Fixing A Freezer Design Flaw With A Little Bit Of Heat

As a shining example of the law of unintended consequences, [Lou] demonstrates how certain types of freezer/refrigerator combinations fail to work in a cold environment, such as a garage during the winter. As [Lou] points out in his video (also linked after the break) – using the freezer unit in his own garage – the problem lies with devices that put the temperature sensor in the refrigerator section, but circulate cold air starting in the freezer section.

This works great in a home environment with a room temperature comfortable for humans, as the refrigerator will constantly warm up slightly due to heat from the outside, triggering the cooling cycle and ensuring the freezer section will stay nice and cold. When placed in, say, a garage when it’s around freezing, the refrigerator section will not warm up, and thus no more cooling cycle gets triggered.

As obviously the freezer section is supposed to stay significantly colder than roughly around 0°C, the freezer section can warm up enough to allow frozen goods to thaw out. The easy fix here as [Lou] demonstrates, is to add a constant source of warmth inside the refrigerator section, such as by keeping the refrigerator light on constantly.

Obvious complaints about the lack of energy efficiency and this combo unit’s optimistically broken sensor design aside, it is a fairly simple and effective fix. Even so, perhaps trading such a combo unit for one with a dedicated temperature sensor in the freezer section would prevent headaches like these.

40 thoughts on “Fixing A Freezer Design Flaw With A Little Bit Of Heat

  1. This is a fairly common problem with many refrigerators. Only some of the high-end models have separate sensors in the freezer and refrigerator sections. Or, some of the VERY old ones… my mom has a 50-year-old Kelvinator that has two sensors (and still works)!

    I ran into a similar problem with a kitchen stove. The oven temperature sensor would “wrap around” if it was too cold. For example, 10 deg.F would indicate 800 deg.F. The consequence was that with the old stove in the garage (for cooking a Christmas goose), it wouldn’t turn on unless you pre-heated the oven with a light bulb!

  2. guess I am “lucky” enough to live in a climate where I am looking at mowing the grass and spray painting some things on Christmas weekend here in the USA where even the coldest months the garage never dips below ~40F thanks to metal door facing sun all day + insulation + gas water heater … which makes it a living hell when its 115 out there in August

      1. I’ve been using this technique for years. The standard appliance bulb is 40 watts, so you’re using close to 1kwh per day. That’s about $0.15 where I live.

        You have to factor in that the fridge is running more than it would to just keep the freezer cold which makes it a little more complicated, but I really don’t think the amount of waste is a huge deal.

  3. Yes, I know this isn’t Buy a Day, but some models you can buy a small heater for the compressor, to keep its lube from being too stiff to let the compressor run in a cold garage.

    1. What types of fridge compressor have this issue?

      All the ones I’m aware of have a coil setup that is a massive heater when the rotor is stalled. They also have an auto-resetting thermal fuse. That means there is *massive* heat generated (ie. 3 kilowatts) for a couple of seconds as it tries to spin up, and if, after 10 seconds it doesn’t spin, the cutout cuts out, and 30 seconds later it tries again. Even in the coldest climates, I don’t see how it wouldn’t melt all the oil within a few minutes.

      If the oil has frozen anywhere else in the pipework, then the gas will condense on it, warming it up too.

      1. older reciprocating compressor units used these to prevent the compressor from “slugging” or trying to pump liquid refrigerant, which is destructive on the valves. IIRC the liquid can tend to pool in the compressor so the danger is at cold startup.

        1. Commercial air conditioning units have a heater around the compressor that is wired to the contactor, so it is on when the contactor is off. This is because in a commercial building the heat load can be high enough to cause the A.C. to run in cold outdoor ambient temps. Refrigerant will always migrate to the coldest part of the system in this case the compressor. The refrigerant winds up as liquid sitting in the suction side of the compressor. When the compressor turns on this liquid gets in the cylinder and and is not compressible. This is referred to as “slugging” and will destroy the compressor. This can absolutely happen on a home refrigerator placed in a garage in a very cold ambient temp. Usually the garage is still warmer than the freezer section, so the refrigerant will stay in the evaporator of the freezer.

        2. Most modern compressors have a crankcase heater to keep the oil warm enough that it doesn’t get diluted with liquid refrigerant. Liquid refrigerant in the oil causes it to be a horrible lubricant, causing premature wear on the bearings, and it also causes the oil to foam as it gets heated by the motor, which can lead to oil being in places you don’t want it. In a reciprocating compressor it can be catastrophic, oil inside of the bore of the piston can lead to broken valves and pistons as it’s not compressible.

