How do air conditioners producing heat “freeze”?


It seems like they’d keep from being frozen because of creating heat for a house.

In: Technology

Air conditioner works by pumping heat from one radiator to another. During summer they pump heat from the inside radiator to the outside one. However some can reverse this and work in winter by pumping heat from the outside radiator to the inside and therefore heating up the house. The problem is that when they cool down the outside radiator it will condense water on this and when it is freezing this water will freeze clogging the radiator. So the air conditioner will stop working. They do often have sensors to detect this and will sometimes pump heat from the inside radiator to the outside radiator in order to clear the ice. But if it is too cold this does not work and you end up pumping more heat out then you are able to pump inn. And if it start freezing inside as well then they start having the same issues with ice on the inside radiator as they do on the outside radiator and everything just freezes up.

Another issue that some heat pumps have is that the gas they use to pump the heat turns into a liquid when it is too cold. Normally the heat pump work by boiling and condensing this liquid based on pressure but if it gets too cold then they are not able to create low enough pressures for the liquid to boil. When this happens the heat pump will just circulate liquid through its system and will end up bringing cold liquid to the inside radiator instead of hot gas like it is supposed to.

Air conditioners don’t really “produce” heat/cold. They “transfer” heat from one side to the other.

In summer, AC takes the heat from inside the house, and push it outside, which makes the inside colder and outside hotter.

In winter, AC takes the heat from outside, and push it inside. Since it’s already pretty cold outside, taking the little heat there makes it *even colder* and thus the outside half of the AC can freeze.

Air conditioners primary purpous is to dry the air, they do this by making a cold surface for water vapor in the air to condense onto if it gets too cold things freeze. There is to my knowlage no AC that can run in reverse (even if there was, that is not how homes are heated).

If you need to both dry and heat air you will need to operate both an AC and a furnace or electric heater which means the AC can still freeze independent of the heater if left running too long.

Are you talking about a heat pump, or when your AC unit outside ices over in the summer?

The unit outside it called a condensing unit. It takes the low-pressure gas and compresses it into a liquid. Basic physics tells us when doing that you generate heat. So to dissipate some of that heat that is why there are the coils and fan. The liquid passes through them and the fan circulates the outside air to help cool off the hot liquid.

The liquid travels inside to your evaporator coil, there it expands back from a high pressure liquid to a low-pressure gas. This creates a temperature drop. Think like when you take the can of compressed air and turn it upside down and it squirts out cold.

If you have a heat pump, essentially this process gets reversed. Literally the compressor goes into reverse. While it can be very cold outside, as long as there is *some* difference in temperature between the ambient air and temperature of the freon gas, the system works. If your unit outside ices over, the system will reverse itself again operating like a normal AC to generate heat and defrost the outside unit. Likewise most heat pump systems have an emergency heat option which is basically just electric heat strips (not very efficient).

When your AC unit ices up during the summer, it is because your system has a leak. Without going into details, when expands into a gas and ‘cools’, it now ends up too cold and ices over the coil. Without air circulation over the coil, now that freon can’t warm up so instead it’s traveling back outside to the unit and ices it over too eventually.