Compressors (for HVAC, fridges, etc. – and not the kind for use with pneumatic tools) – are surprisingly simple feats of engineering which make modern life more comfortable. My experience with compressors is limited to observation and simple mechanics, I am not a specialist nor a physicist. But in short – a compressor moves heat from one location to another. This, in essence, creates a cooler location where desired.

Some applications of a compressor include your refrigerator, house air conditioner, and car air conditioner. There are other technologies being used to cool things recently, like compressor-less fridges with Peltier cooling chips, but not relevant to compressors. Let’s talk about a central cooling HVAC compressor.

A compressor is a closed system loop that gas circulates through. The component outside your house, the condenser unit, is basically a large heat sync that dissipates heat off the outside of the gas loop tubing into the atmosphere. Once the heat has dissipated, the gas inside the tubing cools down to a more neutral temperature and turns into a liquid, which travels back inside the house to your evaporator coil. There it goes through an expansion device which allows the liquid to expand, cool down more, and travel around the coils. The evaporator coils are again basically a giant heat sync, only this time the tubing is colder than the surrounding air, so heat from the house is transferred through the tubing, thus dissipating heat away from your house and making it colder. We run a fan through this coil and that cold air is pumped into individual rooms. Now the gas inside the tubing is still expanded, so it travels through a wider pipe with a larger radius, back outside to the compressor which compresses the gas. It has now completed a full cycle loop, enters the condenser unit to dissipate heat, turn into a liquid, and return inside to continue the cycle.

There is a lot more to these systems and my wording may differ from an HVAC specialist, but for our purposes this will convey the basic concept. Oh, and some compressors can be switched to run the other direction, dumping heat into your house instead of outside your house – these are called heat pumps and may save money on heating bills due to their efficiency. Compressors do not function in all types of weather, so consideration must be given to extreme weather conditions.

Too long, didn’t read version: Inside cooling compressors: matter travels in a circle, changes state between liquid and gas which has the side effect of transferring heat away from one location, and we benefit from having a cold fridge or house!

-Marshall Tramp, CPI, RMP

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Marshall Tramp, CPI, RMP
Author: Marshall Tramp, CPI, RMP
Top Notch Inspection Services llc
Serving Eastern Washington & Northern Idaho