Does air conditioning actually create cold air?

No — air conditioning removes heat from the air rather than creating cold. The evaporator coil absorbs heat energy from indoor air into the refrigerant; the refrigerant carries that heat outdoors and releases it through the condenser coil. What you feel as "cold air" is simply air that has had its heat removed.

Why does my air conditioner drip water?

The water dripping from your indoor unit is condensate — water vapor from the air that condenses on the cold evaporator coil, exactly like condensation on a cold glass. This is normal. The condensate collects in a drain pan and exits through a drain line. If water is dripping inside your home, the drain line is clogged.

What is a ton of air conditioning and what size do I need?

One ton equals 12,000 BTU/hr of cooling capacity. A rough rule of thumb is 1 ton per 500–600 sq ft in an average home, but this varies with insulation, climate, window area, and occupancy. A proper Manual J load calculation is the only accurate way to size a system. Oversizing causes humidity problems; undersizing causes insufficient cooling.

How does an air conditioner remove humidity?

As warm humid air passes across the cold evaporator coil (typically 40-45°F surface temperature), water vapor cools below its dew point and condenses into liquid water on the coil fins. This liquid exits through the condensate drain line. A properly sized AC running full cycles removes substantial moisture; an oversized system that short-cycles removes far less, leaving the home feeling clammy.

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Engineering·10 min read·June 23, 2026

❄️ How Does Air Conditioning Work? The Refrigeration Cycle Explained

Q: Why is R-410A being phased out and what replaces it?

R-410A has a Global Warming Potential (GWP) of 2,088 — over 2,000 times more potent than CO2. The AIM Act requires manufacturers to phase down HFC refrigerants. New residential equipment after January 1, 2025 must use refrigerants with GWP under 700. The primary replacement is R-454B (GWP 466), branded as Puron Advance by Carrier. R-32 (GWP 675) is used in many mini-split systems.

Learn how air conditioning works — the four-component refrigeration cycle, refrigerants, efficiency ratings, and why your AC blows warm air — explained clearly for engineers and homeowners.

📖Single-Family Residence HVAC Design Drawing Set (Full Access)

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The Fundamental Principle

Heat always flows naturally from hot to cold — the Second Law of Thermodynamics. Air conditioning uses mechanical energy to force heat to flow against this gradient — from the cool interior of your home to the even hotter outdoor air. It does this through the vapor-compression refrigeration cycle.

The Four Core Components

Component	Location	What Happens Here	Refrigerant State
Evaporator Coil	Indoors	Refrigerant absorbs heat from indoor air, evaporates	Cold liquid to low-pressure vapor
Compressor	Outdoors	Raises refrigerant pressure and temperature	Low-pressure vapor to high-pressure hot vapor
Condenser Coil	Outdoors	Refrigerant releases heat to outdoor air, condenses	High-pressure hot vapor to high-pressure liquid
Expansion Device (TXV or orifice)	At or near evaporator	Drops refrigerant pressure, temperature plummets	High-pressure liquid to cold low-pressure mix

The Refrigeration Cycle: Step by Step

Step 1 — Evaporator: Cold liquid refrigerant (~40°F) enters the indoor evaporator coil. The blower fan pushes warm indoor air across the coil. Heat transfers from air to refrigerant. Refrigerant boils into a low-pressure vapor. Indoor air exits 15–25°F cooler.

Step 2 — Compressor: Low-pressure vapor (~45°F, ~75 psi for R-410A) enters the compressor. It squeezes refrigerant to ~400 psi. Per the ideal gas law, this raises temperature to ~120–140°F. The compressor motor is the only place external energy enters the system.

Step 3 — Condenser: Hot high-pressure vapor enters the outdoor condenser coil. The condenser fan draws outdoor air across the coil. Refrigerant at 130°F is hotter than 95°F outdoor air, so heat flows from refrigerant to outdoors. Refrigerant condenses back to warm liquid.

Step 4 — Expansion Valve: Warm high-pressure liquid passes through a TXV or fixed orifice. Pressure drops from ~400 psi to ~75 psi. Temperature drops to ~35–40°F. Cold refrigerant re-enters the evaporator and the cycle repeats.

Refrigerants

Refrigerant	Status	GWP
R-22 (Freon)	Phased out (2020)	1,810
R-410A (Puron)	Current standard; being phased down	2,088
R-454B (Puron Advance)	Replacing R-410A (2025+)	466
R-32	Growing adoption	675

The EPA AIM Act mandates phasing down HFCs including R-410A. New residential equipment after January 1, 2025 must use refrigerants with GWP below 700.

Ton of Refrigeration and SEER2

One ton of refrigeration equals 12,000 BTU/hr — historically the rate at which melting one ton of ice absorbs heat. SEER2 measures seasonal cooling efficiency in BTU per watt-hour. Federal minimum: SEER2 13.4 (North) / 14.3 (South). ENERGY STAR: SEER2 15.2+.

Humidity Removal: Latent Cooling

AC removes both sensible heat (temperature) and latent heat (moisture). Water vapor condenses on the cold evaporator coil and drains out. An oversized AC short-cycles — cools temperature quickly then shuts off before removing adequate moisture, leaving the home clammy.

Why Does My AC Blow Warm Air?

Symptom	Likely Cause	Fix
Warm air, outdoor unit running	Low refrigerant charge (leak)	Find and repair leak; recharge
Warm air, outdoor fan not running	Failed condenser fan motor or capacitor	Replace motor or capacitor
Warm air, outdoor unit off	Tripped breaker, failed contactor	Check breaker; inspect contactor
Weak airflow, warm air	Frozen evaporator coil	Replace filter; thaw coil 24 hrs; check refrigerant
Compressor hums, won't start	Failed start capacitor	Replace capacitor

Topics covered

how does air conditioning workrefrigeration cycleair conditioner componentscompressor condenser evaporatorexpansion valve TXVrefrigerant R-410AR-454B refrigerantton of refrigerationSEER2 ratingsplit system ACpackaged unitmini-split AClatent coolingAC blows warm airreversing valve heat pumpR-22 refrigerantBTU air conditioningAC efficiencyhow refrigerant workssensible vs latent cooling