1. Cooling Load Calculation (Tonnage)
This helps estimate the AC capacity you need.
Formula:
For a typical room:
Cooling Factor ≈ 25 BTU/hr per square foot (for moderate climate & average insulation).
Example:
Room size: �
Convert BTU/hr to Tons (1 Ton = 12,000 BTU/hr):
So you’d need roughly a 0.75 Ton AC unit.
2. Airflow Requirement
In HVAC, airflow is usually measured in CFM (Cubic Feet per Minute).
Formula:
Where:
� = constant (air density × specific heat × minutes/hr)
� = temperature difference between supply air and return air.
Example:
Cooling load = 12,000 BTU/hr
ΔT = 20°F
3. Duct Sizing Quick Reference
For every 400 CFM = 1 Ton of cooling.
This helps estimate the AC capacity you need.
Formula:
For a typical room:
Cooling Factor ≈ 25 BTU/hr per square foot (for moderate climate & average insulation).
Example:
Room size: �
Convert BTU/hr to Tons (1 Ton = 12,000 BTU/hr):
So you’d need roughly a 0.75 Ton AC unit.
2. Airflow Requirement
In HVAC, airflow is usually measured in CFM (Cubic Feet per Minute).
Formula:
Where:
� = constant (air density × specific heat × minutes/hr)
� = temperature difference between supply air and return air.
Example:
Cooling load = 12,000 BTU/hr
ΔT = 20°F
3. Duct Sizing Quick Reference
For every 400 CFM = 1 Ton of cooling.
A Pump Down cycle is a process where the solenoid valve closes to allow the compressor to evacuate refrigerant from the low-pressure side and store it in the high-pressure side before shutting off, preventing compressor damage from liquid migration during downtime.
A Thermostatic Expansion Valve (TXV/TEV) remains closed when the system is off because the combined upward force of the spring (P3) and evaporator pressure (P2) exceeds the downward sensing bulb pressure (P1).
HVAC manifold gauge set used by technicians to diagnose, evacuate, and charge refrigeration or air conditioning systems.
"Ever wondered how a large building stays cool? 🏢❄️ This diagram of a Central Chilled Water System breaks down the entire process—from the Chiller in the plant room to the AHUs on every floor and the Cooling Tower on the roof. Perfect visual for anyone studying HVAC! #HVAC #MechanicalEngineering #ChilledWaterSystem #EngineeringLife"