air conditioners and heaters chapter 6.3. hvac general facts in most homes, we use an hvac system to...

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HVAC GENERAL FACTS

• In most homes, we use an HVAC system to heat and cool the air.

• HVAC stands for Heating, Ventilation, and Air Conditioning

• While HVAC systems come in many forms, the most common is called a Split-System AC unit.

CONTROL

• HVAC systems are controlled by a THERMOSTAT.

• The thermostat is set to a specific temperature (Ex: 72) and a tolerance (Ex: 3).

• If the temperature rises above or below the tolerance (So above 75 or below 69) then the HVAC system turns on to correct it.

EVAPORATION AND CONDENSATION

• All HVAC system utilize evaporation and condensation in order to heat and cool the air.

• Evaporation occurs when a liquid turns into a gas. (Like water boiling)

• Condensation occurs when a gas turns back into a liquid. (Like a cold glass of water sweating)

EVAPORATION AND CONDENSATION

• In order for a liquid to evaporate it must absorb heat.

• In order for a gas to condensate it must release heat.

• That is why a liquid like alcohol feels cold on your arm. It absorbs heat from your arm to evaporate.

FREON

• Air conditioners utilize this fact to cool and heat homes.

• A liquid called Freon is inside of your air conditioners.

• Freon has a boiling temperature of around -25°C.

HVAC

• In HVAC systems, we allow Freon to evaporate and condensate in order to heat and cool homes.

• When the Freon evaporates, it provides cold air.

• When the Freon condenses, it provides warm air.

AIR CONDITIONER

• An HVAC system is called an air conditioner when it is used to cool an environment.

Freon begins as a liquid at the expansion valve.The expansion valve allows the liquid to expand and turn into a gas.

When the gas evaporates it COOLS the metal pipes.It then moves to the

compressor that compresses it A LOT.

HOTWhich makes it _________.

AC SYSTEMS

The HOT, high pressure gas is then sent to the condenser where cold air cools down gas.

Cooling off the gas allows it to turn back into a liquid.

But the liquid is still under too high of pressure to evaporate again.

The liquid is now back to the expansion valve that removes the high pressure and allows it to evaporate back into a gas again.

HEAT PUMP

• In the winter, we can run that AC system in reverse.

• In reverse, it is called a heat pump.

• Now we run the pump in reverse which makes the blue region red and the red region blue.

HEAT PUMPS

• Heat pumps are only effective to certain temperatures (each is different).

• Unfortunately that temperature is often higher than the coldest nights.

• Therefore, we have to use heating coils or furnaces in addition to heat pumps.

HEAT PUMP

• A heat pump essentially heats the air in your home by air conditioning the air outside.

• In the same way that an air conditioner cools your home by heating the air outside.

OR

INSULATION

• Insulation is therefore an INTEGRAL part of a home.

• If too much heat is allows to flow through the walls of the home (either in or out) then the HVAC system will have to work harder.