FORMULAS & FACTS
BTU (British Thermal Unit) is the heat required to raise 1 pound of water 1°F
1BTU = 252 cal = 0.252 kcal
1cal = 4.187 Joules
BTU X 1.055 = Kilo Joules
BTU divided by 3,413 = Kilowatt (1 KW)
One gallonof 120°F(49°C )water
weighs approximately 8.25 pounds.
Pounds x .45359 = Kilogram
Gallons x 3.7854 = Liters
%of hot water=
(Mixed Water Temp. – Cold Water
Temp.) divided by (Hot Water Temp.
–Cold Water Temp.)
%thermal efficiency =
(GPH recovery X 8.25 X temp. rise X
1.0) divided by BTU/H Input
BTU output(Gas) =
GPH recoveryx8.25 x temp. rise x 1.0
BTU output(Electric) =
BTU Input (Not exactly true due
to minimal flange heat loss.)
Capacity of a
cylindrical tank
–1⁄ 2diameter (in inches)
x3.146 x length. (in inches)
Divide by 231 for gallons.
Doubling the diameter
of a pipe will increase its flow
capacity (approximately)
5.3 times.
Linear expansion of pipe
–in inches per 100 Ft.
Grain –1grain per gallon = 17.1 Parts Per million
(measurement of water hardness)
FAHRENHEIT CENTIGRADE
32 0
41 5
60.8 16
120.2 49
140 60
180 82
212 100
To convertfrom Fahrenheit to Celsius:
(°F – 32) x 5/9 or .556 = °C.
TEMP °FRISE STEEL COPPER
50°0.38˝ 0.57˝
100°.076˝ 1.14˝
125° .092˝ 1.40˝
150°1.15˝ 1.75˝
TC-092
FORMULAS & FACTS