zmVault/hvac-calculations.md

id, aliases, tags, title

id	aliases	tags	title
		destiny/uncertain status/incomplete topic/electrical type/encyclopedia	HVAC Calculations

HVAC Calculations

Units

British Thermal Unit

Unit of heat energy

There are several definitions of the Btu, HVAC uses the IT definition, abbreviated Btu_IT

\begin{align*}
1 \text{Btu}_\text{IT} &= \left( 4.1868 \times 453.59237 \times{\frac{5}{9}} \right) \text{J} \\
&\approx 1055.056 \text{J}
\end{align*}

More common than Btu itself is thousand British thermal units per hour (MBH), a unit of power.

\begin{align*}
1 \text{MBH} &= 1000 \text{Btu/hr} \\
&\approx 3.412 \text{W}
\end{align*}

Ton of Refrigeration (TR or TOR)

Unit of power

[!info] Also Known As

• refrigeration ton (RT)
• ton (refrigeration)

\begin{align*}
1 \text{TR} &= 12000 \text{Btu}_\text{IT}/\text{h} \\
&\approx 3516.853 \text{W}
\end{align*}

Cubic Feet per Minute (CFM)

Unit of volumetric flow

Measures

Airflow

• CFM

External static pressure (ESP) measured in inches of water

Heating/Cooling Capacity

• Tons (refrigeration)
• MBH

Entering air temperature (EAT) Leaving air temperature (LAT) Mixed air temperature (MAT)

Latent heat Sensible heat

Sensible -> dry bulb Latent -> wet bulb

???

OSA EAT (F) EXH EAT (F)

IN S.L. OUT ALT.

Efficiency

• η (eta)