Eli5: How do building central cool/heat work?

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I’m living in a high rise building with central air, and they switch the entire system from heating in winter to cooling in summer. We have a thermostat, but I’m not sure it does anything. It’s usually too hot or cold, all I can do is turn off the unit or play around with the fan speed.

Do you think there’s a shaft the sends hot or cold air depending on the season up my entire building and my unit turns on a fan to pull in some of that air if needed? Why is my unit always too cold or too hot and adjusting the thermostat doesn’t don much?

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4 Answers

Anonymous 0 Comments

The building is most likely pumping hot or cold water, depending on the season, to a small radiator on your unit’s HVAC system. A fan then blows air through the radiator and then throughout your unit. The thermostat controls a valve that turns the water to the radiator on or off, depending upon the temperature you’ve set.

The location of the thermostat can affect the whole system. I lived in a unit that had the thermostat located directly by the HVAC setup, which happened in the solarium, the room that received the most sunlight during the day. In the summer, the room would warm up and keep the thermostat forcing cold air throughout the rest of the unit, making every other room too cool. In the winter it would often make the thermostat think the temperature was warm enough, and shut off the heat, leaving the rest of the unit cold. Really bad design.

Another issue with the pipe systems is that on extreme weather days, the water temperature diminishes with everyone requiring constant heating or cooling.

It really depends though on how the system is engineered. Every building will have differences.

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