          This is a completely different issue than the op, which is dealing with a sensing element only in the refrigerated section. Seems like you could wire up an additional thermostat in the freezer section to kick it on, but you’d have to block the flow of cold into the fridge section somehow…

  4. Ive often thought that somebody should manufacture a fridge for northern latitudes that features an optional heat exchanger plumbed to the outdoors to take advantage of the natural outdoor cold, when possible.

    It strikes me as silly to run a compressor to chill a box located in a bigger box that you pay to heat, which in turn sits on a suburban lot covered in snow.

    1. On commercial rooftop units they have a door that will open to outside and suck in cold air. Also saw one at a liquor store for the beer cooler. It’s called an econimizer and uses an enthalpy sensor to determine if outside ambient is colder and lower humidity than inside of box. This system could be adapted to a refrigerator fairly easily.

    2. As Dan said, this is actually the opposite way of thinking about it. Running a fridge in a heated house in the winter is more ‘green’ than running a fridge in an AC cooled house in the summer.

      Every watt of heat you put into your house in the winter is a watt of propane/natural gas/electric heat you didn’t have to make.

      Every watt of heat you put into your house in the summer is a watt of heat that your AC will need to negate.

      You may see monthly monetary savings with an external heat exchanger, but I doubt you’d recoup the system cost. For rough numbers, the mini split my neighbor had installed this summer was $5,000 whereas my new fridge was $1,500 and costs at most $10 a month to run. Sure, you wouldn’t need as big of a heat exchanger for just a fridge, but you’d still need the cabinet, insulation, and a more advanced dual zone controller, so 5k installed is probably a good guess. So, even if the mini-split-fridge was free to run, it would be a 30 year payback… ($5000-$1500) / $10perMonth = 350months 350/12 = 29.2years

  5. Been doing this for years with an older side-by-side in the garage. Put a string of 7W XMAS lights into the fridge but right out of their box still in their space efficient holder. Depending how cold it was in the garage, would turn on 1, or 2 or even 3 bulbs, while the rest were unscrewed enough to remain off. Of course, over time, a bulb would burn out, but there lots of others to go through. I’m now down to my last 2 working bulbs. Need to buy a new XMAS light set or a heater as suggested.

  6. There is only one temperature sensor and it is inside the fridge, because that is the simplest engineering and cheapest solution.

    So the root problem is that the floor, during winter time, is colder than inside the fridge which is directly above it, so thermal energy flows from the fridge into the floor. And the eventually the fridge section becomes colder than the freezer section, because there is one layer of insulation between it and the floor and two between the freezer and the floor.

    Sounds like a freezer/refrigerator in a garage needs the option of either being flipped upside down (freezer below during winter time, fridge below during summer time), that would be the cheapest and most energy efficient solution (but you could still end up with the fridge section being hotter than it should be). Or it needs additional insulation beneath the freezer/refrigerator, that would reduce the energy use during summer time, but it will increase then energy used slightly during the winter time. Or a freezer/refrigerator unit that sits side by side (as opposed to above and below), it would use more energy in the summer time and less in the winter time.

    Surely the simplest and most efficient solution would be just to only have a chest freezer in the garage that is accessed at most once a week or once every other week to load/unload.

    1. I’m very confused, because freezer on the bottom is normal in the U.K. it’s for ergonomic reasons – who wants to bend down to get the milk out of the fridge? The fridge is opened several times a day, whereas we might not open the freezer for a few days.
      Why would you ever build a fridge-freezer the other way up?

      Also, why would it only have one temperature sensor? Even basic ones in the U.K. have two sensors so it can warn you if the freezer has defrosted (classic hypothetical case is a power cut whilst you’re on holiday, so the freezer thaws and spoils, but then the power comes back on and everything’s cold when you get home. Without the persistent defrost alert, you’d not know until you got sick. In practice, if houses are without power for more than a day or so it’ll hit the national news).

      1. “who wants to bend down to get the milk out of the fridge?”

        How small are your fridges that one needs to “bend down” to get something out of it?

        “Also, why would it only have one temperature sensor?”

        Because cold air drops from the freezer into the fridge. Therefore, only one sensor is needed, in the fridge.

        “Even basic ones in the U.K. have two sensors…”

        Because your freezer is below your fridge.

