I have heard it once place ever and it sounds good in theory but I’m wondering if it holds up in reality.
The idea is to run your car’s AC for 15 minutes every month (even in the winter) to circulate the oil to keep the seals from drying out. Needed or not?
I have no idea whether it’s universal, but with every a/c-equipped car I’ve had the compressor engages when the heater is turned to “defrost” (the idea being to dehumidify the air). So as long as that’s done I’m not sure whether running the a/c separately is needed.
There may be some truth to that - but usually, cold winter temperatures preclude the compressor from engaging in the first place, so I’ve never figured out how that is supposed to work.
Car A/C units are very robust. This is not necessary but running it a couple of times in the winter isn’t going to hurt it.
Now home dehumidifiers are another story. Every one I have had fail is from a slight leak in the long time you don’t use them. You go to use them and they frost right over. I suspect the shaft seal is the culprit. I have begun running my latest unit a few times to try and help. I also got the extended warranty at Menards since it is dirt cheap.
I have one in our basement. It has run 24/7/365 for several years. If it dies tomorrow I’ll attempt to replace it with the same make/model.
I once had a car that explicitly stated this in the owner’s manual. So it has some provenance.
I don’t remember ever explicitly doing this, but as noted above, winter and dehumidification to help clear the inside of the glass was a common thing to do, so I probably never didn’t meet the requirement.
Yes, my 2005 Subaru and now my 2024 Toyota do this.
Exactly. This has been a nearly universal feature of the “defrost” position since factory air conditioning became a commonly available option in the late 1960s. So about 60 years now.
For those in cold climates, the idea that “defrost” is about well frost removal is pretty ingrained. And you’ll notice it takes a long time to actually remove true frozen frost from the outside of a windshield.
For folks elsewhere, that position is better named “defog” as it solves the problem of humid air condensing on both the interior and exterior of cold glass, just like the mirror in your bathroom. Spraying highly humid air onto a foggy windshield will do exactly zero to clear it until after the glass is heated well above ambient temp. Which takes a long time. Conversely, spraying dry air on the same windshield covered in condensation will quickly clear the condensation. The dry air is available all but instantly after the engine is started and the A/C compressor turned on, unlike hot air that takes a few minutes for the radiator coolant to warm up.
I think home humidifiers are just poorly made!
I’m on #4 in this house, so I tend to get 5-7 years out of them before they lose enough refrigerant that they become worthless - this despite the fact that I run mine year-round. And unfortunately it seems most (all?) of the units available at the big box stores no longer come with a recharge port/nozzle.
ETA - or maybe my expectations are just too high and 5+ years should be considered a win?
For a modern one I would be happy with 5 years. I have had 3 or 4 fail after a couple of years. But the one I had 20 years ago ran for many years. I mentioned buying one at Menard’s since their extended warranty is like $15 and makes the warranty period 3 years. We’ll see.
I do not understand home dehumidifiers loosing their charge. I thought they were a hermetically sealed system. The compressor should be inside a closed can. Am I wrong and are they a semiheretical system with the motor on the outside and a seal going to the compressor?
Looking at some parts diagrams it appears you are correct. However, every dehumidifier I have had that failed had visibly iced up evaporator coils, a sure sign of a small loss of refrigerant. So what happens in a hermetically sealed compressor if the shaft seal goes bad? Is the leaked refrigerant somehow “recycled” back into the system allowing it still keep working or is the refrigerant that escaped into the can lost in the sense of the process but just prevented from escaping to the atmosphere.
I note that there are semi-sealed compressors available that seal the refrigerant inside but can be opened by a tech to refurbish the compressor. This suggests that the compressor can indeed fail to provide the proper pressure without losing the refrigerant to the outside.
Why is that a sign of refrigerant loss? I’ve seen that happen on an old dehumidifier that lasted at least 30 years. I thought that was just part of the normal cycle but haven’t looked much into it.
The refrigerant loss leads to a lower pressure in the evaporator coil. This lower pressure means that the phase change of the refrigerant occurs at a lower temperature that is below the freezing point of water. This results in water in the air condensing and freezing on the evaporator coil, rather than staying liquid and dripping off the coil as it should do. The ice then blocks airflow across the evaporator coil, and pretty soon the coil is far from ideal operating conditions.
That was a beautiful explanation. Thank you.
One of my favorite pleasures here is reading a pro explaining something right in their wheelhouse. No wasted words, no extraneous ideas, just the distilled truth of the matter.
Interesting. I was under the impression this was the result of the dehumidifier running in a cold room. It does make sense to keep the coils no colder than the freezing point. That brings up the question again of how the refrigerant is leaking from a sealed system.
The tubing (or piping) and the coils in refrigeration equipment is typically made of copper or aluminum. For reasons of economy (copper, in particular, is expensive) and efficiency (thin wall tubes can transfer heat faster), the coils are made of thin wall tubes, either bent or soldered into compact coils, and fins are then also attached to the tubing. Minor, probably microscopic, imperfections in the tube walls, or imperfections at soldering points, may eventually over time create a point where corrosion takes place. When that occurs, the thin walls become a liability and eventually you have a leak.
A hermetically sealed unit does not need a seal. The motor and the compressor are in the can together. A seal is needed on a non hermetically sealed unit because there is a shaft between the compressor and the motor. And the motor is outside of the refrigeration cycle on the open air.
There’s still a can penetration to get electricity into the can where the motor is.
There are several penetrations. The suction line is just soldered to the can and refrigerant flows through it. The discharge line from the compressor penetrates the can and is soldered to seal it. Power lines of course and perhaps a temperature sensor.