twisted pipes. The water vapour condenses inside the tubing as it moves over minor obstacles (those bumps and lumps) on the pipe at the top. Those lumps and bumps are called water separators which help burst any water bubbles in the vapour, turning then into condensate (liquid) which flows back DOWN into the boiler area. That is why the pipe slopes upwards (a very important reason for leveling the fridge for proper operation) until it reaches the apex bend where it starts to slope downwards. This allows the max amount of water to be removed and indeed dried out in the lumps and bumps before the downward bend. At this stage, the ammonia is still a very hot GAS and after passing the bend at the top moves down into the condenser (without ANY water content) and into the finned area to be cooled where it changes from a hot gas to ammonia liquid. Where the tube enters the condenser, the pipe and fins will be very hot, but by the time it exits the condenser, most of the heat has been dispersed into the surrounding air and the pipe and fins are somewhat cooler. Having fans move the air over these fins greatly improves the removal of heat especially if exhausted to the outside without obstructions.
That is why one does NOT place the thermo BEFORE the pipe bends downward. The temperature at that point would still be just about the boiling point of water (100C) so you do not want to sense any temperature there. That area needs to be hot!!
The thermo should be placed as close to the entry point to the condenser as possible or at any point on the fins above the pipe. The closer to the entry point will require a hotter setting on the thermo whilst somewhere in the middle is the ideal as it allows some natural cooling to occur before reaching the thermo set temperature which turns on the fans. As the air temperature around the thermo drops, the fans turn off until temperature rises again. Having the spring clips to attach the thermostat to the metal surfaces does allow you to move the thermo to an that ideal position so that your fans are not running needlessly or coming on too late.
Most kits provide a 130F thermo which works out at approx 50C. I have tried out 55C, 50C and 45C and have found that 45C gives me the best results for my fridge fan cooling - not on all the time , but there when the ambient temp gets up around 30C. THIS MAY DIFFER WITH VARIOUS FRIDGES AND INSTALLATIONS. In my set up, my 120mm computer fans (one pushing air in at the bottom vent and one pulling air out at the top vent) are each rated at 92 cubic feet of air per minute so the amount of air moved is considerable, resulting in quick cooling and short operation of fans. Cost of fans on Ebay was approx $3.75 each, the thermos @$1.00each and the clips from Bunnings under $2.00.
Attached is picture of positioning of my thermo. Also pictures of INTERNAL fans to assist others. The bottom internal fan moves the cold air around at the bottom and prevents lettuce, tomatoes, cucumbers etc from freezing (and the wrath of Mrs Boots!!). The top one moves the air over the evaporator plate preventing excessive ice build up in humid conditions. Both fans together help maintain an EVEN temperature throughout ALL of the fridge. Pictures of external fans and top deflector plate to improve cooling will follow soon.
More tips to follow shortly.
http://www.portablefridgesonline.com.au/how-3-way-fridges-work
For those that don't know, when the solution of ammonia and water is heated and boils, the vapours of boiling water and super heated ammonia gas rise up the tube and go through a series of uphill twisted pipes. The water vapour condenses inside the tubing as it moves over minor obstacles (those bumps and lumps) on the pipe at the top. Those lumps and bumps are called water separators which help burst any water bubbles in the vapour, turning then into condensate (liquid) which flows back DOWN into the boiler area. That is why the pipe slopes upwards (a very important reason for leveling the fridge for proper operation) until it reaches the apex bend where it starts to slope downwards. This allows the max amount of water to be removed and indeed dried out in the lumps and bumps before the downward bend. At this stage, the ammonia is still a very hot GAS and after passing the bend at the top moves down into the condenser (without ANY water content) and into the finned area to be cooled where it changes from a hot gas to ammonia liquid. Where the tube enters the condenser, the pipe and fins will be very hot, but by the time it exits the condenser, most of the heat has been dispersed into the surrounding air and the pipe and fins are somewhat cooler. Having fans move the air over these fins greatly improves the removal of heat especially if exhausted to the outside without obstructions.
That is why one does NOT place the thermo BEFORE the pipe bends downward. The temperature at that point would still be just about the boiling point of water (100C) so you do not want to sense any temperature there. That area needs to be hot!!
The thermo should be placed as close to the entry point to the condenser as possible or at any point on the fins above the pipe. The closer to the entry point will require a hotter setting on the thermo whilst somewhere in the middle is the ideal as it allows some natural cooling to occur before reaching the thermo set temperature which turns on the fans. As the air temperature around the thermo drops, the fans turn off until temperature rises again. Having the spring clips to attach the thermostat to the metal surfaces does allow you to move the thermo to an that ideal position so that your fans are not running needlessly or coming on too late.
Most kits provide a 130F thermo which works out at approx 50C. I have tried out 55C, 50C and 45C and have found that 45C gives me the best results for my fridge fan cooling - not on all the time , but there when the ambient temp gets up around 30C. THIS MAY DIFFER WITH VARIOUS FRIDGES AND INSTALLATIONS. In my set up, my 120mm computer fans (one pushing air in at the bottom vent and one pulling air out at the top vent) are each rated at 92 cubic feet of air per minute so the amount of air moved is considerable, resulting in quick cooling and short operation of fans. Cost of fans on Ebay was approx $3.75 each, the thermos @$1.00each and the clips from Bunnings under $2.00.
Attached is picture of positioning of my thermo. Also pictures of INTERNAL fans to assist others. The bottom internal fan moves the cold air around at the bottom and prevents lettuce, tomatoes, cucumbers etc from freezing (and the wrath of Mrs Boots!!). The top one moves the air over the evaporator plate preventing excessive ice build up in humid conditions. Both fans together help maintain an EVEN temperature throughout ALL of the fridge. Pictures of external fans and top deflector plate to improve cooling will follow soon.
More tips to follow shortly.
http://www.portablefridgesonline.com.au/how-3-way-fridges-work
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