vault backup: 2026-02-09 16:31:37

hvac-calculations.md

@@ -16,7 +16,7 @@ dg-publish: true
 
 ### British Thermal Unit
 
-Unit of heat energy
+Unit of **heat energy**
 
 There are several definitions of the Btu,
 HVAC uses the IT definition,
@@ -24,25 +24,25 @@ abbreviated Btu<sub>IT</sub>
 
 $$
 \begin{align*}
-1 \text{Btu}_\text{IT} &\equiv \left( 4.1868 \times 453.59237 \times{\frac{5}{9}} \right)~\text{J} \\
+1~\text{Btu}_\text{IT} &\equiv \left( 4.1868 \times 453.59237 \times{\frac{5}{9}} \right)~\text{J} \\
 &\approx 1055.056~\text{J}
 \end{align*}
 $$
 
 More common than Btu itself is
 thousand British thermal units per hour (MBH),
-a unit of power.
+a unit of **power**.
 
 $$
 \begin{align*}
-1 \text{MBH} &\equiv 1000~\text{Btu/hr} \\
+1~\text{MBH} &\equiv 1000~\text{Btu/hr} \\
 &\approx 3.412~\text{W}
 \end{align*}
 $$
 
 ### Ton of Refrigeration (TR or TOR)
 
-Unit of power
+Unit of **power**
 
 > [!info] Also Known As
 > * refrigeration ton (RT)
@@ -50,21 +50,21 @@ Unit of power
 
 $$
 \begin{align*}
-1 \text{TR} &\equiv 12000~\text{Btu}_\text{IT}/\text{h} \\
+1~\text{TR} &\equiv 12000~\text{Btu}_\text{IT}/\text{h} \\
 &\approx 3516.853~\text{W}
 \end{align*}
 $$
 
 ### Cubic Feet per Minute (CFM)
 
-Unit of volumetric flow
+Unit of **volumetric flow**.
 
 ## Measures
 
 ### Airflow
 
 External static pressure (ESP)
-measured in inches of water
+measured in inches of water (IN WC) "water column inches"
 
 ### Heating/Cooling Capacity
 
@@ -89,6 +89,14 @@ measured in inches of water
 * IN S.L.
 * OUT ALT.
 
+##### Ratings
+
+* MERV
+* SEER2
+* HSPF2
+
 ### Efficiency
 
 * η (eta)
+
+* ISMRE