        1. “How small are your fridges that one needs to “bend down” to get something out of it?”

          A freestanding fridge sits on the floor, so if your milk is on the bottom shelf, you will bend down. ;-)

    2. The main problem is just that there are many places in where the outdoors temperature (and eventually that in the garage) will get lower than the fridge temperature is set to.

      If that happens, the fridge will not call for cooling. As this is not happening, the freezer will also not get any cooling.

      The easiest solution is to use the device where it is intended for (yes, I know this is hackaday). Use a dedicated freezer in the garage or in any place that is not your kitchen and use the combi-units in the kitchen as it will almost always be quite a bit above the fridge temperature.

      I also have one of those combi-units outdoors in a dry location, but empty the freezer section to the big freezer during winters. The freezer section is only used for ice cream during the summers anyway over here. The big freezer is what I use to store food.

      The combi units are created for households that have to keep stuff frozen for a few days and do not have enough space for a large freezer, or to use as an intermediate solution for short term storage.
      The freezer temperature is not really regulated and could be anything between -5C and -25C (23F and -13F) depending on how much the fridge or freezer is opened and what the kitchen temperature is..

      1. Let me clarify:
        Ground temperature is a consistent 55 degrees or so, which is why Geothermal works so well. And your garage has a very large area which is adjacent to that, which is why unless you happen to have a VERY breezy garage, It rarely gets below 32 degrees (You would know this is true by the amount of frozen pipes you have in your garage).
        Continuing: You also have the compressor, which can’t operate upside down due to the oil migrating throughout the system and causing compressor failure.
        There is also an air gap between the fridge and to floor of the garage, this will help insulate the fridge from the floor. You have several walls of the fridge that are in contact with air that is colder than the inside of the fridge. This is your greatest loss of heat to the system.
        all In all, this guys solution is a good one, You have the give the fridge something to chew on, and a light bulb is the best way to simulate a heat load.

        1. But turning a refrigerator/ freezer upside down could result in the lubricant in the sealed system, ending up where it shouldn’t be and not where it should be (in the crankcase of the compressor).

  7. A few short decades back (1970’s) I was a regular customer using a CDC-6600 supercomputer at a CDC data center in Waltham, Massachusetts. Every unscheduled outage, even a power cut, would bring in the service engineers to patch things up so it would run again. We impatiently waiting customers were informed only after the fact. Hot summer days were a particular anti-favorite — when the chillers couldn’t keep up, something would overheat and crash it all down again. On one particularly cold winter day, the sudden quiet dismayed everyone. Not again! Overtemp, we were told. Seriously? It’s winter! Afterwards, they said the Freon all condensed in the outside units, leaving no Freon to chill the inside air. Not quite a fridge in the garage, but similarly counterintuitive.

  8. Partial credit.
    This will only work on the styles where the main control thermostat is in the fresh food compartment, which is between 32 and 40 degrees, Some refrigerators have the thermostat in the freezer compartment and the damper still controls the amount of cold air gets to the fresh food side, but “colder” effect is reversed, by shunting more to the fresh food side, you keep the freezer from reaching its target temperature as quickly and this results in freezer temperatures in the -10 to -15 range, which makes scooping out ice cream that much harder.

    I did like his innovative way with the light, but not many of my customers would be willing to alter their fridge to deal with an issue that’s only seasonal.

  9. The first I became aware of this problem was while browsing new fridge/freezers on the ao website and noticing in the specs that there was a section for minimum ambient temperature. There appeared to be 2 values either 10°C or -15°C. Don’t buy a fridge/freezer for the garage unless it is designed to keep working in an ambient temp of -15°C

    1. I think the issue is that most people don’t go out and buy a combo fridge/freezer for the garage, they get a new one for the house and the old one moves to the garage. Here in the upper midwest, I’d say at least 75% of the people’s garages I’ve been in has the ‘old’ fridge in the garage, lol.

  10. I have fixed this problem with switch near the thermostat which short its terminals and wall socket 24h timer which puts fridge ON each 4 hours for about 30-45 minutes. This works couple of winters without problem.

  11. Wow! I added a lit 60w bulb to garage refrigerator, on a cord plugged in outside the refrigerator. Overnight, freezer thermometer went from barely freezing to deep freeze. Garage is 18 degrees. Turned bulb off now, in til freezer temp rises again out of deep freeze. Happy to trick freezer to work in real cold weather.

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